| =encoding utf8 |
| |
| =head1 NAME |
| |
| perl5100delta - what is new for perl 5.10.0 |
| |
| =head1 DESCRIPTION |
| |
| This document describes the differences between the 5.8.8 release and |
| the 5.10.0 release. |
| |
| Many of the bug fixes in 5.10.0 were already seen in the 5.8.X maintenance |
| releases; they are not duplicated here and are documented in the set of |
| man pages named perl58[1-8]?delta. |
| |
| =head1 Core Enhancements |
| |
| =head2 The C<feature> pragma |
| |
| The C<feature> pragma is used to enable new syntax that would break Perl's |
| backwards-compatibility with older releases of the language. It's a lexical |
| pragma, like C<strict> or C<warnings>. |
| |
| Currently the following new features are available: C<switch> (adds a |
| switch statement), C<say> (adds a C<say> built-in function), and C<state> |
| (adds a C<state> keyword for declaring "static" variables). Those |
| features are described in their own sections of this document. |
| |
| The C<feature> pragma is also implicitly loaded when you require a minimal |
| perl version (with the C<use VERSION> construct) greater than, or equal |
| to, 5.9.5. See L<feature> for details. |
| |
| =head2 New B<-E> command-line switch |
| |
| B<-E> is equivalent to B<-e>, but it implicitly enables all |
| optional features (like C<use feature ":5.10">). |
| |
| =head2 Defined-or operator |
| |
| A new operator C<//> (defined-or) has been implemented. |
| The following expression: |
| |
| $a // $b |
| |
| is merely equivalent to |
| |
| defined $a ? $a : $b |
| |
| and the statement |
| |
| $c //= $d; |
| |
| can now be used instead of |
| |
| $c = $d unless defined $c; |
| |
| The C<//> operator has the same precedence and associativity as C<||>. |
| Special care has been taken to ensure that this operator Do What You Mean |
| while not breaking old code, but some edge cases involving the empty |
| regular expression may now parse differently. See L<perlop> for |
| details. |
| |
| =head2 Switch and Smart Match operator |
| |
| Perl 5 now has a switch statement. It's available when C<use feature |
| 'switch'> is in effect. This feature introduces three new keywords, |
| C<given>, C<when>, and C<default>: |
| |
| given ($foo) { |
| when (/^abc/) { $abc = 1; } |
| when (/^def/) { $def = 1; } |
| when (/^xyz/) { $xyz = 1; } |
| default { $nothing = 1; } |
| } |
| |
| A more complete description of how Perl matches the switch variable |
| against the C<when> conditions is given in L<perlsyn/"Switch statements">. |
| |
| This kind of match is called I<smart match>, and it's also possible to use |
| it outside of switch statements, via the new C<~~> operator. See |
| L<perlsyn/"Smart matching in detail">. |
| |
| This feature was contributed by Robin Houston. |
| |
| =head2 Regular expressions |
| |
| =over 4 |
| |
| =item Recursive Patterns |
| |
| It is now possible to write recursive patterns without using the C<(??{})> |
| construct. This new way is more efficient, and in many cases easier to |
| read. |
| |
| Each capturing parenthesis can now be treated as an independent pattern |
| that can be entered by using the C<(?PARNO)> syntax (C<PARNO> standing for |
| "parenthesis number"). For example, the following pattern will match |
| nested balanced angle brackets: |
| |
| / |
| ^ # start of line |
| ( # start capture buffer 1 |
| < # match an opening angle bracket |
| (?: # match one of: |
| (?> # don't backtrack over the inside of this group |
| [^<>]+ # one or more non angle brackets |
| ) # end non backtracking group |
| | # ... or ... |
| (?1) # recurse to bracket 1 and try it again |
| )* # 0 or more times. |
| > # match a closing angle bracket |
| ) # end capture buffer one |
| $ # end of line |
| /x |
| |
| PCRE users should note that Perl's recursive regex feature allows |
| backtracking into a recursed pattern, whereas in PCRE the recursion is |
| atomic or "possessive" in nature. As in the example above, you can |
| add (?>) to control this selectively. (Yves Orton) |
| |
| =item Named Capture Buffers |
| |
| It is now possible to name capturing parenthesis in a pattern and refer to |
| the captured contents by name. The naming syntax is C<< (?<NAME>....) >>. |
| It's possible to backreference to a named buffer with the C<< \k<NAME> >> |
| syntax. In code, the new magical hashes C<%+> and C<%-> can be used to |
| access the contents of the capture buffers. |
| |
| Thus, to replace all doubled chars with a single copy, one could write |
| |
| s/(?<letter>.)\k<letter>/$+{letter}/g |
| |
| Only buffers with defined contents will be "visible" in the C<%+> hash, so |
| it's possible to do something like |
| |
| foreach my $name (keys %+) { |
| print "content of buffer '$name' is $+{$name}\n"; |
| } |
| |
| The C<%-> hash is a bit more complete, since it will contain array refs |
| holding values from all capture buffers similarly named, if there should |
| be many of them. |
| |
| C<%+> and C<%-> are implemented as tied hashes through the new module |
| C<Tie::Hash::NamedCapture>. |
| |
| Users exposed to the .NET regex engine will find that the perl |
| implementation differs in that the numerical ordering of the buffers |
| is sequential, and not "unnamed first, then named". Thus in the pattern |
| |
| /(A)(?<B>B)(C)(?<D>D)/ |
| |
| $1 will be 'A', $2 will be 'B', $3 will be 'C' and $4 will be 'D' and not |
| $1 is 'A', $2 is 'C' and $3 is 'B' and $4 is 'D' that a .NET programmer |
| would expect. This is considered a feature. :-) (Yves Orton) |
| |
| =item Possessive Quantifiers |
| |
| Perl now supports the "possessive quantifier" syntax of the "atomic match" |
| pattern. Basically a possessive quantifier matches as much as it can and never |
| gives any back. Thus it can be used to control backtracking. The syntax is |
| similar to non-greedy matching, except instead of using a '?' as the modifier |
| the '+' is used. Thus C<?+>, C<*+>, C<++>, C<{min,max}+> are now legal |
| quantifiers. (Yves Orton) |
| |
| =item Backtracking control verbs |
| |
| The regex engine now supports a number of special-purpose backtrack |
| control verbs: (*THEN), (*PRUNE), (*MARK), (*SKIP), (*COMMIT), (*FAIL) |
| and (*ACCEPT). See L<perlre> for their descriptions. (Yves Orton) |
| |
| =item Relative backreferences |
| |
| A new syntax C<\g{N}> or C<\gN> where "N" is a decimal integer allows a |
| safer form of back-reference notation as well as allowing relative |
| backreferences. This should make it easier to generate and embed patterns |
| that contain backreferences. See L<perlre/"Capture buffers">. (Yves Orton) |
| |
| =item C<\K> escape |
| |
| The functionality of Jeff Pinyan's module Regexp::Keep has been added to |
| the core. In regular expressions you can now use the special escape C<\K> |
| as a way to do something like floating length positive lookbehind. It is |
| also useful in substitutions like: |
| |
| s/(foo)bar/$1/g |
| |
| that can now be converted to |
| |
| s/foo\Kbar//g |
| |
| which is much more efficient. (Yves Orton) |
| |
| =item Vertical and horizontal whitespace, and linebreak |
| |
| Regular expressions now recognize the C<\v> and C<\h> escapes that match |
| vertical and horizontal whitespace, respectively. C<\V> and C<\H> |
| logically match their complements. |
| |
| C<\R> matches a generic linebreak, that is, vertical whitespace, plus |
| the multi-character sequence C<"\x0D\x0A">. |
| |
| =back |
| |
| =head2 C<say()> |
| |
| say() is a new built-in, only available when C<use feature 'say'> is in |
