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This is gdb.info, produced by makeinfo version 4.13 from ./gdb.texinfo.
INFO-DIR-SECTION Software development
START-INFO-DIR-ENTRY
* Gdb: (gdb). The GNU debugger.
* gdbserver: (gdb) Server. The GNU debugging server.
END-INFO-DIR-ENTRY
Copyright (C) 1988-2013 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "Free Software" and "Free Software Needs Free
Documentation", with the Front-Cover Texts being "A GNU Manual," and
with the Back-Cover Texts as in (a) below.
(a) The FSF's Back-Cover Text is: "You are free to copy and modify
this GNU Manual. Buying copies from GNU Press supports the FSF in
developing GNU and promoting software freedom."
This file documents the GNU debugger GDB.
This is the Tenth Edition, of `Debugging with GDB: the GNU
Source-Level Debugger' for GDB (GDB) Version 7.6.50.20131211-cvs.
Copyright (C) 1988-2013 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "Free Software" and "Free Software Needs Free
Documentation", with the Front-Cover Texts being "A GNU Manual," and
with the Back-Cover Texts as in (a) below.
(a) The FSF's Back-Cover Text is: "You are free to copy and modify
this GNU Manual. Buying copies from GNU Press supports the FSF in
developing GNU and promoting software freedom."

File: gdb.info, Node: Writing a Frame Filter, Next: Inferiors In Python, Prev: Frame Decorator API, Up: Python API
23.2.2.11 Writing a Frame Filter
................................
There are three basic elements that a frame filter must implement: it
must correctly implement the documented interface (*note Frame Filter
API::), it must register itself with GDB, and finally, it must decide
if it is to work on the data provided by GDB. In all cases, whether it
works on the iterator or not, each frame filter must return an
iterator. A bare-bones frame filter follows the pattern in the
following example.
import gdb
class FrameFilter():
def __init__(self):
# Frame filter attribute creation.
#
# 'name' is the name of the filter that GDB will display.
#
# 'priority' is the priority of the filter relative to other
# filters.
#
# 'enabled' is a boolean that indicates whether this filter is
# enabled and should be executed.
self.name = "Foo"
self.priority = 100
self.enabled = True
# Register this frame filter with the global frame_filters
# dictionary.
gdb.frame_filters[self.name] = self
def filter(self, frame_iter):
# Just return the iterator.
return frame_iter
The frame filter in the example above implements the three
requirements for all frame filters. It implements the API, self
registers, and makes a decision on the iterator (in this case, it just
returns the iterator untouched).
The first step is attribute creation and assignment, and as shown in
the comments the filter assigns the following attributes: `name',
`priority' and whether the filter should be enabled with the `enabled'
attribute.
The second step is registering the frame filter with the dictionary
or dictionaries that the frame filter has interest in. As shown in the
comments, this filter just registers itself with the global dictionary
`gdb.frame_filters'. As noted earlier, `gdb.frame_filters' is a
dictionary that is initialized in the `gdb' module when GDB starts.
What dictionary a filter registers with is an important consideration.
Generally, if a filter is specific to a set of code, it should be
registered either in the `objfile' or `progspace' dictionaries as they
are specific to the program currently loaded in GDB. The global
dictionary is always present in GDB and is never unloaded. Any filters
registered with the global dictionary will exist until GDB exits. To
avoid filters that may conflict, it is generally better to register
frame filters against the dictionaries that more closely align with the
usage of the filter currently in question. *Note Python
Auto-loading::, for further information on auto-loading Python scripts.
GDB takes a hands-off approach to frame filter registration,
therefore it is the frame filter's responsibility to ensure
registration has occurred, and that any exceptions are handled
appropriately. In particular, you may wish to handle exceptions
relating to Python dictionary key uniqueness. It is mandatory that the
dictionary key is the same as frame filter's `name' attribute. When a
user manages frame filters (*note Frame Filter Management::), the names
GDB will display are those contained in the `name' attribute.
The final step of this example is the implementation of the `filter'
method. As shown in the example comments, we define the `filter'
method and note that the method must take an iterator, and also must
return an iterator. In this bare-bones example, the frame filter is
not very useful as it just returns the iterator untouched. However
this is a valid operation for frame filters that have the `enabled'
attribute set, but decide not to operate on any frames.
In the next example, the frame filter operates on all frames and
utilizes a frame decorator to perform some work on the frames. *Note
Frame Decorator API::, for further information on the frame decorator
interface.
This example works on inlined frames. It highlights frames which are
inlined by tagging them with an "[inlined]" tag. By applying a frame
decorator to all frames with the Python `itertools imap' method, the
example defers actions to the frame decorator. Frame decorators are
only processed when GDB prints the backtrace.
This introduces a new decision making topic: whether to perform
decision making operations at the filtering step, or at the printing
step. In this example's approach, it does not perform any filtering
decisions at the filtering step beyond mapping a frame decorator to
each frame. This allows the actual decision making to be performed
when each frame is printed. This is an important consideration, and
well worth reflecting upon when designing a frame filter. An issue
that frame filters should avoid is unwinding the stack if possible.
Some stacks can run very deep, into the tens of thousands in some
cases. To search every frame to determine if it is inlined ahead of
time may be too expensive at the filtering step. The frame filter
cannot know how many frames it has to iterate over, and it would have
to iterate through them all. This ends up duplicating effort as GDB
performs this iteration when it prints the frames.
In this example decision making can be deferred to the printing step.
As each frame is printed, the frame decorator can examine each frame in
turn when GDB iterates. From a performance viewpoint, this is the most
appropriate decision to make as it avoids duplicating the effort that
the printing step would undertake anyway. Also, if there are many
frame filters unwinding the stack during filtering, it can
substantially delay the printing of the backtrace which will result in
large memory usage, and a poor user experience.
class InlineFilter():
def __init__(self):
self.name = "InlinedFrameFilter"
self.priority = 100
self.enabled = True
gdb.frame_filters[self.name] = self
def filter(self, frame_iter):
frame_iter = itertools.imap(InlinedFrameDecorator,
frame_iter)
return frame_iter
This frame filter is somewhat similar to the earlier example, except
that the `filter' method applies a frame decorator object called
`InlinedFrameDecorator' to each element in the iterator. The `imap'
Python method is light-weight. It does not proactively iterate over
the iterator, but rather creates a new iterator which wraps the
existing one.
Below is the frame decorator for this example.
class InlinedFrameDecorator(FrameDecorator):
def __init__(self, fobj):
super(InlinedFrameDecorator, self).__init__(fobj)
def function(self):
frame = fobj.inferior_frame()
name = str(frame.name())
if frame.type() == gdb.INLINE_FRAME:
name = name + " [inlined]"
return name
This frame decorator only defines and overrides the `function'
method. It lets the supplied `FrameDecorator', which is shipped with
GDB, perform the other work associated with printing this frame.
The combination of these two objects create this output from a
backtrace:
#0 0x004004e0 in bar () at inline.c:11
#1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21
#2 0x00400566 in main () at inline.c:31
So in the case of this example, a frame decorator is applied to all
frames, regardless of whether they may be inlined or not. As GDB
iterates over the iterator produced by the frame filters, GDB executes
each frame decorator which then makes a decision on what to print in
the `function' callback. Using a strategy like this is a way to defer
decisions on the frame content to printing time.
Eliding Frames
--------------
It might be that the above example is not desirable for representing
inlined frames, and a hierarchical approach may be preferred. If we
want to hierarchically represent frames, the `elided' frame decorator
interface might be preferable.
This example approaches the issue with the `elided' method. This
example is quite long, but very simplistic. It is out-of-scope for
this section to write a complete example that comprehensively covers
all approaches of finding and printing inlined frames. However, this
example illustrates the approach an author might use.
This example comprises of three sections.
class InlineFrameFilter():
def __init__(self):
self.name = "InlinedFrameFilter"
self.priority = 100
self.enabled = True
gdb.frame_filters[self.name] = self
def filter(self, frame_iter):
return ElidingInlineIterator(frame_iter)
This frame filter is very similar to the other examples. The only
difference is this frame filter is wrapping the iterator provided to it
(`frame_iter') with a custom iterator called `ElidingInlineIterator'.
This again defers actions to when GDB prints the backtrace, as the
iterator is not traversed until printing.
The iterator for this example is as follows. It is in this section
of the example where decisions are made on the content of the backtrace.
class ElidingInlineIterator:
def __init__(self, ii):
self.input_iterator = ii
def __iter__(self):
return self
def next(self):
frame = next(self.input_iterator)
if frame.inferior_frame().type() != gdb.INLINE_FRAME:
return frame
try:
eliding_frame = next(self.input_iterator)
except StopIteration:
return frame
return ElidingFrameDecorator(eliding_frame, [frame])
This iterator implements the Python iterator protocol. When the
`next' function is called (when GDB prints each frame), the iterator
checks if this frame decorator, `frame', is wrapping an inlined frame.
If it is not, it returns the existing frame decorator untouched. If it
is wrapping an inlined frame, it assumes that the inlined frame was
contained within the next oldest frame, `eliding_frame', which it
fetches. It then creates and returns a frame decorator,
`ElidingFrameDecorator', which contains both the elided frame, and the
eliding frame.
class ElidingInlineDecorator(FrameDecorator):
def __init__(self, frame, elided_frames):
super(ElidingInlineDecorator, self).__init__(frame)
self.frame = frame
self.elided_frames = elided_frames
def elided(self):
return iter(self.elided_frames)
This frame decorator overrides one function and returns the inlined
frame in the `elided' method. As before it lets `FrameDecorator' do
the rest of the work involved in printing this frame. This produces
the following output.
#0 0x004004e0 in bar () at inline.c:11
#2 0x00400529 in main () at inline.c:25
#1 0x00400529 in max (b=6, a=12) at inline.c:15
In that output, `max' which has been inlined into `main' is printed
hierarchically. Another approach would be to combine the `function'
method, and the `elided' method to both print a marker in the inlined
frame, and also show the hierarchical relationship.

File: gdb.info, Node: Inferiors In Python, Next: Events In Python, Prev: Writing a Frame Filter, Up: Python API
23.2.2.12 Inferiors In Python
.............................
Programs which are being run under GDB are called inferiors (*note
Inferiors and Programs::). Python scripts can access information about
and manipulate inferiors controlled by GDB via objects of the
`gdb.Inferior' class.
The following inferior-related functions are available in the `gdb'
module:
-- Function: gdb.inferiors ()
Return a tuple containing all inferior objects.
-- Function: gdb.selected_inferior ()
Return an object representing the current inferior.
A `gdb.Inferior' object has the following attributes:
-- Variable: Inferior.num
ID of inferior, as assigned by GDB.
-- Variable: Inferior.pid
Process ID of the inferior, as assigned by the underlying operating
system.
-- Variable: Inferior.was_attached
Boolean signaling whether the inferior was created using `attach',
or started by GDB itself.
A `gdb.Inferior' object has the following methods:
-- Function: Inferior.is_valid ()
Returns `True' if the `gdb.Inferior' object is valid, `False' if
not. A `gdb.Inferior' object will become invalid if the inferior
no longer exists within GDB. All other `gdb.Inferior' methods
will throw an exception if it is invalid at the time the method is
called.
-- Function: Inferior.threads ()
This method returns a tuple holding all the threads which are valid
when it is called. If there are no valid threads, the method will
return an empty tuple.
-- Function: Inferior.read_memory (address, length)
Read LENGTH bytes of memory from the inferior, starting at
ADDRESS. Returns a buffer object, which behaves much like an array
or a string. It can be modified and given to the
`Inferior.write_memory' function. In `Python' 3, the return value
is a `memoryview' object.
-- Function: Inferior.write_memory (address, buffer [, length])
Write the contents of BUFFER to the inferior, starting at ADDRESS.
The BUFFER parameter must be a Python object which supports the
buffer protocol, i.e., a string, an array or the object returned
from `Inferior.read_memory'. If given, LENGTH determines the
number of bytes from BUFFER to be written.
-- Function: Inferior.search_memory (address, length, pattern)
Search a region of the inferior memory starting at ADDRESS with
the given LENGTH using the search pattern supplied in PATTERN.
The PATTERN parameter must be a Python object which supports the
buffer protocol, i.e., a string, an array or the object returned
from `gdb.read_memory'. Returns a Python `Long' containing the
address where the pattern was found, or `None' if the pattern
could not be found.

File: gdb.info, Node: Events In Python, Next: Threads In Python, Prev: Inferiors In Python, Up: Python API
23.2.2.13 Events In Python
..........................
GDB provides a general event facility so that Python code can be
notified of various state changes, particularly changes that occur in
the inferior.
An "event" is just an object that describes some state change. The
type of the object and its attributes will vary depending on the details
of the change. All the existing events are described below.
In order to be notified of an event, you must register an event
handler with an "event registry". An event registry is an object in the
`gdb.events' module which dispatches particular events. A registry
provides methods to register and unregister event handlers:
-- Function: EventRegistry.connect (object)
Add the given callable OBJECT to the registry. This object will be
called when an event corresponding to this registry occurs.
-- Function: EventRegistry.disconnect (object)
Remove the given OBJECT from the registry. Once removed, the
object will no longer receive notifications of events.
Here is an example:
def exit_handler (event):
print "event type: exit"
print "exit code: %d" % (event.exit_code)
gdb.events.exited.connect (exit_handler)
In the above example we connect our handler `exit_handler' to the
registry `events.exited'. Once connected, `exit_handler' gets called
when the inferior exits. The argument "event" in this example is of
type `gdb.ExitedEvent'. As you can see in the example the
`ExitedEvent' object has an attribute which indicates the exit code of
the inferior.
The following is a listing of the event registries that are
available and details of the events they emit:
`events.cont'
Emits `gdb.ThreadEvent'.
Some events can be thread specific when GDB is running in non-stop
mode. When represented in Python, these events all extend
`gdb.ThreadEvent'. Note, this event is not emitted directly;
instead, events which are emitted by this or other modules might
extend this event. Examples of these events are
`gdb.BreakpointEvent' and `gdb.ContinueEvent'.
-- Variable: ThreadEvent.inferior_thread
In non-stop mode this attribute will be set to the specific
thread which was involved in the emitted event. Otherwise, it
will be set to `None'.
Emits `gdb.ContinueEvent' which extends `gdb.ThreadEvent'.
This event indicates that the inferior has been continued after a
stop. For inherited attribute refer to `gdb.ThreadEvent' above.
`events.exited'
Emits `events.ExitedEvent' which indicates that the inferior has
exited. `events.ExitedEvent' has two attributes:
-- Variable: ExitedEvent.exit_code
An integer representing the exit code, if available, which
the inferior has returned. (The exit code could be
unavailable if, for example, GDB detaches from the inferior.)
If the exit code is unavailable, the attribute does not exist.
-- Variable: ExitedEvent inferior
A reference to the inferior which triggered the `exited'
event.
`events.stop'
Emits `gdb.StopEvent' which extends `gdb.ThreadEvent'.
Indicates that the inferior has stopped. All events emitted by
this registry extend StopEvent. As a child of `gdb.ThreadEvent',
`gdb.StopEvent' will indicate the stopped thread when GDB is
running in non-stop mode. Refer to `gdb.ThreadEvent' above for
more details.
Emits `gdb.SignalEvent' which extends `gdb.StopEvent'.
This event indicates that the inferior or one of its threads has
received as signal. `gdb.SignalEvent' has the following
attributes:
-- Variable: SignalEvent.stop_signal
A string representing the signal received by the inferior. A
list of possible signal values can be obtained by running the
command `info signals' in the GDB command prompt.
Also emits `gdb.BreakpointEvent' which extends `gdb.StopEvent'.
`gdb.BreakpointEvent' event indicates that one or more breakpoints
have been hit, and has the following attributes:
-- Variable: BreakpointEvent.breakpoints
A sequence containing references to all the breakpoints (type
`gdb.Breakpoint') that were hit. *Note Breakpoints In
Python::, for details of the `gdb.Breakpoint' object.
-- Variable: BreakpointEvent.breakpoint
A reference to the first breakpoint that was hit. This
function is maintained for backward compatibility and is now
deprecated in favor of the `gdb.BreakpointEvent.breakpoints'
attribute.
`events.new_objfile'
Emits `gdb.NewObjFileEvent' which indicates that a new object file
has been loaded by GDB. `gdb.NewObjFileEvent' has one attribute:
-- Variable: NewObjFileEvent.new_objfile
A reference to the object file (`gdb.Objfile') which has been
loaded. *Note Objfiles In Python::, for details of the
`gdb.Objfile' object.

File: gdb.info, Node: Threads In Python, Next: Commands In Python, Prev: Events In Python, Up: Python API
23.2.2.14 Threads In Python
...........................
Python scripts can access information about, and manipulate inferior
threads controlled by GDB, via objects of the `gdb.InferiorThread'
class.
The following thread-related functions are available in the `gdb'
module:
-- Function: gdb.selected_thread ()
This function returns the thread object for the selected thread.
If there is no selected thread, this will return `None'.
A `gdb.InferiorThread' object has the following attributes:
-- Variable: InferiorThread.name
The name of the thread. If the user specified a name using
`thread name', then this returns that name. Otherwise, if an
OS-supplied name is available, then it is returned. Otherwise,
this returns `None'.
This attribute can be assigned to. The new value must be a string
object, which sets the new name, or `None', which removes any
user-specified thread name.
-- Variable: InferiorThread.num
ID of the thread, as assigned by GDB.
-- Variable: InferiorThread.ptid
ID of the thread, as assigned by the operating system. This
attribute is a tuple containing three integers. The first is the
Process ID (PID); the second is the Lightweight Process ID
(LWPID), and the third is the Thread ID (TID). Either the LWPID
or TID may be 0, which indicates that the operating system does
not use that identifier.
A `gdb.InferiorThread' object has the following methods:
-- Function: InferiorThread.is_valid ()
Returns `True' if the `gdb.InferiorThread' object is valid,
`False' if not. A `gdb.InferiorThread' object will become invalid
if the thread exits, or the inferior that the thread belongs is
deleted. All other `gdb.InferiorThread' methods will throw an
exception if it is invalid at the time the method is called.
-- Function: InferiorThread.switch ()
This changes GDB's currently selected thread to the one represented
by this object.
-- Function: InferiorThread.is_stopped ()
Return a Boolean indicating whether the thread is stopped.
-- Function: InferiorThread.is_running ()
Return a Boolean indicating whether the thread is running.
-- Function: InferiorThread.is_exited ()
Return a Boolean indicating whether the thread is exited.

File: gdb.info, Node: Commands In Python, Next: Parameters In Python, Prev: Threads In Python, Up: Python API
23.2.2.15 Commands In Python
............................
You can implement new GDB CLI commands in Python. A CLI command is
implemented using an instance of the `gdb.Command' class, most commonly
using a subclass.
-- Function: Command.__init__ (name, COMMAND_CLASS [, COMPLETER_CLASS
[, PREFIX]])
The object initializer for `Command' registers the new command
with GDB. This initializer is normally invoked from the subclass'
own `__init__' method.
NAME is the name of the command. If NAME consists of multiple
words, then the initial words are looked for as prefix commands.
In this case, if one of the prefix commands does not exist, an
exception is raised.
There is no support for multi-line commands.
COMMAND_CLASS should be one of the `COMMAND_' constants defined
below. This argument tells GDB how to categorize the new command
in the help system.
COMPLETER_CLASS is an optional argument. If given, it should be
one of the `COMPLETE_' constants defined below. This argument
tells GDB how to perform completion for this command. If not
given, GDB will attempt to complete using the object's `complete'
method (see below); if no such method is found, an error will
occur when completion is attempted.
PREFIX is an optional argument. If `True', then the new command
is a prefix command; sub-commands of this command may be
registered.
The help text for the new command is taken from the Python
documentation string for the command's class, if there is one. If
no documentation string is provided, the default value "This
command is not documented." is used.
-- Function: Command.dont_repeat ()
By default, a GDB command is repeated when the user enters a blank
line at the command prompt. A command can suppress this behavior
by invoking the `dont_repeat' method. This is similar to the user
command `dont-repeat', see *note dont-repeat: Define.
-- Function: Command.invoke (argument, from_tty)
This method is called by GDB when this command is invoked.
ARGUMENT is a string. It is the argument to the command, after
leading and trailing whitespace has been stripped.
FROM_TTY is a boolean argument. When true, this means that the
command was entered by the user at the terminal; when false it
means that the command came from elsewhere.
If this method throws an exception, it is turned into a GDB
`error' call. Otherwise, the return value is ignored.
To break ARGUMENT up into an argv-like string use
`gdb.string_to_argv'. This function behaves identically to GDB's
internal argument lexer `buildargv'. It is recommended to use
this for consistency. Arguments are separated by spaces and may
be quoted. Example:
print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
['1', '2 "3', '4 "5', "6 '7"]
-- Function: Command.complete (text, word)
This method is called by GDB when the user attempts completion on
this command. All forms of completion are handled by this method,
that is, the <TAB> and <M-?> key bindings (*note Completion::),
and the `complete' command (*note complete: Help.).
The arguments TEXT and WORD are both strings. TEXT holds the
complete command line up to the cursor's location. WORD holds the
last word of the command line; this is computed using a
word-breaking heuristic.
The `complete' method can return several values:
* If the return value is a sequence, the contents of the
sequence are used as the completions. It is up to `complete'
to ensure that the contents actually do complete the word. A
zero-length sequence is allowed, it means that there were no
completions available. Only string elements of the sequence
are used; other elements in the sequence are ignored.
* If the return value is one of the `COMPLETE_' constants
defined below, then the corresponding GDB-internal completion
function is invoked, and its result is used.
* All other results are treated as though there were no
available completions.
When a new command is registered, it must be declared as a member of
some general class of commands. This is used to classify top-level
commands in the on-line help system; note that prefix commands are not
listed under their own category but rather that of their top-level
command. The available classifications are represented by constants
defined in the `gdb' module:
`gdb.COMMAND_NONE'
The command does not belong to any particular class. A command in
this category will not be displayed in any of the help categories.
`gdb.COMMAND_RUNNING'
The command is related to running the inferior. For example,
`start', `step', and `continue' are in this category. Type `help
running' at the GDB prompt to see a list of commands in this
category.
`gdb.COMMAND_DATA'
The command is related to data or variables. For example, `call',
`find', and `print' are in this category. Type `help data' at the
GDB prompt to see a list of commands in this category.
`gdb.COMMAND_STACK'
The command has to do with manipulation of the stack. For example,
`backtrace', `frame', and `return' are in this category. Type
`help stack' at the GDB prompt to see a list of commands in this
category.
`gdb.COMMAND_FILES'
This class is used for file-related commands. For example,
`file', `list' and `section' are in this category. Type `help
files' at the GDB prompt to see a list of commands in this
category.
`gdb.COMMAND_SUPPORT'
This should be used for "support facilities", generally meaning
things that are useful to the user when interacting with GDB, but
not related to the state of the inferior. For example, `help',
`make', and `shell' are in this category. Type `help support' at
the GDB prompt to see a list of commands in this category.
`gdb.COMMAND_STATUS'
The command is an `info'-related command, that is, related to the
state of GDB itself. For example, `info', `macro', and `show' are
in this category. Type `help status' at the GDB prompt to see a
list of commands in this category.
`gdb.COMMAND_BREAKPOINTS'
The command has to do with breakpoints. For example, `break',
`clear', and `delete' are in this category. Type `help
breakpoints' at the GDB prompt to see a list of commands in this
category.
`gdb.COMMAND_TRACEPOINTS'
The command has to do with tracepoints. For example, `trace',
`actions', and `tfind' are in this category. Type `help
tracepoints' at the GDB prompt to see a list of commands in this
category.
`gdb.COMMAND_USER'
The command is a general purpose command for the user, and
typically does not fit in one of the other categories. Type `help
user-defined' at the GDB prompt to see a list of commands in this
category, as well as the list of gdb macros (*note Sequences::).
`gdb.COMMAND_OBSCURE'
The command is only used in unusual circumstances, or is not of
general interest to users. For example, `checkpoint', `fork', and
`stop' are in this category. Type `help obscure' at the GDB
prompt to see a list of commands in this category.
`gdb.COMMAND_MAINTENANCE'
The command is only useful to GDB maintainers. The `maintenance'
and `flushregs' commands are in this category. Type `help
internals' at the GDB prompt to see a list of commands in this
category.
A new command can use a predefined completion function, either by
specifying it via an argument at initialization, or by returning it
from the `complete' method. These predefined completion constants are
all defined in the `gdb' module:
`gdb.COMPLETE_NONE'
This constant means that no completion should be done.
`gdb.COMPLETE_FILENAME'
This constant means that filename completion should be performed.
`gdb.COMPLETE_LOCATION'
This constant means that location completion should be done.
*Note Specify Location::.
`gdb.COMPLETE_COMMAND'
This constant means that completion should examine GDB command
names.
`gdb.COMPLETE_SYMBOL'
This constant means that completion should be done using symbol
names as the source.
`gdb.COMPLETE_EXPRESSION'
This constant means that completion should be done on expressions.
Often this means completing on symbol names, but some language
parsers also have support for completing on field names.
The following code snippet shows how a trivial CLI command can be
implemented in Python:
class HelloWorld (gdb.Command):
"""Greet the whole world."""
def __init__ (self):
super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
def invoke (self, arg, from_tty):
print "Hello, World!"
HelloWorld ()
The last line instantiates the class, and is necessary to trigger the
registration of the command with GDB. Depending on how the Python code
is read into GDB, you may need to import the `gdb' module explicitly.

File: gdb.info, Node: Parameters In Python, Next: Functions In Python, Prev: Commands In Python, Up: Python API
23.2.2.16 Parameters In Python
..............................
You can implement new GDB parameters using Python. A new parameter is
implemented as an instance of the `gdb.Parameter' class.
Parameters are exposed to the user via the `set' and `show'
commands. *Note Help::.
There are many parameters that already exist and can be set in GDB.
Two examples are: `set follow fork' and `set charset'. Setting these
parameters influences certain behavior in GDB. Similarly, you can
define parameters that can be used to influence behavior in custom
Python scripts and commands.
-- Function: Parameter.__init__ (name, COMMAND-CLASS, PARAMETER-CLASS
[, ENUM-SEQUENCE])
The object initializer for `Parameter' registers the new parameter
with GDB. This initializer is normally invoked from the subclass'
own `__init__' method.
NAME is the name of the new parameter. If NAME consists of
multiple words, then the initial words are looked for as prefix
parameters. An example of this can be illustrated with the `set
print' set of parameters. If NAME is `print foo', then `print'
will be searched as the prefix parameter. In this case the
parameter can subsequently be accessed in GDB as `set print foo'.
If NAME consists of multiple words, and no prefix parameter group
can be found, an exception is raised.
COMMAND-CLASS should be one of the `COMMAND_' constants (*note
Commands In Python::). This argument tells GDB how to categorize
the new parameter in the help system.
PARAMETER-CLASS should be one of the `PARAM_' constants defined
below. This argument tells GDB the type of the new parameter;
this information is used for input validation and completion.
If PARAMETER-CLASS is `PARAM_ENUM', then ENUM-SEQUENCE must be a
sequence of strings. These strings represent the possible values
for the parameter.
If PARAMETER-CLASS is not `PARAM_ENUM', then the presence of a
fourth argument will cause an exception to be thrown.
The help text for the new parameter is taken from the Python
documentation string for the parameter's class, if there is one.
If there is no documentation string, a default value is used.
-- Variable: Parameter.set_doc
If this attribute exists, and is a string, then its value is used
as the help text for this parameter's `set' command. The value is
examined when `Parameter.__init__' is invoked; subsequent changes
have no effect.
-- Variable: Parameter.show_doc
If this attribute exists, and is a string, then its value is used
as the help text for this parameter's `show' command. The value is
examined when `Parameter.__init__' is invoked; subsequent changes
have no effect.
-- Variable: Parameter.value
The `value' attribute holds the underlying value of the parameter.
It can be read and assigned to just as any other attribute. GDB
does validation when assignments are made.
There are two methods that should be implemented in any `Parameter'
class. These are:
-- Function: Parameter.get_set_string (self)
GDB will call this method when a PARAMETER's value has been
changed via the `set' API (for example, `set foo off'). The
`value' attribute has already been populated with the new value
and may be used in output. This method must return a string.
-- Function: Parameter.get_show_string (self, svalue)
GDB will call this method when a PARAMETER's `show' API has been
invoked (for example, `show foo'). The argument `svalue' receives
the string representation of the current value. This method must
return a string.
When a new parameter is defined, its type must be specified. The
available types are represented by constants defined in the `gdb'
module:
`gdb.PARAM_BOOLEAN'
The value is a plain boolean. The Python boolean values, `True'
and `False' are the only valid values.
`gdb.PARAM_AUTO_BOOLEAN'
The value has three possible states: true, false, and `auto'. In
Python, true and false are represented using boolean constants, and
`auto' is represented using `None'.
`gdb.PARAM_UINTEGER'
The value is an unsigned integer. The value of 0 should be
interpreted to mean "unlimited".
`gdb.PARAM_INTEGER'
The value is a signed integer. The value of 0 should be
interpreted to mean "unlimited".
`gdb.PARAM_STRING'
The value is a string. When the user modifies the string, any
escape sequences, such as `\t', `\f', and octal escapes, are
translated into corresponding characters and encoded into the
current host charset.
`gdb.PARAM_STRING_NOESCAPE'
The value is a string. When the user modifies the string, escapes
are passed through untranslated.
`gdb.PARAM_OPTIONAL_FILENAME'
The value is a either a filename (a string), or `None'.
`gdb.PARAM_FILENAME'
The value is a filename. This is just like
`PARAM_STRING_NOESCAPE', but uses file names for completion.
`gdb.PARAM_ZINTEGER'
The value is an integer. This is like `PARAM_INTEGER', except 0
is interpreted as itself.
`gdb.PARAM_ENUM'
The value is a string, which must be one of a collection string
constants provided when the parameter is created.

