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 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Debugging Support</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.78.1" /><meta name="keywords" content="C++, debug" /><meta name="keywords" content="ISO C++, library" /><meta name="keywords" content="ISO C++, runtime, library" /><link rel="home" href="../index.html" title="The GNU C++ Library" /><link rel="up" href="using.html" title="Chapter 3. Using" /><link rel="prev" href="using_exceptions.html" title="Exceptions" /><link rel="next" href="std_contents.html" title="Part II.  Standard Contents" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Debugging Support</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="using_exceptions.html">Prev</a> </td><th width="60%" align="center">Chapter 3. Using</th><td width="20%" align="right"> <a accesskey="n" href="std_contents.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.intro.using.debug"></a>Debugging Support</h2></div></div></div><p>
   There are numerous things that can be done to improve the ease with
   which C++ binaries are debugged when using the GNU tool chain. Here
   are some of them.
 </p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.compiler"></a>Using <span class="command"><strong>g++</strong></span></h3></div></div></div><p>
     Compiler flags determine how debug information is transmitted
     between compilation and debug or analysis tools.
   </p><p>
     The default optimizations and debug flags for a libstdc++ build
     are <code class="code">-g -O2</code>. However, both debug and optimization
     flags can be varied to change debugging characteristics. For
     instance, turning off all optimization via the <code class="code">-g -O0
     -fno-inline</code> flags will disable inlining and optimizations,
     and add debugging information, so that stepping through all functions,
     (including inlined constructors and destructors) is possible. In
     addition, <code class="code">-fno-eliminate-unused-debug-types</code> can be
     used when additional debug information, such as nested class info,
     is desired.
 </p><p>
   Or, the debug format that the compiler and debugger use to
   communicate information about source constructs can be changed via
   <code class="code">-gdwarf-2</code> or <code class="code">-gstabs</code> flags: some debugging
   formats permit more expressive type and scope information to be
   shown in GDB. Expressiveness can be enhanced by flags like
   <code class="code">-g3</code>. The default debug information for a particular
   platform can be identified via the value set by the
   PREFERRED_DEBUGGING_TYPE macro in the GCC sources.
 </p><p>
   Many other options are available: please see <a class="link" href="http://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html#Debugging%20Options" target="_top">"Options
   for Debugging Your Program"</a> in Using the GNU Compiler
   Collection (GCC) for a complete list.
 </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.req"></a>Debug Versions of Library Binary Files</h3></div></div></div><p>
   If you would like debug symbols in libstdc++, there are two ways to
   build libstdc++ with debug flags. The first is to create a separate
   debug build by running make from the top-level of a tree
   freshly-configured with
 </p><pre class="programlisting">
      --enable-libstdcxx-debug
 </pre><p>and perhaps</p><pre class="programlisting">
      --enable-libstdcxx-debug-flags='...'
 </pre><p>
   Both the normal build and the debug build will persist, without
   having to specify <code class="code">CXXFLAGS</code>, and the debug library will
   be installed in a separate directory tree, in <code class="code">(prefix)/lib/debug</code>.
   For more information, look at the
   <a class="link" href="configure.html" title="Configure">configuration</a> section.
 </p><p>
   A second approach is to use the configuration flags
 </p><pre class="programlisting">
      make CXXFLAGS='-g3 -fno-inline -O0' all
 </pre><p>
   This quick and dirty approach is often sufficient for quick
   debugging tasks, when you cannot or don't want to recompile your
   application to use the <a class="link" href="debug_mode.html" title="Chapter 17. Debug Mode">debug mode</a>.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.memory"></a>Memory Leak Hunting</h3></div></div></div><p>
   There are various third party memory tracing and debug utilities
   that can be used to provide detailed memory allocation information
   about C++ code. An exhaustive list of tools is not going to be
   attempted, but includes <code class="code">mtrace</code>, <code class="code">valgrind</code>,
   <code class="code">mudflap</code>, and the non-free commercial product
   <code class="code">purify</code>. In addition, <code class="code">libcwd</code> has a
   replacement for the global new and delete operators that can track
   memory allocation and deallocation and provide useful memory
   statistics.
