5 [ this is a template for a new perldelta file. Any text flagged as XXX needs
6 to be processed before release. ]
8 perldelta - what is new for perl v5.17.3
12 This document describes differences between the 5.17.2 release and the 5.17.3
15 If you are upgrading from an earlier release such as 5.17.1, first read
16 L<perl5172delta>, which describes differences between 5.17.1 and 5.17.2.
20 XXX Any important notices here
22 =head1 Core Enhancements
24 XXX New core language features go here. Summarize user-visible core language
25 enhancements. Particularly prominent performance optimisations could go
26 here, but most should go in the L</Performance Enhancements> section.
28 [ List each enhancement as a =head2 entry ]
30 =head2 Computed Labels
32 The loop controls C<next>, C<last> and C<redo>, and the special C<dump>
33 operator, now allow arbitrary expressions to be used to compute labels at run
34 time. Previously, any argument that was not a constant was treated as the
39 XXX Any security-related notices go here. In particular, any security
40 vulnerabilities closed should be noted here rather than in the
41 L</Selected Bug Fixes> section.
43 [ List each security issue as a =head2 entry ]
45 =head1 Incompatible Changes
47 [ List each incompatible change as a =head2 entry ]
49 =head2 C<$ENV{foo}=undef> deletes value from environ, like C<delete $ENV{foo}>
51 This facilitates use of C<local()> with C<%ENV> entries. In previous versions
52 of Perl, C<undef> was converted to the empty string.
54 =head2 Defined values stored in environment are forced to byte strings
56 A value stored in an environment variable has always been stringified. In this
57 release, it is converted to be only a byte string. First, it is forced to be a
58 only a string. Then if the string is utf8 and the equivalent of
59 C<utf8::downgrade()> works, that result is used; otherwise, the equivalent of
60 C<utf8::encode()> is used, and a warning is issued about wide characters
63 =head2 C<given> now aliases the global C<$_>
65 Instead of assigning to an implicit lexical C<$_>, C<given> now makes the
66 global C<$_> an alias for its argument, just like C<foreach>. However, it
67 still uses lexical C<$_> if there is lexical C<$_> in scope (again, just like
68 C<foreach>) [perl #114020].
72 XXX Any deprecated features, syntax, modules etc. should be listed here. In
73 particular, deprecated modules should be listed here even if they are listed as
74 an updated module in the L</Modules and Pragmata> section.
76 [ List each deprecation as a =head2 entry ]
78 =head1 Performance Enhancements
80 XXX Changes which enhance performance without changing behaviour go here.
81 There may well be none in a stable release.
83 [ List each enhancement as a =item entry ]
93 =head1 Modules and Pragmata
95 XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
96 go here. If Module::CoreList is updated, generate an initial draft of the
97 following sections using F<Porting/corelist-perldelta.pl>, which prints stub
98 entries to STDOUT. Results can be pasted in place of the '=head2' entries
99 below. A paragraph summary for important changes should then be added by hand.
100 In an ideal world, dual-life modules would have a F<Changes> file that could be
103 [ Within each section, list entries as a =item entry ]
105 =head2 New Modules and Pragmata
115 =head2 Updated Modules and Pragmata
121 L<B> has been upgraded from version 1.36 to 1.37. All C<CVf_*> and C<GVf_*>
122 and more SV-related flag values are now provided as constants in the C<B::>
123 namespace and available for export. The default export list has not changed.
127 L<B::Concise> has been upgraded from version 0.91 to 0.92. The C<-nobanner>
128 option has been fixed, and C<format>s can now be dumped. When passed a sub
129 name to dump, it will check also to see whether it is the name of a format. If
130 a sub and a format share the same name, it will dump both.
134 L<B::Debug> has been upgraded from version 1.17 to 1.18. This adds support
135 (experimentally) for the new C<B::PADLIST>.
139 L<B::Deparse> has been upgraded from version 1.15 to 1.16. It now deparses
140 loop controls with the correct precedence, and multiple statements in a
141 C<format> line are also now deparsed correctly.
145 L<CGI> has been upgraded from version 3.59 to 3.60. Unrecognized HTML escape
146 sequences are now handled better, problematic trailing newlines are no longer
147 inserted after E<lt>formE<gt> tags by C<startform()> or C<start_form()>, and
148 bogus "Insecure Dependency" warnings appearing with some versions of perl are
153 L<Compress::Raw::Bzip2> has been upgraded from version 2.05201 to 2.055. The
154 misuse of Perl's "magic" API has been fixed.
158 L<Compress::Raw::Zlib> has been upgraded from version 2.05401 to 2.056. The
159 misuse of Perl's "magic" API has been fixed.
163 L<Compress::Zlib> has been upgraded from version 2.052 to 2.055.
164 C<compress()>, C<uncompress()>, C<memGzip()> and C<memGunzip()> have been
165 speeded up by making parameter validation more efficient.