File: gdb.info, Node: Functions In Python, Next: Progspaces In Python, Prev: Parameters In Python, Up: Python API
23.2.2.17 Writing new convenience functions
...........................................
You can implement new convenience functions (*note Convenience Vars::)
in Python. A convenience function is an instance of a subclass of the
class `gdb.Function'.
-- Function: Function.__init__ (name)
The initializer for `Function' registers the new function with
GDB. The argument NAME is the name of the function, a string.
The function will be visible to the user as a convenience variable
of type `internal function', whose name is the same as the given
NAME.
The documentation for the new function is taken from the
documentation string for the new class.
-- Function: Function.invoke (*ARGS)
When a convenience function is evaluated, its arguments are
converted to instances of `gdb.Value', and then the function's
`invoke' method is called. Note that GDB does not predetermine
the arity of convenience functions. Instead, all available
arguments are passed to `invoke', following the standard Python
calling convention. In particular, a convenience function can
have default values for parameters without ill effect.
The return value of this method is used as its value in the
enclosing expression. If an ordinary Python value is returned, it
is converted to a `gdb.Value' following the usual rules.
The following code snippet shows how a trivial convenience function
can be implemented in Python:
class Greet (gdb.Function):
"""Return string to greet someone.
Takes a name as argument."""
def __init__ (self):
super (Greet, self).__init__ ("greet")
def invoke (self, name):
return "Hello, %s!" % name.string ()
Greet ()
The last line instantiates the class, and is necessary to trigger the
registration of the function with GDB. Depending on how the Python
code is read into GDB, you may need to import the `gdb' module
explicitly.
Now you can use the function in an expression:
(gdb) print $greet("Bob")
$1 = "Hello, Bob!"

File: gdb.info, Node: Progspaces In Python, Next: Objfiles In Python, Prev: Functions In Python, Up: Python API
23.2.2.18 Program Spaces In Python
..................................
A program space, or "progspace", represents a symbolic view of an
address space. It consists of all of the objfiles of the program.
*Note Objfiles In Python::. *Note program spaces: Inferiors and
Programs, for more details about program spaces.
The following progspace-related functions are available in the `gdb'
module:
-- Function: gdb.current_progspace ()
This function returns the program space of the currently selected
inferior. *Note Inferiors and Programs::.
-- Function: gdb.progspaces ()
Return a sequence of all the progspaces currently known to GDB.
Each progspace is represented by an instance of the `gdb.Progspace'
class.
-- Variable: Progspace.filename
The file name of the progspace as a string.
-- Variable: Progspace.pretty_printers
The `pretty_printers' attribute is a list of functions. It is
used to look up pretty-printers. A `Value' is passed to each
function in order; if the function returns `None', then the search
continues. Otherwise, the return value should be an object which
is used to format the value. *Note Pretty Printing API::, for more
information.
-- Variable: Progspace.type_printers
The `type_printers' attribute is a list of type printer objects.
*Note Type Printing API::, for more information.
-- Variable: Progspace.frame_filters
The `frame_filters' attribute is a dictionary of frame filter
objects. *Note Frame Filter API::, for more information.

File: gdb.info, Node: Objfiles In Python, Next: Frames In Python, Prev: Progspaces In Python, Up: Python API
23.2.2.19 Objfiles In Python
............................
GDB loads symbols for an inferior from various symbol-containing files
(*note Files::). These include the primary executable file, any shared
libraries used by the inferior, and any separate debug info files
(*note Separate Debug Files::). GDB calls these symbol-containing
files "objfiles".
The following objfile-related functions are available in the `gdb'
module:
-- Function: gdb.current_objfile ()
When auto-loading a Python script (*note Python Auto-loading::),
GDB sets the "current objfile" to the corresponding objfile. This
function returns the current objfile. If there is no current
objfile, this function returns `None'.
-- Function: gdb.objfiles ()
Return a sequence of all the objfiles current known to GDB. *Note
Objfiles In Python::.
Each objfile is represented by an instance of the `gdb.Objfile'
class.
-- Variable: Objfile.filename
The file name of the objfile as a string.
-- Variable: Objfile.pretty_printers
The `pretty_printers' attribute is a list of functions. It is
used to look up pretty-printers. A `Value' is passed to each
function in order; if the function returns `None', then the search
continues. Otherwise, the return value should be an object which
is used to format the value. *Note Pretty Printing API::, for more
information.
-- Variable: Objfile.type_printers
The `type_printers' attribute is a list of type printer objects.
*Note Type Printing API::, for more information.
-- Variable: Objfile.frame_filters
The `frame_filters' attribute is a dictionary of frame filter
objects. *Note Frame Filter API::, for more information.
A `gdb.Objfile' object has the following methods:
-- Function: Objfile.is_valid ()
Returns `True' if the `gdb.Objfile' object is valid, `False' if
not. A `gdb.Objfile' object can become invalid if the object file
it refers to is not loaded in GDB any longer. All other
`gdb.Objfile' methods will throw an exception if it is invalid at
the time the method is called.

File: gdb.info, Node: Frames In Python, Next: Blocks In Python, Prev: Objfiles In Python, Up: Python API
23.2.2.20 Accessing inferior stack frames from Python.
......................................................
When the debugged program stops, GDB is able to analyze its call stack
(*note Stack frames: Frames.). The `gdb.Frame' class represents a
frame in the stack. A `gdb.Frame' object is only valid while its
corresponding frame exists in the inferior's stack. If you try to use
an invalid frame object, GDB will throw a `gdb.error' exception (*note
Exception Handling::).
Two `gdb.Frame' objects can be compared for equality with the `=='
operator, like:
(gdb) python print gdb.newest_frame() == gdb.selected_frame ()
True
The following frame-related functions are available in the `gdb'
module:
-- Function: gdb.selected_frame ()
Return the selected frame object. (*note Selecting a Frame:
Selection.).
-- Function: gdb.newest_frame ()
Return the newest frame object for the selected thread.
-- Function: gdb.frame_stop_reason_string (reason)
Return a string explaining the reason why GDB stopped unwinding
frames, as expressed by the given REASON code (an integer, see the
`unwind_stop_reason' method further down in this section).
A `gdb.Frame' object has the following methods:
-- Function: Frame.is_valid ()
Returns true if the `gdb.Frame' object is valid, false if not. A
frame object can become invalid if the frame it refers to doesn't
exist anymore in the inferior. All `gdb.Frame' methods will throw
an exception if it is invalid at the time the method is called.
-- Function: Frame.name ()
Returns the function name of the frame, or `None' if it can't be
obtained.
-- Function: Frame.architecture ()
Returns the `gdb.Architecture' object corresponding to the frame's
architecture. *Note Architectures In Python::.
-- Function: Frame.type ()
Returns the type of the frame. The value can be one of:
`gdb.NORMAL_FRAME'
An ordinary stack frame.
`gdb.DUMMY_FRAME'
A fake stack frame that was created by GDB when performing an
inferior function call.
`gdb.INLINE_FRAME'
A frame representing an inlined function. The function was
inlined into a `gdb.NORMAL_FRAME' that is older than this one.
`gdb.TAILCALL_FRAME'
A frame representing a tail call. *Note Tail Call Frames::.
`gdb.SIGTRAMP_FRAME'
A signal trampoline frame. This is the frame created by the
OS when it calls into a signal handler.
`gdb.ARCH_FRAME'
A fake stack frame representing a cross-architecture call.
`gdb.SENTINEL_FRAME'
This is like `gdb.NORMAL_FRAME', but it is only used for the
newest frame.
-- Function: Frame.unwind_stop_reason ()
Return an integer representing the reason why it's not possible to
find more frames toward the outermost frame. Use
`gdb.frame_stop_reason_string' to convert the value returned by
this function to a string. The value can be one of:
`gdb.FRAME_UNWIND_NO_REASON'
No particular reason (older frames should be available).
`gdb.FRAME_UNWIND_NULL_ID'
The previous frame's analyzer returns an invalid result.
This is no longer used by GDB, and is kept only for backward
compatibility.
`gdb.FRAME_UNWIND_OUTERMOST'
This frame is the outermost.
`gdb.FRAME_UNWIND_UNAVAILABLE'
Cannot unwind further, because that would require knowing the
values of registers or memory that have not been collected.
`gdb.FRAME_UNWIND_INNER_ID'
This frame ID looks like it ought to belong to a NEXT frame,
but we got it for a PREV frame. Normally, this is a sign of
unwinder failure. It could also indicate stack corruption.
`gdb.FRAME_UNWIND_SAME_ID'
This frame has the same ID as the previous one. That means
that unwinding further would almost certainly give us another
frame with exactly the same ID, so break the chain. Normally,
this is a sign of unwinder failure. It could also indicate
stack corruption.
`gdb.FRAME_UNWIND_NO_SAVED_PC'
The frame unwinder did not find any saved PC, but we needed
one to unwind further.
`gdb.FRAME_UNWIND_FIRST_ERROR'
Any stop reason greater or equal to this value indicates some
kind of error. This special value facilitates writing code
that tests for errors in unwinding in a way that will work
correctly even if the list of the other values is modified in
future GDB versions. Using it, you could write:
reason = gdb.selected_frame().unwind_stop_reason ()
reason_str = gdb.frame_stop_reason_string (reason)
if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
print "An error occured: %s" % reason_str
-- Function: Frame.pc ()
Returns the frame's resume address.
-- Function: Frame.block ()
Return the frame's code block. *Note Blocks In Python::.
-- Function: Frame.function ()
Return the symbol for the function corresponding to this frame.
*Note Symbols In Python::.
-- Function: Frame.older ()
Return the frame that called this frame.
-- Function: Frame.newer ()
Return the frame called by this frame.
-- Function: Frame.find_sal ()
Return the frame's symtab and line object. *Note Symbol Tables In
Python::.
-- Function: Frame.read_var (variable [, block])
Return the value of VARIABLE in this frame. If the optional
argument BLOCK is provided, search for the variable from that
block; otherwise start at the frame's current block (which is
determined by the frame's current program counter). VARIABLE must
be a string or a `gdb.Symbol' object. BLOCK must be a `gdb.Block'
object.
-- Function: Frame.select ()
Set this frame to be the selected frame. *Note Examining the
Stack: Stack.

File: gdb.info, Node: Blocks In Python, Next: Symbols In Python, Prev: Frames In Python, Up: Python API
23.2.2.21 Accessing blocks from Python.
.......................................
In GDB, symbols are stored in blocks. A block corresponds roughly to a
scope in the source code. Blocks are organized hierarchically, and are
represented individually in Python as a `gdb.Block'. Blocks rely on
debugging information being available.
A frame has a block. Please see *note Frames In Python::, for a more
in-depth discussion of frames.
The outermost block is known as the "global block". The global
block typically holds public global variables and functions.
The block nested just inside the global block is the "static block".
The static block typically holds file-scoped variables and functions.
GDB provides a method to get a block's superblock, but there is
currently no way to examine the sub-blocks of a block, or to iterate
over all the blocks in a symbol table (*note Symbol Tables In Python::).
Here is a short example that should help explain blocks:
/* This is in the global block. */
int global;
/* This is in the static block. */
static int file_scope;
/* 'function' is in the global block, and 'argument' is
in a block nested inside of 'function'. */
int function (int argument)
{
/* 'local' is in a block inside 'function'. It may or may
not be in the same block as 'argument'. */
int local;
{
/* 'inner' is in a block whose superblock is the one holding
'local'. */
int inner;
/* If this call is expanded by the compiler, you may see
a nested block here whose function is 'inline_function'
and whose superblock is the one holding 'inner'. */
inline_function ();
}
}
A `gdb.Block' is iterable. The iterator returns the symbols (*note
Symbols In Python::) local to the block. Python programs should not
assume that a specific block object will always contain a given symbol,
since changes in GDB features and infrastructure may cause symbols move
across blocks in a symbol table.
The following block-related functions are available in the `gdb'
module:
-- Function: gdb.block_for_pc (pc)
Return the innermost `gdb.Block' containing the given PC value.
If the block cannot be found for the PC value specified, the
function will return `None'.
A `gdb.Block' object has the following methods:
-- Function: Block.is_valid ()
Returns `True' if the `gdb.Block' object is valid, `False' if not.
A block object can become invalid if the block it refers to
doesn't exist anymore in the inferior. All other `gdb.Block'
methods will throw an exception if it is invalid at the time the
method is called. The block's validity is also checked during
iteration over symbols of the block.
A `gdb.Block' object has the following attributes:
-- Variable: Block.start
The start address of the block. This attribute is not writable.
-- Variable: Block.end
The end address of the block. This attribute is not writable.
-- Variable: Block.function
The name of the block represented as a `gdb.Symbol'. If the block
is not named, then this attribute holds `None'. This attribute is
not writable.
For ordinary function blocks, the superblock is the static block.
However, you should note that it is possible for a function block
to have a superblock that is not the static block - for instance
this happens for an inlined function.
-- Variable: Block.superblock
The block containing this block. If this parent block does not
exist, this attribute holds `None'. This attribute is not
writable.
-- Variable: Block.global_block
The global block associated with this block. This attribute is not
writable.
-- Variable: Block.static_block
The static block associated with this block. This attribute is not
writable.
-- Variable: Block.is_global
`True' if the `gdb.Block' object is a global block, `False' if
not. This attribute is not writable.
-- Variable: Block.is_static
`True' if the `gdb.Block' object is a static block, `False' if
not. This attribute is not writable.

File: gdb.info, Node: Symbols In Python, Next: Symbol Tables In Python, Prev: Blocks In Python, Up: Python API
23.2.2.22 Python representation of Symbols.
...........................................
GDB represents every variable, function and type as an entry in a
symbol table. *Note Examining the Symbol Table: Symbols. Similarly,
Python represents these symbols in GDB with the `gdb.Symbol' object.
The following symbol-related functions are available in the `gdb'
module:
-- Function: gdb.lookup_symbol (name [, block [, domain]])
This function searches for a symbol by name. The search scope can
be restricted to the parameters defined in the optional domain and
block arguments.
NAME is the name of the symbol. It must be a string. The
optional BLOCK argument restricts the search to symbols visible in
that BLOCK. The BLOCK argument must be a `gdb.Block' object. If
omitted, the block for the current frame is used. The optional
DOMAIN argument restricts the search to the domain type. The
DOMAIN argument must be a domain constant defined in the `gdb'
module and described later in this chapter.
The result is a tuple of two elements. The first element is a
`gdb.Symbol' object or `None' if the symbol is not found. If the
symbol is found, the second element is `True' if the symbol is a
field of a method's object (e.g., `this' in C++), otherwise it is
`False'. If the symbol is not found, the second element is
`False'.
-- Function: gdb.lookup_global_symbol (name [, domain])
This function searches for a global symbol by name. The search
scope can be restricted to by the domain argument.
NAME is the name of the symbol. It must be a string. The
optional DOMAIN argument restricts the search to the domain type.
The DOMAIN argument must be a domain constant defined in the `gdb'
module and described later in this chapter.
The result is a `gdb.Symbol' object or `None' if the symbol is not
found.
A `gdb.Symbol' object has the following attributes:
-- Variable: Symbol.type
The type of the symbol or `None' if no type is recorded. This
attribute is represented as a `gdb.Type' object. *Note Types In
Python::. This attribute is not writable.
-- Variable: Symbol.symtab
The symbol table in which the symbol appears. This attribute is
represented as a `gdb.Symtab' object. *Note Symbol Tables In
Python::. This attribute is not writable.
-- Variable: Symbol.line
The line number in the source code at which the symbol was defined.
This is an integer.
-- Variable: Symbol.name
The name of the symbol as a string. This attribute is not
writable.
-- Variable: Symbol.linkage_name
The name of the symbol, as used by the linker (i.e., may be
mangled). This attribute is not writable.
-- Variable: Symbol.print_name
The name of the symbol in a form suitable for output. This is
either `name' or `linkage_name', depending on whether the user
asked GDB to display demangled or mangled names.
-- Variable: Symbol.addr_class
The address class of the symbol. This classifies how to find the
value of a symbol. Each address class is a constant defined in the
`gdb' module and described later in this chapter.
-- Variable: Symbol.needs_frame
This is `True' if evaluating this symbol's value requires a frame
(*note Frames In Python::) and `False' otherwise. Typically,
local variables will require a frame, but other symbols will not.
-- Variable: Symbol.is_argument
`True' if the symbol is an argument of a function.
-- Variable: Symbol.is_constant
`True' if the symbol is a constant.
-- Variable: Symbol.is_function
`True' if the symbol is a function or a method.
-- Variable: Symbol.is_variable
`True' if the symbol is a variable.
A `gdb.Symbol' object has the following methods:
-- Function: Symbol.is_valid ()
Returns `True' if the `gdb.Symbol' object is valid, `False' if
not. A `gdb.Symbol' object can become invalid if the symbol it
refers to does not exist in GDB any longer. All other
`gdb.Symbol' methods will throw an exception if it is invalid at
the time the method is called.
-- Function: Symbol.value ([frame])
Compute the value of the symbol, as a `gdb.Value'. For functions,
this computes the address of the function, cast to the appropriate
type. If the symbol requires a frame in order to compute its
value, then FRAME must be given. If FRAME is not given, or if
FRAME is invalid, then this method will throw an exception.
The available domain categories in `gdb.Symbol' are represented as
constants in the `gdb' module:
`gdb.SYMBOL_UNDEF_DOMAIN'
This is used when a domain has not been discovered or none of the
following domains apply. This usually indicates an error either
in the symbol information or in GDB's handling of symbols.
`gdb.SYMBOL_VAR_DOMAIN'
This domain contains variables, function names, typedef names and
enum type values.
`gdb.SYMBOL_STRUCT_DOMAIN'
This domain holds struct, union and enum type names.
`gdb.SYMBOL_LABEL_DOMAIN'
This domain contains names of labels (for gotos).
`gdb.SYMBOL_VARIABLES_DOMAIN'
This domain holds a subset of the `SYMBOLS_VAR_DOMAIN'; it
contains everything minus functions and types.
`gdb.SYMBOL_FUNCTION_DOMAIN'
This domain contains all functions.
`gdb.SYMBOL_TYPES_DOMAIN'
This domain contains all types.
The available address class categories in `gdb.Symbol' are
represented as constants in the `gdb' module:
`gdb.SYMBOL_LOC_UNDEF'
If this is returned by address class, it indicates an error either
in the symbol information or in GDB's handling of symbols.
`gdb.SYMBOL_LOC_CONST'
Value is constant int.
`gdb.SYMBOL_LOC_STATIC'
Value is at a fixed address.
`gdb.SYMBOL_LOC_REGISTER'
Value is in a register.
`gdb.SYMBOL_LOC_ARG'
Value is an argument. This value is at the offset stored within
the symbol inside the frame's argument list.
`gdb.SYMBOL_LOC_REF_ARG'
Value address is stored in the frame's argument list. Just like
`LOC_ARG' except that the value's address is stored at the offset,
not the value itself.
`gdb.SYMBOL_LOC_REGPARM_ADDR'
Value is a specified register. Just like `LOC_REGISTER' except
the register holds the address of the argument instead of the
argument itself.
`gdb.SYMBOL_LOC_LOCAL'
Value is a local variable.
`gdb.SYMBOL_LOC_TYPEDEF'
Value not used. Symbols in the domain `SYMBOL_STRUCT_DOMAIN' all
have this class.
`gdb.SYMBOL_LOC_BLOCK'
Value is a block.
`gdb.SYMBOL_LOC_CONST_BYTES'
Value is a byte-sequence.
`gdb.SYMBOL_LOC_UNRESOLVED'
Value is at a fixed address, but the address of the variable has
to be determined from the minimal symbol table whenever the
variable is referenced.
`gdb.SYMBOL_LOC_OPTIMIZED_OUT'
The value does not actually exist in the program.
`gdb.SYMBOL_LOC_COMPUTED'
The value's address is a computed location.

File: gdb.info, Node: Symbol Tables In Python, Next: Line Tables In Python, Prev: Symbols In Python, Up: Python API
23.2.2.23 Symbol table representation in Python.
................................................
Access to symbol table data maintained by GDB on the inferior is
exposed to Python via two objects: `gdb.Symtab_and_line' and
`gdb.Symtab'. Symbol table and line data for a frame is returned from
the `find_sal' method in `gdb.Frame' object. *Note Frames In Python::.
For more information on GDB's symbol table management, see *note
Examining the Symbol Table: Symbols, for more information.
A `gdb.Symtab_and_line' object has the following attributes:
-- Variable: Symtab_and_line.symtab
The symbol table object (`gdb.Symtab') for this frame. This
attribute is not writable.
-- Variable: Symtab_and_line.pc
Indicates the start of the address range occupied by code for the
current source line. This attribute is not writable.
-- Variable: Symtab_and_line.last
Indicates the end of the address range occupied by code for the
current source line. This attribute is not writable.
-- Variable: Symtab_and_line.line
Indicates the current line number for this object. This attribute
is not writable.
A `gdb.Symtab_and_line' object has the following methods:
-- Function: Symtab_and_line.is_valid ()
Returns `True' if the `gdb.Symtab_and_line' object is valid,
`False' if not. A `gdb.Symtab_and_line' object can become invalid
if the Symbol table and line object it refers to does not exist in
GDB any longer. All other `gdb.Symtab_and_line' methods will
throw an exception if it is invalid at the time the method is
called.
A `gdb.Symtab' object has the following attributes:
-- Variable: Symtab.filename
The symbol table's source filename. This attribute is not
writable.
-- Variable: Symtab.objfile
The symbol table's backing object file. *Note Objfiles In
Python::. This attribute is not writable.
A `gdb.Symtab' object has the following methods:
-- Function: Symtab.is_valid ()
Returns `True' if the `gdb.Symtab' object is valid, `False' if
not. A `gdb.Symtab' object can become invalid if the symbol table
it refers to does not exist in GDB any longer. All other
`gdb.Symtab' methods will throw an exception if it is invalid at
the time the method is called.
-- Function: Symtab.fullname ()
Return the symbol table's source absolute file name.
-- Function: Symtab.global_block ()
Return the global block of the underlying symbol table. *Note
Blocks In Python::.
-- Function: Symtab.static_block ()
Return the static block of the underlying symbol table. *Note
Blocks In Python::.
-- Function: Symtab.linetable ()
Return the line table associated with the symbol table. *Note
Line Tables In Python::.

File: gdb.info, Node: Line Tables In Python, Next: Breakpoints In Python, Prev: Symbol Tables In Python, Up: Python API
23.2.2.24 Manipulating line tables using Python
...............................................
Python code can request and inspect line table information from a
symbol table that is loaded in GDB. A line table is a mapping of
source lines to their executable locations in memory. To acquire the
line table information for a particular symbol table, use the
`linetable' function (*note Symbol Tables In Python::).
A `gdb.LineTable' is iterable. The iterator returns
`LineTableEntry' objects that correspond to the source line and address
for each line table entry. `LineTableEntry' objects have the following
attributes:
-- Variable: LineTableEntry.line
The source line number for this line table entry. This number
corresponds to the actual line of source. This attribute is not
writable.
-- Variable: LineTableEntry.pc
The address that is associated with the line table entry where the
executable code for that source line resides in memory. This
attribute is not writable.
As there can be multiple addresses for a single source line, you may
receive multiple `LineTableEntry' objects with matching `line'
attributes, but with different `pc' attributes. The iterator is sorted
in ascending `pc' order. Here is a small example illustrating
iterating over a line table.
symtab = gdb.selected_frame().find_sal().symtab
linetable = symtab.linetable()
for line in linetable:
print "Line: "+str(line.line)+" Address: "+hex(line.pc)
This will have the following output:
Line: 33 Address: 0x4005c8L
Line: 37 Address: 0x4005caL
Line: 39 Address: 0x4005d2L
Line: 40 Address: 0x4005f8L
Line: 42 Address: 0x4005ffL
Line: 44 Address: 0x400608L
Line: 42 Address: 0x40060cL
Line: 45 Address: 0x400615L
In addition to being able to iterate over a `LineTable', it also has
the following direct access methods:
-- Function: LineTable.line (line)
Return a Python `Tuple' of `LineTableEntry' objects for any
entries in the line table for the given LINE. LINE refers to the
source code line. If there are no entries for that source code
LINE, the Python `None' is returned.
-- Function: LineTable.has_line (line)
Return a Python `Boolean' indicating whether there is an entry in
the line table for this source line. Return `True' if an entry is
found, or `False' if not.
-- Function: LineTable.source_lines ()
Return a Python `List' of the source line numbers in the symbol
table. Only lines with executable code locations are returned.
The contents of the `List' will just be the source line entries
represented as Python `Long' values.

