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 v5.19.1
12 This document describes differences between the 5.19.0 release and the 5.19.1
17 XXX Any important notices here
19 =head1 Core Enhancements
21 XXX New core language features go here. Summarize user-visible core language
22 enhancements. Particularly prominent performance optimisations could go
23 here, but most should go in the L</Performance Enhancements> section.
25 [ List each enhancement as a =head2 entry ]
29 XXX Any security-related notices go here. In particular, any security
30 vulnerabilities closed should be noted here rather than in the
31 L</Selected Bug Fixes> section.
33 [ List each security issue as a =head2 entry ]
35 =head1 Incompatible Changes
37 XXX For a release on a stable branch, this section aspires to be:
39 There are no changes intentionally incompatible with 5.XXX.XXX
40 If any exist, they are bugs, and we request that you submit a
41 report. See L</Reporting Bugs> below.
43 [ List each incompatible change as a =head2 entry ]
47 XXX Any deprecated features, syntax, modules etc. should be listed here.
49 =head2 Module removals
51 XXX Remove this section if inapplicable.
53 The following modules will be removed from the core distribution in a future
54 release, and will at that time need to be installed from CPAN. Distributions
55 on CPAN which require these modules will need to list them as prerequisites.
57 The core versions of these modules will now issue C<"deprecated">-category
58 warnings to alert you to this fact. To silence these deprecation warnings,
59 install the modules in question from CPAN.
61 Note that these are (with rare exceptions) fine modules that you are encouraged
62 to continue to use. Their disinclusion from core primarily hinges on their
63 necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
64 not usually on concerns over their design.
66 XXX Note that deprecated modules should be listed here even if they are listed
67 as an updated module in the L</Modules and Pragmata> section.
77 [ List each other deprecation as a =head2 entry ]
79 =head1 Performance Enhancements
81 XXX Changes which enhance performance without changing behaviour go here.
82 There may well be none in a stable release.
84 [ List each enhancement as a =item entry ]
90 Perl has a new copy-on-write mechanism that avoids the need to copy the
91 internal string buffer when assigning from one scalar to another. This
92 makes copying large strings appear much faster. Modifying one of the two
93 (or more) strings after an assignment will force a copy internally. This
94 makes it unnecessary to pass strings by reference for efficiency.
96 This feature was already available in 5.18.0, but wasn't enabled by
97 default. It is the default now, and so you no longer need build perl with
98 the F<Configure> argument:
100 -Accflags=PERL_NEW_COPY_ON_WRITE
102 It can be disabled (for now) in a perl build with:
104 -Accflags=PERL_NO_COW
108 =head1 Modules and Pragmata
110 XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
111 go here. If Module::CoreList is updated, generate an initial draft of the
112 following sections using F<Porting/corelist-perldelta.pl>, which prints stub
113 entries to STDOUT. Results can be pasted in place of the '=head2' entries
114 below. A paragraph summary for important changes should then be added by hand.
115 In an ideal world, dual-life modules would have a F<Changes> file that could be
118 [ Within each section, list entries as a =item entry ]
120 =head2 New Modules and Pragmata
130 =head2 Updated Modules and Pragmata
136 Test::Harness has been upgraded from version 3.26 to 3.28
138 Memory usage is dramatically reduced. t/harness now uses about 10% of the
139 memory used by 3.26 and earlier.
141 C<PERL5LIB> is always propagated to a test's C<@INC>, even under C<-T>.
145 Unicode::UCD has been upgraded from version 0.51 to 0.52.
147 A function, L<Unicode::UCD/search_invlist()> is now available to do
148 search an inversion list or map for a code point.
152 =head2 Removed Modules and Pragmata
164 XXX Changes to files in F<pod/> go here. Consider grouping entries by
165 file and be sure to link to the appropriate page, e.g. L<perlfunc>.
167 =head2 New Documentation
169 XXX Changes which create B<new> files in F<pod/> go here.
173 XXX Description of the purpose of the new file here
175 =head2 Changes to Existing Documentation
177 XXX Changes which significantly change existing files in F<pod/> go here.
178 However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
187 XXX Description of the change here
193 The following additions or changes have been made to diagnostic output,
194 including warnings and fatal error messages. For the complete list of
195 diagnostic messages, see L<perldiag>.
197 XXX New or changed warnings emitted by the core's C<C> code go here. Also
198 include any changes in L<perldiag> that reconcile it to the C<C> code.
200 =head2 New Diagnostics
202 XXX Newly added diagnostic messages go under here, separated into New Errors
211 XXX L<message|perldiag/"message">
221 XXX L<message|perldiag/"message">
225 =head2 Changes to Existing Diagnostics
227 XXX Changes (i.e. rewording) of diagnostic messages go here
233 XXX Describe change here
237 =head1 Utility Changes
239 XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
240 Most of these are built within the directories F<utils> and F<x2p>.
242 [ List utility changes as a =head3 entry for each utility and =item
243 entries for each change
244 Use L<XXX> with program names to get proper documentation linking. ]
256 =head1 Configuration and Compilation
258 XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
259 go here. Any other changes to the Perl build process should be listed here.