| effect, that is similar to print(), but that implicitly appends a newline |
| to the printed string. See L<perlfunc/say>. (Robin Houston) |
| |
| =head2 Lexical C<$_> |
| |
| The default variable C<$_> can now be lexicalized, by declaring it like |
| any other lexical variable, with a simple |
| |
| my $_; |
| |
| The operations that default on C<$_> will use the lexically-scoped |
| version of C<$_> when it exists, instead of the global C<$_>. |
| |
| In a C<map> or a C<grep> block, if C<$_> was previously my'ed, then the |
| C<$_> inside the block is lexical as well (and scoped to the block). |
| |
| In a scope where C<$_> has been lexicalized, you can still have access to |
| the global version of C<$_> by using C<$::_>, or, more simply, by |
| overriding the lexical declaration with C<our $_>. (Rafael Garcia-Suarez) |
| |
| =head2 The C<_> prototype |
| |
| A new prototype character has been added. C<_> is equivalent to C<$> but |
| defaults to C<$_> if the corresponding argument isn't supplied (both C<$> |
| and C<_> denote a scalar). Due to the optional nature of the argument, |
| you can only use it at the end of a prototype, or before a semicolon. |
| |
| This has a small incompatible consequence: the prototype() function has |
| been adjusted to return C<_> for some built-ins in appropriate cases (for |
| example, C<prototype('CORE::rmdir')>). (Rafael Garcia-Suarez) |
| |
| =head2 UNITCHECK blocks |
| |
| C<UNITCHECK>, a new special code block has been introduced, in addition to |
| C<BEGIN>, C<CHECK>, C<INIT> and C<END>. |
| |
| C<CHECK> and C<INIT> blocks, while useful for some specialized purposes, |
| are always executed at the transition between the compilation and the |
| execution of the main program, and thus are useless whenever code is |
| loaded at runtime. On the other hand, C<UNITCHECK> blocks are executed |
| just after the unit which defined them has been compiled. See L<perlmod> |
| for more information. (Alex Gough) |
| |
| =head2 New Pragma, C<mro> |
| |
| A new pragma, C<mro> (for Method Resolution Order) has been added. It |
| permits to switch, on a per-class basis, the algorithm that perl uses to |
| find inherited methods in case of a multiple inheritance hierarchy. The |
| default MRO hasn't changed (DFS, for Depth First Search). Another MRO is |
| available: the C3 algorithm. See L<mro> for more information. |
| (Brandon Black) |
| |
| Note that, due to changes in the implementation of class hierarchy search, |
| code that used to undef the C<*ISA> glob will most probably break. Anyway, |
| undef'ing C<*ISA> had the side-effect of removing the magic on the @ISA |
| array and should not have been done in the first place. Also, the |
| cache C<*::ISA::CACHE::> no longer exists; to force reset the @ISA cache, |
| you now need to use the C<mro> API, or more simply to assign to @ISA |
| (e.g. with C<@ISA = @ISA>). |
| |
| =head2 readdir() may return a "short filename" on Windows |
| |
| The readdir() function may return a "short filename" when the long |
| filename contains characters outside the ANSI codepage. Similarly |
| Cwd::cwd() may return a short directory name, and glob() may return short |
| names as well. On the NTFS file system these short names can always be |
| represented in the ANSI codepage. This will not be true for all other file |
| system drivers; e.g. the FAT filesystem stores short filenames in the OEM |
| codepage, so some files on FAT volumes remain unaccessible through the |
| ANSI APIs. |
| |
| Similarly, $^X, @INC, and $ENV{PATH} are preprocessed at startup to make |
| sure all paths are valid in the ANSI codepage (if possible). |
| |
| The Win32::GetLongPathName() function now returns the UTF-8 encoded |
| correct long file name instead of using replacement characters to force |
| the name into the ANSI codepage. The new Win32::GetANSIPathName() |
| function can be used to turn a long pathname into a short one only if the |
| long one cannot be represented in the ANSI codepage. |
| |
| Many other functions in the C<Win32> module have been improved to accept |
| UTF-8 encoded arguments. Please see L<Win32> for details. |
| |
| =head2 readpipe() is now overridable |
| |
| The built-in function readpipe() is now overridable. Overriding it permits |
| also to override its operator counterpart, C<qx//> (a.k.a. C<``>). |
| Moreover, it now defaults to C<$_> if no argument is provided. (Rafael |
| Garcia-Suarez) |
| |
| =head2 Default argument for readline() |
| |
| readline() now defaults to C<*ARGV> if no argument is provided. (Rafael |
| Garcia-Suarez) |
| |
| =head2 state() variables |
| |
| A new class of variables has been introduced. State variables are similar |
| to C<my> variables, but are declared with the C<state> keyword in place of |
| C<my>. They're visible only in their lexical scope, but their value is |
| persistent: unlike C<my> variables, they're not undefined at scope entry, |
| but retain their previous value. (Rafael Garcia-Suarez, Nicholas Clark) |
| |
| To use state variables, one needs to enable them by using |
| |
| use feature 'state'; |
| |
| or by using the C<-E> command-line switch in one-liners. |
| See L<perlsub/"Persistent Private Variables">. |
| |
| =head2 Stacked filetest operators |
| |
| As a new form of syntactic sugar, it's now possible to stack up filetest |
| operators. You can now write C<-f -w -x $file> in a row to mean |
| C<-x $file && -w _ && -f _>. See L<perlfunc/-X>. |
| |
| =head2 UNIVERSAL::DOES() |
| |
| The C<UNIVERSAL> class has a new method, C<DOES()>. It has been added to |
| solve semantic problems with the C<isa()> method. C<isa()> checks for |
| inheritance, while C<DOES()> has been designed to be overridden when |
| module authors use other types of relations between classes (in addition |
| to inheritance). (chromatic) |
| |
| See L<< UNIVERSAL/"$obj->DOES( ROLE )" >>. |
| |
| =head2 Formats |
| |
| Formats were improved in several ways. A new field, C<^*>, can be used for |
| variable-width, one-line-at-a-time text. Null characters are now handled |
| correctly in picture lines. Using C<@#> and C<~~> together will now |
| produce a compile-time error, as those format fields are incompatible. |
| L<perlform> has been improved, and miscellaneous bugs fixed. |
| |
| =head2 Byte-order modifiers for pack() and unpack() |
| |
| There are two new byte-order modifiers, C<E<gt>> (big-endian) and C<E<lt>> |
| (little-endian), that can be appended to most pack() and unpack() template |
| characters and groups to force a certain byte-order for that type or group. |
| See L<perlfunc/pack> and L<perlpacktut> for details. |
| |
| =head2 C<no VERSION> |
| |
| You can now use C<no> followed by a version number to specify that you |
| want to use a version of perl older than the specified one. |
| |
| =head2 C<chdir>, C<chmod> and C<chown> on filehandles |
| |
| C<chdir>, C<chmod> and C<chown> can now work on filehandles as well as |
| filenames, if the system supports respectively C<fchdir>, C<fchmod> and |
| C<fchown>, thanks to a patch provided by Gisle Aas. |
| |
| =head2 OS groups |
| |
| C<$(> and C<$)> now return groups in the order where the OS returns them, |
| thanks to Gisle Aas. This wasn't previously the case. |
| |
| =head2 Recursive sort subs |
| |
| You can now use recursive subroutines with sort(), thanks to Robin Houston. |
| |
| =head2 Exceptions in constant folding |
| |
| The constant folding routine is now wrapped in an exception handler, and |