File: gdb.info, Node: Breakpoints In Python, Next: Finish Breakpoints in Python, Prev: Line Tables In Python, Up: Python API
23.2.2.25 Manipulating breakpoints using Python
...............................................
Python code can manipulate breakpoints via the `gdb.Breakpoint' class.
-- Function: Breakpoint.__init__ (spec [, type [, wp_class [,internal
[,temporary]]]])
Create a new breakpoint. SPEC is a string naming the location of
the breakpoint, or an expression that defines a watchpoint. The
contents can be any location recognized by the `break' command, or
in the case of a watchpoint, by the `watch' command. The optional
TYPE denotes the breakpoint to create from the types defined later
in this chapter. This argument can be either: `gdb.BP_BREAKPOINT'
or `gdb.BP_WATCHPOINT'. TYPE defaults to `gdb.BP_BREAKPOINT'.
The optional INTERNAL argument allows the breakpoint to become
invisible to the user. The breakpoint will neither be reported
when created, nor will it be listed in the output from `info
breakpoints' (but will be listed with the `maint info breakpoints'
command). The optional TEMPORARY argument makes the breakpoint a
temporary breakpoint. Temporary breakpoints are deleted after
they have been hit. Any further access to the Python breakpoint
after it has been hit will result in a runtime error (as that
breakpoint has now been automatically deleted). The optional
WP_CLASS argument defines the class of watchpoint to create, if
TYPE is `gdb.BP_WATCHPOINT'. If a watchpoint class is not
provided, it is assumed to be a `gdb.WP_WRITE' class.
-- Function: Breakpoint.stop (self)
The `gdb.Breakpoint' class can be sub-classed and, in particular,
you may choose to implement the `stop' method. If this method is
defined in a sub-class of `gdb.Breakpoint', it will be called when
the inferior reaches any location of a breakpoint which
instantiates that sub-class. If the method returns `True', the
inferior will be stopped at the location of the breakpoint,
otherwise the inferior will continue.
If there are multiple breakpoints at the same location with a
`stop' method, each one will be called regardless of the return
status of the previous. This ensures that all `stop' methods have
a chance to execute at that location. In this scenario if one of
the methods returns `True' but the others return `False', the
inferior will still be stopped.
You should not alter the execution state of the inferior (i.e.,
step, next, etc.), alter the current frame context (i.e., change
the current active frame), or alter, add or delete any breakpoint.
As a general rule, you should not alter any data within GDB or the
inferior at this time.
Example `stop' implementation:
class MyBreakpoint (gdb.Breakpoint):
def stop (self):
inf_val = gdb.parse_and_eval("foo")
if inf_val == 3:
return True
return False
The available watchpoint types represented by constants are defined
in the `gdb' module:
`gdb.WP_READ'
Read only watchpoint.
`gdb.WP_WRITE'
Write only watchpoint.
`gdb.WP_ACCESS'
Read/Write watchpoint.
-- Function: Breakpoint.is_valid ()
Return `True' if this `Breakpoint' object is valid, `False'
otherwise. A `Breakpoint' object can become invalid if the user
deletes the breakpoint. In this case, the object still exists,
but the underlying breakpoint does not. In the cases of
watchpoint scope, the watchpoint remains valid even if execution
of the inferior leaves the scope of that watchpoint.
-- Function: Breakpoint.delete
Permanently deletes the GDB breakpoint. This also invalidates the
Python `Breakpoint' object. Any further access to this object's
attributes or methods will raise an error.
-- Variable: Breakpoint.enabled
This attribute is `True' if the breakpoint is enabled, and `False'
otherwise. This attribute is writable.
-- Variable: Breakpoint.silent
This attribute is `True' if the breakpoint is silent, and `False'
otherwise. This attribute is writable.
Note that a breakpoint can also be silent if it has commands and
the first command is `silent'. This is not reported by the
`silent' attribute.
-- Variable: Breakpoint.thread
If the breakpoint is thread-specific, this attribute holds the
thread id. If the breakpoint is not thread-specific, this
attribute is `None'. This attribute is writable.
-- Variable: Breakpoint.task
If the breakpoint is Ada task-specific, this attribute holds the
Ada task id. If the breakpoint is not task-specific (or the
underlying language is not Ada), this attribute is `None'. This
attribute is writable.
-- Variable: Breakpoint.ignore_count
This attribute holds the ignore count for the breakpoint, an
integer. This attribute is writable.
-- Variable: Breakpoint.number
This attribute holds the breakpoint's number -- the identifier
used by the user to manipulate the breakpoint. This attribute is
not writable.
-- Variable: Breakpoint.type
This attribute holds the breakpoint's type -- the identifier used
to determine the actual breakpoint type or use-case. This
attribute is not writable.
-- Variable: Breakpoint.visible
This attribute tells whether the breakpoint is visible to the user
when set, or when the `info breakpoints' command is run. This
attribute is not writable.
-- Variable: Breakpoint.temporary
This attribute indicates whether the breakpoint was created as a
temporary breakpoint. Temporary breakpoints are automatically
deleted after that breakpoint has been hit. Access to this
attribute, and all other attributes and functions other than the
`is_valid' function, will result in an error after the breakpoint
has been hit (as it has been automatically deleted). This
attribute is not writable.
The available types are represented by constants defined in the `gdb'
module:
`gdb.BP_BREAKPOINT'
Normal code breakpoint.
`gdb.BP_WATCHPOINT'
Watchpoint breakpoint.
`gdb.BP_HARDWARE_WATCHPOINT'
Hardware assisted watchpoint.
`gdb.BP_READ_WATCHPOINT'
Hardware assisted read watchpoint.
`gdb.BP_ACCESS_WATCHPOINT'
Hardware assisted access watchpoint.
-- Variable: Breakpoint.hit_count
This attribute holds the hit count for the breakpoint, an integer.
This attribute is writable, but currently it can only be set to
zero.
-- Variable: Breakpoint.location
This attribute holds the location of the breakpoint, as specified
by the user. It is a string. If the breakpoint does not have a
location (that is, it is a watchpoint) the attribute's value is
`None'. This attribute is not writable.
-- Variable: Breakpoint.expression
This attribute holds a breakpoint expression, as specified by the
user. It is a string. If the breakpoint does not have an
expression (the breakpoint is not a watchpoint) the attribute's
value is `None'. This attribute is not writable.
-- Variable: Breakpoint.condition
This attribute holds the condition of the breakpoint, as specified
by the user. It is a string. If there is no condition, this
attribute's value is `None'. This attribute is writable.
-- Variable: Breakpoint.commands
This attribute holds the commands attached to the breakpoint. If
there are commands, this attribute's value is a string holding all
the commands, separated by newlines. If there are no commands,
this attribute is `None'. This attribute is not writable.

File: gdb.info, Node: Finish Breakpoints in Python, Next: Lazy Strings In Python, Prev: Breakpoints In Python, Up: Python API
23.2.2.26 Finish Breakpoints
............................
A finish breakpoint is a temporary breakpoint set at the return address
of a frame, based on the `finish' command. `gdb.FinishBreakpoint'
extends `gdb.Breakpoint'. The underlying breakpoint will be disabled
and deleted when the execution will run out of the breakpoint scope
(i.e. `Breakpoint.stop' or `FinishBreakpoint.out_of_scope' triggered).
Finish breakpoints are thread specific and must be create with the right
thread selected.
-- Function: FinishBreakpoint.__init__ ([frame] [, internal])
Create a finish breakpoint at the return address of the `gdb.Frame'
object FRAME. If FRAME is not provided, this defaults to the
newest frame. The optional INTERNAL argument allows the
breakpoint to become invisible to the user. *Note Breakpoints In
Python::, for further details about this argument.
-- Function: FinishBreakpoint.out_of_scope (self)
In some circumstances (e.g. `longjmp', C++ exceptions, GDB
`return' command, ...), a function may not properly terminate, and
thus never hit the finish breakpoint. When GDB notices such a
situation, the `out_of_scope' callback will be triggered.
You may want to sub-class `gdb.FinishBreakpoint' and override this
method:
class MyFinishBreakpoint (gdb.FinishBreakpoint)
def stop (self):
print "normal finish"
return True
def out_of_scope ():
print "abnormal finish"
-- Variable: FinishBreakpoint.return_value
When GDB is stopped at a finish breakpoint and the frame used to
build the `gdb.FinishBreakpoint' object had debug symbols, this
attribute will contain a `gdb.Value' object corresponding to the
return value of the function. The value will be `None' if the
function return type is `void' or if the return value was not
computable. This attribute is not writable.

File: gdb.info, Node: Lazy Strings In Python, Next: Architectures In Python, Prev: Finish Breakpoints in Python, Up: Python API
23.2.2.27 Python representation of lazy strings.
................................................
A "lazy string" is a string whose contents is not retrieved or encoded
until it is needed.
A `gdb.LazyString' is represented in GDB as an `address' that points
to a region of memory, an `encoding' that will be used to encode that
region of memory, and a `length' to delimit the region of memory that
represents the string. The difference between a `gdb.LazyString' and a
string wrapped within a `gdb.Value' is that a `gdb.LazyString' will be
treated differently by GDB when printing. A `gdb.LazyString' is
retrieved and encoded during printing, while a `gdb.Value' wrapping a
string is immediately retrieved and encoded on creation.
A `gdb.LazyString' object has the following functions:
-- Function: LazyString.value ()
Convert the `gdb.LazyString' to a `gdb.Value'. This value will
point to the string in memory, but will lose all the delayed
retrieval, encoding and handling that GDB applies to a
`gdb.LazyString'.
-- Variable: LazyString.address
This attribute holds the address of the string. This attribute is
not writable.
-- Variable: LazyString.length
This attribute holds the length of the string in characters. If
the length is -1, then the string will be fetched and encoded up
to the first null of appropriate width. This attribute is not
writable.
-- Variable: LazyString.encoding
This attribute holds the encoding that will be applied to the
string when the string is printed by GDB. If the encoding is not
set, or contains an empty string, then GDB will select the most
appropriate encoding when the string is printed. This attribute
is not writable.
-- Variable: LazyString.type
This attribute holds the type that is represented by the lazy
string's type. For a lazy string this will always be a pointer
type. To resolve this to the lazy string's character type, use
the type's `target' method. *Note Types In Python::. This
attribute is not writable.

File: gdb.info, Node: Architectures In Python, Prev: Lazy Strings In Python, Up: Python API
23.2.2.28 Python representation of architectures
................................................
GDB uses architecture specific parameters and artifacts in a number of
its various computations. An architecture is represented by an
instance of the `gdb.Architecture' class.
A `gdb.Architecture' class has the following methods:
-- Function: Architecture.name ()
Return the name (string value) of the architecture.
-- Function: Architecture.disassemble (START_PC [, END_PC [, COUNT]])
Return a list of disassembled instructions starting from the memory
address START_PC. The optional arguments END_PC and COUNT
determine the number of instructions in the returned list. If
both the optional arguments END_PC and COUNT are specified, then a
list of at most COUNT disassembled instructions whose start
address falls in the closed memory address interval from START_PC
to END_PC are returned. If END_PC is not specified, but COUNT is
specified, then COUNT number of instructions starting from the
address START_PC are returned. If COUNT is not specified but
END_PC is specified, then all instructions whose start address
falls in the closed memory address interval from START_PC to
END_PC are returned. If neither END_PC nor COUNT are specified,
then a single instruction at START_PC is returned. For all of
these cases, each element of the returned list is a Python `dict'
with the following string keys:
`addr'
The value corresponding to this key is a Python long integer
capturing the memory address of the instruction.
`asm'
The value corresponding to this key is a string value which
represents the instruction with assembly language mnemonics.
The assembly language flavor used is the same as that
specified by the current CLI variable `disassembly-flavor'.
*Note Machine Code::.
`length'
The value corresponding to this key is the length (integer
value) of the instruction in bytes.

File: gdb.info, Node: Python Auto-loading, Next: Python modules, Prev: Python API, Up: Python
23.2.3 Python Auto-loading
--------------------------
When a new object file is read (for example, due to the `file' command,
or because the inferior has loaded a shared library), GDB will look for
Python support scripts in several ways: `OBJFILE-gdb.py' (*note
objfile-gdb.py file::) and `.debug_gdb_scripts' section (*note
dotdebug_gdb_scripts section::).
The auto-loading feature is useful for supplying application-specific
debugging commands and scripts.
Auto-loading can be enabled or disabled, and the list of auto-loaded
scripts can be printed.
`set auto-load python-scripts [on|off]'
Enable or disable the auto-loading of Python scripts.
`show auto-load python-scripts'
Show whether auto-loading of Python scripts is enabled or disabled.
`info auto-load python-scripts [REGEXP]'
Print the list of all Python scripts that GDB auto-loaded.
Also printed is the list of Python scripts that were mentioned in
the `.debug_gdb_scripts' section and were not found (*note
dotdebug_gdb_scripts section::). This is useful because their
names are not printed when GDB tries to load them and fails.
There may be many of them, and printing an error message for each
one is problematic.
If REGEXP is supplied only Python scripts with matching names are
printed.
Example:
(gdb) info auto-load python-scripts
Loaded Script
Yes py-section-script.py
full name: /tmp/py-section-script.py
No my-foo-pretty-printers.py
When reading an auto-loaded file, GDB sets the "current objfile".
This is available via the `gdb.current_objfile' function (*note
Objfiles In Python::). This can be useful for registering
objfile-specific pretty-printers and frame-filters.
* Menu:
* objfile-gdb.py file:: The `OBJFILE-gdb.py' file
* dotdebug_gdb_scripts section:: The `.debug_gdb_scripts' section
* Which flavor to choose?::

File: gdb.info, Node: objfile-gdb.py file, Next: dotdebug_gdb_scripts section, Up: Python Auto-loading
23.2.3.1 The `OBJFILE-gdb.py' file
..................................
When a new object file is read, GDB looks for a file named
`OBJFILE-gdb.py' (we call it SCRIPT-NAME below), where OBJFILE is the
object file's real name, formed by ensuring that the file name is
absolute, following all symlinks, and resolving `.' and `..'
components. If this file exists and is readable, GDB will evaluate it
as a Python script.
If this file does not exist, then GDB will look for SCRIPT-NAME file
in all of the directories as specified below.
Note that loading of this script file also requires accordingly
configured `auto-load safe-path' (*note Auto-loading safe path::).
For object files using `.exe' suffix GDB tries to load first the
scripts normally according to its `.exe' filename. But if no scripts
are found GDB also tries script filenames matching the object file
without its `.exe' suffix. This `.exe' stripping is case insensitive
and it is attempted on any platform. This makes the script filenames
compatible between Unix and MS-Windows hosts.
`set auto-load scripts-directory [DIRECTORIES]'
Control GDB auto-loaded scripts location. Multiple directory
entries may be delimited by the host platform path separator in use
(`:' on Unix, `;' on MS-Windows and MS-DOS).
Each entry here needs to be covered also by the security setting
`set auto-load safe-path' (*note set auto-load safe-path::).
This variable defaults to `$debugdir:$datadir/auto-load'. The
default `set auto-load safe-path' value can be also overriden by
GDB configuration option `--with-auto-load-dir'.
Any reference to `$debugdir' will get replaced by
DEBUG-FILE-DIRECTORY value (*note Separate Debug Files::) and any
reference to `$datadir' will get replaced by DATA-DIRECTORY which
is determined at GDB startup (*note Data Files::). `$debugdir' and
`$datadir' must be placed as a directory component -- either alone
or delimited by `/' or `\' directory separators, depending on the
host platform.
The list of directories uses path separator (`:' on GNU and Unix
systems, `;' on MS-Windows and MS-DOS) to separate directories,
similarly to the `PATH' environment variable.
`show auto-load scripts-directory'
Show GDB auto-loaded scripts location.
GDB does not track which files it has already auto-loaded this way.
GDB will load the associated script every time the corresponding
OBJFILE is opened. So your `-gdb.py' file should be careful to avoid
errors if it is evaluated more than once.

File: gdb.info, Node: dotdebug_gdb_scripts section, Next: Which flavor to choose?, Prev: objfile-gdb.py file, Up: Python Auto-loading
23.2.3.2 The `.debug_gdb_scripts' section
.........................................
For systems using file formats like ELF and COFF, when GDB loads a new
object file it will look for a special section named
`.debug_gdb_scripts'. If this section exists, its contents is a list
of names of scripts to load.
GDB will look for each specified script file first in the current
directory and then along the source search path (*note Specifying
Source Directories: Source Path.), except that `$cdir' is not searched,
since the compilation directory is not relevant to scripts.
Entries can be placed in section `.debug_gdb_scripts' with, for
example, this GCC macro:
/* Note: The "MS" section flags are to remove duplicates. */
#define DEFINE_GDB_SCRIPT(script_name) \
asm("\
.pushsection \".debug_gdb_scripts\", \"MS\",@progbits,1\n\
.byte 1\n\
.asciz \"" script_name "\"\n\
.popsection \n\
");
Then one can reference the macro in a header or source file like this:
DEFINE_GDB_SCRIPT ("my-app-scripts.py")
The script name may include directories if desired.
Note that loading of this script file also requires accordingly
configured `auto-load safe-path' (*note Auto-loading safe path::).
If the macro is put in a header, any application or library using
this header will get a reference to the specified script.

File: gdb.info, Node: Which flavor to choose?, Prev: dotdebug_gdb_scripts section, Up: Python Auto-loading
23.2.3.3 Which flavor to choose?
................................
Given the multiple ways of auto-loading Python scripts, it might not
always be clear which one to choose. This section provides some
guidance.
Benefits of the `-gdb.py' way:
* Can be used with file formats that don't support multiple sections.
* Ease of finding scripts for public libraries.
Scripts specified in the `.debug_gdb_scripts' section are searched
for in the source search path. For publicly installed libraries,
e.g., `libstdc++', there typically isn't a source directory in
which to find the script.
* Doesn't require source code additions.
Benefits of the `.debug_gdb_scripts' way:
* Works with static linking.
Scripts for libraries done the `-gdb.py' way require an objfile to
trigger their loading. When an application is statically linked
the only objfile available is the executable, and it is cumbersome
to attach all the scripts from all the input libraries to the
executable's `-gdb.py' script.
* Works with classes that are entirely inlined.
Some classes can be entirely inlined, and thus there may not be an
associated shared library to attach a `-gdb.py' script to.
* Scripts needn't be copied out of the source tree.
In some circumstances, apps can be built out of large collections
of internal libraries, and the build infrastructure necessary to
install the `-gdb.py' scripts in a place where GDB can find them is
cumbersome. It may be easier to specify the scripts in the
`.debug_gdb_scripts' section as relative paths, and add a path to
the top of the source tree to the source search path.

File: gdb.info, Node: Python modules, Prev: Python Auto-loading, Up: Python
23.2.4 Python modules
---------------------
GDB comes with several modules to assist writing Python code.
* Menu:
* gdb.printing:: Building and registering pretty-printers.
* gdb.types:: Utilities for working with types.
* gdb.prompt:: Utilities for prompt value substitution.

File: gdb.info, Node: gdb.printing, Next: gdb.types, Up: Python modules
23.2.4.1 gdb.printing
.....................
This module provides a collection of utilities for working with
pretty-printers.
`PrettyPrinter (NAME, SUBPRINTERS=None)'
This class specifies the API that makes `info pretty-printer',
`enable pretty-printer' and `disable pretty-printer' work.
Pretty-printers should generally inherit from this class.
`SubPrettyPrinter (NAME)'
For printers that handle multiple types, this class specifies the
corresponding API for the subprinters.
`RegexpCollectionPrettyPrinter (NAME)'
Utility class for handling multiple printers, all recognized via
regular expressions. *Note Writing a Pretty-Printer::, for an
example.
`FlagEnumerationPrinter (NAME)'
A pretty-printer which handles printing of `enum' values. Unlike
GDB's built-in `enum' printing, this printer attempts to work
properly when there is some overlap between the enumeration
constants. NAME is the name of the printer and also the name of
the `enum' type to look up.
`register_pretty_printer (OBJ, PRINTER, REPLACE=False)'
Register PRINTER with the pretty-printer list of OBJ. If REPLACE
is `True' then any existing copy of the printer is replaced.
Otherwise a `RuntimeError' exception is raised if a printer with
the same name already exists.

File: gdb.info, Node: gdb.types, Next: gdb.prompt, Prev: gdb.printing, Up: Python modules
23.2.4.2 gdb.types
..................
This module provides a collection of utilities for working with
`gdb.Type' objects.
`get_basic_type (TYPE)'
Return TYPE with const and volatile qualifiers stripped, and with
typedefs and C++ references converted to the underlying type.
C++ example:
typedef const int const_int;
const_int foo (3);
const_int& foo_ref (foo);
int main () { return 0; }
Then in gdb:
(gdb) start
(gdb) python import gdb.types
(gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
(gdb) python print gdb.types.get_basic_type(foo_ref.type)
int
`has_field (TYPE, FIELD)'
Return `True' if TYPE, assumed to be a type with fields (e.g., a
structure or union), has field FIELD.
`make_enum_dict (ENUM_TYPE)'
Return a Python `dictionary' type produced from ENUM_TYPE.
`deep_items (TYPE)'
Returns a Python iterator similar to the standard
`gdb.Type.iteritems' method, except that the iterator returned by
`deep_items' will recursively traverse anonymous struct or union
fields. For example:
struct A
{
int a;
union {
int b0;
int b1;
};
};
Then in GDB:
(gdb) python import gdb.types
(gdb) python struct_a = gdb.lookup_type("struct A")
(gdb) python print struct_a.keys ()
{['a', '']}
(gdb) python print [k for k,v in gdb.types.deep_items(struct_a)]
{['a', 'b0', 'b1']}
`get_type_recognizers ()'
Return a list of the enabled type recognizers for the current
context. This is called by GDB during the type-printing process
(*note Type Printing API::).
`apply_type_recognizers (recognizers, type_obj)'
Apply the type recognizers, RECOGNIZERS, to the type object
TYPE_OBJ. If any recognizer returns a string, return that string.
Otherwise, return `None'. This is called by GDB during the
type-printing process (*note Type Printing API::).
`register_type_printer (locus, printer)'
This is a convenience function to register a type printer.
PRINTER is the type printer to register. It must implement the
type printer protocol. LOCUS is either a `gdb.Objfile', in which
case the printer is registered with that objfile; a
`gdb.Progspace', in which case the printer is registered with that
progspace; or `None', in which case the printer is registered
globally.
`TypePrinter'
This is a base class that implements the type printer protocol.
Type printers are encouraged, but not required, to derive from
this class. It defines a constructor:
-- Method on TypePrinter: __init__ (self, name)
Initialize the type printer with the given name. The new
printer starts in the enabled state.

File: gdb.info, Node: gdb.prompt, Prev: gdb.types, Up: Python modules
23.2.4.3 gdb.prompt
...................
This module provides a method for prompt value-substitution.
`substitute_prompt (STRING)'
Return STRING with escape sequences substituted by values. Some
escape sequences take arguments. You can specify arguments inside
"{}" immediately following the escape sequence.
The escape sequences you can pass to this function are:
`\\'
Substitute a backslash.
`\e'
Substitute an ESC character.
`\f'
Substitute the selected frame; an argument names a frame
parameter.
`\n'
Substitute a newline.
`\p'
Substitute a parameter's value; the argument names the
parameter.
`\r'
Substitute a carriage return.
`\t'
Substitute the selected thread; an argument names a thread
parameter.
`\v'
Substitute the version of GDB.
`\w'
Substitute the current working directory.
`\['
Begin a sequence of non-printing characters. These sequences
are typically used with the ESC character, and are not
counted in the string length. Example:
"\[\e[0;34m\](gdb)\[\e[0m\]" will return a blue-colored
"(gdb)" prompt where the length is five.
`\]'
End a sequence of non-printing characters.
For example:
substitute_prompt (``frame: \f,
print arguments: \p{print frame-arguments}'')
will return the string:
"frame: main, print arguments: scalars"

File: gdb.info, Node: Aliases, Prev: Python, Up: Extending GDB
23.3 Creating new spellings of existing commands
================================================
It is often useful to define alternate spellings of existing commands.
For example, if a new GDB command defined in Python has a long name to
type, it is handy to have an abbreviated version of it that involves
less typing.
GDB itself uses aliases. For example `s' is an alias of the `step'
command even though it is otherwise an ambiguous abbreviation of other
commands like `set' and `show'.
Aliases are also used to provide shortened or more common versions
of multi-word commands. For example, GDB provides the `tty' alias of
the `set inferior-tty' command.
You can define a new alias with the `alias' command.
`alias [-a] [--] ALIAS = COMMAND'
ALIAS specifies the name of the new alias. Each word of ALIAS must
consist of letters, numbers, dashes and underscores.
COMMAND specifies the name of an existing command that is being
aliased.
The `-a' option specifies that the new alias is an abbreviation of
the command. Abbreviations are not shown in command lists displayed by
the `help' command.
The `--' option specifies the end of options, and is useful when
ALIAS begins with a dash.
Here is a simple example showing how to make an abbreviation of a
command so that there is less to type. Suppose you were tired of
typing `disas', the current shortest unambiguous abbreviation of the
`disassemble' command and you wanted an even shorter version named `di'.
The following will accomplish this.
(gdb) alias -a di = disas
Note that aliases are different from user-defined commands. With a
user-defined command, you also need to write documentation for it with
the `document' command. An alias automatically picks up the
documentation of the existing command.
Here is an example where we make `elms' an abbreviation of
`elements' in the `set print elements' command. This is to show that
you can make an abbreviation of any part of a command.
(gdb) alias -a set print elms = set print elements
(gdb) alias -a show print elms = show print elements
(gdb) set p elms 20
(gdb) show p elms
Limit on string chars or array elements to print is 200.
Note that if you are defining an alias of a `set' command, and you
want to have an alias for the corresponding `show' command, then you
need to define the latter separately.
Unambiguously abbreviated commands are allowed in COMMAND and ALIAS,
just as they are normally.
(gdb) alias -a set pr elms = set p ele
Finally, here is an example showing the creation of a one word alias
for a more complex command. This creates alias `spe' of the command
`set print elements'.
(gdb) alias spe = set print elements
(gdb) spe 20

File: gdb.info, Node: Interpreters, Next: TUI, Prev: Extending GDB, Up: Top
24 Command Interpreters
***********************
GDB supports multiple command interpreters, and some command
infrastructure to allow users or user interface writers to switch
between interpreters or run commands in other interpreters.
GDB currently supports two command interpreters, the console
interpreter (sometimes called the command-line interpreter or CLI) and
the machine interface interpreter (or GDB/MI). This manual describes
both of these interfaces in great detail.
By default, GDB will start with the console interpreter. However,
the user may choose to start GDB with another interpreter by specifying
the `-i' or `--interpreter' startup options. Defined interpreters
include:
`console'
The traditional console or command-line interpreter. This is the
most often used interpreter with GDB. With no interpreter
specified at runtime, GDB will use this interpreter.
`mi'
The newest GDB/MI interface (currently `mi2'). Used primarily by
programs wishing to use GDB as a backend for a debugger GUI or an
IDE. For more information, see *note The GDB/MI Interface: GDB/MI.
`mi2'
The current GDB/MI interface.
`mi1'
The GDB/MI interface included in GDB 5.1, 5.2, and 5.3.
The interpreter being used by GDB may not be dynamically switched at
runtime. Although possible, this could lead to a very precarious
situation. Consider an IDE using GDB/MI. If a user enters the command
"interpreter-set console" in a console view, GDB would switch to using
the console interpreter, rendering the IDE inoperable!
Although you may only choose a single interpreter at startup, you
may execute commands in any interpreter from the current interpreter
using the appropriate command. If you are running the console
interpreter, simply use the `interpreter-exec' command:
interpreter-exec mi "-data-list-register-names"
GDB/MI has a similar command, although it is only available in
versions of GDB which support GDB/MI version 2 (or greater).

File: gdb.info, Node: TUI, Next: Emacs, Prev: Interpreters, Up: Top
25 GDB Text User Interface
**************************
* Menu:
* TUI Overview:: TUI overview
* TUI Keys:: TUI key bindings
* TUI Single Key Mode:: TUI single key mode
* TUI Commands:: TUI-specific commands
* TUI Configuration:: TUI configuration variables
The GDB Text User Interface (TUI) is a terminal interface which uses
the `curses' library to show the source file, the assembly output, the
program registers and GDB commands in separate text windows. The TUI
mode is supported only on platforms where a suitable version of the
`curses' library is available.
The TUI mode is enabled by default when you invoke GDB as `gdb -tui'.
You can also switch in and out of TUI mode while GDB runs by using
various TUI commands and key bindings, such as `C-x C-a'. *Note TUI
Key Bindings: TUI Keys.

File: gdb.info, Node: TUI Overview, Next: TUI Keys, Up: TUI
25.1 TUI Overview
=================
In TUI mode, GDB can display several text windows:
_command_
This window is the GDB command window with the GDB prompt and the
GDB output. The GDB input is still managed using readline.
_source_
The source window shows the source file of the program. The
current line and active breakpoints are displayed in this window.
_assembly_
The assembly window shows the disassembly output of the program.
_register_
This window shows the processor registers. Registers are
highlighted when their values change.
The source and assembly windows show the current program position by
highlighting the current line and marking it with a `>' marker.
Breakpoints are indicated with two markers. The first marker indicates
the breakpoint type:
`B'
Breakpoint which was hit at least once.
`b'
Breakpoint which was never hit.
`H'
Hardware breakpoint which was hit at least once.
`h'
Hardware breakpoint which was never hit.
The second marker indicates whether the breakpoint is enabled or not:
`+'
Breakpoint is enabled.
`-'
Breakpoint is disabled.
The source, assembly and register windows are updated when the
current thread changes, when the frame changes, or when the program
counter changes.
These windows are not all visible at the same time. The command
window is always visible. The others can be arranged in several
layouts:
* source only,
* assembly only,
* source and assembly,
* source and registers, or
* assembly and registers.
A status line above the command window shows the following
information:
_target_
Indicates the current GDB target. (*note Specifying a Debugging
Target: Targets.).
_process_
Gives the current process or thread number. When no process is
being debugged, this field is set to `No process'.
_function_
Gives the current function name for the selected frame. The name
is demangled if demangling is turned on (*note Print Settings::).
When there is no symbol corresponding to the current program
counter, the string `??' is displayed.
_line_
Indicates the current line number for the selected frame. When
the current line number is not known, the string `??' is displayed.
_pc_
Indicates the current program counter address.