169 L<Data::Dumper> has been upgraded from version 2.135_06 to 2.135_07. It has
170 been optimized to only build a seen-scalar hash as necessary, thereby speeding
171 up serialization drastically.
175 L<Devel::Peek> has been upgraded from version 1.08 to 1.09. The only change
176 has been to the test script, to account for changes to some flags in perl's
181 L<Encode> has been upgraded from version 2.44 to 2.47. The Mac alias x-mac-ce
182 has been added, and various bugs have been fixed in Encode::Unicode,
183 Encode::UTF7 and Encode::GSM0338.
187 L<Module::Build> has been upgraded from version 0.40 to 0.4002. A minor bug
188 fix allows markup to be used around the leading "Name" in a POD "abstract"
189 line, and some documentation improvements have been made.
193 L<Module::CoreList> has been upgraded from version 2.69 to 2.70. Version
194 information is now stored as a delta, which greatly reduces the size of the
199 L<Module::Load::Conditional> has been upgraded from version 0.50 to 0.54.
200 Various enhancements include the new use of Module::Metadata.
204 L<Module::Metadata> has been upgraded from version 1.000009 to 1.000010. The
205 creation of a Module::Metadata object for a typical module file has been sped
210 L<Module::Pluggable> has been upgraded from version 4.0 to 4.3. Amongst other
211 changes, triggers are now allowed on events, which gives a powerful way to
216 L<perlfaq> has been upgraded from version 5.0150040 to 5.0150041. This
217 contains a couple of minor corrections and lists one new editor.
221 L<Pod::Simple> has been upgraded from version 3.20 to 3.23. Numerous
222 improvements have been made, mostly to Pod::Simple::XHTML, which also has a
223 compatibility change: the C<codes_in_verbatim> option is now disabled by
224 default. See F<cpan/Pod-Simple/ChangeLog> for the full details.
228 L<re> has been upgraded from version 0.21 to 0.22. Single character [class]es
229 like C</[s]/> or C</[s]/i> are now optimized as if they did not have the
230 brackets, i.e. C</s/> or C</s/i>.
234 L<Socket> has been upgraded from version 2.002 to 2.004. Constants and
235 functions required for IP multicast source group membership have been added.
239 L<Storable> has been upgraded from version 2.37 to 2.38. It can now freeze and
240 thaw vstrings correctly. This causes a slight incompatible change in the
241 storage format, so the format version has increased to 2.9.
245 L<Sys::Syslog> has been upgraded from version 0.29 to 0.30. An issue with
246 C<POSIX::strftime()> on Windows and a build problem on Haiku-OS have been
247 resolved, and <getservbyname()> is no longer called when the port is specified.
251 L<Time::Local> has been upgraded from version 1.2000 to 1.2300. Seconds values
252 greater than 59 but less than 60 no longer cause C<timegm()> and C<timelocal()>
257 L<Unicode::UCD> has been upgraded from version 0.44 to 0.45. This has been
258 modified slightly for reasons of perl internal use only.
262 L<Win32> has been upgraded from version 0.44 to 0.45. New APIs have been added
263 for getting and setting the current code page.
267 L<Win32CORE> has been upgraded from version 0.02 to 0.03. The use of
268 PERL_NO_GET_CONTEXT here has resulted in smaller machine code.
274 XXX Changes to files in F<pod/> go here. Consider grouping entries by file and
275 be sure to link to the appropriate page, e.g. L<perlfunc>.
277 =head2 New Documentation
279 XXX Changes which create B<new> files in F<pod/> go here.
283 XXX Description of the purpose of the new file here
285 =head2 Changes to Existing Documentation
287 XXX Changes which significantly change existing files in F<pod/> go here.
288 However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
291 =head3 L<perlfunc>, L<perlop>
297 Loop control verbs (C<dump>, C<goto>, C<next>, C<last> and C<redo>) have always
298 had the same precedence as assignment operators, but this was not documented
309 A caveat has been added to the documentation for C<$_> warning against the use
310 of lexical C<$_> [perl #114020].
316 The following additions or changes have been made to diagnostic output,
317 including warnings and fatal error messages. For the complete list of
318 diagnostic messages, see L<perldiag>.
320 XXX New or changed warnings emitted by the core's C<C> code go here. Also
321 include any changes in L<perldiag> that reconcile it to the C<C> code.
323 =head2 New Diagnostics
325 XXX Newly added diagnostic messages go under here, separated into New Errors
334 L<Unterminated delimiter for here document|perldiag/"Unterminated delimiter for here document">
336 This message now occurs when a here document label has an initial quotation
337 mark but the final quotation mark is missing.