| if folding throws an exception (such as attempting to evaluate 0/0), perl |
| now retains the current optree, rather than aborting the whole program. |
| Without this change, programs would not compile if they had expressions that |
| happened to generate exceptions, even though those expressions were in code |
| that could never be reached at runtime. (Nicholas Clark, Dave Mitchell) |
| |
| =head2 Source filters in @INC |
| |
| It's possible to enhance the mechanism of subroutine hooks in @INC by |
| adding a source filter on top of the filehandle opened and returned by the |
| hook. This feature was planned a long time ago, but wasn't quite working |
| until now. See L<perlfunc/require> for details. (Nicholas Clark) |
| |
| =head2 New internal variables |
| |
| =over 4 |
| |
| =item C<${^RE_DEBUG_FLAGS}> |
| |
| This variable controls what debug flags are in effect for the regular |
| expression engine when running under C<use re "debug">. See L<re> for |
| details. |
| |
| =item C<${^CHILD_ERROR_NATIVE}> |
| |
| This variable gives the native status returned by the last pipe close, |
| backtick command, successful call to wait() or waitpid(), or from the |
| system() operator. See L<perlvar> for details. (Contributed by Gisle Aas.) |
| |
| =item C<${^RE_TRIE_MAXBUF}> |
| |
| See L</"Trie optimisation of literal string alternations">. |
| |
| =item C<${^WIN32_SLOPPY_STAT}> |
| |
| See L</"Sloppy stat on Windows">. |
| |
| =back |
| |
| =head2 Miscellaneous |
| |
| C<unpack()> now defaults to unpacking the C<$_> variable. |
| |
| C<mkdir()> without arguments now defaults to C<$_>. |
| |
| The internal dump output has been improved, so that non-printable characters |
| such as newline and backspace are output in C<\x> notation, rather than |
| octal. |
| |
| The B<-C> option can no longer be used on the C<#!> line. It wasn't |
| working there anyway, since the standard streams are already set up |
| at this point in the execution of the perl interpreter. You can use |
| binmode() instead to get the desired behaviour. |
| |
| =head2 UCD 5.0.0 |
| |
| The copy of the Unicode Character Database included in Perl 5 has |
| been updated to version 5.0.0. |
| |
| =head2 MAD |
| |
| MAD, which stands for I<Miscellaneous Attribute Decoration>, is a |
| still-in-development work leading to a Perl 5 to Perl 6 converter. To |
| enable it, it's necessary to pass the argument C<-Dmad> to Configure. The |
| obtained perl isn't binary compatible with a regular perl 5.10, and has |
| space and speed penalties; moreover not all regression tests still pass |
| with it. (Larry Wall, Nicholas Clark) |
| |
| =head2 kill() on Windows |
| |
| On Windows platforms, C<kill(-9, $pid)> now kills a process tree. |
| (On Unix, this delivers the signal to all processes in the same process |
| group.) |
| |
| =head1 Incompatible Changes |
| |
| =head2 Packing and UTF-8 strings |
| |
| The semantics of pack() and unpack() regarding UTF-8-encoded data has been |
| changed. Processing is now by default character per character instead of |
| byte per byte on the underlying encoding. Notably, code that used things |
| like C<pack("a*", $string)> to see through the encoding of string will now |
| simply get back the original $string. Packed strings can also get upgraded |
| during processing when you store upgraded characters. You can get the old |
| behaviour by using C<use bytes>. |
| |
| To be consistent with pack(), the C<C0> in unpack() templates indicates |
| that the data is to be processed in character mode, i.e. character by |
| character; on the contrary, C<U0> in unpack() indicates UTF-8 mode, where |
| the packed string is processed in its UTF-8-encoded Unicode form on a byte |
| by byte basis. This is reversed with regard to perl 5.8.X, but now consistent |
| between pack() and unpack(). |
| |
| Moreover, C<C0> and C<U0> can also be used in pack() templates to specify |
| respectively character and byte modes. |
| |
| C<C0> and C<U0> in the middle of a pack or unpack format now switch to the |
| specified encoding mode, honoring parens grouping. Previously, parens were |
| ignored. |
| |
| Also, there is a new pack() character format, C<W>, which is intended to |
| replace the old C<C>. C<C> is kept for unsigned chars coded as bytes in |
| the strings internal representation. C<W> represents unsigned (logical) |
| character values, which can be greater than 255. It is therefore more |
| robust when dealing with potentially UTF-8-encoded data (as C<C> will wrap |
| values outside the range 0..255, and not respect the string encoding). |
| |
| In practice, that means that pack formats are now encoding-neutral, except |
| C<C>. |
| |
| For consistency, C<A> in unpack() format now trims all Unicode whitespace |
| from the end of the string. Before perl 5.9.2, it used to strip only the |
| classical ASCII space characters. |
| |
| =head2 Byte/character count feature in unpack() |
| |
| A new unpack() template character, C<".">, returns the number of bytes or |
| characters (depending on the selected encoding mode, see above) read so far. |
| |
| =head2 The C<$*> and C<$#> variables have been removed |
| |
| C<$*>, which was deprecated in favor of the C</s> and C</m> regexp |
| modifiers, has been removed. |
| |
| The deprecated C<$#> variable (output format for numbers) has been |
| removed. |
| |
| Two new severe warnings, C<$#/$* is no longer supported>, have been added. |
| |
| =head2 substr() lvalues are no longer fixed-length |
| |
| The lvalues returned by the three argument form of substr() used to be a |
| "fixed length window" on the original string. In some cases this could |
| cause surprising action at distance or other undefined behaviour. Now the |
| length of the window adjusts itself to the length of the string assigned to |
| it. |
| |
| =head2 Parsing of C<-f _> |
| |
| The identifier C<_> is now forced to be a bareword after a filetest |
| operator. This solves a number of misparsing issues when a global C<_> |
| subroutine is defined. |
| |
| =head2 C<:unique> |
| |
| The C<:unique> attribute has been made a no-op, since its current |
| implementation was fundamentally flawed and not threadsafe. |
| |
| =head2 Effect of pragmas in eval |
| |
| The compile-time value of the C<%^H> hint variable can now propagate into |
| eval("")uated code. This makes it more useful to implement lexical |
| pragmas. |
| |
| As a side-effect of this, the overloaded-ness of constants now propagates |
| into eval(""). |
| |
| =head2 chdir FOO |
| |
| A bareword argument to chdir() is now recognized as a file handle. |
| Earlier releases interpreted the bareword as a directory name. |
| (Gisle Aas) |
| |
| =head2 Handling of .pmc files |
| |
| An old feature of perl was that before C<require> or C<use> look for a |
| file with a F<.pm> extension, they will first look for a similar filename |
| with a F<.pmc> extension. If this file is found, it will be loaded in |
| place of any potentially existing file ending in a F<.pm> extension. |
| |
| Previously, F<.pmc> files were loaded only if more recent than the |
| matching F<.pm> file. Starting with 5.9.4, they'll be always loaded if |
| they exist. |
| |
| =head2 $^V is now a C<version> object instead of a v-string |
| |
| $^V can still be used with the C<%vd> format in printf, but any |
| character-level operations will now access the string representation |
| of the C<version> object and not the ordinals of a v-string. |