File: gdb.info, Node: TUI Keys, Next: TUI Single Key Mode, Prev: TUI Overview, Up: TUI
25.2 TUI Key Bindings
=====================
The TUI installs several key bindings in the readline keymaps (*note
Command Line Editing::). The following key bindings are installed for
both TUI mode and the GDB standard mode.
`C-x C-a'
`C-x a'
`C-x A'
Enter or leave the TUI mode. When leaving the TUI mode, the
curses window management stops and GDB operates using its standard
mode, writing on the terminal directly. When reentering the TUI
mode, control is given back to the curses windows. The screen is
then refreshed.
`C-x 1'
Use a TUI layout with only one window. The layout will either be
`source' or `assembly'. When the TUI mode is not active, it will
switch to the TUI mode.
Think of this key binding as the Emacs `C-x 1' binding.
`C-x 2'
Use a TUI layout with at least two windows. When the current
layout already has two windows, the next layout with two windows
is used. When a new layout is chosen, one window will always be
common to the previous layout and the new one.
Think of it as the Emacs `C-x 2' binding.
`C-x o'
Change the active window. The TUI associates several key bindings
(like scrolling and arrow keys) with the active window. This
command gives the focus to the next TUI window.
Think of it as the Emacs `C-x o' binding.
`C-x s'
Switch in and out of the TUI SingleKey mode that binds single keys
to GDB commands (*note TUI Single Key Mode::).
The following key bindings only work in the TUI mode:
<PgUp>
Scroll the active window one page up.
<PgDn>
Scroll the active window one page down.
<Up>
Scroll the active window one line up.
<Down>
Scroll the active window one line down.
<Left>
Scroll the active window one column left.
<Right>
Scroll the active window one column right.
`C-L'
Refresh the screen.
Because the arrow keys scroll the active window in the TUI mode, they
are not available for their normal use by readline unless the command
window has the focus. When another window is active, you must use
other readline key bindings such as `C-p', `C-n', `C-b' and `C-f' to
control the command window.

File: gdb.info, Node: TUI Single Key Mode, Next: TUI Commands, Prev: TUI Keys, Up: TUI
25.3 TUI Single Key Mode
========================
The TUI also provides a "SingleKey" mode, which binds several
frequently used GDB commands to single keys. Type `C-x s' to switch
into this mode, where the following key bindings are used:
`c'
continue
`d'
down
`f'
finish
`n'
next
`q'
exit the SingleKey mode.
`r'
run
`s'
step
`u'
up
`v'
info locals
`w'
where
Other keys temporarily switch to the GDB command prompt. The key
that was pressed is inserted in the editing buffer so that it is
possible to type most GDB commands without interaction with the TUI
SingleKey mode. Once the command is entered the TUI SingleKey mode is
restored. The only way to permanently leave this mode is by typing `q'
or `C-x s'.

File: gdb.info, Node: TUI Commands, Next: TUI Configuration, Prev: TUI Single Key Mode, Up: TUI
25.4 TUI-specific Commands
==========================
The TUI has specific commands to control the text windows. These
commands are always available, even when GDB is not in the TUI mode.
When GDB is in the standard mode, most of these commands will
automatically switch to the TUI mode.
Note that if GDB's `stdout' is not connected to a terminal, or GDB
has been started with the machine interface interpreter (*note The
GDB/MI Interface: GDB/MI.), most of these commands will fail with an
error, because it would not be possible or desirable to enable curses
window management.
`info win'
List and give the size of all displayed windows.
`layout next'
Display the next layout.
`layout prev'
Display the previous layout.
`layout src'
Display the source window only.
`layout asm'
Display the assembly window only.
`layout split'
Display the source and assembly window.
`layout regs'
Display the register window together with the source or assembly
window.
`focus next'
Make the next window active for scrolling.
`focus prev'
Make the previous window active for scrolling.
`focus src'
Make the source window active for scrolling.
`focus asm'
Make the assembly window active for scrolling.
`focus regs'
Make the register window active for scrolling.
`focus cmd'
Make the command window active for scrolling.
`refresh'
Refresh the screen. This is similar to typing `C-L'.
`tui reg float'
Show the floating point registers in the register window.
`tui reg general'
Show the general registers in the register window.
`tui reg next'
Show the next register group. The list of register groups as well
as their order is target specific. The predefined register groups
are the following: `general', `float', `system', `vector', `all',
`save', `restore'.
`tui reg system'
Show the system registers in the register window.
`update'
Update the source window and the current execution point.
`winheight NAME +COUNT'
`winheight NAME -COUNT'
Change the height of the window NAME by COUNT lines. Positive
counts increase the height, while negative counts decrease it.
`tabset NCHARS'
Set the width of tab stops to be NCHARS characters.

File: gdb.info, Node: TUI Configuration, Prev: TUI Commands, Up: TUI
25.5 TUI Configuration Variables
================================
Several configuration variables control the appearance of TUI windows.
`set tui border-kind KIND'
Select the border appearance for the source, assembly and register
windows. The possible values are the following:
`space'
Use a space character to draw the border.
`ascii'
Use ASCII characters `+', `-' and `|' to draw the border.
`acs'
Use the Alternate Character Set to draw the border. The
border is drawn using character line graphics if the terminal
supports them.
`set tui border-mode MODE'
`set tui active-border-mode MODE'
Select the display attributes for the borders of the inactive
windows or the active window. The MODE can be one of the
following:
`normal'
Use normal attributes to display the border.
`standout'
Use standout mode.
`reverse'
Use reverse video mode.
`half'
Use half bright mode.
`half-standout'
Use half bright and standout mode.
`bold'
Use extra bright or bold mode.
`bold-standout'
Use extra bright or bold and standout mode.

File: gdb.info, Node: Emacs, Next: GDB/MI, Prev: TUI, Up: Top
26 Using GDB under GNU Emacs
****************************
A special interface allows you to use GNU Emacs to view (and edit) the
source files for the program you are debugging with GDB.
To use this interface, use the command `M-x gdb' in Emacs. Give the
executable file you want to debug as an argument. This command starts
GDB as a subprocess of Emacs, with input and output through a newly
created Emacs buffer.
Running GDB under Emacs can be just like running GDB normally except
for two things:
* All "terminal" input and output goes through an Emacs buffer,
called the GUD buffer.
This applies both to GDB commands and their output, and to the
input and output done by the program you are debugging.
This is useful because it means that you can copy the text of
previous commands and input them again; you can even use parts of
the output in this way.
All the facilities of Emacs' Shell mode are available for
interacting with your program. In particular, you can send
signals the usual way--for example, `C-c C-c' for an interrupt,
`C-c C-z' for a stop.
* GDB displays source code through Emacs.
Each time GDB displays a stack frame, Emacs automatically finds the
source file for that frame and puts an arrow (`=>') at the left
margin of the current line. Emacs uses a separate buffer for
source display, and splits the screen to show both your GDB session
and the source.
Explicit GDB `list' or search commands still produce output as
usual, but you probably have no reason to use them from Emacs.
We call this "text command mode". Emacs 22.1, and later, also uses
a graphical mode, enabled by default, which provides further buffers
that can control the execution and describe the state of your program.
*Note GDB Graphical Interface: (Emacs)GDB Graphical Interface.
If you specify an absolute file name when prompted for the `M-x gdb'
argument, then Emacs sets your current working directory to where your
program resides. If you only specify the file name, then Emacs sets
your current working directory to the directory associated with the
previous buffer. In this case, GDB may find your program by searching
your environment's `PATH' variable, but on some operating systems it
might not find the source. So, although the GDB input and output
session proceeds normally, the auxiliary buffer does not display the
current source and line of execution.
The initial working directory of GDB is printed on the top line of
the GUD buffer and this serves as a default for the commands that
specify files for GDB to operate on. *Note Commands to Specify Files:
Files.
By default, `M-x gdb' calls the program called `gdb'. If you need
to call GDB by a different name (for example, if you keep several
configurations around, with different names) you can customize the
Emacs variable `gud-gdb-command-name' to run the one you want.
In the GUD buffer, you can use these special Emacs commands in
addition to the standard Shell mode commands:
`C-h m'
Describe the features of Emacs' GUD Mode.
`C-c C-s'
Execute to another source line, like the GDB `step' command; also
update the display window to show the current file and location.
`C-c C-n'
Execute to next source line in this function, skipping all function
calls, like the GDB `next' command. Then update the display window
to show the current file and location.
`C-c C-i'
Execute one instruction, like the GDB `stepi' command; update
display window accordingly.
`C-c C-f'
Execute until exit from the selected stack frame, like the GDB
`finish' command.
`C-c C-r'
Continue execution of your program, like the GDB `continue'
command.
`C-c <'
Go up the number of frames indicated by the numeric argument
(*note Numeric Arguments: (Emacs)Arguments.), like the GDB `up'
command.
`C-c >'
Go down the number of frames indicated by the numeric argument,
like the GDB `down' command.
In any source file, the Emacs command `C-x <SPC>' (`gud-break')
tells GDB to set a breakpoint on the source line point is on.
In text command mode, if you type `M-x speedbar', Emacs displays a
separate frame which shows a backtrace when the GUD buffer is current.
Move point to any frame in the stack and type <RET> to make it become
the current frame and display the associated source in the source
buffer. Alternatively, click `Mouse-2' to make the selected frame
become the current one. In graphical mode, the speedbar displays watch
expressions.
If you accidentally delete the source-display buffer, an easy way to
get it back is to type the command `f' in the GDB buffer, to request a
frame display; when you run under Emacs, this recreates the source
buffer if necessary to show you the context of the current frame.
The source files displayed in Emacs are in ordinary Emacs buffers
which are visiting the source files in the usual way. You can edit the
files with these buffers if you wish; but keep in mind that GDB
communicates with Emacs in terms of line numbers. If you add or delete
lines from the text, the line numbers that GDB knows cease to
correspond properly with the code.
A more detailed description of Emacs' interaction with GDB is given
in the Emacs manual (*note Debuggers: (Emacs)Debuggers.).

File: gdb.info, Node: GDB/MI, Next: Annotations, Prev: Emacs, Up: Top
27 The GDB/MI Interface
***********************
Function and Purpose
====================
GDB/MI is a line based machine oriented text interface to GDB and is
activated by specifying using the `--interpreter' command line option
(*note Mode Options::). It is specifically intended to support the
development of systems which use the debugger as just one small
component of a larger system.
This chapter is a specification of the GDB/MI interface. It is
written in the form of a reference manual.
Note that GDB/MI is still under construction, so some of the
features described below are incomplete and subject to change (*note
GDB/MI Development and Front Ends: GDB/MI Development and Front Ends.).
Notation and Terminology
========================
This chapter uses the following notation:
* `|' separates two alternatives.
* `[ SOMETHING ]' indicates that SOMETHING is optional: it may or
may not be given.
* `( GROUP )*' means that GROUP inside the parentheses may repeat
zero or more times.
* `( GROUP )+' means that GROUP inside the parentheses may repeat
one or more times.
* `"STRING"' means a literal STRING.
* Menu:
* GDB/MI General Design::
* GDB/MI Command Syntax::
* GDB/MI Compatibility with CLI::
* GDB/MI Development and Front Ends::
* GDB/MI Output Records::
* GDB/MI Simple Examples::
* GDB/MI Command Description Format::
* GDB/MI Breakpoint Commands::
* GDB/MI Catchpoint Commands::
* GDB/MI Program Context::
* GDB/MI Thread Commands::
* GDB/MI Ada Tasking Commands::
* GDB/MI Program Execution::
* GDB/MI Stack Manipulation::
* GDB/MI Variable Objects::
* GDB/MI Data Manipulation::
* GDB/MI Tracepoint Commands::
* GDB/MI Symbol Query::
* GDB/MI File Commands::
* GDB/MI Target Manipulation::
* GDB/MI File Transfer Commands::
* GDB/MI Ada Exceptions Commands::
* GDB/MI Miscellaneous Commands::

File: gdb.info, Node: GDB/MI General Design, Next: GDB/MI Command Syntax, Up: GDB/MI
27.1 GDB/MI General Design
==========================
Interaction of a GDB/MI frontend with GDB involves three
parts--commands sent to GDB, responses to those commands and
notifications. Each command results in exactly one response,
indicating either successful completion of the command, or an error.
For the commands that do not resume the target, the response contains
the requested information. For the commands that resume the target, the
response only indicates whether the target was successfully resumed.
Notifications is the mechanism for reporting changes in the state of the
target, or in GDB state, that cannot conveniently be associated with a
command and reported as part of that command response.
The important examples of notifications are:
* Exec notifications. These are used to report changes in target
state--when a target is resumed, or stopped. It would not be
feasible to include this information in response of resuming
commands, because one resume commands can result in multiple
events in different threads. Also, quite some time may pass
before any event happens in the target, while a frontend needs to
know whether the resuming command itself was successfully executed.
* Console output, and status notifications. Console output
notifications are used to report output of CLI commands, as well as
diagnostics for other commands. Status notifications are used to
report the progress of a long-running operation. Naturally,
including this information in command response would mean no
output is produced until the command is finished, which is
undesirable.
* General notifications. Commands may have various side effects on
the GDB or target state beyond their official purpose. For
example, a command may change the selected thread. Although such
changes can be included in command response, using notification
allows for more orthogonal frontend design.
There's no guarantee that whenever an MI command reports an error,
GDB or the target are in any specific state, and especially, the state
is not reverted to the state before the MI command was processed.
Therefore, whenever an MI command results in an error, we recommend
that the frontend refreshes all the information shown in the user
interface.
* Menu:
* Context management::
* Asynchronous and non-stop modes::
* Thread groups::

File: gdb.info, Node: Context management, Next: Asynchronous and non-stop modes, Up: GDB/MI General Design
27.1.1 Context management
-------------------------
27.1.1.1 Threads and Frames
...........................
In most cases when GDB accesses the target, this access is done in
context of a specific thread and frame (*note Frames::). Often, even
when accessing global data, the target requires that a thread be
specified. The CLI interface maintains the selected thread and frame,
and supplies them to target on each command. This is convenient,
because a command line user would not want to specify that information
explicitly on each command, and because user interacts with GDB via a
single terminal, so no confusion is possible as to what thread and
frame are the current ones.
In the case of MI, the concept of selected thread and frame is less
useful. First, a frontend can easily remember this information itself.
Second, a graphical frontend can have more than one window, each one
used for debugging a different thread, and the frontend might want to
access additional threads for internal purposes. This increases the
risk that by relying on implicitly selected thread, the frontend may be
operating on a wrong one. Therefore, each MI command should explicitly
specify which thread and frame to operate on. To make it possible,
each MI command accepts the `--thread' and `--frame' options, the value
to each is GDB identifier for thread and frame to operate on.
Usually, each top-level window in a frontend allows the user to
select a thread and a frame, and remembers the user selection for
further operations. However, in some cases GDB may suggest that the
current thread be changed. For example, when stopping on a breakpoint
it is reasonable to switch to the thread where breakpoint is hit. For
another example, if the user issues the CLI `thread' command via the
frontend, it is desirable to change the frontend's selected thread to
the one specified by user. GDB communicates the suggestion to change
current thread using the `=thread-selected' notification. No such
notification is available for the selected frame at the moment.
Note that historically, MI shares the selected thread with CLI, so
frontends used the `-thread-select' to execute commands in the right
context. However, getting this to work right is cumbersome. The
simplest way is for frontend to emit `-thread-select' command before
every command. This doubles the number of commands that need to be
sent. The alternative approach is to suppress `-thread-select' if the
selected thread in GDB is supposed to be identical to the thread the
frontend wants to operate on. However, getting this optimization right
can be tricky. In particular, if the frontend sends several commands
to GDB, and one of the commands changes the selected thread, then the
behaviour of subsequent commands will change. So, a frontend should
either wait for response from such problematic commands, or explicitly
add `-thread-select' for all subsequent commands. No frontend is known
to do this exactly right, so it is suggested to just always pass the
`--thread' and `--frame' options.
27.1.1.2 Language
.................
The execution of several commands depends on which language is selected.
By default, the current language (*note show language::) is used. But
for commands known to be language-sensitive, it is recommended to use
the `--language' option. This option takes one argument, which is the
name of the language to use while executing the command. For instance:
-data-evaluate-expression --language c "sizeof (void*)"
^done,value="4"
(gdb)
The valid language names are the same names accepted by the `set
language' command (*note Manually::), excluding `auto', `local' or
`unknown'.

File: gdb.info, Node: Asynchronous and non-stop modes, Next: Thread groups, Prev: Context management, Up: GDB/MI General Design
27.1.2 Asynchronous command execution and non-stop mode
-------------------------------------------------------
On some targets, GDB is capable of processing MI commands even while
the target is running. This is called "asynchronous command execution"
(*note Background Execution::). The frontend may specify a preferrence
for asynchronous execution using the `-gdb-set target-async 1' command,
which should be emitted before either running the executable or
attaching to the target. After the frontend has started the executable
or attached to the target, it can find if asynchronous execution is
enabled using the `-list-target-features' command.
Even if GDB can accept a command while target is running, many
commands that access the target do not work when the target is running.
Therefore, asynchronous command execution is most useful when combined
with non-stop mode (*note Non-Stop Mode::). Then, it is possible to
examine the state of one thread, while other threads are running.
When a given thread is running, MI commands that try to access the
target in the context of that thread may not work, or may work only on
some targets. In particular, commands that try to operate on thread's
stack will not work, on any target. Commands that read memory, or
modify breakpoints, may work or not work, depending on the target. Note
that even commands that operate on global state, such as `print',
`set', and breakpoint commands, still access the target in the context
of a specific thread, so frontend should try to find a stopped thread
and perform the operation on that thread (using the `--thread' option).
Which commands will work in the context of a running thread is
highly target dependent. However, the two commands `-exec-interrupt',
to stop a thread, and `-thread-info', to find the state of a thread,
will always work.

File: gdb.info, Node: Thread groups, Prev: Asynchronous and non-stop modes, Up: GDB/MI General Design
27.1.3 Thread groups
--------------------
GDB may be used to debug several processes at the same time. On some
platfroms, GDB may support debugging of several hardware systems, each
one having several cores with several different processes running on
each core. This section describes the MI mechanism to support such
debugging scenarios.
The key observation is that regardless of the structure of the
target, MI can have a global list of threads, because most commands that
accept the `--thread' option do not need to know what process that
thread belongs to. Therefore, it is not necessary to introduce neither
additional `--process' option, nor an notion of the current process in
the MI interface. The only strictly new feature that is required is
the ability to find how the threads are grouped into processes.
To allow the user to discover such grouping, and to support arbitrary
hierarchy of machines/cores/processes, MI introduces the concept of a
"thread group". Thread group is a collection of threads and other
thread groups. A thread group always has a string identifier, a type,
and may have additional attributes specific to the type. A new
command, `-list-thread-groups', returns the list of top-level thread
groups, which correspond to processes that GDB is debugging at the
moment. By passing an identifier of a thread group to the
`-list-thread-groups' command, it is possible to obtain the members of
specific thread group.
To allow the user to easily discover processes, and other objects, he
wishes to debug, a concept of "available thread group" is introduced.
Available thread group is an thread group that GDB is not debugging,
but that can be attached to, using the `-target-attach' command. The
list of available top-level thread groups can be obtained using
`-list-thread-groups --available'. In general, the content of a thread
group may be only retrieved only after attaching to that thread group.
Thread groups are related to inferiors (*note Inferiors and
Programs::). Each inferior corresponds to a thread group of a special
type `process', and some additional operations are permitted on such
thread groups.

File: gdb.info, Node: GDB/MI Command Syntax, Next: GDB/MI Compatibility with CLI, Prev: GDB/MI General Design, Up: GDB/MI
27.2 GDB/MI Command Syntax
==========================
* Menu:
* GDB/MI Input Syntax::
* GDB/MI Output Syntax::

File: gdb.info, Node: GDB/MI Input Syntax, Next: GDB/MI Output Syntax, Up: GDB/MI Command Syntax
27.2.1 GDB/MI Input Syntax
--------------------------
`COMMAND ==>'
`CLI-COMMAND | MI-COMMAND'
`CLI-COMMAND ==>'
`[ TOKEN ] CLI-COMMAND NL', where CLI-COMMAND is any existing GDB
CLI command.
`MI-COMMAND ==>'
`[ TOKEN ] "-" OPERATION ( " " OPTION )* `[' " --" `]' ( " "
PARAMETER )* NL'
`TOKEN ==>'
"any sequence of digits"
`OPTION ==>'
`"-" PARAMETER [ " " PARAMETER ]'
`PARAMETER ==>'
`NON-BLANK-SEQUENCE | C-STRING'
`OPERATION ==>'
_any of the operations described in this chapter_
`NON-BLANK-SEQUENCE ==>'
_anything, provided it doesn't contain special characters such as
"-", NL, """ and of course " "_
`C-STRING ==>'
`""" SEVEN-BIT-ISO-C-STRING-CONTENT """'
`NL ==>'
`CR | CR-LF'
Notes:
* The CLI commands are still handled by the MI interpreter; their
output is described below.
* The `TOKEN', when present, is passed back when the command
finishes.
* Some MI commands accept optional arguments as part of the parameter
list. Each option is identified by a leading `-' (dash) and may be
followed by an optional argument parameter. Options occur first
in the parameter list and can be delimited from normal parameters
using `--' (this is useful when some parameters begin with a dash).
Pragmatics:
* We want easy access to the existing CLI syntax (for debugging).
* We want it to be easy to spot a MI operation.

File: gdb.info, Node: GDB/MI Output Syntax, Prev: GDB/MI Input Syntax, Up: GDB/MI Command Syntax
27.2.2 GDB/MI Output Syntax
---------------------------
The output from GDB/MI consists of zero or more out-of-band records
followed, optionally, by a single result record. This result record is
for the most recent command. The sequence of output records is
terminated by `(gdb)'.
If an input command was prefixed with a `TOKEN' then the
corresponding output for that command will also be prefixed by that same
TOKEN.
`OUTPUT ==>'
`( OUT-OF-BAND-RECORD )* [ RESULT-RECORD ] "(gdb)" NL'
`RESULT-RECORD ==>'
` [ TOKEN ] "^" RESULT-CLASS ( "," RESULT )* NL'
`OUT-OF-BAND-RECORD ==>'
`ASYNC-RECORD | STREAM-RECORD'
`ASYNC-RECORD ==>'
`EXEC-ASYNC-OUTPUT | STATUS-ASYNC-OUTPUT | NOTIFY-ASYNC-OUTPUT'
`EXEC-ASYNC-OUTPUT ==>'
`[ TOKEN ] "*" ASYNC-OUTPUT'
`STATUS-ASYNC-OUTPUT ==>'
`[ TOKEN ] "+" ASYNC-OUTPUT'
`NOTIFY-ASYNC-OUTPUT ==>'
`[ TOKEN ] "=" ASYNC-OUTPUT'
`ASYNC-OUTPUT ==>'
`ASYNC-CLASS ( "," RESULT )* NL'
`RESULT-CLASS ==>'
`"done" | "running" | "connected" | "error" | "exit"'
`ASYNC-CLASS ==>'
`"stopped" | OTHERS' (where OTHERS will be added depending on the
needs--this is still in development).
`RESULT ==>'
` VARIABLE "=" VALUE'
`VARIABLE ==>'
` STRING '
`VALUE ==>'
` CONST | TUPLE | LIST '
`CONST ==>'
`C-STRING'
`TUPLE ==>'
` "{}" | "{" RESULT ( "," RESULT )* "}" '
`LIST ==>'
` "[]" | "[" VALUE ( "," VALUE )* "]" | "[" RESULT ( "," RESULT )*
"]" '
`STREAM-RECORD ==>'
`CONSOLE-STREAM-OUTPUT | TARGET-STREAM-OUTPUT | LOG-STREAM-OUTPUT'
`CONSOLE-STREAM-OUTPUT ==>'
`"~" C-STRING'
`TARGET-STREAM-OUTPUT ==>'
`"@" C-STRING'
`LOG-STREAM-OUTPUT ==>'
`"&" C-STRING'
`NL ==>'
`CR | CR-LF'
`TOKEN ==>'
_any sequence of digits_.
Notes:
* All output sequences end in a single line containing a period.
* The `TOKEN' is from the corresponding request. Note that for all
async output, while the token is allowed by the grammar and may be
output by future versions of GDB for select async output messages,
it is generally omitted. Frontends should treat all async output
as reporting general changes in the state of the target and there
should be no need to associate async output to any prior command.
* STATUS-ASYNC-OUTPUT contains on-going status information about the
progress of a slow operation. It can be discarded. All status
output is prefixed by `+'.
* EXEC-ASYNC-OUTPUT contains asynchronous state change on the target
(stopped, started, disappeared). All async output is prefixed by
`*'.
* NOTIFY-ASYNC-OUTPUT contains supplementary information that the
client should handle (e.g., a new breakpoint information). All
notify output is prefixed by `='.
* CONSOLE-STREAM-OUTPUT is output that should be displayed as is in
the console. It is the textual response to a CLI command. All
the console output is prefixed by `~'.
* TARGET-STREAM-OUTPUT is the output produced by the target program.
All the target output is prefixed by `@'.
* LOG-STREAM-OUTPUT is output text coming from GDB's internals, for
instance messages that should be displayed as part of an error
log. All the log output is prefixed by `&'.
* New GDB/MI commands should only output LISTS containing VALUES.
*Note GDB/MI Stream Records: GDB/MI Stream Records, for more details
about the various output records.

File: gdb.info, Node: GDB/MI Compatibility with CLI, Next: GDB/MI Development and Front Ends, Prev: GDB/MI Command Syntax, Up: GDB/MI
27.3 GDB/MI Compatibility with CLI
==================================
For the developers convenience CLI commands can be entered directly,
but there may be some unexpected behaviour. For example, commands that
query the user will behave as if the user replied yes, breakpoint
command lists are not executed and some CLI commands, such as `if',
`when' and `define', prompt for further input with `>', which is not
valid MI output.
This feature may be removed at some stage in the future and it is
recommended that front ends use the `-interpreter-exec' command (*note
-interpreter-exec::).

File: gdb.info, Node: GDB/MI Development and Front Ends, Next: GDB/MI Output Records, Prev: GDB/MI Compatibility with CLI, Up: GDB/MI
27.4 GDB/MI Development and Front Ends
======================================
The application which takes the MI output and presents the state of the
program being debugged to the user is called a "front end".
Although GDB/MI is still incomplete, it is currently being used by a
variety of front ends to GDB. This makes it difficult to introduce new
functionality without breaking existing usage. This section tries to
minimize the problems by describing how the protocol might change.
Some changes in MI need not break a carefully designed front end, and
for these the MI version will remain unchanged. The following is a
list of changes that may occur within one level, so front ends should
parse MI output in a way that can handle them:
* New MI commands may be added.
* New fields may be added to the output of any MI command.
* The range of values for fields with specified values, e.g.,
`in_scope' (*note -var-update::) may be extended.
If the changes are likely to break front ends, the MI version level
will be increased by one. This will allow the front end to parse the
output according to the MI version. Apart from mi0, new versions of
GDB will not support old versions of MI and it will be the
responsibility of the front end to work with the new one.
The best way to avoid unexpected changes in MI that might break your
front end is to make your project known to GDB developers and follow
development on <gdb@sourceware.org> and <gdb-patches@sourceware.org>.

File: gdb.info, Node: GDB/MI Output Records, Next: GDB/MI Simple Examples, Prev: GDB/MI Development and Front Ends, Up: GDB/MI
27.5 GDB/MI Output Records
==========================
* Menu:
* GDB/MI Result Records::
* GDB/MI Stream Records::
* GDB/MI Async Records::
* GDB/MI Breakpoint Information::
* GDB/MI Frame Information::
* GDB/MI Thread Information::
* GDB/MI Ada Exception Information::

File: gdb.info, Node: GDB/MI Result Records, Next: GDB/MI Stream Records, Up: GDB/MI Output Records
27.5.1 GDB/MI Result Records
----------------------------
In addition to a number of out-of-band notifications, the response to a
GDB/MI command includes one of the following result indications:
`"^done" [ "," RESULTS ]'
The synchronous operation was successful, `RESULTS' are the return
values.
`"^running"'
This result record is equivalent to `^done'. Historically, it was
output instead of `^done' if the command has resumed the target.
This behaviour is maintained for backward compatibility, but all
frontends should treat `^done' and `^running' identically and rely
on the `*running' output record to determine which threads are
resumed.
`"^connected"'
GDB has connected to a remote target.
`"^error" "," "msg=" C-STRING [ "," "code=" C-STRING ]'
The operation failed. The `msg=C-STRING' variable contains the
corresponding error message.
If present, the `code=C-STRING' variable provides an error code on
which consumers can rely on to detect the corresponding error
condition. At present, only one error code is defined:
`"undefined-command"'
Indicates that the command causing the error does not exist.
`"^exit"'
GDB has terminated.

File: gdb.info, Node: GDB/MI Stream Records, Next: GDB/MI Async Records, Prev: GDB/MI Result Records, Up: GDB/MI Output Records
27.5.2 GDB/MI Stream Records
----------------------------
GDB internally maintains a number of output streams: the console, the
target, and the log. The output intended for each of these streams is
funneled through the GDB/MI interface using "stream records".
Each stream record begins with a unique "prefix character" which
identifies its stream (*note GDB/MI Output Syntax: GDB/MI Output
Syntax.). In addition to the prefix, each stream record contains a
`STRING-OUTPUT'. This is either raw text (with an implicit new line)
or a quoted C string (which does not contain an implicit newline).
`"~" STRING-OUTPUT'
The console output stream contains text that should be displayed
in the CLI console window. It contains the textual responses to
CLI commands.
`"@" STRING-OUTPUT'
The target output stream contains any textual output from the
running target. This is only present when GDB's event loop is
truly asynchronous, which is currently only the case for remote
targets.
`"&" STRING-OUTPUT'
The log stream contains debugging messages being produced by GDB's
internals.