 </p><p>
   Regardless of the memory debugging tool being used, there is one
   thing of great importance to keep in mind when debugging C++ code
   that uses <code class="code">new</code> and <code class="code">delete</code>: there are
   different kinds of allocation schemes that can be used by <code class="code">
   std::allocator</code>. For implementation details, see the <a class="link" href="mt_allocator.html" title="Chapter 20. The mt_allocator">mt allocator</a> documentation and
   look specifically for <code class="code">GLIBCXX_FORCE_NEW</code>.
 </p><p>
   In a nutshell, the optional <code class="classname">mt_allocator</code>
   is a high-performance pool allocator, and can
   give the mistaken impression that in a suspect executable, memory is
   being leaked, when in reality the memory "leak" is a pool being used
   by the library's allocator and is reclaimed after program
   termination.
 </p><p>
   For valgrind, there are some specific items to keep in mind. First
   of all, use a version of valgrind that will work with current GNU
   C++ tools: the first that can do this is valgrind 1.0.4, but later
   versions should work at least as well. Second of all, use a
   completely unoptimized build to avoid confusing valgrind. Third, use
   GLIBCXX_FORCE_NEW to keep extraneous pool allocation noise from
   cluttering debug information.
 </p><p>
   Fourth, it may be necessary to force deallocation in other libraries
   as well, namely the "C" library. On linux, this can be accomplished
   with the appropriate use of the <code class="code">__cxa_atexit</code> or
   <code class="code">atexit</code> functions.
 </p><pre class="programlisting">
    #include &lt;cstdlib&gt;

    extern "C" void __libc_freeres(void);

    void do_something() { }

    int main()
    {
      atexit(__libc_freeres);
      do_something();
      return 0;
    }
 </pre><p>or, using <code class="code">__cxa_atexit</code>:</p><pre class="programlisting">
    extern "C" void __libc_freeres(void);
    extern "C" int __cxa_atexit(void (*func) (void *), void *arg, void *d);

    void do_something() { }

    int main()
    {
       extern void* __dso_handle __attribute__ ((__weak__));
       __cxa_atexit((void (*) (void *)) __libc_freeres, NULL,
 		   &amp;__dso_handle ? __dso_handle : NULL);
       do_test();
       return 0;
    }
 </pre><p>
   Suggested valgrind flags, given the suggestions above about setting
   up the runtime environment, library, and test file, might be:
 </p><pre class="programlisting">
    valgrind -v --num-callers=20 --leak-check=yes --leak-resolution=high --show-reachable=yes a.out
 </pre></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.races"></a>Data Race Hunting</h3></div></div></div><p>
   All synchronization primitives used in the library internals need to be
   understood by race detectors so that they do not produce false reports.
 </p><p>
   Two annotation macros are used to explain low-level synchronization
   to race detectors:
   <code class="code">_GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE()</code> and
   <code class="code"> _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER()</code>.
   By default, these macros are defined empty -- anyone who wants
   to use a race detector needs to redefine them to call an
   appropriate API.
   Since these macros are empty by default when the library is built,
   redefining them will only affect inline functions and template
   instantiations which are compiled in user code. This allows annotation
   of templates such as <code class="code">shared_ptr</code>, but not code which is
   only instantiated in the library.  Code which is only instantiated in
   the library needs to be recompiled with the annotation macros defined.
   That can be done by rebuilding the entire
   <code class="filename">libstdc++.so</code> file but a simpler
   alternative exists for ELF platforms such as GNU/Linux, because ELF
   symbol interposition allows symbols defined in the shared library to be
   overridden by symbols with the same name that appear earlier in the
   runtime search path. This means you only need to recompile the functions
   that are affected by the annotation macros, which can be done by
   recompiling individual files.
   Annotating <code class="code">std::string</code> and <code class="code">std::wstring</code>
   reference counting can be done by disabling extern templates (by defining
   <code class="code">_GLIBCXX_EXTERN_TEMPLATE=-1</code>) or by rebuilding the
   <code class="filename">src/string-inst.cc</code> file.
   Annotating the remaining atomic operations (at the time of writing these
   are in <code class="code">ios_base::Init::~Init</code>, <code class="code">locale::_Impl</code>,
   <code class="code">locale::facet</code> and <code class="code">thread::_M_start_thread</code>)
   requires rebuilding the relevant source files.