| Expressions like C<< substr($^V, 0, 2) >> or C<< split //, $^V >> |
| no longer work and must be rewritten. |
| |
| =head2 @- and @+ in patterns |
| |
| The special arrays C<@-> and C<@+> are no longer interpolated in regular |
| expressions. (Sadahiro Tomoyuki) |
| |
| =head2 $AUTOLOAD can now be tainted |
| |
| If you call a subroutine by a tainted name, and if it defers to an |
| AUTOLOAD function, then $AUTOLOAD will be (correctly) tainted. |
| (Rick Delaney) |
| |
| =head2 Tainting and printf |
| |
| When perl is run under taint mode, C<printf()> and C<sprintf()> will now |
| reject any tainted format argument. (Rafael Garcia-Suarez) |
| |
| =head2 undef and signal handlers |
| |
| Undefining or deleting a signal handler via C<undef $SIG{FOO}> is now |
| equivalent to setting it to C<'DEFAULT'>. (Rafael Garcia-Suarez) |
| |
| =head2 strictures and dereferencing in defined() |
| |
| C<use strict 'refs'> was ignoring taking a hard reference in an argument |
| to defined(), as in : |
| |
| use strict 'refs'; |
| my $x = 'foo'; |
| if (defined $$x) {...} |
| |
| This now correctly produces the run-time error C<Can't use string as a |
| SCALAR ref while "strict refs" in use>. |
| |
| C<defined @$foo> and C<defined %$bar> are now also subject to C<strict |
| 'refs'> (that is, C<$foo> and C<$bar> shall be proper references there.) |
| (C<defined(@foo)> and C<defined(%bar)> are discouraged constructs anyway.) |
| (Nicholas Clark) |
| |
| =head2 C<(?p{})> has been removed |
| |
| The regular expression construct C<(?p{})>, which was deprecated in perl |
| 5.8, has been removed. Use C<(??{})> instead. (Rafael Garcia-Suarez) |
| |
| =head2 Pseudo-hashes have been removed |
| |
| Support for pseudo-hashes has been removed from Perl 5.9. (The C<fields> |
| pragma remains here, but uses an alternate implementation.) |
| |
| =head2 Removal of the bytecode compiler and of perlcc |
| |
| C<perlcc>, the byteloader and the supporting modules (B::C, B::CC, |
| B::Bytecode, etc.) are no longer distributed with the perl sources. Those |
| experimental tools have never worked reliably, and, due to the lack of |
| volunteers to keep them in line with the perl interpreter developments, it |
| was decided to remove them instead of shipping a broken version of those. |
| The last version of those modules can be found with perl 5.9.4. |
| |
| However the B compiler framework stays supported in the perl core, as with |
| the more useful modules it has permitted (among others, B::Deparse and |
| B::Concise). |
| |
| =head2 Removal of the JPL |
| |
| The JPL (Java-Perl Lingo) has been removed from the perl sources tarball. |
| |
| =head2 Recursive inheritance detected earlier |
| |
| Perl will now immediately throw an exception if you modify any package's |
| C<@ISA> in such a way that it would cause recursive inheritance. |
| |
| Previously, the exception would not occur until Perl attempted to make |
| use of the recursive inheritance while resolving a method or doing a |
| C<$foo-E<gt>isa($bar)> lookup. |
| |
| =head2 warnings::enabled and warnings::warnif changed to favor users of modules |
| |
| The behaviour in 5.10.x favors the person using the module; |
| The behaviour in 5.8.x favors the module writer; |
| |
| Assume the following code: |
| |
| main calls Foo::Bar::baz() |
| Foo::Bar inherits from Foo::Base |
| Foo::Bar::baz() calls Foo::Base::_bazbaz() |
| Foo::Base::_bazbaz() calls: warnings::warnif('substr', 'some warning |
| message'); |
| |
| On 5.8.x, the code warns when Foo::Bar contains C<use warnings;> |
| It does not matter if Foo::Base or main have warnings enabled |
| to disable the warning one has to modify Foo::Bar. |
| |
| On 5.10.0 and newer, the code warns when main contains C<use warnings;> |
| It does not matter if Foo::Base or Foo::Bar have warnings enabled |
| to disable the warning one has to modify main. |
| |
| =head1 Modules and Pragmata |
| |
| =head2 Upgrading individual core modules |
| |
| Even more core modules are now also available separately through the |
| CPAN. If you wish to update one of these modules, you don't need to |
| wait for a new perl release. From within the cpan shell, running the |
| 'r' command will report on modules with upgrades available. See |
| C<perldoc CPAN> for more information. |
| |
| =head2 Pragmata Changes |
| |
| =over 4 |
| |
| =item C<feature> |
| |
| The new pragma C<feature> is used to enable new features that might break |
| old code. See L</"The C<feature> pragma"> above. |
| |
| =item C<mro> |
| |
| This new pragma enables to change the algorithm used to resolve inherited |
| methods. See L</"New Pragma, C<mro>"> above. |
| |
| =item Scoping of the C<sort> pragma |
| |
| The C<sort> pragma is now lexically scoped. Its effect used to be global. |
| |
| =item Scoping of C<bignum>, C<bigint>, C<bigrat> |
| |
| The three numeric pragmas C<bignum>, C<bigint> and C<bigrat> are now |
| lexically scoped. (Tels) |
| |
| =item C<base> |
| |
| The C<base> pragma now warns if a class tries to inherit from itself. |
| (Curtis "Ovid" Poe) |
| |
| =item C<strict> and C<warnings> |
| |
| C<strict> and C<warnings> will now complain loudly if they are loaded via |
| incorrect casing (as in C<use Strict;>). (Johan Vromans) |
| |
| =item C<version> |
| |
| The C<version> module provides support for version objects. |
| |
| =item C<warnings> |
| |
| The C<warnings> pragma doesn't load C<Carp> anymore. That means that code |
| that used C<Carp> routines without having loaded it at compile time might |
| need to be adjusted; typically, the following (faulty) code won't work |
| anymore, and will require parentheses to be added after the function name: |
| |
| use warnings; |
| require Carp; |
| Carp::confess 'argh'; |
| |
| =item C<less> |
| |
| C<less> now does something useful (or at least it tries to). In fact, it |
| has been turned into a lexical pragma. So, in your modules, you can now |
| test whether your users have requested to use less CPU, or less memory, |
| less magic, or maybe even less fat. See L<less> for more. (Joshua ben |
| Jore) |
| |
| =back |
| |
| =head2 New modules |
| |
| =over 4 |
| |
| =item * |
| |
| C<encoding::warnings>, by Audrey Tang, is a module to emit warnings |
| whenever an ASCII character string containing high-bit bytes is implicitly |
| converted into UTF-8. It's a lexical pragma since Perl 5.9.4; on older |
| perls, its effect is global. |
| |
| =item * |
| |
| C<Module::CoreList>, by Richard Clamp, is a small handy module that tells |
| you what versions of core modules ship with any versions of Perl 5. It |
| comes with a command-line frontend, C<corelist>. |
| |
| =item * |
| |
| C<Math::BigInt::FastCalc> is an XS-enabled, and thus faster, version of |
| C<Math::BigInt::Calc>. |
| |
| =item * |
| |
| C<Compress::Zlib> is an interface to the zlib compression library. It |
| comes with a bundled version of zlib, so having a working zlib is not a |
| prerequisite to install it. It's used by C<Archive::Tar> (see below). |
| |
| =item * |
| |
| C<IO::Zlib> is an C<IO::>-style interface to C<Compress::Zlib>. |
| |
| =item * |
| |
| C<Archive::Tar> is a module to manipulate C<tar> archives. |
| |
| =item * |
| |
| C<Digest::SHA> is a module used to calculate many types of SHA digests, |
| has been included for SHA support in the CPAN module. |
| |
| =item * |
| |
| C<ExtUtils::CBuilder> and C<ExtUtils::ParseXS> have been added. |
| |
| =item * |
| |
| C<Hash::Util::FieldHash>, by Anno Siegel, has been added. This module |