File: gdb.info, Node: GDB/MI Async Records, Next: GDB/MI Breakpoint Information, Prev: GDB/MI Stream Records, Up: GDB/MI Output Records
27.5.3 GDB/MI Async Records
---------------------------
"Async" records are used to notify the GDB/MI client of additional
changes that have occurred. Those changes can either be a consequence
of GDB/MI commands (e.g., a breakpoint modified) or a result of target
activity (e.g., target stopped).
The following is the list of possible async records:
`*running,thread-id="THREAD"'
The target is now running. The THREAD field tells which specific
thread is now running, and can be `all' if all threads are
running. The frontend should assume that no interaction with a
running thread is possible after this notification is produced.
The frontend should not assume that this notification is output
only once for any command. GDB may emit this notification several
times, either for different threads, because it cannot resume all
threads together, or even for a single thread, if the thread must
be stepped though some code before letting it run freely.
`*stopped,reason="REASON",thread-id="ID",stopped-threads="STOPPED",core="CORE"'
The target has stopped. The REASON field can have one of the
following values:
`breakpoint-hit'
A breakpoint was reached.
`watchpoint-trigger'
A watchpoint was triggered.
`read-watchpoint-trigger'
A read watchpoint was triggered.
`access-watchpoint-trigger'
An access watchpoint was triggered.
`function-finished'
An -exec-finish or similar CLI command was accomplished.
`location-reached'
An -exec-until or similar CLI command was accomplished.
`watchpoint-scope'
A watchpoint has gone out of scope.
`end-stepping-range'
An -exec-next, -exec-next-instruction, -exec-step,
-exec-step-instruction or similar CLI command was
accomplished.
`exited-signalled'
The inferior exited because of a signal.
`exited'
The inferior exited.
`exited-normally'
The inferior exited normally.
`signal-received'
A signal was received by the inferior.
`solib-event'
The inferior has stopped due to a library being loaded or
unloaded. This can happen when `stop-on-solib-events' (*note
Files::) is set or when a `catch load' or `catch unload'
catchpoint is in use (*note Set Catchpoints::).
`fork'
The inferior has forked. This is reported when `catch fork'
(*note Set Catchpoints::) has been used.
`vfork'
The inferior has vforked. This is reported in when `catch
vfork' (*note Set Catchpoints::) has been used.
`syscall-entry'
The inferior entered a system call. This is reported when
`catch syscall' (*note Set Catchpoints::) has been used.
`syscall-entry'
The inferior returned from a system call. This is reported
when `catch syscall' (*note Set Catchpoints::) has been used.
`exec'
The inferior called `exec'. This is reported when `catch
exec' (*note Set Catchpoints::) has been used.
The ID field identifies the thread that directly caused the stop -
for example by hitting a breakpoint. Depending on whether all-stop
mode is in effect (*note All-Stop Mode::), GDB may either stop all
threads, or only the thread that directly triggered the stop. If
all threads are stopped, the STOPPED field will have the value of
`"all"'. Otherwise, the value of the STOPPED field will be a list
of thread identifiers. Presently, this list will always include a
single thread, but frontend should be prepared to see several
threads in the list. The CORE field reports the processor core on
which the stop event has happened. This field may be absent if
such information is not available.
`=thread-group-added,id="ID"'
`=thread-group-removed,id="ID"'
A thread group was either added or removed. The ID field contains
the GDB identifier of the thread group. When a thread group is
added, it generally might not be associated with a running
process. When a thread group is removed, its id becomes invalid
and cannot be used in any way.
`=thread-group-started,id="ID",pid="PID"'
A thread group became associated with a running program, either
because the program was just started or the thread group was
attached to a program. The ID field contains the GDB identifier
of the thread group. The PID field contains process identifier,
specific to the operating system.
`=thread-group-exited,id="ID"[,exit-code="CODE"]'
A thread group is no longer associated with a running program,
either because the program has exited, or because it was detached
from. The ID field contains the GDB identifier of the thread
group. CODE is the exit code of the inferior; it exists only when
the inferior exited with some code.
`=thread-created,id="ID",group-id="GID"'
`=thread-exited,id="ID",group-id="GID"'
A thread either was created, or has exited. The ID field contains
the GDB identifier of the thread. The GID field identifies the
thread group this thread belongs to.
`=thread-selected,id="ID"'
Informs that the selected thread was changed as result of the last
command. This notification is not emitted as result of
`-thread-select' command but is emitted whenever an MI command
that is not documented to change the selected thread actually
changes it. In particular, invoking, directly or indirectly (via
user-defined command), the CLI `thread' command, will generate
this notification.
We suggest that in response to this notification, front ends
highlight the selected thread and cause subsequent commands to
apply to that thread.
`=library-loaded,...'
Reports that a new library file was loaded by the program. This
notification has 4 fields--ID, TARGET-NAME, HOST-NAME, and
SYMBOLS-LOADED. The ID field is an opaque identifier of the
library. For remote debugging case, TARGET-NAME and HOST-NAME
fields give the name of the library file on the target, and on the
host respectively. For native debugging, both those fields have
the same value. The SYMBOLS-LOADED field is emitted only for
backward compatibility and should not be relied on to convey any
useful information. The THREAD-GROUP field, if present, specifies
the id of the thread group in whose context the library was
loaded. If the field is absent, it means the library was loaded
in the context of all present thread groups.
`=library-unloaded,...'
Reports that a library was unloaded by the program. This
notification has 3 fields--ID, TARGET-NAME and HOST-NAME with the
same meaning as for the `=library-loaded' notification. The
THREAD-GROUP field, if present, specifies the id of the thread
group in whose context the library was unloaded. If the field is
absent, it means the library was unloaded in the context of all
present thread groups.
`=traceframe-changed,num=TFNUM,tracepoint=TPNUM'
`=traceframe-changed,end'
Reports that the trace frame was changed and its new number is
TFNUM. The number of the tracepoint associated with this trace
frame is TPNUM.
`=tsv-created,name=NAME,initial=INITIAL'
Reports that the new trace state variable NAME is created with
initial value INITIAL.
`=tsv-deleted,name=NAME'
`=tsv-deleted'
Reports that the trace state variable NAME is deleted or all trace
state variables are deleted.
`=tsv-modified,name=NAME,initial=INITIAL[,current=CURRENT]'
Reports that the trace state variable NAME is modified with the
initial value INITIAL. The current value CURRENT of trace state
variable is optional and is reported if the current value of trace
state variable is known.
`=breakpoint-created,bkpt={...}'
`=breakpoint-modified,bkpt={...}'
`=breakpoint-deleted,id=NUMBER'
Reports that a breakpoint was created, modified, or deleted,
respectively. Only user-visible breakpoints are reported to the MI
user.
The BKPT argument is of the same form as returned by the various
breakpoint commands; *Note GDB/MI Breakpoint Commands::. The
NUMBER is the ordinal number of the breakpoint.
Note that if a breakpoint is emitted in the result record of a
command, then it will not also be emitted in an async record.
`=record-started,thread-group="ID"'
`=record-stopped,thread-group="ID"'
Execution log recording was either started or stopped on an
inferior. The ID is the GDB identifier of the thread group
corresponding to the affected inferior.
`=cmd-param-changed,param=PARAM,value=VALUE'
Reports that a parameter of the command `set PARAM' is changed to
VALUE. In the multi-word `set' command, the PARAM is the whole
parameter list to `set' command. For example, In command `set
check type on', PARAM is `check type' and VALUE is `on'.
`=memory-changed,thread-group=ID,addr=ADDR,len=LEN[,type="code"]'
Reports that bytes from ADDR to DATA + LEN were written in an
inferior. The ID is the identifier of the thread group
corresponding to the affected inferior. The optional
`type="code"' part is reported if the memory written to holds
executable code.

File: gdb.info, Node: GDB/MI Breakpoint Information, Next: GDB/MI Frame Information, Prev: GDB/MI Async Records, Up: GDB/MI Output Records
27.5.4 GDB/MI Breakpoint Information
------------------------------------
When GDB reports information about a breakpoint, a tracepoint, a
watchpoint, or a catchpoint, it uses a tuple with the following fields:
`number'
The breakpoint number. For a breakpoint that represents one
location of a multi-location breakpoint, this will be a dotted
pair, like `1.2'.
`type'
The type of the breakpoint. For ordinary breakpoints this will be
`breakpoint', but many values are possible.
`catch-type'
If the type of the breakpoint is `catchpoint', then this indicates
the exact type of catchpoint.
`disp'
This is the breakpoint disposition--either `del', meaning that the
breakpoint will be deleted at the next stop, or `keep', meaning
that the breakpoint will not be deleted.
`enabled'
This indicates whether the breakpoint is enabled, in which case the
value is `y', or disabled, in which case the value is `n'. Note
that this is not the same as the field `enable'.
`addr'
The address of the breakpoint. This may be a hexidecimal number,
giving the address; or the string `<PENDING>', for a pending
breakpoint; or the string `<MULTIPLE>', for a breakpoint with
multiple locations. This field will not be present if no address
can be determined. For example, a watchpoint does not have an
address.
`func'
If known, the function in which the breakpoint appears. If not
known, this field is not present.
`filename'
The name of the source file which contains this function, if known.
If not known, this field is not present.
`fullname'
The full file name of the source file which contains this
function, if known. If not known, this field is not present.
`line'
The line number at which this breakpoint appears, if known. If
not known, this field is not present.
`at'
If the source file is not known, this field may be provided. If
provided, this holds the address of the breakpoint, possibly
followed by a symbol name.
`pending'
If this breakpoint is pending, this field is present and holds the
text used to set the breakpoint, as entered by the user.
`evaluated-by'
Where this breakpoint's condition is evaluated, either `host' or
`target'.
`thread'
If this is a thread-specific breakpoint, then this identifies the
thread in which the breakpoint can trigger.
`task'
If this breakpoint is restricted to a particular Ada task, then
this field will hold the task identifier.
`cond'
If the breakpoint is conditional, this is the condition expression.
`ignore'
The ignore count of the breakpoint.
`enable'
The enable count of the breakpoint.
`traceframe-usage'
FIXME.
`static-tracepoint-marker-string-id'
For a static tracepoint, the name of the static tracepoint marker.
`mask'
For a masked watchpoint, this is the mask.
`pass'
A tracepoint's pass count.
`original-location'
The location of the breakpoint as originally specified by the user.
This field is optional.
`times'
The number of times the breakpoint has been hit.
`installed'
This field is only given for tracepoints. This is either `y',
meaning that the tracepoint is installed, or `n', meaning that it
is not.
`what'
Some extra data, the exact contents of which are type-dependent.
For example, here is what the output of `-break-insert' (*note
GDB/MI Breakpoint Commands::) might be:
-> -break-insert main
<- ^done,bkpt={number="1",type="breakpoint",disp="keep",
enabled="y",addr="0x08048564",func="main",file="myprog.c",
fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
times="0"}
<- (gdb)

File: gdb.info, Node: GDB/MI Frame Information, Next: GDB/MI Thread Information, Prev: GDB/MI Breakpoint Information, Up: GDB/MI Output Records
27.5.5 GDB/MI Frame Information
-------------------------------
Response from many MI commands includes an information about stack
frame. This information is a tuple that may have the following fields:
`level'
The level of the stack frame. The innermost frame has the level of
zero. This field is always present.
`func'
The name of the function corresponding to the frame. This field
may be absent if GDB is unable to determine the function name.
`addr'
The code address for the frame. This field is always present.
`file'
The name of the source files that correspond to the frame's code
address. This field may be absent.
`line'
The source line corresponding to the frames' code address. This
field may be absent.
`from'
The name of the binary file (either executable or shared library)
the corresponds to the frame's code address. This field may be
absent.

File: gdb.info, Node: GDB/MI Thread Information, Next: GDB/MI Ada Exception Information, Prev: GDB/MI Frame Information, Up: GDB/MI Output Records
27.5.6 GDB/MI Thread Information
--------------------------------
Whenever GDB has to report an information about a thread, it uses a
tuple with the following fields:
`id'
The numeric id assigned to the thread by GDB. This field is
always present.
`target-id'
Target-specific string identifying the thread. This field is
always present.
`details'
Additional information about the thread provided by the target.
It is supposed to be human-readable and not interpreted by the
frontend. This field is optional.
`state'
Either `stopped' or `running', depending on whether the thread is
presently running. This field is always present.
`core'
The value of this field is an integer number of the processor core
the thread was last seen on. This field is optional.

File: gdb.info, Node: GDB/MI Ada Exception Information, Prev: GDB/MI Thread Information, Up: GDB/MI Output Records
27.5.7 GDB/MI Ada Exception Information
---------------------------------------
Whenever a `*stopped' record is emitted because the program stopped
after hitting an exception catchpoint (*note Set Catchpoints::), GDB
provides the name of the exception that was raised via the
`exception-name' field.

File: gdb.info, Node: GDB/MI Simple Examples, Next: GDB/MI Command Description Format, Prev: GDB/MI Output Records, Up: GDB/MI
27.6 Simple Examples of GDB/MI Interaction
==========================================
This subsection presents several simple examples of interaction using
the GDB/MI interface. In these examples, `->' means that the following
line is passed to GDB/MI as input, while `<-' means the output received
from GDB/MI.
Note the line breaks shown in the examples are here only for
readability, they don't appear in the real output.
Setting a Breakpoint
--------------------
Setting a breakpoint generates synchronous output which contains
detailed information of the breakpoint.
-> -break-insert main
<- ^done,bkpt={number="1",type="breakpoint",disp="keep",
enabled="y",addr="0x08048564",func="main",file="myprog.c",
fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
times="0"}
<- (gdb)
Program Execution
-----------------
Program execution generates asynchronous records and MI gives the
reason that execution stopped.
-> -exec-run
<- ^running
<- (gdb)
<- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
frame={addr="0x08048564",func="main",
args=[{name="argc",value="1"},{name="argv",value="0xbfc4d4d4"}],
file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"}
<- (gdb)
-> -exec-continue
<- ^running
<- (gdb)
<- *stopped,reason="exited-normally"
<- (gdb)
Quitting GDB
------------
Quitting GDB just prints the result class `^exit'.
-> (gdb)
<- -gdb-exit
<- ^exit
Please note that `^exit' is printed immediately, but it might take
some time for GDB to actually exit. During that time, GDB performs
necessary cleanups, including killing programs being debugged or
disconnecting from debug hardware, so the frontend should wait till GDB
exits and should only forcibly kill GDB if it fails to exit in
reasonable time.
A Bad Command
-------------
Here's what happens if you pass a non-existent command:
-> -rubbish
<- ^error,msg="Undefined MI command: rubbish"
<- (gdb)

File: gdb.info, Node: GDB/MI Command Description Format, Next: GDB/MI Breakpoint Commands, Prev: GDB/MI Simple Examples, Up: GDB/MI
27.7 GDB/MI Command Description Format
======================================
The remaining sections describe blocks of commands. Each block of
commands is laid out in a fashion similar to this section.
Motivation
----------
The motivation for this collection of commands.
Introduction
------------
A brief introduction to this collection of commands as a whole.
Commands
--------
For each command in the block, the following is described:
Synopsis
........
-command ARGS...
Result
......
GDB Command
...........
The corresponding GDB CLI command(s), if any.
Example
.......
Example(s) formatted for readability. Some of the described commands
have not been implemented yet and these are labeled N.A. (not
available).

File: gdb.info, Node: GDB/MI Breakpoint Commands, Next: GDB/MI Catchpoint Commands, Prev: GDB/MI Command Description Format, Up: GDB/MI
27.8 GDB/MI Breakpoint Commands
===============================
This section documents GDB/MI commands for manipulating breakpoints.
The `-break-after' Command
--------------------------
Synopsis
........
-break-after NUMBER COUNT
The breakpoint number NUMBER is not in effect until it has been hit
COUNT times. To see how this is reflected in the output of the
`-break-list' command, see the description of the `-break-list' command
below.
GDB Command
...........
The corresponding GDB command is `ignore'.
Example
.......
(gdb)
-break-insert main
^done,bkpt={number="1",type="breakpoint",disp="keep",
enabled="y",addr="0x000100d0",func="main",file="hello.c",
fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
times="0"}
(gdb)
-break-after 1 3
~
^done
(gdb)
-break-list
^done,BreakpointTable={nr_rows="1",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",
addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
line="5",thread-groups=["i1"],times="0",ignore="3"}]}
(gdb)
The `-break-commands' Command
-----------------------------
Synopsis
........
-break-commands NUMBER [ COMMAND1 ... COMMANDN ]
Specifies the CLI commands that should be executed when breakpoint
NUMBER is hit. The parameters COMMAND1 to COMMANDN are the commands.
If no command is specified, any previously-set commands are cleared.
*Note Break Commands::. Typical use of this functionality is tracing a
program, that is, printing of values of some variables whenever
breakpoint is hit and then continuing.
GDB Command
...........
The corresponding GDB command is `commands'.
Example
.......
(gdb)
-break-insert main
^done,bkpt={number="1",type="breakpoint",disp="keep",
enabled="y",addr="0x000100d0",func="main",file="hello.c",
fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
times="0"}
(gdb)
-break-commands 1 "print v" "continue"
^done
(gdb)
The `-break-condition' Command
------------------------------
Synopsis
........
-break-condition NUMBER EXPR
Breakpoint NUMBER will stop the program only if the condition in
EXPR is true. The condition becomes part of the `-break-list' output
(see the description of the `-break-list' command below).
GDB Command
...........
The corresponding GDB command is `condition'.
Example
.......
(gdb)
-break-condition 1 1
^done
(gdb)
-break-list
^done,BreakpointTable={nr_rows="1",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",
addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"}]}
(gdb)
The `-break-delete' Command
---------------------------
Synopsis
........
-break-delete ( BREAKPOINT )+
Delete the breakpoint(s) whose number(s) are specified in the
argument list. This is obviously reflected in the breakpoint list.
GDB Command
...........
The corresponding GDB command is `delete'.
Example
.......
(gdb)
-break-delete 1
^done
(gdb)
-break-list
^done,BreakpointTable={nr_rows="0",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[]}
(gdb)
The `-break-disable' Command
----------------------------
Synopsis
........
-break-disable ( BREAKPOINT )+
Disable the named BREAKPOINT(s). The field `enabled' in the break
list is now set to `n' for the named BREAKPOINT(s).
GDB Command
...........
The corresponding GDB command is `disable'.
Example
.......
(gdb)
-break-disable 2
^done
(gdb)
-break-list
^done,BreakpointTable={nr_rows="1",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="2",type="breakpoint",disp="keep",enabled="n",
addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
line="5",thread-groups=["i1"],times="0"}]}
(gdb)
The `-break-enable' Command
---------------------------
Synopsis
........
-break-enable ( BREAKPOINT )+
Enable (previously disabled) BREAKPOINT(s).
GDB Command
...........
The corresponding GDB command is `enable'.
Example
.......
(gdb)
-break-enable 2
^done
(gdb)
-break-list
^done,BreakpointTable={nr_rows="1",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="2",type="breakpoint",disp="keep",enabled="y",
addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
line="5",thread-groups=["i1"],times="0"}]}
(gdb)
The `-break-info' Command
-------------------------
Synopsis
........
-break-info BREAKPOINT
Get information about a single breakpoint.
The result is a table of breakpoints. *Note GDB/MI Breakpoint
Information::, for details on the format of each breakpoint in the
table.
GDB Command
...........
The corresponding GDB command is `info break BREAKPOINT'.
Example
.......
N.A.
The `-break-insert' Command
---------------------------
Synopsis
........
-break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
[ -c CONDITION ] [ -i IGNORE-COUNT ]
[ -p THREAD-ID ] [ LOCATION ]
If specified, LOCATION, can be one of:
* function
* filename:linenum
* filename:function
* *address
The possible optional parameters of this command are:
`-t'
Insert a temporary breakpoint.
`-h'
Insert a hardware breakpoint.
`-f'
If LOCATION cannot be parsed (for example if it refers to unknown
files or functions), create a pending breakpoint. Without this
flag, GDB will report an error, and won't create a breakpoint, if
LOCATION cannot be parsed.
`-d'
Create a disabled breakpoint.
`-a'
Create a tracepoint. *Note Tracepoints::. When this parameter is
used together with `-h', a fast tracepoint is created.
`-c CONDITION'
Make the breakpoint conditional on CONDITION.
`-i IGNORE-COUNT'
Initialize the IGNORE-COUNT.
`-p THREAD-ID'
Restrict the breakpoint to the specified THREAD-ID.
Result
......
*Note GDB/MI Breakpoint Information::, for details on the format of the
resulting breakpoint.
Note: this format is open to change.
GDB Command
...........
The corresponding GDB commands are `break', `tbreak', `hbreak', and
`thbreak'.
Example
.......
(gdb)
-break-insert main
^done,bkpt={number="1",addr="0x0001072c",file="recursive2.c",
fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
times="0"}
(gdb)
-break-insert -t foo
^done,bkpt={number="2",addr="0x00010774",file="recursive2.c",
fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
times="0"}
(gdb)
-break-list
^done,BreakpointTable={nr_rows="2",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",
addr="0x0001072c", func="main",file="recursive2.c",
fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
times="0"},
bkpt={number="2",type="breakpoint",disp="del",enabled="y",
addr="0x00010774",func="foo",file="recursive2.c",
fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
times="0"}]}
(gdb)
The `-dprintf-insert' Command
-----------------------------
Synopsis
........
-dprintf-insert [ -t ] [ -f ] [ -d ]
[ -c CONDITION ] [ -i IGNORE-COUNT ]
[ -p THREAD-ID ] [ LOCATION ] [ FORMAT ]
[ ARGUMENT ]
If specified, LOCATION, can be one of:
* FUNCTION
* FILENAME:LINENUM
* FILENAME:function
* *ADDRESS
The possible optional parameters of this command are:
`-t'
Insert a temporary breakpoint.
`-f'
If LOCATION cannot be parsed (for example, if it refers to unknown
files or functions), create a pending breakpoint. Without this
flag, GDB will report an error, and won't create a breakpoint, if
LOCATION cannot be parsed.
`-d'
Create a disabled breakpoint.
`-c CONDITION'
Make the breakpoint conditional on CONDITION.
`-i IGNORE-COUNT'
Set the ignore count of the breakpoint (*note ignore count:
Conditions.) to IGNORE-COUNT.
`-p THREAD-ID'
Restrict the breakpoint to the specified THREAD-ID.
Result
......
*Note GDB/MI Breakpoint Information::, for details on the format of the
resulting breakpoint.
GDB Command
...........
The corresponding GDB command is `dprintf'.
Example
.......
(gdb)
4-dprintf-insert foo "At foo entry\n"
4^done,bkpt={number="1",type="dprintf",disp="keep",enabled="y",
addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
times="0",script={"printf \"At foo entry\\n\"","continue"},
original-location="foo"}
(gdb)
5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
5^done,bkpt={number="2",type="dprintf",disp="keep",enabled="y",
addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
times="0",script={"printf \"arg=%d, g=%d\\n\", arg, g","continue"},
original-location="mi-dprintf.c:26"}
(gdb)
The `-break-list' Command
-------------------------
Synopsis
........
-break-list
Displays the list of inserted breakpoints, showing the following
fields:
`Number'
number of the breakpoint
`Type'
type of the breakpoint: `breakpoint' or `watchpoint'
`Disposition'
should the breakpoint be deleted or disabled when it is hit: `keep'
or `nokeep'
`Enabled'
is the breakpoint enabled or no: `y' or `n'
`Address'
memory location at which the breakpoint is set
`What'
logical location of the breakpoint, expressed by function name,
file name, line number
`Thread-groups'
list of thread groups to which this breakpoint applies
`Times'
number of times the breakpoint has been hit
If there are no breakpoints or watchpoints, the `BreakpointTable'
`body' field is an empty list.
GDB Command
...........
The corresponding GDB command is `info break'.
Example
.......
(gdb)
-break-list
^done,BreakpointTable={nr_rows="2",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",
addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
times="0"},
bkpt={number="2",type="breakpoint",disp="keep",enabled="y",
addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
line="13",thread-groups=["i1"],times="0"}]}
(gdb)
Here's an example of the result when there are no breakpoints:
(gdb)
-break-list
^done,BreakpointTable={nr_rows="0",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[]}
(gdb)
The `-break-passcount' Command
------------------------------
Synopsis
........
-break-passcount TRACEPOINT-NUMBER PASSCOUNT
Set the passcount for tracepoint TRACEPOINT-NUMBER to PASSCOUNT. If
the breakpoint referred to by TRACEPOINT-NUMBER is not a tracepoint,
error is emitted. This corresponds to CLI command `passcount'.
The `-break-watch' Command
--------------------------
Synopsis
........
-break-watch [ -a | -r ]
Create a watchpoint. With the `-a' option it will create an
"access" watchpoint, i.e., a watchpoint that triggers either on a read
from or on a write to the memory location. With the `-r' option, the
watchpoint created is a "read" watchpoint, i.e., it will trigger only
when the memory location is accessed for reading. Without either of
the options, the watchpoint created is a regular watchpoint, i.e., it
will trigger when the memory location is accessed for writing. *Note
Setting Watchpoints: Set Watchpoints.
Note that `-break-list' will report a single list of watchpoints and
breakpoints inserted.
GDB Command
...........
The corresponding GDB commands are `watch', `awatch', and `rwatch'.
Example
.......
Setting a watchpoint on a variable in the `main' function:
(gdb)
-break-watch x
^done,wpt={number="2",exp="x"}
(gdb)
-exec-continue
^running
(gdb)
*stopped,reason="watchpoint-trigger",wpt={number="2",exp="x"},
value={old="-268439212",new="55"},
frame={func="main",args=[],file="recursive2.c",
fullname="/home/foo/bar/recursive2.c",line="5"}
(gdb)
Setting a watchpoint on a variable local to a function. GDB will
stop the program execution twice: first for the variable changing
value, then for the watchpoint going out of scope.
(gdb)
-break-watch C
^done,wpt={number="5",exp="C"}
(gdb)
-exec-continue
^running
(gdb)
*stopped,reason="watchpoint-trigger",
wpt={number="5",exp="C"},value={old="-276895068",new="3"},
frame={func="callee4",args=[],
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"}
(gdb)
-exec-continue
^running
(gdb)
*stopped,reason="watchpoint-scope",wpnum="5",
frame={func="callee3",args=[{name="strarg",
value="0x11940 \"A string argument.\""}],
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"}
(gdb)
Listing breakpoints and watchpoints, at different points in the
program execution. Note that once the watchpoint goes out of scope, it
is deleted.
(gdb)
-break-watch C
^done,wpt={number="2",exp="C"}
(gdb)
-break-list
^done,BreakpointTable={nr_rows="2",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",
addr="0x00010734",func="callee4",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
times="1"},
bkpt={number="2",type="watchpoint",disp="keep",
enabled="y",addr="",what="C",thread-groups=["i1"],times="0"}]}
(gdb)
-exec-continue
^running
(gdb)
*stopped,reason="watchpoint-trigger",wpt={number="2",exp="C"},
value={old="-276895068",new="3"},
frame={func="callee4",args=[],
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"}
(gdb)
-break-list
^done,BreakpointTable={nr_rows="2",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",
addr="0x00010734",func="callee4",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
times="1"},
bkpt={number="2",type="watchpoint",disp="keep",
enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"}]}
(gdb)
-exec-continue
^running
^done,reason="watchpoint-scope",wpnum="2",
frame={func="callee3",args=[{name="strarg",
value="0x11940 \"A string argument.\""}],
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"}
(gdb)
-break-list
^done,BreakpointTable={nr_rows="1",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",
addr="0x00010734",func="callee4",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
thread-groups=["i1"],times="1"}]}
(gdb)

File: gdb.info, Node: GDB/MI Catchpoint Commands, Next: GDB/MI Program Context, Prev: GDB/MI Breakpoint Commands, Up: GDB/MI
27.9 GDB/MI Catchpoint Commands
===============================
This section documents GDB/MI commands for manipulating catchpoints.
* Menu:
* Shared Library GDB/MI Catchpoint Commands::
* Ada Exception GDB/MI Catchpoint Commands::