 </p><p>
   The approach described above is known to work with the following race
   detection tools:
   <a class="link" href="http://valgrind.org/docs/manual/drd-manual.html" target="_top">
   DRD</a>,
   <a class="link" href="http://valgrind.org/docs/manual/hg-manual.html" target="_top">
   Helgrind</a>, and
   <a class="link" href="http://code.google.com/p/data-race-test/" target="_top">
   ThreadSanitizer</a>.
 </p><p>
   With DRD, Helgrind and ThreadSanitizer you will need to define
   the macros like this:
 </p><pre class="programlisting">
   #define _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(A) ANNOTATE_HAPPENS_BEFORE(A)
   #define _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(A)  ANNOTATE_HAPPENS_AFTER(A)
 </pre><p>
   Refer to the documentation of each particular tool for details.
 </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.gdb"></a>Using <span class="command"><strong>gdb</strong></span></h3></div></div></div><p>
   </p><p>
   Many options are available for GDB itself: please see <a class="link" href="http://sourceware.org/gdb/current/onlinedocs/gdb/" target="_top">
   "GDB features for C++" </a> in the GDB documentation. Also
   recommended: the other parts of this manual.
 </p><p>
   These settings can either be switched on in at the GDB command line,
   or put into a .gdbint file to establish default debugging
   characteristics, like so:
 </p><pre class="programlisting">
    set print pretty on
    set print object on
    set print static-members on
    set print vtbl on
    set print demangle on
    set demangle-style gnu-v3
 </pre><p>
   Starting with version 7.0, GDB includes support for writing
   pretty-printers in Python.  Pretty printers for STL classes are
   distributed with GCC from version 4.5.0.  The most recent version of
   these printers are always found in libstdc++ svn repository.
   To enable these printers, check-out the latest printers to a local
   directory:
 </p><pre class="programlisting">
   svn co svn://gcc.gnu.org/svn/gcc/trunk/libstdc++-v3/python
 </pre><p>
   Next, add the following section to your ~/.gdbinit  The path must
   match the location where the Python module above was checked-out.
   So if checked out to: /home/maude/gdb_printers/, the path would be as
   written in the example below.
 </p><pre class="programlisting">
   python
   import sys
   sys.path.insert(0, '/home/maude/gdb_printers/python')
   from libstdcxx.v6.printers import register_libstdcxx_printers
   register_libstdcxx_printers (None)
   end
 </pre><p>
   The path should be the only element that needs to be adjusted in the
   example.  Once loaded, STL classes that the printers support
   should print in a more human-readable format.  To print the classes
   in the old style, use the /r (raw) switch in the print command
   (i.e., print /r foo).  This will print the classes as if the Python
   pretty-printers were not loaded.
 </p><p>
   For additional information on STL support and GDB please visit:
   <a class="link" href="http://sourceware.org/gdb/wiki/STLSupport" target="_top"> "GDB Support
   for STL" </a> in the GDB wiki.  Additionally, in-depth
   documentation and discussion of the pretty printing feature can be
   found in "Pretty Printing" node in the GDB manual.  You can find
   on-line versions of the GDB user manual in GDB's homepage, at
   <a class="link" href="http://sourceware.org/gdb/" target="_top"> "GDB: The GNU Project
   Debugger" </a>.
 </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.exceptions"></a>Tracking uncaught exceptions</h3></div></div></div><p>
   The <a class="link" href="termination.html#support.termination.verbose" title="Verbose Terminate Handler">verbose
   termination handler</a> gives information about uncaught
   exceptions which are killing the program.  It is described in the
   linked-to page.
 </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.debug_mode"></a>Debug Mode</h3></div></div></div><p> The <a class="link" href="debug_mode.html" title="Chapter 17. Debug Mode">Debug Mode</a>
   has compile and run-time checks for many containers.
   </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.compile_time_checks"></a>Compile Time Checking</h3></div></div></div><p> The <a class="link" href="ext_compile_checks.html" title="Chapter 16. Compile Time Checks">Compile-Time
   Checks</a> Extension has compile-time checks for many algorithms.
   </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.profile_mode"></a>Profile-based Performance Analysis</h3></div></div></div><p> The <a class="link" href="profile_mode.html" title="Chapter 19. Profile Mode">Profile-based
   Performance Analysis</a> Extension has performance checks for many
   algorithms.
   </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="using_exceptions.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="using.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="std_contents.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Exceptions </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Part II.