| provides support for I<field hashes>: hashes that maintain an association |
| of a reference with a value, in a thread-safe garbage-collected way. |
| Such hashes are useful to implement inside-out objects. |
| |
| =item * |
| |
| C<Module::Build>, by Ken Williams, has been added. It's an alternative to |
| C<ExtUtils::MakeMaker> to build and install perl modules. |
| |
| =item * |
| |
| C<Module::Load>, by Jos Boumans, has been added. It provides a single |
| interface to load Perl modules and F<.pl> files. |
| |
| =item * |
| |
| C<Module::Loaded>, by Jos Boumans, has been added. It's used to mark |
| modules as loaded or unloaded. |
| |
| =item * |
| |
| C<Package::Constants>, by Jos Boumans, has been added. It's a simple |
| helper to list all constants declared in a given package. |
| |
| =item * |
| |
| C<Win32API::File>, by Tye McQueen, has been added (for Windows builds). |
| This module provides low-level access to Win32 system API calls for |
| files/dirs. |
| |
| =item * |
| |
| C<Locale::Maketext::Simple>, needed by CPANPLUS, is a simple wrapper around |
| C<Locale::Maketext::Lexicon>. Note that C<Locale::Maketext::Lexicon> isn't |
| included in the perl core; the behaviour of C<Locale::Maketext::Simple> |
| gracefully degrades when the later isn't present. |
| |
| =item * |
| |
| C<Params::Check> implements a generic input parsing/checking mechanism. It |
| is used by CPANPLUS. |
| |
| =item * |
| |
| C<Term::UI> simplifies the task to ask questions at a terminal prompt. |
| |
| =item * |
| |
| C<Object::Accessor> provides an interface to create per-object accessors. |
| |
| =item * |
| |
| C<Module::Pluggable> is a simple framework to create modules that accept |
| pluggable sub-modules. |
| |
| =item * |
| |
| C<Module::Load::Conditional> provides simple ways to query and possibly |
| load installed modules. |
| |
| =item * |
| |
| C<Time::Piece> provides an object oriented interface to time functions, |
| overriding the built-ins localtime() and gmtime(). |
| |
| =item * |
| |
| C<IPC::Cmd> helps to find and run external commands, possibly |
| interactively. |
| |
| =item * |
| |
| C<File::Fetch> provide a simple generic file fetching mechanism. |
| |
| =item * |
| |
| C<Log::Message> and C<Log::Message::Simple> are used by the log facility |
| of C<CPANPLUS>. |
| |
| =item * |
| |
| C<Archive::Extract> is a generic archive extraction mechanism |
| for F<.tar> (plain, gzipped or bzipped) or F<.zip> files. |
| |
| =item * |
| |
| C<CPANPLUS> provides an API and a command-line tool to access the CPAN |
| mirrors. |
| |
| =item * |
| |
| C<Pod::Escapes> provides utilities that are useful in decoding Pod |
| EE<lt>...E<gt> sequences. |
| |
| =item * |
| |
| C<Pod::Simple> is now the backend for several of the Pod-related modules |
| included with Perl. |
| |
| =back |
| |
| =head2 Selected Changes to Core Modules |
| |
| =over 4 |
| |
| =item C<Attribute::Handlers> |
| |
| C<Attribute::Handlers> can now report the caller's file and line number. |
| (David Feldman) |
| |
| All interpreted attributes are now passed as array references. (Damian |
| Conway) |
| |
| =item C<B::Lint> |
| |
| C<B::Lint> is now based on C<Module::Pluggable>, and so can be extended |
| with plugins. (Joshua ben Jore) |
| |
| =item C<B> |
| |
| It's now possible to access the lexical pragma hints (C<%^H>) by using the |
| method B::COP::hints_hash(). It returns a C<B::RHE> object, which in turn |
| can be used to get a hash reference via the method B::RHE::HASH(). (Joshua |
| ben Jore) |
| |
| =item C<Thread> |
| |
| As the old 5005thread threading model has been removed, in favor of the |
| ithreads scheme, the C<Thread> module is now a compatibility wrapper, to |
| be used in old code only. It has been removed from the default list of |
| dynamic extensions. |
| |
| =back |
| |
| =head1 Utility Changes |
| |
| =over 4 |
| |
| =item perl -d |
| |
| The Perl debugger can now save all debugger commands for sourcing later; |
| notably, it can now emulate stepping backwards, by restarting and |
| rerunning all bar the last command from a saved command history. |
| |
| It can also display the parent inheritance tree of a given class, with the |
| C<i> command. |
| |
| =item ptar |
| |
| C<ptar> is a pure perl implementation of C<tar> that comes with |
| C<Archive::Tar>. |
| |
| =item ptardiff |
| |
| C<ptardiff> is a small utility used to generate a diff between the contents |
| of a tar archive and a directory tree. Like C<ptar>, it comes with |
| C<Archive::Tar>. |
| |
| =item shasum |
| |
| C<shasum> is a command-line utility, used to print or to check SHA |
| digests. It comes with the new C<Digest::SHA> module. |
| |
| =item corelist |
| |
| The C<corelist> utility is now installed with perl (see L</"New modules"> |
| above). |
| |
| =item h2ph and h2xs |
| |
| C<h2ph> and C<h2xs> have been made more robust with regard to |
| "modern" C code. |
| |
| C<h2xs> implements a new option C<--use-xsloader> to force use of |
| C<XSLoader> even in backwards compatible modules. |
| |
| The handling of authors' names that had apostrophes has been fixed. |
| |
| Any enums with negative values are now skipped. |
| |
| =item perlivp |
| |
| C<perlivp> no longer checks for F<*.ph> files by default. Use the new C<-a> |
| option to run I<all> tests. |
| |
| =item find2perl |
| |
| C<find2perl> now assumes C<-print> as a default action. Previously, it |
| needed to be specified explicitly. |
| |
| Several bugs have been fixed in C<find2perl>, regarding C<-exec> and |
| C<-eval>. Also the options C<-path>, C<-ipath> and C<-iname> have been |
| added. |
| |
| =item config_data |
| |
| C<config_data> is a new utility that comes with C<Module::Build>. It |
| provides a command-line interface to the configuration of Perl modules |
| that use Module::Build's framework of configurability (that is, |
| C<*::ConfigData> modules that contain local configuration information for |
| their parent modules.) |
| |
| =item cpanp |
| |
| C<cpanp>, the CPANPLUS shell, has been added. (C<cpanp-run-perl>, a |
| helper for CPANPLUS operation, has been added too, but isn't intended for |
| direct use). |
| |
| =item cpan2dist |
| |
| C<cpan2dist> is a new utility that comes with CPANPLUS. It's a tool to |
| create distributions (or packages) from CPAN modules. |
| |
| =item pod2html |
| |
| The output of C<pod2html> has been enhanced to be more customizable via |
| CSS. Some formatting problems were also corrected. (Jari Aalto) |
| |
| =back |
| |
| =head1 New Documentation |
| |
| The L<perlpragma> manpage documents how to write one's own lexical |
| pragmas in pure Perl (something that is possible starting with 5.9.4). |
| |
| The new L<perlglossary> manpage is a glossary of terms used in the Perl |
| documentation, technical and otherwise, kindly provided by O'Reilly Media, |
| Inc. |
| |
| The L<perlreguts> manpage, courtesy of Yves Orton, describes internals of the |
| Perl regular expression engine. |
| |
| The L<perlreapi> manpage describes the interface to the perl interpreter |
| used to write pluggable regular expression engines (by Ævar Arnfjörð |
| Bjarmason). |
| |
| The L<perlunitut> manpage is an tutorial for programming with Unicode and |
| string encodings in Perl, courtesy of Juerd Waalboer. |
| |
| A new manual page, L<perlunifaq> (the Perl Unicode FAQ), has been added |
| (Juerd Waalboer). |
| |
| The L<perlcommunity> manpage gives a description of the Perl community |
| on the Internet and in real life. (Edgar "Trizor" Bering) |