File: gdb.info, Node: Shared Library GDB/MI Catchpoint Commands, Next: Ada Exception GDB/MI Catchpoint Commands, Up: GDB/MI Catchpoint Commands
27.9.1 Shared Library GDB/MI Catchpoints
----------------------------------------
The `-catch-load' Command
-------------------------
Synopsis
........
-catch-load [ -t ] [ -d ] REGEXP
Add a catchpoint for library load events. If the `-t' option is
used, the catchpoint is a temporary one (*note Setting Breakpoints: Set
Breaks.). If the `-d' option is used, the catchpoint is created in a
disabled state. The `regexp' argument is a regular expression used to
match the name of the loaded library.
GDB Command
...........
The corresponding GDB command is `catch load'.
Example
.......
-catch-load -t foo.so
^done,bkpt={number="1",type="catchpoint",disp="del",enabled="y",
what="load of library matching foo.so",catch-type="load",times="0"}
(gdb)
The `-catch-unload' Command
---------------------------
Synopsis
........
-catch-unload [ -t ] [ -d ] REGEXP
Add a catchpoint for library unload events. If the `-t' option is
used, the catchpoint is a temporary one (*note Setting Breakpoints: Set
Breaks.). If the `-d' option is used, the catchpoint is created in a
disabled state. The `regexp' argument is a regular expression used to
match the name of the unloaded library.
GDB Command
...........
The corresponding GDB command is `catch unload'.
Example
.......
-catch-unload -d bar.so
^done,bkpt={number="2",type="catchpoint",disp="keep",enabled="n",
what="load of library matching bar.so",catch-type="unload",times="0"}
(gdb)

File: gdb.info, Node: Ada Exception GDB/MI Catchpoint Commands, Prev: Shared Library GDB/MI Catchpoint Commands, Up: GDB/MI Catchpoint Commands
27.9.2 Ada Exception GDB/MI Catchpoints
---------------------------------------
The following GDB/MI commands can be used to create catchpoints that
stop the execution when Ada exceptions are being raised.
The `-catch-assert' Command
---------------------------
Synopsis
........
-catch-assert [ -c CONDITION] [ -d ] [ -t ]
Add a catchpoint for failed Ada assertions.
The possible optional parameters for this command are:
`-c CONDITION'
Make the catchpoint conditional on CONDITION.
`-d'
Create a disabled catchpoint.
`-t'
Create a temporary catchpoint.
GDB Command
...........
The corresponding GDB command is `catch assert'.
Example
.......
-catch-assert
^done,bkptno="5",bkpt={number="5",type="breakpoint",disp="keep",
enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
thread-groups=["i1"],times="0",
original-location="__gnat_debug_raise_assert_failure"}
(gdb)
The `-catch-exception' Command
------------------------------
Synopsis
........
-catch-exception [ -c CONDITION] [ -d ] [ -e EXCEPTION-NAME ]
[ -t ] [ -u ]
Add a catchpoint stopping when Ada exceptions are raised. By
default, the command stops the program when any Ada exception gets
raised. But it is also possible, by using some of the optional
parameters described below, to create more selective catchpoints.
The possible optional parameters for this command are:
`-c CONDITION'
Make the catchpoint conditional on CONDITION.
`-d'
Create a disabled catchpoint.
`-e EXCEPTION-NAME'
Only stop when EXCEPTION-NAME is raised. This option cannot be
used combined with `-u'.
`-t'
Create a temporary catchpoint.
`-u'
Stop only when an unhandled exception gets raised. This option
cannot be used combined with `-e'.
GDB Command
...........
The corresponding GDB commands are `catch exception' and `catch
exception unhandled'.
Example
.......
-catch-exception -e Program_Error
^done,bkptno="4",bkpt={number="4",type="breakpoint",disp="keep",
enabled="y",addr="0x0000000000404874",
what="`Program_Error' Ada exception", thread-groups=["i1"],
times="0",original-location="__gnat_debug_raise_exception"}
(gdb)

File: gdb.info, Node: GDB/MI Program Context, Next: GDB/MI Thread Commands, Prev: GDB/MI Catchpoint Commands, Up: GDB/MI
27.10 GDB/MI Program Context
=============================
The `-exec-arguments' Command
-----------------------------
Synopsis
........
-exec-arguments ARGS
Set the inferior program arguments, to be used in the next
`-exec-run'.
GDB Command
...........
The corresponding GDB command is `set args'.
Example
.......
(gdb)
-exec-arguments -v word
^done
(gdb)
The `-environment-cd' Command
-----------------------------
Synopsis
........
-environment-cd PATHDIR
Set GDB's working directory.
GDB Command
...........
The corresponding GDB command is `cd'.
Example
.......
(gdb)
-environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
^done
(gdb)
The `-environment-directory' Command
------------------------------------
Synopsis
........
-environment-directory [ -r ] [ PATHDIR ]+
Add directories PATHDIR to beginning of search path for source files.
If the `-r' option is used, the search path is reset to the default
search path. If directories PATHDIR are supplied in addition to the
`-r' option, the search path is first reset and then addition occurs as
normal. Multiple directories may be specified, separated by blanks.
Specifying multiple directories in a single command results in the
directories added to the beginning of the search path in the same order
they were presented in the command. If blanks are needed as part of a
directory name, double-quotes should be used around the name. In the
command output, the path will show up separated by the system
directory-separator character. The directory-separator character must
not be used in any directory name. If no directories are specified,
the current search path is displayed.
GDB Command
...........
The corresponding GDB command is `dir'.
Example
.......
(gdb)
-environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
(gdb)
-environment-directory ""
^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
(gdb)
-environment-directory -r /home/jjohnstn/src/gdb /usr/src
^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
(gdb)
-environment-directory -r
^done,source-path="$cdir:$cwd"
(gdb)
The `-environment-path' Command
-------------------------------
Synopsis
........
-environment-path [ -r ] [ PATHDIR ]+
Add directories PATHDIR to beginning of search path for object files.
If the `-r' option is used, the search path is reset to the original
search path that existed at gdb start-up. If directories PATHDIR are
supplied in addition to the `-r' option, the search path is first reset
and then addition occurs as normal. Multiple directories may be
specified, separated by blanks. Specifying multiple directories in a
single command results in the directories added to the beginning of the
search path in the same order they were presented in the command. If
blanks are needed as part of a directory name, double-quotes should be
used around the name. In the command output, the path will show up
separated by the system directory-separator character. The
directory-separator character must not be used in any directory name.
If no directories are specified, the current path is displayed.
GDB Command
...........
The corresponding GDB command is `path'.
Example
.......
(gdb)
-environment-path
^done,path="/usr/bin"
(gdb)
-environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
(gdb)
-environment-path -r /usr/local/bin
^done,path="/usr/local/bin:/usr/bin"
(gdb)
The `-environment-pwd' Command
------------------------------
Synopsis
........
-environment-pwd
Show the current working directory.
GDB Command
...........
The corresponding GDB command is `pwd'.
Example
.......
(gdb)
-environment-pwd
^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
(gdb)

File: gdb.info, Node: GDB/MI Thread Commands, Next: GDB/MI Ada Tasking Commands, Prev: GDB/MI Program Context, Up: GDB/MI
27.11 GDB/MI Thread Commands
============================
The `-thread-info' Command
--------------------------
Synopsis
........
-thread-info [ THREAD-ID ]
Reports information about either a specific thread, if the THREAD-ID
parameter is present, or about all threads. When printing information
about all threads, also reports the current thread.
GDB Command
...........
The `info thread' command prints the same information about all threads.
Result
......
The result is a list of threads. The following attributes are defined
for a given thread:
`current'
This field exists only for the current thread. It has the value
`*'.
`id'
The identifier that GDB uses to refer to the thread.
`target-id'
The identifier that the target uses to refer to the thread.
`details'
Extra information about the thread, in a target-specific format.
This field is optional.
`name'
The name of the thread. If the user specified a name using the
`thread name' command, then this name is given. Otherwise, if GDB
can extract the thread name from the target, then that name is
given. If GDB cannot find the thread name, then this field is
omitted.
`frame'
The stack frame currently executing in the thread.
`state'
The thread's state. The `state' field may have the following
values:
`stopped'
The thread is stopped. Frame information is available for
stopped threads.
`running'
The thread is running. There's no frame information for
running threads.
`core'
If GDB can find the CPU core on which this thread is running, then
this field is the core identifier. This field is optional.
Example
.......
-thread-info
^done,threads=[
{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
frame={level="0",addr="0xffffe410",func="__kernel_vsyscall",
args=[]},state="running"},
{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
frame={level="0",addr="0x0804891f",func="foo",
args=[{name="i",value="10"}],
file="/tmp/a.c",fullname="/tmp/a.c",line="158"},
state="running"}],
current-thread-id="1"
(gdb)
The `-thread-list-ids' Command
------------------------------
Synopsis
........
-thread-list-ids
Produces a list of the currently known GDB thread ids. At the end
of the list it also prints the total number of such threads.
This command is retained for historical reasons, the `-thread-info'
command should be used instead.
GDB Command
...........
Part of `info threads' supplies the same information.
Example
.......
(gdb)
-thread-list-ids
^done,thread-ids={thread-id="3",thread-id="2",thread-id="1"},
current-thread-id="1",number-of-threads="3"
(gdb)
The `-thread-select' Command
----------------------------
Synopsis
........
-thread-select THREADNUM
Make THREADNUM the current thread. It prints the number of the new
current thread, and the topmost frame for that thread.
This command is deprecated in favor of explicitly using the
`--thread' option to each command.
GDB Command
...........
The corresponding GDB command is `thread'.
Example
.......
(gdb)
-exec-next
^running
(gdb)
*stopped,reason="end-stepping-range",thread-id="2",line="187",
file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
(gdb)
-thread-list-ids
^done,
thread-ids={thread-id="3",thread-id="2",thread-id="1"},
number-of-threads="3"
(gdb)
-thread-select 3
^done,new-thread-id="3",
frame={level="0",func="vprintf",
args=[{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""},
{name="arg",value="0x2"}],file="vprintf.c",line="31"}
(gdb)

File: gdb.info, Node: GDB/MI Ada Tasking Commands, Next: GDB/MI Program Execution, Prev: GDB/MI Thread Commands, Up: GDB/MI
27.12 GDB/MI Ada Tasking Commands
=================================
The `-ada-task-info' Command
----------------------------
Synopsis
........
-ada-task-info [ TASK-ID ]
Reports information about either a specific Ada task, if the TASK-ID
parameter is present, or about all Ada tasks.
GDB Command
...........
The `info tasks' command prints the same information about all Ada
tasks (*note Ada Tasks::).
Result
......
The result is a table of Ada tasks. The following columns are defined
for each Ada task:
`current'
This field exists only for the current thread. It has the value
`*'.
`id'
The identifier that GDB uses to refer to the Ada task.
`task-id'
The identifier that the target uses to refer to the Ada task.
`thread-id'
The identifier of the thread corresponding to the Ada task.
This field should always exist, as Ada tasks are always implemented
on top of a thread. But if GDB cannot find this corresponding
thread for any reason, the field is omitted.
`parent-id'
This field exists only when the task was created by another task.
In this case, it provides the ID of the parent task.
`priority'
The base priority of the task.
`state'
The current state of the task. For a detailed description of the
possible states, see *note Ada Tasks::.
`name'
The name of the task.
Example
.......
-ada-task-info
^done,tasks={nr_rows="3",nr_cols="8",
hdr=[{width="1",alignment="-1",col_name="current",colhdr=""},
{width="3",alignment="1",col_name="id",colhdr="ID"},
{width="9",alignment="1",col_name="task-id",colhdr="TID"},
{width="4",alignment="1",col_name="thread-id",colhdr=""},
{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"},
{width="3",alignment="1",col_name="priority",colhdr="Pri"},
{width="22",alignment="-1",col_name="state",colhdr="State"},
{width="1",alignment="2",col_name="name",colhdr="Name"}],
body=[{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
state="Child Termination Wait",name="main_task"}]}
(gdb)

File: gdb.info, Node: GDB/MI Program Execution, Next: GDB/MI Stack Manipulation, Prev: GDB/MI Ada Tasking Commands, Up: GDB/MI
27.13 GDB/MI Program Execution
==============================
These are the asynchronous commands which generate the out-of-band
record `*stopped'. Currently GDB only really executes asynchronously
with remote targets and this interaction is mimicked in other cases.
The `-exec-continue' Command
----------------------------
Synopsis
........
-exec-continue [--reverse] [--all|--thread-group N]
Resumes the execution of the inferior program, which will continue
to execute until it reaches a debugger stop event. If the `--reverse'
option is specified, execution resumes in reverse until it reaches a
stop event. Stop events may include
* breakpoints or watchpoints
* signals or exceptions
* the end of the process (or its beginning under `--reverse')
* the end or beginning of a replay log if one is being used.
In all-stop mode (*note All-Stop Mode::), may resume only one
thread, or all threads, depending on the value of the
`scheduler-locking' variable. If `--all' is specified, all threads (in
all inferiors) will be resumed. The `--all' option is ignored in
all-stop mode. If the `--thread-group' options is specified, then all
threads in that thread group are resumed.
GDB Command
...........
The corresponding GDB corresponding is `continue'.
Example
.......
-exec-continue
^running
(gdb)
@Hello world
*stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame={
func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
line="13"}
(gdb)
The `-exec-finish' Command
--------------------------
Synopsis
........
-exec-finish [--reverse]
Resumes the execution of the inferior program until the current
function is exited. Displays the results returned by the function. If
the `--reverse' option is specified, resumes the reverse execution of
the inferior program until the point where current function was called.
GDB Command
...........
The corresponding GDB command is `finish'.
Example
.......
Function returning `void'.
-exec-finish
^running
(gdb)
@hello from foo
*stopped,reason="function-finished",frame={func="main",args=[],
file="hello.c",fullname="/home/foo/bar/hello.c",line="7"}
(gdb)
Function returning other than `void'. The name of the internal GDB
variable storing the result is printed, together with the value itself.
-exec-finish
^running
(gdb)
*stopped,reason="function-finished",frame={addr="0x000107b0",func="foo",
args=[{name="a",value="1"],{name="b",value="9"}},
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
gdb-result-var="$1",return-value="0"
(gdb)
The `-exec-interrupt' Command
-----------------------------
Synopsis
........
-exec-interrupt [--all|--thread-group N]
Interrupts the background execution of the target. Note how the
token associated with the stop message is the one for the execution
command that has been interrupted. The token for the interrupt itself
only appears in the `^done' output. If the user is trying to interrupt
a non-running program, an error message will be printed.
Note that when asynchronous execution is enabled, this command is
asynchronous just like other execution commands. That is, first the
`^done' response will be printed, and the target stop will be reported
after that using the `*stopped' notification.
In non-stop mode, only the context thread is interrupted by default.
All threads (in all inferiors) will be interrupted if the `--all'
option is specified. If the `--thread-group' option is specified, all
threads in that group will be interrupted.
GDB Command
...........
The corresponding GDB command is `interrupt'.
Example
.......
(gdb)
111-exec-continue
111^running
(gdb)
222-exec-interrupt
222^done
(gdb)
111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
frame={addr="0x00010140",func="foo",args=[],file="try.c",
fullname="/home/foo/bar/try.c",line="13"}
(gdb)
(gdb)
-exec-interrupt
^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
(gdb)
The `-exec-jump' Command
------------------------
Synopsis
........
-exec-jump LOCATION
Resumes execution of the inferior program at the location specified
by parameter. *Note Specify Location::, for a description of the
different forms of LOCATION.
GDB Command
...........
The corresponding GDB command is `jump'.
Example
.......
-exec-jump foo.c:10
*running,thread-id="all"
^running
The `-exec-next' Command
------------------------
Synopsis
........
-exec-next [--reverse]
Resumes execution of the inferior program, stopping when the
beginning of the next source line is reached.
If the `--reverse' option is specified, resumes reverse execution of
the inferior program, stopping at the beginning of the previous source
line. If you issue this command on the first line of a function, it
will take you back to the caller of that function, to the source line
where the function was called.
GDB Command
...........
The corresponding GDB command is `next'.
Example
.......
-exec-next
^running
(gdb)
*stopped,reason="end-stepping-range",line="8",file="hello.c"
(gdb)
The `-exec-next-instruction' Command
------------------------------------
Synopsis
........
-exec-next-instruction [--reverse]
Executes one machine instruction. If the instruction is a function
call, continues until the function returns. If the program stops at an
instruction in the middle of a source line, the address will be printed
as well.
If the `--reverse' option is specified, resumes reverse execution of
the inferior program, stopping at the previous instruction. If the
previously executed instruction was a return from another function, it
will continue to execute in reverse until the call to that function
(from the current stack frame) is reached.
GDB Command
...........
The corresponding GDB command is `nexti'.
Example
.......
(gdb)
-exec-next-instruction
^running
(gdb)
*stopped,reason="end-stepping-range",
addr="0x000100d4",line="5",file="hello.c"
(gdb)
The `-exec-return' Command
--------------------------
Synopsis
........
-exec-return
Makes current function return immediately. Doesn't execute the
inferior. Displays the new current frame.
GDB Command
...........
The corresponding GDB command is `return'.
Example
.......
(gdb)
200-break-insert callee4
200^done,bkpt={number="1",addr="0x00010734",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"}
(gdb)
000-exec-run
000^running
(gdb)
000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
frame={func="callee4",args=[],
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"}
(gdb)
205-break-delete
205^done
(gdb)
111-exec-return
111^done,frame={level="0",func="callee3",
args=[{name="strarg",
value="0x11940 \"A string argument.\""}],
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"}
(gdb)
The `-exec-run' Command
-----------------------
Synopsis
........
-exec-run [ --all | --thread-group N ] [ --start ]
Starts execution of the inferior from the beginning. The inferior
executes until either a breakpoint is encountered or the program exits.
In the latter case the output will include an exit code, if the program
has exited exceptionally.
When neither the `--all' nor the `--thread-group' option is
specified, the current inferior is started. If the `--thread-group'
option is specified, it should refer to a thread group of type
`process', and that thread group will be started. If the `--all'
option is specified, then all inferiors will be started.
Using the `--start' option instructs the debugger to stop the
execution at the start of the inferior's main subprogram, following the
same behavior as the `start' command (*note Starting::).
GDB Command
...........
The corresponding GDB command is `run'.
Examples
........
(gdb)
-break-insert main
^done,bkpt={number="1",addr="0x0001072c",file="recursive2.c",line="4"}
(gdb)
-exec-run
^running
(gdb)
*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
frame={func="main",args=[],file="recursive2.c",
fullname="/home/foo/bar/recursive2.c",line="4"}
(gdb)
Program exited normally:
(gdb)
-exec-run
^running
(gdb)
x = 55
*stopped,reason="exited-normally"
(gdb)
Program exited exceptionally:
(gdb)
-exec-run
^running
(gdb)
x = 55
*stopped,reason="exited",exit-code="01"
(gdb)
Another way the program can terminate is if it receives a signal
such as `SIGINT'. In this case, GDB/MI displays this:
(gdb)
*stopped,reason="exited-signalled",signal-name="SIGINT",
signal-meaning="Interrupt"
The `-exec-step' Command
------------------------
Synopsis
........
-exec-step [--reverse]
Resumes execution of the inferior program, stopping when the
beginning of the next source line is reached, if the next source line
is not a function call. If it is, stop at the first instruction of the
called function. If the `--reverse' option is specified, resumes
reverse execution of the inferior program, stopping at the beginning of
the previously executed source line.
GDB Command
...........
The corresponding GDB command is `step'.
Example
.......
Stepping into a function:
-exec-step
^running
(gdb)
*stopped,reason="end-stepping-range",
frame={func="foo",args=[{name="a",value="10"},
{name="b",value="0"}],file="recursive2.c",
fullname="/home/foo/bar/recursive2.c",line="11"}
(gdb)
Regular stepping:
-exec-step
^running
(gdb)
*stopped,reason="end-stepping-range",line="14",file="recursive2.c"
(gdb)
The `-exec-step-instruction' Command
------------------------------------
Synopsis
........
-exec-step-instruction [--reverse]
Resumes the inferior which executes one machine instruction. If the
`--reverse' option is specified, resumes reverse execution of the
inferior program, stopping at the previously executed instruction. The
output, once GDB has stopped, will vary depending on whether we have
stopped in the middle of a source line or not. In the former case, the
address at which the program stopped will be printed as well.
GDB Command
...........
The corresponding GDB command is `stepi'.
Example
.......
(gdb)
-exec-step-instruction
^running
(gdb)
*stopped,reason="end-stepping-range",
frame={func="foo",args=[],file="try.c",
fullname="/home/foo/bar/try.c",line="10"}
(gdb)
-exec-step-instruction
^running
(gdb)
*stopped,reason="end-stepping-range",
frame={addr="0x000100f4",func="foo",args=[],file="try.c",
fullname="/home/foo/bar/try.c",line="10"}
(gdb)
The `-exec-until' Command
-------------------------
Synopsis
........
-exec-until [ LOCATION ]
Executes the inferior until the LOCATION specified in the argument
is reached. If there is no argument, the inferior executes until a
source line greater than the current one is reached. The reason for
stopping in this case will be `location-reached'.
GDB Command
...........
The corresponding GDB command is `until'.
Example
.......
(gdb)
-exec-until recursive2.c:6
^running
(gdb)
x = 55
*stopped,reason="location-reached",frame={func="main",args=[],
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"}
(gdb)

File: gdb.info, Node: GDB/MI Stack Manipulation, Next: GDB/MI Variable Objects, Prev: GDB/MI Program Execution, Up: GDB/MI
27.14 GDB/MI Stack Manipulation Commands
========================================
The `-enable-frame-filters' Command
-----------------------------------
-enable-frame-filters
GDB allows Python-based frame filters to affect the output of the MI
commands relating to stack traces. As there is no way to implement
this in a fully backward-compatible way, a front end must request that
this functionality be enabled.
Once enabled, this feature cannot be disabled.
Note that if Python support has not been compiled into GDB, this
command will still succeed (and do nothing).
The `-stack-info-frame' Command
-------------------------------
Synopsis
........
-stack-info-frame
Get info on the selected frame.
GDB Command
...........
The corresponding GDB command is `info frame' or `frame' (without
arguments).
Example
.......
(gdb)
-stack-info-frame
^done,frame={level="1",addr="0x0001076c",func="callee3",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"}
(gdb)
The `-stack-info-depth' Command
-------------------------------
Synopsis
........
-stack-info-depth [ MAX-DEPTH ]
Return the depth of the stack. If the integer argument MAX-DEPTH is
specified, do not count beyond MAX-DEPTH frames.
GDB Command
...........
There's no equivalent GDB command.
Example
.......
For a stack with frame levels 0 through 11:
(gdb)
-stack-info-depth
^done,depth="12"
(gdb)
-stack-info-depth 4
^done,depth="4"
(gdb)
-stack-info-depth 12
^done,depth="12"
(gdb)
-stack-info-depth 11
^done,depth="11"
(gdb)
-stack-info-depth 13
^done,depth="12"
(gdb)
The `-stack-list-arguments' Command
-----------------------------------
Synopsis
........
-stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] PRINT-VALUES
[ LOW-FRAME HIGH-FRAME ]
Display a list of the arguments for the frames between LOW-FRAME and
HIGH-FRAME (inclusive). If LOW-FRAME and HIGH-FRAME are not provided,
list the arguments for the whole call stack. If the two arguments are
equal, show the single frame at the corresponding level. It is an
error if LOW-FRAME is larger than the actual number of frames. On the
other hand, HIGH-FRAME may be larger than the actual number of frames,
in which case only existing frames will be returned.
If PRINT-VALUES is 0 or `--no-values', print only the names of the
variables; if it is 1 or `--all-values', print also their values; and
if it is 2 or `--simple-values', print the name, type and value for
simple data types, and the name and type for arrays, structures and
unions. If the option `--no-frame-filters' is supplied, then Python
frame filters will not be executed.
If the `--skip-unavailable' option is specified, arguments that are
not available are not listed. Partially available arguments are still
displayed, however.
Use of this command to obtain arguments in a single frame is
deprecated in favor of the `-stack-list-variables' command.
GDB Command
...........
GDB does not have an equivalent command. `gdbtk' has a `gdb_get_args'
command which partially overlaps with the functionality of
`-stack-list-arguments'.
Example
.......
(gdb)
-stack-list-frames
^done,
stack=[
frame={level="0",addr="0x00010734",func="callee4",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"},
frame={level="1",addr="0x0001076c",func="callee3",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"},
frame={level="2",addr="0x0001078c",func="callee2",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"},
frame={level="3",addr="0x000107b4",func="callee1",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"},
frame={level="4",addr="0x000107e0",func="main",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"}]
(gdb)
-stack-list-arguments 0
^done,
stack-args=[
frame={level="0",args=[]},
frame={level="1",args=[name="strarg"]},
frame={level="2",args=[name="intarg",name="strarg"]},
frame={level="3",args=[name="intarg",name="strarg",name="fltarg"]},
frame={level="4",args=[]}]
(gdb)
-stack-list-arguments 1
^done,
stack-args=[
frame={level="0",args=[]},
frame={level="1",
args=[{name="strarg",value="0x11940 \"A string argument.\""}]},
frame={level="2",args=[
{name="intarg",value="2"},
{name="strarg",value="0x11940 \"A string argument.\""}]},
{frame={level="3",args=[
{name="intarg",value="2"},
{name="strarg",value="0x11940 \"A string argument.\""},
{name="fltarg",value="3.5"}]},
frame={level="4",args=[]}]
(gdb)
-stack-list-arguments 0 2 2
^done,stack-args=[frame={level="2",args=[name="intarg",name="strarg"]}]
(gdb)
-stack-list-arguments 1 2 2
^done,stack-args=[frame={level="2",
args=[{name="intarg",value="2"},
{name="strarg",value="0x11940 \"A string argument.\""}]}]
(gdb)
The `-stack-list-frames' Command
--------------------------------
Synopsis
........
-stack-list-frames [ --no-frame-filters LOW-FRAME HIGH-FRAME ]
List the frames currently on the stack. For each frame it displays
the following info:
`LEVEL'
The frame number, 0 being the topmost frame, i.e., the innermost
function.
`ADDR'
The `$pc' value for that frame.
`FUNC'
Function name.
`FILE'
File name of the source file where the function lives.
`FULLNAME'
The full file name of the source file where the function lives.
`LINE'
Line number corresponding to the `$pc'.
`FROM'
The shared library where this function is defined. This is only
given if the frame's function is not known.
If invoked without arguments, this command prints a backtrace for the
whole stack. If given two integer arguments, it shows the frames whose
levels are between the two arguments (inclusive). If the two arguments
are equal, it shows the single frame at the corresponding level. It is
an error if LOW-FRAME is larger than the actual number of frames. On
the other hand, HIGH-FRAME may be larger than the actual number of
frames, in which case only existing frames will be returned. If the
option `--no-frame-filters' is supplied, then Python frame filters will
not be executed.
GDB Command
...........
The corresponding GDB commands are `backtrace' and `where'.
Example
.......
Full stack backtrace:
(gdb)
-stack-list-frames
^done,stack=
[frame={level="0",addr="0x0001076c",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"},
frame={level="1",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="2",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="3",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="4",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="5",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="6",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="7",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="8",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="9",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="10",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="11",addr="0x00010738",func="main",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"}]
(gdb)
Show frames between LOW_FRAME and HIGH_FRAME:
(gdb)
-stack-list-frames 3 5
^done,stack=
[frame={level="3",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="4",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="5",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"}]
(gdb)
Show a single frame:
(gdb)
-stack-list-frames 3 3
^done,stack=
[frame={level="3",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"}]
(gdb)
The `-stack-list-locals' Command
--------------------------------
Synopsis
........
-stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] PRINT-VALUES
Display the local variable names for the selected frame. If
PRINT-VALUES is 0 or `--no-values', print only the names of the
variables; if it is 1 or `--all-values', print also their values; and
if it is 2 or `--simple-values', print the name, type and value for
simple data types, and the name and type for arrays, structures and
unions. In this last case, a frontend can immediately display the
value of simple data types and create variable objects for other data
types when the user wishes to explore their values in more detail. If
the option `--no-frame-filters' is supplied, then Python frame filters
will not be executed.
If the `--skip-unavailable' option is specified, local variables
that are not available are not listed. Partially available local
variables are still displayed, however.
This command is deprecated in favor of the `-stack-list-variables'
command.
GDB Command
...........
`info locals' in GDB, `gdb_get_locals' in `gdbtk'.
Example
.......
(gdb)
-stack-list-locals 0
^done,locals=[name="A",name="B",name="C"]
(gdb)
-stack-list-locals --all-values
^done,locals=[{name="A",value="1"},{name="B",value="2"},
{name="C",value="{1, 2, 3}"}]
-stack-list-locals --simple-values
^done,locals=[{name="A",type="int",value="1"},
{name="B",type="int",value="2"},{name="C",type="int [3]"}]
(gdb)
The `-stack-list-variables' Command
-----------------------------------
Synopsis
........
-stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] PRINT-VALUES
Display the names of local variables and function arguments for the
selected frame. If PRINT-VALUES is 0 or `--no-values', print only the
names of the variables; if it is 1 or `--all-values', print also their
values; and if it is 2 or `--simple-values', print the name, type and
value for simple data types, and the name and type for arrays,
structures and unions. If the option `--no-frame-filters' is supplied,
then Python frame filters will not be executed.
If the `--skip-unavailable' option is specified, local variables and
arguments that are not available are not listed. Partially available
arguments and local variables are still displayed, however.
Example
.......
(gdb)
-stack-list-variables --thread 1 --frame 0 --all-values
^done,variables=[{name="x",value="11"},{name="s",value="{a = 1, b = 2}"}]
(gdb)
The `-stack-select-frame' Command
---------------------------------
Synopsis
........
-stack-select-frame FRAMENUM
Change the selected frame. Select a different frame FRAMENUM on the
stack.
This command in deprecated in favor of passing the `--frame' option
to every command.
GDB Command
...........
The corresponding GDB commands are `frame', `up', `down',
`select-frame', `up-silent', and `down-silent'.
Example
.......
(gdb)
-stack-select-frame 2
^done
(gdb)