     Standard Contents
   </td></tr></table></div></body></html>
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	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Debugging Support</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.78.1" /><meta name="keywords" content="C++, debug" /><meta name="keywords" content="ISO C++, library" /><meta name="keywords" content="ISO C++, runtime, library" /><link rel="home" href="../index.html" title="The GNU C++ Library" /><link rel="up" href="using.html" title="Chapter 3. Using" /><link rel="prev" href="using_exceptions.html" title="Exceptions" /><link rel="next" href="std_contents.html" title="Part II. Standard Contents" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Debugging Support</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="using_exceptions.html">Prev</a> </td><th width="60%" align="center">Chapter 3. Using</th><td width="20%" align="right"> <a accesskey="n" href="std_contents.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.intro.using.debug"></a>Debugging Support</h2></div></div></div><p>
	There are numerous things that can be done to improve the ease with
	which C++ binaries are debugged when using the GNU tool chain. Here
	are some of them.
	</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.compiler"></a>Using <span class="command"><strong>g++</strong></span></h3></div></div></div><p>
	Compiler flags determine how debug information is transmitted
	between compilation and debug or analysis tools.
	</p><p>
	The default optimizations and debug flags for a libstdc++ build
	are <code class="code">-g -O2</code>. However, both debug and optimization
	flags can be varied to change debugging characteristics. For
	instance, turning off all optimization via the <code class="code">-g -O0
	-fno-inline</code> flags will disable inlining and optimizations,
	and add debugging information, so that stepping through all functions,
	(including inlined constructors and destructors) is possible. In
	addition, <code class="code">-fno-eliminate-unused-debug-types</code> can be
	used when additional debug information, such as nested class info,
	is desired.
	</p><p>
	Or, the debug format that the compiler and debugger use to
	communicate information about source constructs can be changed via
	<code class="code">-gdwarf-2</code> or <code class="code">-gstabs</code> flags: some debugging
	formats permit more expressive type and scope information to be
	shown in GDB. Expressiveness can be enhanced by flags like
	<code class="code">-g3</code>. The default debug information for a particular
	platform can be identified via the value set by the
	PREFERRED_DEBUGGING_TYPE macro in the GCC sources.
	</p><p>
	Many other options are available: please see <a class="link" href="http://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html#Debugging%20Options" target="_top">"Options
	for Debugging Your Program"</a> in Using the GNU Compiler
	Collection (GCC) for a complete list.
	</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.req"></a>Debug Versions of Library Binary Files</h3></div></div></div><p>
	If you would like debug symbols in libstdc++, there are two ways to
	build libstdc++ with debug flags. The first is to create a separate
	debug build by running make from the top-level of a tree
	freshly-configured with
	</p><pre class="programlisting">
	--enable-libstdcxx-debug
	</pre><p>and perhaps</p><pre class="programlisting">
	--enable-libstdcxx-debug-flags='...'
	</pre><p>
	Both the normal build and the debug build will persist, without
	having to specify <code class="code">CXXFLAGS</code>, and the debug library will
	be installed in a separate directory tree, in <code class="code">(prefix)/lib/debug</code>.
	For more information, look at the
	<a class="link" href="configure.html" title="Configure">configuration</a> section.
	</p><p>
	A second approach is to use the configuration flags
	</p><pre class="programlisting">
	make CXXFLAGS='-g3 -fno-inline -O0' all
	</pre><p>
	This quick and dirty approach is often sufficient for quick
	debugging tasks, when you cannot or don't want to recompile your
	application to use the <a class="link" href="debug_mode.html" title="Chapter 17. Debug Mode">debug mode</a>.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.memory"></a>Memory Leak Hunting</h3></div></div></div><p>
	There are various third party memory tracing and debug utilities
	that can be used to provide detailed memory allocation information
	about C++ code. An exhaustive list of tools is not going to be
	attempted, but includes <code class="code">mtrace</code>, <code class="code">valgrind</code>,
	<code class="code">mudflap</code>, and the non-free commercial product
	<code class="code">purify</code>. In addition, <code class="code">libcwd</code> has a
	replacement for the global new and delete operators that can track
	memory allocation and deallocation and provide useful memory
	statistics.