339 This replaces a bogus and misleading error message about not finding the label
340 itself [perl #114104].
344 L<panic: child pseudo-process was never scheduled|perldiag/"panic: child pseudo-process was never scheduled">
346 This error is thrown when a child pseudo-process in the ithreads implementation
347 on Windows was not scheduled within the time period allowed and therefore was
348 not able to initialize properly [perl #88840].
358 L<Wide character in setenv|perldiag/"Wide character in %s">
360 Attempts to put wide characters into environment variables via C<%ENV> now
361 provoke this warning.
365 =head2 Changes to Existing Diagnostics
367 XXX Changes (i.e. rewording) of diagnostic messages go here
373 XXX Describe change here
377 =head1 Utility Changes
379 XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
380 Most of these are built within the directories F<utils> and F<x2p>.
382 [ List utility changes as a =head3 entry for each utility and =item
383 entries for each change
384 Use L<XXX> with program names to get proper documentation linking. ]
396 =head1 Configuration and Compilation
398 XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
399 go here. Any other changes to the Perl build process should be listed here.
400 However, any platform-specific changes should be listed in the
401 L</Platform Support> section, instead.
403 [ List changes as a =item entry ].
409 The pager detection in F<Configure> has been improved to allow responses which
410 specify options after the program name, e.g. B</usr/bin/less -R>, if the user
411 accepts the default value. This helps B<perldoc> when handling ANSI escapes
418 XXX Any significant changes to the testing of a freshly built perl should be
419 listed here. Changes which create B<new> files in F<t/> go here as do any
420 large changes to the testing harness (e.g. when parallel testing was added).
421 Changes to existing files in F<t/> aren't worth summarizing, although the bugs
422 that they represent may be covered elsewhere.
424 [ List each test improvement as a =item entry ]
434 =head1 Platform Support
436 XXX Any changes to platform support should be listed in the sections below.
438 [ Within the sections, list each platform as a =item entry with specific
439 changes as paragraphs below it. ]
443 XXX List any platforms that this version of perl compiles on, that previous
444 versions did not. These will either be enabled by new files in the F<hints/>
445 directories, or new subdirectories and F<README> files at the top level of the
450 =item XXX-some-platform
456 =head2 Discontinued Platforms
462 Support code relating to UTS global has been removed. UTS was a mainframe
463 version of System V created by Amdahl, subsequently sold to UTS Global. The
464 port has not been touched since before 5.8.0, and UTS Global is now defunct.
468 =head2 Platform-Specific Notes
470 XXX List any changes for specific platforms. This could include configuration
471 and compilation changes or changes in portability/compatibility. However,
472 changes within modules for platforms should generally be listed in the
473 L</Modules and Pragmata> section.
479 A new makefile option, USE_64_BIT_INT, has been added to the Windows makefiles.
480 Set this to "define" when building a 32-bit perl if you want it to use 64-bit
483 Machine code size reductions, already made to the DLLs of XS modules in Perl
484 5.17.2, have now been extended to the perl DLL itself.
486 Building with VC++ 6.0 was inadvertently broken in Perl 5.17.2 but has now been
487 fixed again. XXX Actually, it's now been broken again, so ensure that it gets
488 fixed once more before release, or remove this comment!
492 The B<a2p> build has been fixed for the HP C++ compiler on OpenVMS.
496 =head1 Internal Changes
498 XXX Changes which affect the interface available to C<XS> code go here. Other
499 significant internal changes for future core maintainers should be noted as
502 [ List each change as a =item entry ]
512 =head1 Selected Bug Fixes
514 XXX Important bug fixes in the core language are summarized here. Bug fixes in
515 files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
517 [ List each fix as a =item entry ]
523 C<\w> now matches the code points U+200C (ZERO WIDTH NON-JOINER) and U+200D
524 (ZERO WIDTH JOINER). C<\W> no longer matches these. This change is because
525 Unicode corrected their definition of what C<\w> should match.
529 C<dump LABEL> no longer leaks its label.
533 Constant folding no longer changes the behaviour of functions like C<stat()>
534 and C<truncate()> that can take either filenames or handles.
535 C<stat 1 ? foo : bar> nows treats its argument as a file name (since it is an
536 arbitrary expression), rather than the handle "foo".
540 C<truncate FOO, $len> no longer falls back to treating "FOO" as a file name if
541 the filehandle has been deleted. This was broken in Perl 5.16.0.
545 Subroutine redefinitions after sub-to-glob and glob-to-glob assignments no
546 longer cause double frees or panic messages.
550 C<s///> now turns vstrings into plain strings when performing a substitution,
551 even if the resulting string is the same (C<s/a/a/>).
555 Prototype mismatch warnings no longer erroneously treat constant subs as having
556 no prototype when they actually have "".