File: gdb.info, Node: GDB/MI Variable Objects, Next: GDB/MI Data Manipulation, Prev: GDB/MI Stack Manipulation, Up: GDB/MI
27.15 GDB/MI Variable Objects
=============================
Introduction to Variable Objects
--------------------------------
Variable objects are "object-oriented" MI interface for examining and
changing values of expressions. Unlike some other MI interfaces that
work with expressions, variable objects are specifically designed for
simple and efficient presentation in the frontend. A variable object
is identified by string name. When a variable object is created, the
frontend specifies the expression for that variable object. The
expression can be a simple variable, or it can be an arbitrary complex
expression, and can even involve CPU registers. After creating a
variable object, the frontend can invoke other variable object
operations--for example to obtain or change the value of a variable
object, or to change display format.
Variable objects have hierarchical tree structure. Any variable
object that corresponds to a composite type, such as structure in C, has
a number of child variable objects, for example corresponding to each
element of a structure. A child variable object can itself have
children, recursively. Recursion ends when we reach leaf variable
objects, which always have built-in types. Child variable objects are
created only by explicit request, so if a frontend is not interested in
the children of a particular variable object, no child will be created.
For a leaf variable object it is possible to obtain its value as a
string, or set the value from a string. String value can be also
obtained for a non-leaf variable object, but it's generally a string
that only indicates the type of the object, and does not list its
contents. Assignment to a non-leaf variable object is not allowed.
A frontend does not need to read the values of all variable objects
each time the program stops. Instead, MI provides an update command
that lists all variable objects whose values has changed since the last
update operation. This considerably reduces the amount of data that
must be transferred to the frontend. As noted above, children variable
objects are created on demand, and only leaf variable objects have a
real value. As result, gdb will read target memory only for leaf
variables that frontend has created.
The automatic update is not always desirable. For example, a
frontend might want to keep a value of some expression for future
reference, and never update it. For another example, fetching memory
is relatively slow for embedded targets, so a frontend might want to
disable automatic update for the variables that are either not visible
on the screen, or "closed". This is possible using so called "frozen
variable objects". Such variable objects are never implicitly updated.
Variable objects can be either "fixed" or "floating". For the fixed
variable object, the expression is parsed when the variable object is
created, including associating identifiers to specific variables. The
meaning of expression never changes. For a floating variable object
the values of variables whose names appear in the expressions are
re-evaluated every time in the context of the current frame. Consider
this example:
void do_work(...)
{
struct work_state state;
if (...)
do_work(...);
}
If a fixed variable object for the `state' variable is created in
this function, and we enter the recursive call, the variable object
will report the value of `state' in the top-level `do_work' invocation.
On the other hand, a floating variable object will report the value of
`state' in the current frame.
If an expression specified when creating a fixed variable object
refers to a local variable, the variable object becomes bound to the
thread and frame in which the variable object is created. When such
variable object is updated, GDB makes sure that the thread/frame
combination the variable object is bound to still exists, and
re-evaluates the variable object in context of that thread/frame.
The following is the complete set of GDB/MI operations defined to
access this functionality:
*Operation* *Description*
`-enable-pretty-printing' enable Python-based pretty-printing
`-var-create' create a variable object
`-var-delete' delete the variable object and/or its
children
`-var-set-format' set the display format of this variable
`-var-show-format' show the display format of this variable
`-var-info-num-children' tells how many children this object has
`-var-list-children' return a list of the object's children
`-var-info-type' show the type of this variable object
`-var-info-expression' print parent-relative expression that this
variable object represents
`-var-info-path-expression' print full expression that this variable
object represents
`-var-show-attributes' is this variable editable? does it exist
here?
`-var-evaluate-expression' get the value of this variable
`-var-assign' set the value of this variable
`-var-update' update the variable and its children
`-var-set-frozen' set frozeness attribute
`-var-set-update-range' set range of children to display on update
In the next subsection we describe each operation in detail and
suggest how it can be used.
Description And Use of Operations on Variable Objects
-----------------------------------------------------
The `-enable-pretty-printing' Command
-------------------------------------
-enable-pretty-printing
GDB allows Python-based visualizers to affect the output of the MI
variable object commands. However, because there was no way to
implement this in a fully backward-compatible way, a front end must
request that this functionality be enabled.
Once enabled, this feature cannot be disabled.
Note that if Python support has not been compiled into GDB, this
command will still succeed (and do nothing).
This feature is currently (as of GDB 7.0) experimental, and may work
differently in future versions of GDB.
The `-var-create' Command
-------------------------
Synopsis
........
-var-create {NAME | "-"}
{FRAME-ADDR | "*" | "@"} EXPRESSION
This operation creates a variable object, which allows the
monitoring of a variable, the result of an expression, a memory cell or
a CPU register.
The NAME parameter is the string by which the object can be
referenced. It must be unique. If `-' is specified, the varobj system
will generate a string "varNNNNNN" automatically. It will be unique
provided that one does not specify NAME of that format. The command
fails if a duplicate name is found.
The frame under which the expression should be evaluated can be
specified by FRAME-ADDR. A `*' indicates that the current frame should
be used. A `@' indicates that a floating variable object must be
created.
EXPRESSION is any expression valid on the current language set (must
not begin with a `*'), or one of the following:
* `*ADDR', where ADDR is the address of a memory cell
* `*ADDR-ADDR' -- a memory address range (TBD)
* `$REGNAME' -- a CPU register name
A varobj's contents may be provided by a Python-based
pretty-printer. In this case the varobj is known as a "dynamic
varobj". Dynamic varobjs have slightly different semantics in some
cases. If the `-enable-pretty-printing' command is not sent, then GDB
will never create a dynamic varobj. This ensures backward
compatibility for existing clients.
Result
......
This operation returns attributes of the newly-created varobj. These
are:
`name'
The name of the varobj.
`numchild'
The number of children of the varobj. This number is not
necessarily reliable for a dynamic varobj. Instead, you must
examine the `has_more' attribute.
`value'
The varobj's scalar value. For a varobj whose type is some sort of
aggregate (e.g., a `struct'), or for a dynamic varobj, this value
will not be interesting.
`type'
The varobj's type. This is a string representation of the type, as
would be printed by the GDB CLI. If `print object' (*note set
print object: Print Settings.) is set to `on', the _actual_
(derived) type of the object is shown rather than the _declared_
one.
`thread-id'
If a variable object is bound to a specific thread, then this is
the thread's identifier.
`has_more'
For a dynamic varobj, this indicates whether there appear to be any
children available. For a non-dynamic varobj, this will be 0.
`dynamic'
This attribute will be present and have the value `1' if the
varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
then this attribute will not be present.
`displayhint'
A dynamic varobj can supply a display hint to the front end. The
value comes directly from the Python pretty-printer object's
`display_hint' method. *Note Pretty Printing API::.
Typical output will look like this:
name="NAME",numchild="N",type="TYPE",thread-id="M",
has_more="HAS_MORE"
The `-var-delete' Command
-------------------------
Synopsis
........
-var-delete [ -c ] NAME
Deletes a previously created variable object and all of its children.
With the `-c' option, just deletes the children.
Returns an error if the object NAME is not found.
The `-var-set-format' Command
-----------------------------
Synopsis
........
-var-set-format NAME FORMAT-SPEC
Sets the output format for the value of the object NAME to be
FORMAT-SPEC.
The syntax for the FORMAT-SPEC is as follows:
FORMAT-SPEC ==>
{binary | decimal | hexadecimal | octal | natural}
The natural format is the default format choosen automatically based
on the variable type (like decimal for an `int', hex for pointers,
etc.).
For a variable with children, the format is set only on the variable
itself, and the children are not affected.
The `-var-show-format' Command
------------------------------
Synopsis
........
-var-show-format NAME
Returns the format used to display the value of the object NAME.
FORMAT ==>
FORMAT-SPEC
The `-var-info-num-children' Command
------------------------------------
Synopsis
........
-var-info-num-children NAME
Returns the number of children of a variable object NAME:
numchild=N
Note that this number is not completely reliable for a dynamic
varobj. It will return the current number of children, but more
children may be available.
The `-var-list-children' Command
--------------------------------
Synopsis
........
-var-list-children [PRINT-VALUES] NAME [FROM TO]
Return a list of the children of the specified variable object and
create variable objects for them, if they do not already exist. With a
single argument or if PRINT-VALUES has a value of 0 or `--no-values',
print only the names of the variables; if PRINT-VALUES is 1 or
`--all-values', also print their values; and if it is 2 or
`--simple-values' print the name and value for simple data types and
just the name for arrays, structures and unions.
FROM and TO, if specified, indicate the range of children to report.
If FROM or TO is less than zero, the range is reset and all children
will be reported. Otherwise, children starting at FROM (zero-based)
and up to and excluding TO will be reported.
If a child range is requested, it will only affect the current call
to `-var-list-children', but not future calls to `-var-update'. For
this, you must instead use `-var-set-update-range'. The intent of this
approach is to enable a front end to implement any update approach it
likes; for example, scrolling a view may cause the front end to request
more children with `-var-list-children', and then the front end could
call `-var-set-update-range' with a different range to ensure that
future updates are restricted to just the visible items.
For each child the following results are returned:
NAME
Name of the variable object created for this child.
EXP
The expression to be shown to the user by the front end to
designate this child. For example this may be the name of a
structure member.
For a dynamic varobj, this value cannot be used to form an
expression. There is no way to do this at all with a dynamic
varobj.
For C/C++ structures there are several pseudo children returned to
designate access qualifiers. For these pseudo children EXP is
`public', `private', or `protected'. In this case the type and
value are not present.
A dynamic varobj will not report the access qualifying
pseudo-children, regardless of the language. This information is
not available at all with a dynamic varobj.
NUMCHILD
Number of children this child has. For a dynamic varobj, this
will be 0.
TYPE
The type of the child. If `print object' (*note set print object:
Print Settings.) is set to `on', the _actual_ (derived) type of
the object is shown rather than the _declared_ one.
VALUE
If values were requested, this is the value.
THREAD-ID
If this variable object is associated with a thread, this is the
thread id. Otherwise this result is not present.
FROZEN
If the variable object is frozen, this variable will be present
with a value of 1.
DISPLAYHINT
A dynamic varobj can supply a display hint to the front end. The
value comes directly from the Python pretty-printer object's
`display_hint' method. *Note Pretty Printing API::.
DYNAMIC
This attribute will be present and have the value `1' if the
varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
then this attribute will not be present.
The result may have its own attributes:
`displayhint'
A dynamic varobj can supply a display hint to the front end. The
value comes directly from the Python pretty-printer object's
`display_hint' method. *Note Pretty Printing API::.
`has_more'
This is an integer attribute which is nonzero if there are children
remaining after the end of the selected range.
Example
.......
(gdb)
-var-list-children n
^done,numchild=N,children=[child={name=NAME,exp=EXP,
numchild=N,type=TYPE},(repeats N times)]
(gdb)
-var-list-children --all-values n
^done,numchild=N,children=[child={name=NAME,exp=EXP,
numchild=N,value=VALUE,type=TYPE},(repeats N times)]
The `-var-info-type' Command
----------------------------
Synopsis
........
-var-info-type NAME
Returns the type of the specified variable NAME. The type is
returned as a string in the same format as it is output by the GDB CLI:
type=TYPENAME
The `-var-info-expression' Command
----------------------------------
Synopsis
........
-var-info-expression NAME
Returns a string that is suitable for presenting this variable
object in user interface. The string is generally not valid expression
in the current language, and cannot be evaluated.
For example, if `a' is an array, and variable object `A' was created
for `a', then we'll get this output:
(gdb) -var-info-expression A.1
^done,lang="C",exp="1"
Here, the value of `lang' is the language name, which can be found in
*note Supported Languages::.
Note that the output of the `-var-list-children' command also
includes those expressions, so the `-var-info-expression' command is of
limited use.
The `-var-info-path-expression' Command
---------------------------------------
Synopsis
........
-var-info-path-expression NAME
Returns an expression that can be evaluated in the current context
and will yield the same value that a variable object has. Compare this
with the `-var-info-expression' command, which result can be used only
for UI presentation. Typical use of the `-var-info-path-expression'
command is creating a watchpoint from a variable object.
This command is currently not valid for children of a dynamic varobj,
and will give an error when invoked on one.
For example, suppose `C' is a C++ class, derived from class `Base',
and that the `Base' class has a member called `m_size'. Assume a
variable `c' is has the type of `C' and a variable object `C' was
created for variable `c'. Then, we'll get this output:
(gdb) -var-info-path-expression C.Base.public.m_size
^done,path_expr=((Base)c).m_size)
The `-var-show-attributes' Command
----------------------------------
Synopsis
........
-var-show-attributes NAME
List attributes of the specified variable object NAME:
status=ATTR [ ( ,ATTR )* ]
where ATTR is `{ { editable | noneditable } | TBD }'.
The `-var-evaluate-expression' Command
--------------------------------------
Synopsis
........
-var-evaluate-expression [-f FORMAT-SPEC] NAME
Evaluates the expression that is represented by the specified
variable object and returns its value as a string. The format of the
string can be specified with the `-f' option. The possible values of
this option are the same as for `-var-set-format' (*note
-var-set-format::). If the `-f' option is not specified, the current
display format will be used. The current display format can be changed
using the `-var-set-format' command.
value=VALUE
Note that one must invoke `-var-list-children' for a variable before
the value of a child variable can be evaluated.
The `-var-assign' Command
-------------------------
Synopsis
........
-var-assign NAME EXPRESSION
Assigns the value of EXPRESSION to the variable object specified by
NAME. The object must be `editable'. If the variable's value is
altered by the assign, the variable will show up in any subsequent
`-var-update' list.
Example
.......
(gdb)
-var-assign var1 3
^done,value="3"
(gdb)
-var-update *
^done,changelist=[{name="var1",in_scope="true",type_changed="false"}]
(gdb)
The `-var-update' Command
-------------------------
Synopsis
........
-var-update [PRINT-VALUES] {NAME | "*"}
Reevaluate the expressions corresponding to the variable object NAME
and all its direct and indirect children, and return the list of
variable objects whose values have changed; NAME must be a root
variable object. Here, "changed" means that the result of
`-var-evaluate-expression' before and after the `-var-update' is
different. If `*' is used as the variable object names, all existing
variable objects are updated, except for frozen ones (*note
-var-set-frozen::). The option PRINT-VALUES determines whether both
names and values, or just names are printed. The possible values of
this option are the same as for `-var-list-children' (*note
-var-list-children::). It is recommended to use the `--all-values'
option, to reduce the number of MI commands needed on each program stop.
With the `*' parameter, if a variable object is bound to a currently
running thread, it will not be updated, without any diagnostic.
If `-var-set-update-range' was previously used on a varobj, then
only the selected range of children will be reported.
`-var-update' reports all the changed varobjs in a tuple named
`changelist'.
Each item in the change list is itself a tuple holding:
`name'
The name of the varobj.
`value'
If values were requested for this update, then this field will be
present and will hold the value of the varobj.
`in_scope'
This field is a string which may take one of three values:
`"true"'
The variable object's current value is valid.
`"false"'
The variable object does not currently hold a valid value but
it may hold one in the future if its associated expression
comes back into scope.
`"invalid"'
The variable object no longer holds a valid value. This can
occur when the executable file being debugged has changed,
either through recompilation or by using the GDB `file'
command. The front end should normally choose to delete
these variable objects.
In the future new values may be added to this list so the front
should be prepared for this possibility. *Note GDB/MI Development
and Front Ends: GDB/MI Development and Front Ends.
`type_changed'
This is only present if the varobj is still valid. If the type
changed, then this will be the string `true'; otherwise it will be
`false'.
When a varobj's type changes, its children are also likely to have
become incorrect. Therefore, the varobj's children are
automatically deleted when this attribute is `true'. Also, the
varobj's update range, when set using the `-var-set-update-range'
command, is unset.
`new_type'
If the varobj's type changed, then this field will be present and
will hold the new type.
`new_num_children'
For a dynamic varobj, if the number of children changed, or if the
type changed, this will be the new number of children.
The `numchild' field in other varobj responses is generally not
valid for a dynamic varobj - it will show the number of children
that GDB knows about, but because dynamic varobjs lazily
instantiate their children, this will not reflect the number of
children which may be available.
The `new_num_children' attribute only reports changes to the
number of children known by GDB. This is the only way to detect
whether an update has removed children (which necessarily can only
happen at the end of the update range).
`displayhint'
The display hint, if any.
`has_more'
This is an integer value, which will be 1 if there are more
children available outside the varobj's update range.
`dynamic'
This attribute will be present and have the value `1' if the
varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
then this attribute will not be present.
`new_children'
If new children were added to a dynamic varobj within the selected
update range (as set by `-var-set-update-range'), then they will
be listed in this attribute.
Example
.......
(gdb)
-var-assign var1 3
^done,value="3"
(gdb)
-var-update --all-values var1
^done,changelist=[{name="var1",value="3",in_scope="true",
type_changed="false"}]
(gdb)
The `-var-set-frozen' Command
-----------------------------
Synopsis
........
-var-set-frozen NAME FLAG
Set the frozenness flag on the variable object NAME. The FLAG
parameter should be either `1' to make the variable frozen or `0' to
make it unfrozen. If a variable object is frozen, then neither itself,
nor any of its children, are implicitly updated by `-var-update' of a
parent variable or by `-var-update *'. Only `-var-update' of the
variable itself will update its value and values of its children.
After a variable object is unfrozen, it is implicitly updated by all
subsequent `-var-update' operations. Unfreezing a variable does not
update it, only subsequent `-var-update' does.
Example
.......
(gdb)
-var-set-frozen V 1
^done
(gdb)
The `-var-set-update-range' command
-----------------------------------
Synopsis
........
-var-set-update-range NAME FROM TO
Set the range of children to be returned by future invocations of
`-var-update'.
FROM and TO indicate the range of children to report. If FROM or TO
is less than zero, the range is reset and all children will be
reported. Otherwise, children starting at FROM (zero-based) and up to
and excluding TO will be reported.
Example
.......
(gdb)
-var-set-update-range V 1 2
^done
The `-var-set-visualizer' command
---------------------------------
Synopsis
........
-var-set-visualizer NAME VISUALIZER
Set a visualizer for the variable object NAME.
VISUALIZER is the visualizer to use. The special value `None' means
to disable any visualizer in use.
If not `None', VISUALIZER must be a Python expression. This
expression must evaluate to a callable object which accepts a single
argument. GDB will call this object with the value of the varobj NAME
as an argument (this is done so that the same Python pretty-printing
code can be used for both the CLI and MI). When called, this object
must return an object which conforms to the pretty-printing interface
(*note Pretty Printing API::).
The pre-defined function `gdb.default_visualizer' may be used to
select a visualizer by following the built-in process (*note Selecting
Pretty-Printers::). This is done automatically when a varobj is
created, and so ordinarily is not needed.
This feature is only available if Python support is enabled. The MI
command `-list-features' (*note GDB/MI Miscellaneous Commands::) can be
used to check this.
Example
.......
Resetting the visualizer:
(gdb)
-var-set-visualizer V None
^done
Reselecting the default (type-based) visualizer:
(gdb)
-var-set-visualizer V gdb.default_visualizer
^done
Suppose `SomeClass' is a visualizer class. A lambda expression can
be used to instantiate this class for a varobj:
(gdb)
-var-set-visualizer V "lambda val: SomeClass()"
^done