| |
| The L<CORE> manual page documents the C<CORE::> namespace. (Tels) |
| |
| The long-existing feature of C</(?{...})/> regexps setting C<$_> and pos() |
| is now documented. |
| |
| =head1 Performance Enhancements |
| |
| =head2 In-place sorting |
| |
| Sorting arrays in place (C<@a = sort @a>) is now optimized to avoid |
| making a temporary copy of the array. |
| |
| Likewise, C<reverse sort ...> is now optimized to sort in reverse, |
| avoiding the generation of a temporary intermediate list. |
| |
| =head2 Lexical array access |
| |
| Access to elements of lexical arrays via a numeric constant between 0 and |
| 255 is now faster. (This used to be only the case for global arrays.) |
| |
| =head2 XS-assisted SWASHGET |
| |
| Some pure-perl code that perl was using to retrieve Unicode properties and |
| transliteration mappings has been reimplemented in XS. |
| |
| =head2 Constant subroutines |
| |
| The interpreter internals now support a far more memory efficient form of |
| inlineable constants. Storing a reference to a constant value in a symbol |
| table is equivalent to a full typeglob referencing a constant subroutine, |
| but using about 400 bytes less memory. This proxy constant subroutine is |
| automatically upgraded to a real typeglob with subroutine if necessary. |
| The approach taken is analogous to the existing space optimisation for |
| subroutine stub declarations, which are stored as plain scalars in place |
| of the full typeglob. |
| |
| Several of the core modules have been converted to use this feature for |
| their system dependent constants - as a result C<use POSIX;> now takes about |
| 200K less memory. |
| |
| =head2 C<PERL_DONT_CREATE_GVSV> |
| |
| The new compilation flag C<PERL_DONT_CREATE_GVSV>, introduced as an option |
| in perl 5.8.8, is turned on by default in perl 5.9.3. It prevents perl |
| from creating an empty scalar with every new typeglob. See L<perl589delta> |
| for details. |
| |
| =head2 Weak references are cheaper |
| |
| Weak reference creation is now I<O(1)> rather than I<O(n)>, courtesy of |
| Nicholas Clark. Weak reference deletion remains I<O(n)>, but if deletion only |
| happens at program exit, it may be skipped completely. |
| |
| =head2 sort() enhancements |
| |
| Salvador Fandiño provided improvements to reduce the memory usage of C<sort> |
| and to speed up some cases. |
| |
| =head2 Memory optimisations |
| |
| Several internal data structures (typeglobs, GVs, CVs, formats) have been |
| restructured to use less memory. (Nicholas Clark) |
| |
| =head2 UTF-8 cache optimisation |
| |
| The UTF-8 caching code is now more efficient, and used more often. |
| (Nicholas Clark) |
| |
| =head2 Sloppy stat on Windows |
| |
| On Windows, perl's stat() function normally opens the file to determine |
| the link count and update attributes that may have been changed through |
| hard links. Setting ${^WIN32_SLOPPY_STAT} to a true value speeds up |
| stat() by not performing this operation. (Jan Dubois) |
| |
| =head2 Regular expressions optimisations |
| |
| =over 4 |
| |
| =item Engine de-recursivised |
| |
| The regular expression engine is no longer recursive, meaning that |
| patterns that used to overflow the stack will either die with useful |
| explanations, or run to completion, which, since they were able to blow |
| the stack before, will likely take a very long time to happen. If you were |
| experiencing the occasional stack overflow (or segfault) and upgrade to |
| discover that now perl apparently hangs instead, look for a degenerate |
| regex. (Dave Mitchell) |
| |
| =item Single char char-classes treated as literals |
| |
| Classes of a single character are now treated the same as if the character |
| had been used as a literal, meaning that code that uses char-classes as an |
| escaping mechanism will see a speedup. (Yves Orton) |
| |
| =item Trie optimisation of literal string alternations |
| |
| Alternations, where possible, are optimised into more efficient matching |
| structures. String literal alternations are merged into a trie and are |
| matched simultaneously. This means that instead of O(N) time for matching |
| N alternations at a given point, the new code performs in O(1) time. |
| A new special variable, ${^RE_TRIE_MAXBUF}, has been added to fine-tune |
| this optimization. (Yves Orton) |
| |
| B<Note:> Much code exists that works around perl's historic poor |
| performance on alternations. Often the tricks used to do so will disable |
| the new optimisations. Hopefully the utility modules used for this purpose |
| will be educated about these new optimisations. |
| |
| =item Aho-Corasick start-point optimisation |
| |
| When a pattern starts with a trie-able alternation and there aren't |
| better optimisations available, the regex engine will use Aho-Corasick |
| matching to find the start point. (Yves Orton) |
| |
| =back |
| |
| =head1 Installation and Configuration Improvements |
| |
| =head2 Configuration improvements |
| |
| =over 4 |
| |
| =item C<-Dusesitecustomize> |
| |
| Run-time customization of @INC can be enabled by passing the |
| C<-Dusesitecustomize> flag to Configure. When enabled, this will make perl |
| run F<$sitelibexp/sitecustomize.pl> before anything else. This script can |
| then be set up to add additional entries to @INC. |
| |
| =item Relocatable installations |
| |
| There is now Configure support for creating a relocatable perl tree. If |
| you Configure with C<-Duserelocatableinc>, then the paths in @INC (and |
| everything else in %Config) can be optionally located via the path of the |
| perl executable. |
| |
| That means that, if the string C<".../"> is found at the start of any |
| path, it's substituted with the directory of $^X. So, the relocation can |
| be configured on a per-directory basis, although the default with |
| C<-Duserelocatableinc> is that everything is relocated. The initial |
| install is done to the original configured prefix. |
| |
| =item strlcat() and strlcpy() |
| |
| The configuration process now detects whether strlcat() and strlcpy() are |
| available. When they are not available, perl's own version is used (from |
| Russ Allbery's public domain implementation). Various places in the perl |
| interpreter now use them. (Steve Peters) |
| |
| =item C<d_pseudofork> and C<d_printf_format_null> |
| |
| A new configuration variable, available as C<$Config{d_pseudofork}> in |
| the L<Config> module, has been added, to distinguish real fork() support |
| from fake pseudofork used on Windows platforms. |
| |
| A new configuration variable, C<d_printf_format_null>, has been added, |
| to see if printf-like formats are allowed to be NULL. |
| |
| =item Configure help |
| |
| C<Configure -h> has been extended with the most commonly used options. |
| |
| =back |
| |
| =head2 Compilation improvements |
| |
| =over 4 |
| |
| =item Parallel build |
| |
| Parallel makes should work properly now, although there may still be problems |
| if C<make test> is instructed to run in parallel. |
| |
| =item Borland's compilers support |
| |
| Building with Borland's compilers on Win32 should work more smoothly. In |
| particular Steve Hay has worked to side step many warnings emitted by their |
| compilers and at least one C compiler internal error. |
| |
| =item Static build on Windows |
| |
| Perl extensions on Windows now can be statically built into the Perl DLL. |
| |
| Also, it's now possible to build a C<perl-static.exe> that doesn't depend |