560 Constant subroutines and forward declarations no longer prevent prototype
561 mismatch warnings from omitting the sub name.
565 C<undef> on a subroutine now clears call checkers.
569 The C<ref> operator started leaking memory on blessed objects in Perl 5.16.0.
570 This has been fixed [perl #114340].
574 C<use> no longer tries to parse its arguments as a statement, making
575 C<use constant { () };> a syntax error [perl #114222].
579 On debugging builds, "uninitialized" warnings inside formats no longer cause
584 On debugging builds, subroutines nested inside formats no longer cause
585 assertion failures [perl #78550].
589 Formats and C<use> statements are now permitted inside formats.
593 C<print $x> and C<sub { print $x }->()> now always produce the same output. It
594 was possible for the latter to refuse to close over $x if the variable was not
595 active; e.g., if it was defined outside a currently-running named subroutine.
599 Similarly, C<print $x> and C<print eval '$x'> now produce the same output.
600 This also allows "my $x if 0" variables to be seen in the debugger [perl
605 Formats called recursively no longer stomp on their own lexical variables, but
606 each recursive call has its own set of lexicals.
610 Attempting to free an active format or the handle associated with it no longer
615 Format parsing no longer gets confused by braces, semicolons and low-precedence
616 operators. It used to be possible to use braces as format delimiters (instead
617 of C<=> and C<.>), but only sometimes. Semicolons and low-precedence operators
618 in format argument lines no longer confuse the parser into ignoring the line's
619 return value. In format argument lines, braces can now be used for anonymous
620 hashes, instead of being treated always as C<do> blocks.
624 Formats can now be nested inside code blocks in regular expressions and other
625 quoted constructs (C</(?{...})/> and C<qq/${...}/>) [perl #114040].
629 Formats are no longer created after compilation errors.
633 Some format syntax errors started causing crashes in Perl 5.17.2, but have now
638 Under debugging builds, the B<-DA> command line option started crashing in Perl
639 5.16.0. It has been fixed [perl #114368].
643 Scope::Escape compatibility, which was broken in Perl 5.17.2, has been restored
648 A potential deadlock scenario involving the premature termination of a
649 pseudo-forked child in a Windows build with ithreads enabled has been fixed.
650 This resolves the common problem of the F<t/op/fork.t> test hanging on Windows
655 The microperl build, broken since Perl 5.15.7, has now been restored.
659 The code which generates errors from C<require()> could potentially read one or
660 two bytes before the start of the filename for filenames less than three bytes
661 long and ending C</\.p?\z/>. This has now been fixed. Note that it could
662 never have happened with module names given to C<use()> or C<require()> anyway.
666 The handling of pathnames of modules given to C<require()> has been made
671 The C<re_compile()> API function, the entry point for perl's regex compiler,
672 was accidentally changed in Perl 5.17.1 to operate on the current engine. This
673 has now been restored to its former core-engine-specific state [perl #114302].
677 Perl 5.17.1 introduced a memory leak into the re-use of run-time regexes where
678 the pattern hasn't changed (i.e. C</$unchanging/>). This has now been fixed.
682 A bug in the compilation of a C</(?{})/> expression which affected the TryCatch
683 test suite has been fixed [perl #114242].
687 =head1 Known Problems
689 XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
690 tests that had to be C<TODO>ed for the release would be noted here. Unfixed
691 platform specific bugs also go here.
693 [ List each fix as a =item entry ]
705 XXX If any significant core contributor has died, we've added a short obituary
708 =head1 Acknowledgements
710 XXX Generate this with:
712 perl Porting/acknowledgements.pl v5.17.2..HEAD
714 =head1 Reporting Bugs
716 If you find what you think is a bug, you might check the articles recently
717 posted to the comp.lang.perl.misc newsgroup and the perl bug database at
718 http://rt.perl.org/perlbug/ . There may also be information at
719 http://www.perl.org/ , the Perl Home Page.
721 If you believe you have an unreported bug, please run the L<perlbug> program
722 included with your release. Be sure to trim your bug down to a tiny but
723 sufficient test case. Your bug report, along with the output of C<perl -V>,
724 will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
726 If the bug you are reporting has security implications, which make it
727 inappropriate to send to a publicly archived mailing list, then please send it
728 to perl5-security-report@perl.org. This points to a closed subscription
729 unarchived mailing list, which includes all the core committers, who will be
730 able to help assess the impact of issues, figure out a resolution, and help
731 co-ordinate the release of patches to mitigate or fix the problem across all
732 platforms on which Perl is supported. Please only use this address for
733 security issues in the Perl core, not for modules independently distributed on
738 The F<Changes> file for an explanation of how to view exhaustive details on
741 The F<INSTALL> file for how to build Perl.
743 The F<README> file for general stuff.
745 The F<Artistic> and F<Copying> files for copyright information.