	</p><p>
	Regardless of the memory debugging tool being used, there is one
	thing of great importance to keep in mind when debugging C++ code
	that uses <code class="code">new</code> and <code class="code">delete</code>: there are
	different kinds of allocation schemes that can be used by <code class="code">
	std::allocator</code>. For implementation details, see the <a class="link" href="mt_allocator.html" title="Chapter 20. The mt_allocator">mt allocator</a> documentation and
	look specifically for <code class="code">GLIBCXX_FORCE_NEW</code>.
	</p><p>
	In a nutshell, the optional <code class="classname">mt_allocator</code>
	is a high-performance pool allocator, and can
	give the mistaken impression that in a suspect executable, memory is
	being leaked, when in reality the memory "leak" is a pool being used
	by the library's allocator and is reclaimed after program
	termination.
	</p><p>
	For valgrind, there are some specific items to keep in mind. First
	of all, use a version of valgrind that will work with current GNU
	C++ tools: the first that can do this is valgrind 1.0.4, but later
	versions should work at least as well. Second of all, use a
	completely unoptimized build to avoid confusing valgrind. Third, use
	GLIBCXX_FORCE_NEW to keep extraneous pool allocation noise from
	cluttering debug information.
	</p><p>
	Fourth, it may be necessary to force deallocation in other libraries
	as well, namely the "C" library. On linux, this can be accomplished
	with the appropriate use of the <code class="code">__cxa_atexit</code> or
	<code class="code">atexit</code> functions.
	</p><pre class="programlisting">
	#include <cstdlib>

	extern "C" void __libc_freeres(void);

	void do_something() { }

	int main()
	{
	atexit(__libc_freeres);
	do_something();
	return 0;
	}
	</pre><p>or, using <code class="code">__cxa_atexit</code>:</p><pre class="programlisting">
	extern "C" void __libc_freeres(void);
	extern "C" int __cxa_atexit(void (func) (void ), void arg, void d);

	void do_something() { }

	int main()
	{
	extern void* __dso_handle __attribute__ ((__weak__));
	__cxa_atexit((void () (void )) __libc_freeres, NULL,
	&__dso_handle ? __dso_handle : NULL);
	do_test();
	return 0;
	}
	</pre><p>
	Suggested valgrind flags, given the suggestions above about setting
	up the runtime environment, library, and test file, might be:
	</p><pre class="programlisting">
	valgrind -v --num-callers=20 --leak-check=yes --leak-resolution=high --show-reachable=yes a.out
	</pre></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.races"></a>Data Race Hunting</h3></div></div></div><p>
	All synchronization primitives used in the library internals need to be
	understood by race detectors so that they do not produce false reports.
	</p><p>
	Two annotation macros are used to explain low-level synchronization
	to race detectors:
	<code class="code">_GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE()</code> and
	<code class="code"> _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER()</code>.
	By default, these macros are defined empty -- anyone who wants
	to use a race detector needs to redefine them to call an
	appropriate API.
	Since these macros are empty by default when the library is built,
	redefining them will only affect inline functions and template
	instantiations which are compiled in user code. This allows annotation
	of templates such as <code class="code">shared_ptr</code>, but not code which is
	only instantiated in the library. Code which is only instantiated in
	the library needs to be recompiled with the annotation macros defined.
	That can be done by rebuilding the entire
	<code class="filename">libstdc++.so</code> file but a simpler
	alternative exists for ELF platforms such as GNU/Linux, because ELF
	symbol interposition allows symbols defined in the shared library to be
	overridden by symbols with the same name that appear earlier in the
	runtime search path. This means you only need to recompile the functions
	that are affected by the annotation macros, which can be done by
	recompiling individual files.
	Annotating <code class="code">std::string</code> and <code class="code">std::wstring</code>
	reference counting can be done by disabling extern templates (by defining
	<code class="code">_GLIBCXX_EXTERN_TEMPLATE=-1</code>) or by rebuilding the
	<code class="filename">src/string-inst.cc</code> file.
	Annotating the remaining atomic operations (at the time of writing these
	are in <code class="code">ios_base::Init::~Init</code>, <code class="code">locale::_Impl</code>,
	<code class="code">locale::facet</code> and <code class="code">thread::_M_start_thread</code>)
	requires rebuilding the relevant source files.