File: gdb.info, Node: GDB/MI Data Manipulation, Next: GDB/MI Tracepoint Commands, Prev: GDB/MI Variable Objects, Up: GDB/MI
27.16 GDB/MI Data Manipulation
==============================
This section describes the GDB/MI commands that manipulate data:
examine memory and registers, evaluate expressions, etc.
The `-data-disassemble' Command
-------------------------------
Synopsis
........
-data-disassemble
[ -s START-ADDR -e END-ADDR ]
| [ -f FILENAME -l LINENUM [ -n LINES ] ]
-- MODE
Where:
`START-ADDR'
is the beginning address (or `$pc')
`END-ADDR'
is the end address
`FILENAME'
is the name of the file to disassemble
`LINENUM'
is the line number to disassemble around
`LINES'
is the number of disassembly lines to be produced. If it is -1,
the whole function will be disassembled, in case no END-ADDR is
specified. If END-ADDR is specified as a non-zero value, and
LINES is lower than the number of disassembly lines between
START-ADDR and END-ADDR, only LINES lines are displayed; if LINES
is higher than the number of lines between START-ADDR and
END-ADDR, only the lines up to END-ADDR are displayed.
`MODE'
is either 0 (meaning only disassembly), 1 (meaning mixed source and
disassembly), 2 (meaning disassembly with raw opcodes), or 3
(meaning mixed source and disassembly with raw opcodes).
Result
......
The result of the `-data-disassemble' command will be a list named
`asm_insns', the contents of this list depend on the MODE used with the
`-data-disassemble' command.
For modes 0 and 2 the `asm_insns' list contains tuples with the
following fields:
`address'
The address at which this instruction was disassembled.
`func-name'
The name of the function this instruction is within.
`offset'
The decimal offset in bytes from the start of `func-name'.
`inst'
The text disassembly for this `address'.
`opcodes'
This field is only present for mode 2. This contains the raw
opcode bytes for the `inst' field.
For modes 1 and 3 the `asm_insns' list contains tuples named
`src_and_asm_line', each of which has the following fields:
`line'
The line number within `file'.
`file'
The file name from the compilation unit. This might be an absolute
file name or a relative file name depending on the compile command
used.
`fullname'
Absolute file name of `file'. It is converted to a canonical form
using the source file search path (*note Specifying Source
Directories: Source Path.) and after resolving all the symbolic
links.
If the source file is not found this field will contain the path as
present in the debug information.
`line_asm_insn'
This is a list of tuples containing the disassembly for `line' in
`file'. The fields of each tuple are the same as for
`-data-disassemble' in MODE 0 and 2, so `address', `func-name',
`offset', `inst', and optionally `opcodes'.
Note that whatever included in the `inst' field, is not manipulated
directly by GDB/MI, i.e., it is not possible to adjust its format.
GDB Command
...........
The corresponding GDB command is `disassemble'.
Example
.......
Disassemble from the current value of `$pc' to `$pc + 20':
(gdb)
-data-disassemble -s $pc -e "$pc + 20" -- 0
^done,
asm_insns=[
{address="0x000107c0",func-name="main",offset="4",
inst="mov 2, %o0"},
{address="0x000107c4",func-name="main",offset="8",
inst="sethi %hi(0x11800), %o2"},
{address="0x000107c8",func-name="main",offset="12",
inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"},
{address="0x000107cc",func-name="main",offset="16",
inst="sethi %hi(0x11800), %o2"},
{address="0x000107d0",func-name="main",offset="20",
inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"}]
(gdb)
Disassemble the whole `main' function. Line 32 is part of `main'.
-data-disassemble -f basics.c -l 32 -- 0
^done,asm_insns=[
{address="0x000107bc",func-name="main",offset="0",
inst="save %sp, -112, %sp"},
{address="0x000107c0",func-name="main",offset="4",
inst="mov 2, %o0"},
{address="0x000107c4",func-name="main",offset="8",
inst="sethi %hi(0x11800), %o2"},
[...]
{address="0x0001081c",func-name="main",offset="96",inst="ret "},
{address="0x00010820",func-name="main",offset="100",inst="restore "}]
(gdb)
Disassemble 3 instructions from the start of `main':
(gdb)
-data-disassemble -f basics.c -l 32 -n 3 -- 0
^done,asm_insns=[
{address="0x000107bc",func-name="main",offset="0",
inst="save %sp, -112, %sp"},
{address="0x000107c0",func-name="main",offset="4",
inst="mov 2, %o0"},
{address="0x000107c4",func-name="main",offset="8",
inst="sethi %hi(0x11800), %o2"}]
(gdb)
Disassemble 3 instructions from the start of `main' in mixed mode:
(gdb)
-data-disassemble -f basics.c -l 32 -n 3 -- 1
^done,asm_insns=[
src_and_asm_line={line="31",
file="../../../src/gdb/testsuite/gdb.mi/basics.c",
fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
line_asm_insn=[{address="0x000107bc",
func-name="main",offset="0",inst="save %sp, -112, %sp"}]},
src_and_asm_line={line="32",
file="../../../src/gdb/testsuite/gdb.mi/basics.c",
fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
line_asm_insn=[{address="0x000107c0",
func-name="main",offset="4",inst="mov 2, %o0"},
{address="0x000107c4",func-name="main",offset="8",
inst="sethi %hi(0x11800), %o2"}]}]
(gdb)
The `-data-evaluate-expression' Command
---------------------------------------
Synopsis
........
-data-evaluate-expression EXPR
Evaluate EXPR as an expression. The expression could contain an
inferior function call. The function call will execute synchronously.
If the expression contains spaces, it must be enclosed in double quotes.
GDB Command
...........
The corresponding GDB commands are `print', `output', and `call'. In
`gdbtk' only, there's a corresponding `gdb_eval' command.
Example
.......
In the following example, the numbers that precede the commands are the
"tokens" described in *note GDB/MI Command Syntax: GDB/MI Command
Syntax. Notice how GDB/MI returns the same tokens in its output.
211-data-evaluate-expression A
211^done,value="1"
(gdb)
311-data-evaluate-expression &A
311^done,value="0xefffeb7c"
(gdb)
411-data-evaluate-expression A+3
411^done,value="4"
(gdb)
511-data-evaluate-expression "A + 3"
511^done,value="4"
(gdb)
The `-data-list-changed-registers' Command
------------------------------------------
Synopsis
........
-data-list-changed-registers
Display a list of the registers that have changed.
GDB Command
...........
GDB doesn't have a direct analog for this command; `gdbtk' has the
corresponding command `gdb_changed_register_list'.
Example
.......
On a PPC MBX board:
(gdb)
-exec-continue
^running
(gdb)
*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame={
func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
line="5"}
(gdb)
-data-list-changed-registers
^done,changed-registers=["0","1","2","4","5","6","7","8","9",
"10","11","13","14","15","16","17","18","19","20","21","22","23",
"24","25","26","27","28","30","31","64","65","66","67","69"]
(gdb)
The `-data-list-register-names' Command
---------------------------------------
Synopsis
........
-data-list-register-names [ ( REGNO )+ ]
Show a list of register names for the current target. If no
arguments are given, it shows a list of the names of all the registers.
If integer numbers are given as arguments, it will print a list of the
names of the registers corresponding to the arguments. To ensure
consistency between a register name and its number, the output list may
include empty register names.
GDB Command
...........
GDB does not have a command which corresponds to
`-data-list-register-names'. In `gdbtk' there is a corresponding
command `gdb_regnames'.
Example
.......
For the PPC MBX board:
(gdb)
-data-list-register-names
^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
"r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
"r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
"r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
"f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
"f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
"", "pc","ps","cr","lr","ctr","xer"]
(gdb)
-data-list-register-names 1 2 3
^done,register-names=["r1","r2","r3"]
(gdb)
The `-data-list-register-values' Command
----------------------------------------
Synopsis
........
-data-list-register-values
[ `--skip-unavailable' ] FMT [ ( REGNO )*]
Display the registers' contents. FMT is the format according to
which the registers' contents are to be returned, followed by an
optional list of numbers specifying the registers to display. A
missing list of numbers indicates that the contents of all the
registers must be returned. The `--skip-unavailable' option indicates
that only the available registers are to be returned.
Allowed formats for FMT are:
`x'
Hexadecimal
`o'
Octal
`t'
Binary
`d'
Decimal
`r'
Raw
`N'
Natural
GDB Command
...........
The corresponding GDB commands are `info reg', `info all-reg', and (in
`gdbtk') `gdb_fetch_registers'.
Example
.......
For a PPC MBX board (note: line breaks are for readability only, they
don't appear in the actual output):
(gdb)
-data-list-register-values r 64 65
^done,register-values=[{number="64",value="0xfe00a300"},
{number="65",value="0x00029002"}]
(gdb)
-data-list-register-values x
^done,register-values=[{number="0",value="0xfe0043c8"},
{number="1",value="0x3fff88"},{number="2",value="0xfffffffe"},
{number="3",value="0x0"},{number="4",value="0xa"},
{number="5",value="0x3fff68"},{number="6",value="0x3fff58"},
{number="7",value="0xfe011e98"},{number="8",value="0x2"},
{number="9",value="0xfa202820"},{number="10",value="0xfa202808"},
{number="11",value="0x1"},{number="12",value="0x0"},
{number="13",value="0x4544"},{number="14",value="0xffdfffff"},
{number="15",value="0xffffffff"},{number="16",value="0xfffffeff"},
{number="17",value="0xefffffed"},{number="18",value="0xfffffffe"},
{number="19",value="0xffffffff"},{number="20",value="0xffffffff"},
{number="21",value="0xffffffff"},{number="22",value="0xfffffff7"},
{number="23",value="0xffffffff"},{number="24",value="0xffffffff"},
{number="25",value="0xffffffff"},{number="26",value="0xfffffffb"},
{number="27",value="0xffffffff"},{number="28",value="0xf7bfffff"},
{number="29",value="0x0"},{number="30",value="0xfe010000"},
{number="31",value="0x0"},{number="32",value="0x0"},
{number="33",value="0x0"},{number="34",value="0x0"},
{number="35",value="0x0"},{number="36",value="0x0"},
{number="37",value="0x0"},{number="38",value="0x0"},
{number="39",value="0x0"},{number="40",value="0x0"},
{number="41",value="0x0"},{number="42",value="0x0"},
{number="43",value="0x0"},{number="44",value="0x0"},
{number="45",value="0x0"},{number="46",value="0x0"},
{number="47",value="0x0"},{number="48",value="0x0"},
{number="49",value="0x0"},{number="50",value="0x0"},
{number="51",value="0x0"},{number="52",value="0x0"},
{number="53",value="0x0"},{number="54",value="0x0"},
{number="55",value="0x0"},{number="56",value="0x0"},
{number="57",value="0x0"},{number="58",value="0x0"},
{number="59",value="0x0"},{number="60",value="0x0"},
{number="61",value="0x0"},{number="62",value="0x0"},
{number="63",value="0x0"},{number="64",value="0xfe00a300"},
{number="65",value="0x29002"},{number="66",value="0x202f04b5"},
{number="67",value="0xfe0043b0"},{number="68",value="0xfe00b3e4"},
{number="69",value="0x20002b03"}]
(gdb)
The `-data-read-memory' Command
-------------------------------
This command is deprecated, use `-data-read-memory-bytes' instead.
Synopsis
........
-data-read-memory [ -o BYTE-OFFSET ]
ADDRESS WORD-FORMAT WORD-SIZE
NR-ROWS NR-COLS [ ASCHAR ]
where:
`ADDRESS'
An expression specifying the address of the first memory word to be
read. Complex expressions containing embedded white space should
be quoted using the C convention.
`WORD-FORMAT'
The format to be used to print the memory words. The notation is
the same as for GDB's `print' command (*note Output Formats:
Output Formats.).
`WORD-SIZE'
The size of each memory word in bytes.
`NR-ROWS'
The number of rows in the output table.
`NR-COLS'
The number of columns in the output table.
`ASCHAR'
If present, indicates that each row should include an ASCII dump.
The value of ASCHAR is used as a padding character when a byte is
not a member of the printable ASCII character set (printable ASCII
characters are those whose code is between 32 and 126,
inclusively).
`BYTE-OFFSET'
An offset to add to the ADDRESS before fetching memory.
This command displays memory contents as a table of NR-ROWS by
NR-COLS words, each word being WORD-SIZE bytes. In total, `NR-ROWS *
NR-COLS * WORD-SIZE' bytes are read (returned as `total-bytes').
Should less than the requested number of bytes be returned by the
target, the missing words are identified using `N/A'. The number of
bytes read from the target is returned in `nr-bytes' and the starting
address used to read memory in `addr'.
The address of the next/previous row or page is available in
`next-row' and `prev-row', `next-page' and `prev-page'.
GDB Command
...........
The corresponding GDB command is `x'. `gdbtk' has `gdb_get_mem' memory
read command.
Example
.......
Read six bytes of memory starting at `bytes+6' but then offset by `-6'
bytes. Format as three rows of two columns. One byte per word.
Display each word in hex.
(gdb)
9-data-read-memory -o -6 -- bytes+6 x 1 3 2
9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
prev-page="0x0000138a",memory=[
{addr="0x00001390",data=["0x00","0x01"]},
{addr="0x00001392",data=["0x02","0x03"]},
{addr="0x00001394",data=["0x04","0x05"]}]
(gdb)
Read two bytes of memory starting at address `shorts + 64' and
display as a single word formatted in decimal.
(gdb)
5-data-read-memory shorts+64 d 2 1 1
5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
next-row="0x00001512",prev-row="0x0000150e",
next-page="0x00001512",prev-page="0x0000150e",memory=[
{addr="0x00001510",data=["128"]}]
(gdb)
Read thirty two bytes of memory starting at `bytes+16' and format as
eight rows of four columns. Include a string encoding with `x' used as
the non-printable character.
(gdb)
4-data-read-memory bytes+16 x 1 8 4 x
4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
next-row="0x000013c0",prev-row="0x0000139c",
next-page="0x000013c0",prev-page="0x00001380",memory=[
{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"},
{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"},
{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"},
{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"},
{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"},
{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"},
{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"},
{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"}]
(gdb)
The `-data-read-memory-bytes' Command
-------------------------------------
Synopsis
........
-data-read-memory-bytes [ -o BYTE-OFFSET ]
ADDRESS COUNT
where:
`ADDRESS'
An expression specifying the address of the first memory word to be
read. Complex expressions containing embedded white space should
be quoted using the C convention.
`COUNT'
The number of bytes to read. This should be an integer literal.
`BYTE-OFFSET'
The offsets in bytes relative to ADDRESS at which to start
reading. This should be an integer literal. This option is
provided so that a frontend is not required to first evaluate
address and then perform address arithmetics itself.
This command attempts to read all accessible memory regions in the
specified range. First, all regions marked as unreadable in the memory
map (if one is defined) will be skipped. *Note Memory Region
Attributes::. Second, GDB will attempt to read the remaining regions.
For each one, if reading full region results in an errors, GDB will try
to read a subset of the region.
In general, every single byte in the region may be readable or not,
and the only way to read every readable byte is to try a read at every
address, which is not practical. Therefore, GDB will attempt to read
all accessible bytes at either beginning or the end of the region,
using a binary division scheme. This heuristic works well for reading
accross a memory map boundary. Note that if a region has a readable
range that is neither at the beginning or the end, GDB will not read it.
The result record (*note GDB/MI Result Records::) that is output of
the command includes a field named `memory' whose content is a list of
tuples. Each tuple represent a successfully read memory block and has
the following fields:
`begin'
The start address of the memory block, as hexadecimal literal.
`end'
The end address of the memory block, as hexadecimal literal.
`offset'
The offset of the memory block, as hexadecimal literal, relative to
the start address passed to `-data-read-memory-bytes'.
`contents'
The contents of the memory block, in hex.
GDB Command
...........
The corresponding GDB command is `x'.
Example
.......
(gdb)
-data-read-memory-bytes &a 10
^done,memory=[{begin="0xbffff154",offset="0x00000000",
end="0xbffff15e",
contents="01000000020000000300"}]
(gdb)
The `-data-write-memory-bytes' Command
--------------------------------------
Synopsis
........
-data-write-memory-bytes ADDRESS CONTENTS
-data-write-memory-bytes ADDRESS CONTENTS [COUNT]
where:
`ADDRESS'
An expression specifying the address of the first memory word to be
read. Complex expressions containing embedded white space should
be quoted using the C convention.
`CONTENTS'
The hex-encoded bytes to write.
`COUNT'
Optional argument indicating the number of bytes to be written.
If COUNT is greater than CONTENTS' length, GDB will repeatedly
write CONTENTS until it fills COUNT bytes.
GDB Command
...........
There's no corresponding GDB command.
Example
.......
(gdb)
-data-write-memory-bytes &a "aabbccdd"
^done
(gdb)
(gdb)
-data-write-memory-bytes &a "aabbccdd" 16e
^done
(gdb)

File: gdb.info, Node: GDB/MI Tracepoint Commands, Next: GDB/MI Symbol Query, Prev: GDB/MI Data Manipulation, Up: GDB/MI
27.17 GDB/MI Tracepoint Commands
================================
The commands defined in this section implement MI support for
tracepoints. For detailed introduction, see *note Tracepoints::.
The `-trace-find' Command
-------------------------
Synopsis
........
-trace-find MODE [PARAMETERS...]
Find a trace frame using criteria defined by MODE and PARAMETERS.
The following table lists permissible modes and their parameters. For
details of operation, see *note tfind::.
`none'
No parameters are required. Stops examining trace frames.
`frame-number'
An integer is required as parameter. Selects tracepoint frame with
that index.
`tracepoint-number'
An integer is required as parameter. Finds next trace frame that
corresponds to tracepoint with the specified number.
`pc'
An address is required as parameter. Finds next trace frame that
corresponds to any tracepoint at the specified address.
`pc-inside-range'
Two addresses are required as parameters. Finds next trace frame
that corresponds to a tracepoint at an address inside the
specified range. Both bounds are considered to be inside the
range.
`pc-outside-range'
Two addresses are required as parameters. Finds next trace frame
that corresponds to a tracepoint at an address outside the
specified range. Both bounds are considered to be inside the
range.
`line'
Line specification is required as parameter. *Note Specify
Location::. Finds next trace frame that corresponds to a
tracepoint at the specified location.
If `none' was passed as MODE, the response does not have fields.
Otherwise, the response may have the following fields:
`found'
This field has either `0' or `1' as the value, depending on
whether a matching tracepoint was found.
`traceframe'
The index of the found traceframe. This field is present iff the
`found' field has value of `1'.
`tracepoint'
The index of the found tracepoint. This field is present iff the
`found' field has value of `1'.
`frame'
The information about the frame corresponding to the found trace
frame. This field is present only if a trace frame was found.
*Note GDB/MI Frame Information::, for description of this field.
GDB Command
...........
The corresponding GDB command is `tfind'.
-trace-define-variable
----------------------
Synopsis
........
-trace-define-variable NAME [ VALUE ]
Create trace variable NAME if it does not exist. If VALUE is
specified, sets the initial value of the specified trace variable to
that value. Note that the NAME should start with the `$' character.
GDB Command
...........
The corresponding GDB command is `tvariable'.
The `-trace-frame-collected' Command
------------------------------------
Synopsis
........
-trace-frame-collected
[--var-print-values VAR_PVAL]
[--comp-print-values COMP_PVAL]
[--registers-format REGFORMAT]
[--memory-contents]
This command returns the set of collected objects, register names,
trace state variable names, memory ranges and computed expressions that
have been collected at a particular trace frame. The optional
parameters to the command affect the output format in different ways.
See the output description table below for more details.
The reported names can be used in the normal manner to create
varobjs and inspect the objects themselves. The items returned by this
command are categorized so that it is clear which is a variable, which
is a register, which is a trace state variable, which is a memory range
and which is a computed expression.
For instance, if the actions were
collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
collect *(int*)0xaf02bef0@40
the object collected in its entirety would be `myVar'. The object
`myArray' would be partially collected, because only the element at
index `myIndex' would be collected. The remaining objects would be
computed expressions.
An example output would be:
(gdb)
-trace-frame-collected
^done,
explicit-variables=[{name="myVar",value="1"}],
computed-expressions=[{name="myArray[myIndex]",value="0"},
{name="myObj.field",value="0"},
{name="myPtr->field",value="1"},
{name="myCount + 2",value="3"},
{name="$tvar1 + 1",value="43970027"}],
registers=[{number="0",value="0x7fe2c6e79ec8"},
{number="1",value="0x0"},
{number="2",value="0x4"},
...
{number="125",value="0x0"}],
tvars=[{name="$tvar1",current="43970026"}],
memory=[{address="0x0000000000602264",length="4"},
{address="0x0000000000615bc0",length="4"}]
(gdb)
Where:
`explicit-variables'
The set of objects that have been collected in their entirety (as
opposed to collecting just a few elements of an array or a few
struct members). For each object, its name and value are printed.
The `--var-print-values' option affects how or whether the value
field is output. If VAR_PVAL is 0, then print only the names; if
it is 1, print also their values; and if it is 2, print the name,
type and value for simple data types, and the name and type for
arrays, structures and unions.
`computed-expressions'
The set of computed expressions that have been collected at the
current trace frame. The `--comp-print-values' option affects
this set like the `--var-print-values' option affects the
`explicit-variables' set. See above.
`registers'
The registers that have been collected at the current trace frame.
For each register collected, the name and current value are
returned. The value is formatted according to the
`--registers-format' option. See the `-data-list-register-values'
command for a list of the allowed formats. The default is `x'.
`tvars'
The trace state variables that have been collected at the current
trace frame. For each trace state variable collected, the name and
current value are returned.
`memory'
The set of memory ranges that have been collected at the current
trace frame. Its content is a list of tuples. Each tuple
represents a collected memory range and has the following fields:
`address'
The start address of the memory range, as hexadecimal literal.
`length'
The length of the memory range, as decimal literal.
`contents'
The contents of the memory block, in hex. This field is only
present if the `--memory-contents' option is specified.
GDB Command
...........
There is no corresponding GDB command.
Example
.......
-trace-list-variables
---------------------
Synopsis
........
-trace-list-variables
Return a table of all defined trace variables. Each element of the
table has the following fields:
`name'
The name of the trace variable. This field is always present.
`initial'
The initial value. This is a 64-bit signed integer. This field
is always present.
`current'
The value the trace variable has at the moment. This is a 64-bit
signed integer. This field is absent iff current value is not
defined, for example if the trace was never run, or is presently
running.
GDB Command
...........
The corresponding GDB command is `tvariables'.
Example
.......
(gdb)
-trace-list-variables
^done,trace-variables={nr_rows="1",nr_cols="3",
hdr=[{width="15",alignment="-1",col_name="name",colhdr="Name"},
{width="11",alignment="-1",col_name="initial",colhdr="Initial"},
{width="11",alignment="-1",col_name="current",colhdr="Current"}],
body=[variable={name="$trace_timestamp",initial="0"}
variable={name="$foo",initial="10",current="15"}]}
(gdb)
-trace-save
-----------
Synopsis
........
-trace-save [-r ] FILENAME
Saves the collected trace data to FILENAME. Without the `-r'
option, the data is downloaded from the target and saved in a local
file. With the `-r' option the target is asked to perform the save.
GDB Command
...........
The corresponding GDB command is `tsave'.
-trace-start
------------
Synopsis
........
-trace-start
Starts a tracing experiments. The result of this command does not
have any fields.
GDB Command
...........
The corresponding GDB command is `tstart'.
-trace-status
-------------
Synopsis
........
-trace-status
Obtains the status of a tracing experiment. The result may include
the following fields:
`supported'
May have a value of either `0', when no tracing operations are
supported, `1', when all tracing operations are supported, or
`file' when examining trace file. In the latter case, examining
of trace frame is possible but new tracing experiement cannot be
started. This field is always present.
`running'
May have a value of either `0' or `1' depending on whether tracing
experiement is in progress on target. This field is present if
`supported' field is not `0'.
`stop-reason'
Report the reason why the tracing was stopped last time. This
field may be absent iff tracing was never stopped on target yet.
The value of `request' means the tracing was stopped as result of
the `-trace-stop' command. The value of `overflow' means the
tracing buffer is full. The value of `disconnection' means
tracing was automatically stopped when GDB has disconnected. The
value of `passcount' means tracing was stopped when a tracepoint
was passed a maximal number of times for that tracepoint. This
field is present if `supported' field is not `0'.
`stopping-tracepoint'
The number of tracepoint whose passcount as exceeded. This field
is present iff the `stop-reason' field has the value of
`passcount'.
`frames'
`frames-created'
The `frames' field is a count of the total number of trace frames
in the trace buffer, while `frames-created' is the total created
during the run, including ones that were discarded, such as when a
circular trace buffer filled up. Both fields are optional.
`buffer-size'
`buffer-free'
These fields tell the current size of the tracing buffer and the
remaining space. These fields are optional.
`circular'
The value of the circular trace buffer flag. `1' means that the
trace buffer is circular and old trace frames will be discarded if
necessary to make room, `0' means that the trace buffer is linear
and may fill up.
`disconnected'
The value of the disconnected tracing flag. `1' means that
tracing will continue after GDB disconnects, `0' means that the
trace run will stop.
`trace-file'
The filename of the trace file being examined. This field is
optional, and only present when examining a trace file.
GDB Command
...........
The corresponding GDB command is `tstatus'.
-trace-stop
-----------
Synopsis
........
-trace-stop
Stops a tracing experiment. The result of this command has the same
fields as `-trace-status', except that the `supported' and `running'
fields are not output.
GDB Command
...........
The corresponding GDB command is `tstop'.

File: gdb.info, Node: GDB/MI Symbol Query, Next: GDB/MI File Commands, Prev: GDB/MI Tracepoint Commands, Up: GDB/MI
27.18 GDB/MI Symbol Query Commands
==================================
The `-symbol-list-lines' Command
--------------------------------
Synopsis
........
-symbol-list-lines FILENAME
Print the list of lines that contain code and their associated
program addresses for the given source filename. The entries are
sorted in ascending PC order.
GDB Command
...........
There is no corresponding GDB command.
Example
.......
(gdb)
-symbol-list-lines basics.c
^done,lines=[{pc="0x08048554",line="7"},{pc="0x0804855a",line="8"}]
(gdb)

File: gdb.info, Node: GDB/MI File Commands, Next: GDB/MI Target Manipulation, Prev: GDB/MI Symbol Query, Up: GDB/MI
27.19 GDB/MI File Commands
==========================
This section describes the GDB/MI commands to specify executable file
names and to read in and obtain symbol table information.
The `-file-exec-and-symbols' Command
------------------------------------
Synopsis
........
-file-exec-and-symbols FILE
Specify the executable file to be debugged. This file is the one
from which the symbol table is also read. If no file is specified, the
command clears the executable and symbol information. If breakpoints
are set when using this command with no arguments, GDB will produce
error messages. Otherwise, no output is produced, except a completion
notification.
GDB Command
...........
The corresponding GDB command is `file'.
Example
.......
(gdb)
-file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
^done
(gdb)
The `-file-exec-file' Command
-----------------------------
Synopsis
........
-file-exec-file FILE
Specify the executable file to be debugged. Unlike
`-file-exec-and-symbols', the symbol table is _not_ read from this
file. If used without argument, GDB clears the information about the
executable file. No output is produced, except a completion
notification.
GDB Command
...........
The corresponding GDB command is `exec-file'.
Example
.......
(gdb)
-file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
^done
(gdb)
The `-file-list-exec-source-file' Command
-----------------------------------------
Synopsis
........
-file-list-exec-source-file
List the line number, the current source file, and the absolute path
to the current source file for the current executable. The macro
information field has a value of `1' or `0' depending on whether or not
the file includes preprocessor macro information.
GDB Command
...........
The GDB equivalent is `info source'
Example
.......
(gdb)
123-file-list-exec-source-file
123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
(gdb)
The `-file-list-exec-source-files' Command
------------------------------------------
Synopsis
........
-file-list-exec-source-files
List the source files for the current executable.
It will always output both the filename and fullname (absolute file
name) of a source file.
GDB Command
...........
The GDB equivalent is `info sources'. `gdbtk' has an analogous command
`gdb_listfiles'.
Example
.......
(gdb)
-file-list-exec-source-files
^done,files=[
{file=foo.c,fullname=/home/foo.c},
{file=/home/bar.c,fullname=/home/bar.c},
{file=gdb_could_not_find_fullpath.c}]
(gdb)
The `-file-symbol-file' Command
-------------------------------
Synopsis
........
-file-symbol-file FILE
Read symbol table info from the specified FILE argument. When used
without arguments, clears GDB's symbol table info. No output is
produced, except for a completion notification.
GDB Command
...........
The corresponding GDB command is `symbol-file'.
Example
.......
(gdb)
-file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
^done
(gdb)

File: gdb.info, Node: GDB/MI Target Manipulation, Next: GDB/MI File Transfer Commands, Prev: GDB/MI File Commands, Up: GDB/MI
27.20 GDB/MI Target Manipulation Commands
=========================================
The `-target-attach' Command
----------------------------
Synopsis
........
-target-attach PID | GID | FILE
Attach to a process PID or a file FILE outside of GDB, or a thread
group GID. If attaching to a thread group, the id previously returned
by `-list-thread-groups --available' must be used.
GDB Command
...........
The corresponding GDB command is `attach'.
Example
.......
(gdb)
-target-attach 34
=thread-created,id="1"
*stopped,thread-id="1",frame={addr="0xb7f7e410",func="bar",args=[]}
^done
(gdb)
The `-target-detach' Command
----------------------------
Synopsis
........
-target-detach [ PID | GID ]
Detach from the remote target which normally resumes its execution.
If either PID or GID is specified, detaches from either the specified
process, or specified thread group. There's no output.
GDB Command
...........
The corresponding GDB command is `detach'.
Example
.......
(gdb)
-target-detach
^done
(gdb)
The `-target-disconnect' Command
--------------------------------
Synopsis
........
-target-disconnect
Disconnect from the remote target. There's no output and the target
is generally not resumed.
GDB Command
...........
The corresponding GDB command is `disconnect'.
Example
.......
(gdb)
-target-disconnect
^done
(gdb)
The `-target-download' Command
------------------------------
Synopsis
........
-target-download
Loads the executable onto the remote target. It prints out an
update message every half second, which includes the fields:
`section'
The name of the section.
`section-sent'
The size of what has been sent so far for that section.
`section-size'
The size of the section.
`total-sent'
The total size of what was sent so far (the current and the
previous sections).
`total-size'
The size of the overall executable to download.
Each message is sent as status record (*note GDB/MI Output Syntax:
GDB/MI Output Syntax.).
In addition, it prints the name and size of the sections, as they are
downloaded. These messages include the following fields:
`section'
The name of the section.
`section-size'
The size of the section.
`total-size'
The size of the overall executable to download.
At the end, a summary is printed.
GDB Command
...........
The corresponding GDB command is `load'.
Example
.......
Note: each status message appears on a single line. Here the messages
have been broken down so that they can fit onto a page.
(gdb)
-target-download
+download,{section=".text",section-size="6668",total-size="9880"}
+download,{section=".text",section-sent="512",section-size="6668",
total-sent="512",total-size="9880"}
+download,{section=".text",section-sent="1024",section-size="6668",
total-sent="1024",total-size="9880"}
+download,{section=".text",section-sent="1536",section-size="6668",
total-sent="1536",total-size="9880"}
+download,{section=".text",section-sent="2048",section-size="6668",
total-sent="2048",total-size="9880"}
+download,{section=".text",section-sent="2560",section-size="6668",
total-sent="2560",total-size="9880"}
+download,{section=".text",section-sent="3072",section-size="6668",
total-sent="3072",total-size="9880"}
+download,{section=".text",section-sent="3584",section-size="6668",
total-sent="3584",total-size="9880"}
+download,{section=".text",section-sent="4096",section-size="6668",
total-sent="4096",total-size="9880"}
+download,{section=".text",section-sent="4608",section-size="6668",
total-sent="4608",total-size="9880"}
+download,{section=".text",section-sent="5120",section-size="6668",
total-sent="5120",total-size="9880"}
+download,{section=".text",section-sent="5632",section-size="6668",
total-sent="5632",total-size="9880"}
+download,{section=".text",section-sent="6144",section-size="6668",
total-sent="6144",total-size="9880"}
+download,{section=".text",section-sent="6656",section-size="6668",
total-sent="6656",total-size="9880"}
+download,{section=".init",section-size="28",total-size="9880"}
+download,{section=".fini",section-size="28",total-size="9880"}
+download,{section=".data",section-size="3156",total-size="9880"}
+download,{section=".data",section-sent="512",section-size="3156",
total-sent="7236",total-size="9880"}
+download,{section=".data",section-sent="1024",section-size="3156",
total-sent="7748",total-size="9880"}
+download,{section=".data",section-sent="1536",section-size="3156",
total-sent="8260",total-size="9880"}
+download,{section=".data",section-sent="2048",section-size="3156",
total-sent="8772",total-size="9880"}
+download,{section=".data",section-sent="2560",section-size="3156",
total-sent="9284",total-size="9880"}
+download,{section=".data",section-sent="3072",section-size="3156",
total-sent="9796",total-size="9880"}
^done,address="0x10004",load-size="9880",transfer-rate="6586",
write-rate="429"
(gdb)
GDB Command
...........
No equivalent.
Example
.......
N.A.
The `-target-select' Command
----------------------------
Synopsis
........
-target-select TYPE PARAMETERS ...
Connect GDB to the remote target. This command takes two args:
`TYPE'
The type of target, for instance `remote', etc.
`PARAMETERS'
Device names, host names and the like. *Note Commands for
Managing Targets: Target Commands, for more details.
The output is a connection notification, followed by the address at
which the target program is, in the following form:
^connected,addr="ADDRESS",func="FUNCTION NAME",
args=[ARG LIST]
GDB Command
...........
The corresponding GDB command is `target'.
Example
.......
(gdb)
-target-select remote /dev/ttya
^connected,addr="0xfe00a300",func="??",args=[]
(gdb)

File: gdb.info, Node: GDB/MI File Transfer Commands, Next: GDB/MI Ada Exceptions Commands, Prev: GDB/MI Target Manipulation, Up: GDB/MI
27.21 GDB/MI File Transfer Commands
===================================
The `-target-file-put' Command
------------------------------
Synopsis
........
-target-file-put HOSTFILE TARGETFILE
Copy file HOSTFILE from the host system (the machine running GDB) to
TARGETFILE on the target system.
GDB Command
...........
The corresponding GDB command is `remote put'.
Example
.......
(gdb)
-target-file-put localfile remotefile
^done
(gdb)
The `-target-file-get' Command
------------------------------
Synopsis
........
-target-file-get TARGETFILE HOSTFILE
Copy file TARGETFILE from the target system to HOSTFILE on the host
system.
GDB Command
...........
The corresponding GDB command is `remote get'.
Example
.......
(gdb)
-target-file-get remotefile localfile
^done
(gdb)
The `-target-file-delete' Command
---------------------------------
Synopsis
........
-target-file-delete TARGETFILE
Delete TARGETFILE from the target system.
GDB Command
...........
The corresponding GDB command is `remote delete'.
Example
.......
(gdb)
-target-file-delete remotefile
^done
(gdb)

File: gdb.info, Node: GDB/MI Ada Exceptions Commands, Next: GDB/MI Miscellaneous Commands, Prev: GDB/MI File Transfer Commands, Up: GDB/MI
27.22 Ada Exceptions GDB/MI Commands
====================================
The `-info-ada-exceptions' Command
----------------------------------
Synopsis
........
-info-ada-exceptions [ REGEXP]
List all Ada exceptions defined within the program being debugged.
With a regular expression REGEXP, only those exceptions whose names
match REGEXP are listed.
GDB Command
...........
The corresponding GDB command is `info exceptions'.
Result
......
The result is a table of Ada exceptions. The following columns are
defined for each exception:
`name'
The name of the exception.
`address'
The address of the exception.
Example
.......
-info-ada-exceptions aint
^done,ada-exceptions={nr_rows="2",nr_cols="2",
hdr=[{width="1",alignment="-1",col_name="name",colhdr="Name"},
{width="1",alignment="-1",col_name="address",colhdr="Address"}],
body=[{name="constraint_error",address="0x0000000000613da0"},
{name="const.aint_global_e",address="0x0000000000613b00"}]}
Catching Ada Exceptions
-----------------------
The commands describing how to ask GDB to stop when a program raises an
exception are described at *note Ada Exception GDB/MI Catchpoint
Commands::.