| on the Perl DLL on Win32. See the Win32 makefiles for details. |
| (Vadim Konovalov) |
| |
| =item ppport.h files |
| |
| All F<ppport.h> files in the XS modules bundled with perl are now |
| autogenerated at build time. (Marcus Holland-Moritz) |
| |
| =item C++ compatibility |
| |
| Efforts have been made to make perl and the core XS modules compilable |
| with various C++ compilers (although the situation is not perfect with |
| some of the compilers on some of the platforms tested.) |
| |
| =item Support for Microsoft 64-bit compiler |
| |
| Support for building perl with Microsoft's 64-bit compiler has been |
| improved. (ActiveState) |
| |
| =item Visual C++ |
| |
| Perl can now be compiled with Microsoft Visual C++ 2005 (and 2008 Beta 2). |
| |
| =item Win32 builds |
| |
| All win32 builds (MS-Win, WinCE) have been merged and cleaned up. |
| |
| =back |
| |
| =head2 Installation improvements |
| |
| =over 4 |
| |
| =item Module auxiliary files |
| |
| README files and changelogs for CPAN modules bundled with perl are no |
| longer installed. |
| |
| =back |
| |
| =head2 New Or Improved Platforms |
| |
| Perl has been reported to work on Symbian OS. See L<perlsymbian> for more |
| information. |
| |
| Many improvements have been made towards making Perl work correctly on |
| z/OS. |
| |
| Perl has been reported to work on DragonFlyBSD and MidnightBSD. |
| |
| Perl has also been reported to work on NexentaOS |
| ( http://www.gnusolaris.org/ ). |
| |
| The VMS port has been improved. See L<perlvms>. |
| |
| Support for Cray XT4 Catamount/Qk has been added. See |
| F<hints/catamount.sh> in the source code distribution for more |
| information. |
| |
| Vendor patches have been merged for RedHat and Gentoo. |
| |
| DynaLoader::dl_unload_file() now works on Windows. |
| |
| =head1 Selected Bug Fixes |
| |
| =over 4 |
| |
| =item strictures in regexp-eval blocks |
| |
| C<strict> wasn't in effect in regexp-eval blocks (C</(?{...})/>). |
| |
| =item Calling CORE::require() |
| |
| CORE::require() and CORE::do() were always parsed as require() and do() |
| when they were overridden. This is now fixed. |
| |
| =item Subscripts of slices |
| |
| You can now use a non-arrowed form for chained subscripts after a list |
| slice, like in: |
| |
| ({foo => "bar"})[0]{foo} |
| |
| This used to be a syntax error; a C<< -> >> was required. |
| |
| =item C<no warnings 'category'> works correctly with -w |
| |
| Previously when running with warnings enabled globally via C<-w>, selective |
| disabling of specific warning categories would actually turn off all warnings. |
| This is now fixed; now C<no warnings 'io';> will only turn off warnings in the |
| C<io> class. Previously it would erroneously turn off all warnings. |
| |
| =item threads improvements |
| |
| Several memory leaks in ithreads were closed. Also, ithreads were made |
| less memory-intensive. |
| |
| C<threads> is now a dual-life module, also available on CPAN. It has been |
| expanded in many ways. A kill() method is available for thread signalling. |
| One can get thread status, or the list of running or joinable threads. |
| |
| A new C<< threads->exit() >> method is used to exit from the application |
| (this is the default for the main thread) or from the current thread only |
| (this is the default for all other threads). On the other hand, the exit() |
| built-in now always causes the whole application to terminate. (Jerry |
| D. Hedden) |
| |
| =item chr() and negative values |
| |
| chr() on a negative value now gives C<\x{FFFD}>, the Unicode replacement |
| character, unless when the C<bytes> pragma is in effect, where the low |
| eight bits of the value are used. |
| |
| =item PERL5SHELL and tainting |
| |
| On Windows, the PERL5SHELL environment variable is now checked for |
| taintedness. (Rafael Garcia-Suarez) |
| |
| =item Using *FILE{IO} |
| |
| C<stat()> and C<-X> filetests now treat *FILE{IO} filehandles like *FILE |
| filehandles. (Steve Peters) |
| |
| =item Overloading and reblessing |
| |
| Overloading now works when references are reblessed into another class. |
| Internally, this has been implemented by moving the flag for "overloading" |
| from the reference to the referent, which logically is where it should |
| always have been. (Nicholas Clark) |
| |
| =item Overloading and UTF-8 |
| |
| A few bugs related to UTF-8 handling with objects that have |
| stringification overloaded have been fixed. (Nicholas Clark) |
| |
| =item eval memory leaks fixed |
| |
| Traditionally, C<eval 'syntax error'> has leaked badly. Many (but not all) |
| of these leaks have now been eliminated or reduced. (Dave Mitchell) |
| |
| =item Random device on Windows |
| |
| In previous versions, perl would read the file F</dev/urandom> if it |
| existed when seeding its random number generator. That file is unlikely |
| to exist on Windows, and if it did would probably not contain appropriate |
| data, so perl no longer tries to read it on Windows. (Alex Davies) |
| |
| =item PERLIO_DEBUG |
| |
| The C<PERLIO_DEBUG> environment variable no longer has any effect for |
| setuid scripts and for scripts run with B<-T>. |
| |
| Moreover, with a thread-enabled perl, using C<PERLIO_DEBUG> could lead to |
| an internal buffer overflow. This has been fixed. |
| |
| =item PerlIO::scalar and read-only scalars |
| |
| PerlIO::scalar will now prevent writing to read-only scalars. Moreover, |
| seek() is now supported with PerlIO::scalar-based filehandles, the |
| underlying string being zero-filled as needed. (Rafael, Jarkko Hietaniemi) |
| |
| =item study() and UTF-8 |
| |
| study() never worked for UTF-8 strings, but could lead to false results. |
| It's now a no-op on UTF-8 data. (Yves Orton) |
| |
| =item Critical signals |
| |
| The signals SIGILL, SIGBUS and SIGSEGV are now always delivered in an |
| "unsafe" manner (contrary to other signals, that are deferred until the |
| perl interpreter reaches a reasonably stable state; see |
| L<perlipc/"Deferred Signals (Safe Signals)">). (Rafael) |
| |
| =item @INC-hook fix |
| |
| When a module or a file is loaded through an @INC-hook, and when this hook |
| has set a filename entry in %INC, __FILE__ is now set for this module |
| accordingly to the contents of that %INC entry. (Rafael) |
| |
| =item C<-t> switch fix |
| |
| The C<-w> and C<-t> switches can now be used together without messing |
| up which categories of warnings are activated. (Rafael) |
| |
| =item Duping UTF-8 filehandles |
| |
| Duping a filehandle which has the C<:utf8> PerlIO layer set will now |
| properly carry that layer on the duped filehandle. (Rafael) |
| |
| =item Localisation of hash elements |
| |
| Localizing a hash element whose key was given as a variable didn't work |
| correctly if the variable was changed while the local() was in effect (as |
| in C<local $h{$x}; ++$x>). (Bo Lindbergh) |
| |
| =back |
| |
| =head1 New or Changed Diagnostics |
| |
| =over 4 |
| |
| =item Use of uninitialized value |
| |
| Perl will now try to tell you the name of the variable (if any) that was |
| undefined. |
| |
| =item Deprecated use of my() in false conditional |
| |
| A new deprecation warning, I<Deprecated use of my() in false conditional>, |
| has been added, to warn against the use of the dubious and deprecated |
| construct |
| |
| my $x if 0; |
| |
| See L<perldiag>. Use C<state> variables instead. |
| |
| =item !=~ should be !~ |
| |
| A new warning, C<!=~ should be !~>, is emitted to prevent this misspelling |