	</p><p>
	The approach described above is known to work with the following race
	detection tools:
	<a class="link" href="http://valgrind.org/docs/manual/drd-manual.html" target="_top">
	DRD</a>,
	<a class="link" href="http://valgrind.org/docs/manual/hg-manual.html" target="_top">
	Helgrind</a>, and
	<a class="link" href="http://code.google.com/p/data-race-test/" target="_top">
	ThreadSanitizer</a>.
	</p><p>
	With DRD, Helgrind and ThreadSanitizer you will need to define
	the macros like this:
	</p><pre class="programlisting">
	#define _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(A) ANNOTATE_HAPPENS_BEFORE(A)
	#define _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(A) ANNOTATE_HAPPENS_AFTER(A)
	</pre><p>
	Refer to the documentation of each particular tool for details.
	</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.gdb"></a>Using <span class="command"><strong>gdb</strong></span></h3></div></div></div><p>
	</p><p>
	Many options are available for GDB itself: please see <a class="link" href="http://sourceware.org/gdb/current/onlinedocs/gdb/" target="_top">
	"GDB features for C++" </a> in the GDB documentation. Also
	recommended: the other parts of this manual.
	</p><p>
	These settings can either be switched on in at the GDB command line,
	or put into a .gdbint file to establish default debugging
	characteristics, like so:
	</p><pre class="programlisting">
	set print pretty on
	set print object on
	set print static-members on
	set print vtbl on
	set print demangle on
	set demangle-style gnu-v3
	</pre><p>
	Starting with version 7.0, GDB includes support for writing
	pretty-printers in Python. Pretty printers for STL classes are
	distributed with GCC from version 4.5.0. The most recent version of
	these printers are always found in libstdc++ svn repository.
	To enable these printers, check-out the latest printers to a local
	directory:
	</p><pre class="programlisting">
	svn co svn://gcc.gnu.org/svn/gcc/trunk/libstdc++-v3/python
	</pre><p>
	Next, add the following section to your ~/.gdbinit The path must
	match the location where the Python module above was checked-out.
	So if checked out to: /home/maude/gdb_printers/, the path would be as
	written in the example below.
	</p><pre class="programlisting">
	python
	import sys
	sys.path.insert(0, '/home/maude/gdb_printers/python')
	from libstdcxx.v6.printers import register_libstdcxx_printers
	register_libstdcxx_printers (None)
	end
	</pre><p>
	The path should be the only element that needs to be adjusted in the
	example. Once loaded, STL classes that the printers support
	should print in a more human-readable format. To print the classes
	in the old style, use the /r (raw) switch in the print command
	(i.e., print /r foo). This will print the classes as if the Python
	pretty-printers were not loaded.
	</p><p>
	For additional information on STL support and GDB please visit:
	<a class="link" href="http://sourceware.org/gdb/wiki/STLSupport" target="_top"> "GDB Support
	for STL" </a> in the GDB wiki. Additionally, in-depth
	documentation and discussion of the pretty printing feature can be
	found in "Pretty Printing" node in the GDB manual. You can find
	on-line versions of the GDB user manual in GDB's homepage, at
	<a class="link" href="http://sourceware.org/gdb/" target="_top"> "GDB: The GNU Project
	Debugger" </a>.
	</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.exceptions"></a>Tracking uncaught exceptions</h3></div></div></div><p>
	The <a class="link" href="termination.html#support.termination.verbose" title="Verbose Terminate Handler">verbose
	termination handler</a> gives information about uncaught
	exceptions which are killing the program. It is described in the
	linked-to page.
	</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.debug_mode"></a>Debug Mode</h3></div></div></div><p> The <a class="link" href="debug_mode.html" title="Chapter 17. Debug Mode">Debug Mode</a>
	has compile and run-time checks for many containers.
	</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.compile_time_checks"></a>Compile Time Checking</h3></div></div></div><p> The <a class="link" href="ext_compile_checks.html" title="Chapter 16. Compile Time Checks">Compile-Time
	Checks</a> Extension has compile-time checks for many algorithms.
	</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug.profile_mode"></a>Profile-based Performance Analysis</h3></div></div></div><p> The <a class="link" href="profile_mode.html" title="Chapter 19. Profile Mode">Profile-based
	Performance Analysis</a> Extension has performance checks for many
	algorithms.
	</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="using_exceptions.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="using.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="std_contents.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Exceptions </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Part II.
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