| of the non-matching operator. |
| |
| =item Newline in left-justified string |
| |
| The warning I<Newline in left-justified string> has been removed. |
| |
| =item Too late for "-T" option |
| |
| The error I<Too late for "-T" option> has been reformulated to be more |
| descriptive. |
| |
| =item "%s" variable %s masks earlier declaration |
| |
| This warning is now emitted in more consistent cases; in short, when one |
| of the declarations involved is a C<my> variable: |
| |
| my $x; my $x; # warns |
| my $x; our $x; # warns |
| our $x; my $x; # warns |
| |
| On the other hand, the following: |
| |
| our $x; our $x; |
| |
| now gives a C<"our" variable %s redeclared> warning. |
| |
| =item readdir()/closedir()/etc. attempted on invalid dirhandle |
| |
| These new warnings are now emitted when a dirhandle is used but is |
| either closed or not really a dirhandle. |
| |
| =item Opening dirhandle/filehandle %s also as a file/directory |
| |
| Two deprecation warnings have been added: (Rafael) |
| |
| Opening dirhandle %s also as a file |
| Opening filehandle %s also as a directory |
| |
| =item Use of -P is deprecated |
| |
| Perl's command-line switch C<-P> is now deprecated. |
| |
| =item v-string in use/require is non-portable |
| |
| Perl will warn you against potential backwards compatibility problems with |
| the C<use VERSION> syntax. |
| |
| =item perl -V |
| |
| C<perl -V> has several improvements, making it more useable from shell |
| scripts to get the value of configuration variables. See L<perlrun> for |
| details. |
| |
| =back |
| |
| =head1 Changed Internals |
| |
| In general, the source code of perl has been refactored, tidied up, |
| and optimized in many places. Also, memory management and allocation |
| has been improved in several points. |
| |
| When compiling the perl core with gcc, as many gcc warning flags are |
| turned on as is possible on the platform. (This quest for cleanliness |
| doesn't extend to XS code because we cannot guarantee the tidiness of |
| code we didn't write.) Similar strictness flags have been added or |
| tightened for various other C compilers. |
| |
| =head2 Reordering of SVt_* constants |
| |
| The relative ordering of constants that define the various types of C<SV> |
| have changed; in particular, C<SVt_PVGV> has been moved before C<SVt_PVLV>, |
| C<SVt_PVAV>, C<SVt_PVHV> and C<SVt_PVCV>. This is unlikely to make any |
| difference unless you have code that explicitly makes assumptions about that |
| ordering. (The inheritance hierarchy of C<B::*> objects has been changed |
| to reflect this.) |
| |
| =head2 Elimination of SVt_PVBM |
| |
| Related to this, the internal type C<SVt_PVBM> has been removed. This |
| dedicated type of C<SV> was used by the C<index> operator and parts of the |
| regexp engine to facilitate fast Boyer-Moore matches. Its use internally has |
| been replaced by C<SV>s of type C<SVt_PVGV>. |
| |
| =head2 New type SVt_BIND |
| |
| A new type C<SVt_BIND> has been added, in readiness for the project to |
| implement Perl 6 on 5. There deliberately is no implementation yet, and |
| they cannot yet be created or destroyed. |
| |
| =head2 Removal of CPP symbols |
| |
| The C preprocessor symbols C<PERL_PM_APIVERSION> and |
| C<PERL_XS_APIVERSION>, which were supposed to give the version number of |
| the oldest perl binary-compatible (resp. source-compatible) with the |
| present one, were not used, and sometimes had misleading values. They have |
| been removed. |
| |
| =head2 Less space is used by ops |
| |
| The C<BASEOP> structure now uses less space. The C<op_seq> field has been |
| removed and replaced by a single bit bit-field C<op_opt>. C<op_type> is now 9 |
| bits long. (Consequently, the C<B::OP> class doesn't provide an C<seq> |
| method anymore.) |
| |
| =head2 New parser |
| |
| perl's parser is now generated by bison (it used to be generated by |
| byacc.) As a result, it seems to be a bit more robust. |
| |
| Also, Dave Mitchell improved the lexer debugging output under C<-DT>. |
| |
| =head2 Use of C<const> |
| |
| Andy Lester supplied many improvements to determine which function |
| parameters and local variables could actually be declared C<const> to the C |
| compiler. Steve Peters provided new C<*_set> macros and reworked the core to |
| use these rather than assigning to macros in LVALUE context. |
| |
| =head2 Mathoms |
| |
| A new file, F<mathoms.c>, has been added. It contains functions that are |
| no longer used in the perl core, but that remain available for binary or |
| source compatibility reasons. However, those functions will not be |
| compiled in if you add C<-DNO_MATHOMS> in the compiler flags. |
| |
| =head2 C<AvFLAGS> has been removed |
| |
| The C<AvFLAGS> macro has been removed. |
| |
| =head2 C<av_*> changes |
| |
| The C<av_*()> functions, used to manipulate arrays, no longer accept null |
| C<AV*> parameters. |
| |
| =head2 $^H and %^H |
| |
| The implementation of the special variables $^H and %^H has changed, to |
| allow implementing lexical pragmas in pure Perl. |
| |
| =head2 B:: modules inheritance changed |
| |
| The inheritance hierarchy of C<B::> modules has changed; C<B::NV> now |
| inherits from C<B::SV> (it used to inherit from C<B::IV>). |
| |
| =head2 Anonymous hash and array constructors |
| |
| The anonymous hash and array constructors now take 1 op in the optree |
| instead of 3, now that pp_anonhash and pp_anonlist return a reference to |
| an hash/array when the op is flagged with OPf_SPECIAL. (Nicholas Clark) |
| |
| =head1 Known Problems |
| |
| There's still a remaining problem in the implementation of the lexical |
| C<$_>: it doesn't work inside C</(?{...})/> blocks. (See the TODO test in |
| F<t/op/mydef.t>.) |
| |
| Stacked filetest operators won't work when the C<filetest> pragma is in |
| effect, because they rely on the stat() buffer C<_> being populated, and |
| filetest bypasses stat(). |
| |
| =head2 UTF-8 problems |
| |
| The handling of Unicode still is unclean in several places, where it's |
| dependent on whether a string is internally flagged as UTF-8. This will |
| be made more consistent in perl 5.12, but that won't be possible without |
| a certain amount of backwards incompatibility. |
| |
| =head1 Platform Specific Problems |
| |
| When compiled with g++ and thread support on Linux, it's reported that the |
| C<$!> stops working correctly. This is related to the fact that the glibc |
| provides two strerror_r(3) implementation, and perl selects the wrong |
| one. |
| |
| =head1 Reporting Bugs |
| |
| If you find what you think is a bug, you might check the articles |
| recently posted to the comp.lang.perl.misc newsgroup and the perl |
| bug database at http://rt.perl.org/rt3/ . There may also be |
| information at http://www.perl.org/ , the Perl Home Page. |
| |
| If you believe you have an unreported bug, please run the B<perlbug> |
| program included with your release. Be sure to trim your bug down |
| to a tiny but sufficient test case. Your bug report, along with the |
| output of C<perl -V>, will be sent off to perlbug@perl.org to be |
| analysed by the Perl porting team. |
| |
| =head1 SEE ALSO |
| |
| The F<Changes> file and the perl590delta to perl595delta man pages for |
| exhaustive details on what changed. |
| |
| The F<INSTALL> file for how to build Perl. |
| |
| The F<README> file for general stuff. |
| |
| The F<Artistic> and F<Copying> files for copyright information. |
| |
| =cut |