260 However, any platform-specific changes should be listed in the
261 L</Platform Support> section, instead.
263 [ List changes as a =item entry ].
275 XXX Any significant changes to the testing of a freshly built perl should be
276 listed here. Changes which create B<new> files in F<t/> go here as do any
277 large changes to the testing harness (e.g. when parallel testing was added).
278 Changes to existing files in F<t/> aren't worth summarizing, although the bugs
279 that they represent may be covered elsewhere.
281 [ List each test improvement as a =item entry ]
291 =head1 Platform Support
293 XXX Any changes to platform support should be listed in the sections below.
295 [ Within the sections, list each platform as a =item entry with specific
296 changes as paragraphs below it. ]
300 XXX List any platforms that this version of perl compiles on, that previous
301 versions did not. These will either be enabled by new files in the F<hints/>
302 directories, or new subdirectories and F<README> files at the top level of the
307 =item XXX-some-platform
313 =head2 Discontinued Platforms
315 XXX List any platforms that this version of perl no longer compiles on.
319 =item XXX-some-platform
325 =head2 Platform-Specific Notes
327 XXX List any changes for specific platforms. This could include configuration
328 and compilation changes or changes in portability/compatibility. However,
329 changes within modules for platforms should generally be listed in the
330 L</Modules and Pragmata> section.
334 =item Mixed-endian platforms
336 The code supporting C<pack> and C<unpack> operations on mixed endian
337 platforms has been removed. We believe that Perl has long been unable to
338 build on mixed endian architectures (such as PDP-11s), so we don't think
339 that this change will affect any platforms which are able to build v5.18.0.
343 =head1 Internal Changes
345 XXX Changes which affect the interface available to C<XS> code go here. Other
346 significant internal changes for future core maintainers should be noted as
349 [ List each change as a =item entry ]
355 Perl's new copy-on-write mechanism (which is now enabled by default),
356 allows any C<SvPOK> scalar to be automatically upgraded to a copy-on-write
357 scalar when copied. A reference count on the string buffer is stored in
358 the string buffer itself.
362 $ perl -MDevel::Peek -e'$a="abc"; $b = $a; Dump $a; Dump $b'
363 SV = PV(0x260cd80) at 0x2620ad8
365 FLAGS = (POK,IsCOW,pPOK)
366 PV = 0x2619bc0 "abc"\0
370 SV = PV(0x260ce30) at 0x2620b20
372 FLAGS = (POK,IsCOW,pPOK)
373 PV = 0x2619bc0 "abc"\0
378 Note that both scalars share the same PV buffer and have a COW_REFCNT
381 This means that XS code which wishes to modify the C<SvPVX()> buffer of an
382 SV should call C<SvPV_force()> or similar first, to ensure a valid (and
383 unshared) buffer, and to call C<SvSETMAGIC()> afterwards. This in fact has
384 always been the case (for example hash keys were already copy-on-write);
385 this change just spreads the COW behaviour to a wider variety of SVs.
387 One important difference is that before 5.18.0, shared hash-key scalars
388 used to have the C<SvREADONLY> flag set; this is no longer the case.
390 This new behaviour can still be disabled by running F<Configure> with
391 B<-Accflags=-DPERL_NO_COW>. This option will probably be removed in Perl
396 C<PL_sawampersand> is now a constant. The switch this variable provided
397 (to enable/disable the pre-match copy depending on whether C<$&> had been
398 seen) has been removed and replaced with copy-on-write, eliminating a few
401 The previous behaviour can still be enabled by running F<Configure> with
402 B<-Accflags=-DPERL_SAWAMPERSAND>.
406 The functions C<my_swap>, C<my_htonl> and C<my_ntohl> have been removed.
407 It is unclear why these functions were ever marked as I<A>, part of the
408 API. XS code can't call them directly, as it can't rely on them being
409 compiled. Unsurprisingly, no code on CPAN references them.
413 =head1 Selected Bug Fixes
415 XXX Important bug fixes in the core language are summarized here. Bug fixes in
416 files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
418 [ List each fix as a =item entry ]
424 The OP allocation code now returns correctly aligned memory in all cases
425 for C<struct pmop>. Previously it could return memory only aligned to a
426 4-byte boundary, which is not correct for an ithreads build with 64 bit IVs
427 on some 32 bit platforms. Notably, this caused the build to fail completely
428 on sparc GNU/Linux. [RT #118055]
432 The debugger's C<man> command been fixed. It was broken in the v5.18.0
433 release. The C<man> command is aliased to the names C<doc> and C<perldoc> -
438 =head1 Known Problems
440 XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
441 tests that had to be C<TODO>ed for the release would be noted here. Unfixed
442 platform specific bugs also go here.
444 [ List each fix as a =item entry ]
456 XXX If any significant core contributor has died, we've added a short obituary
459 =head1 Acknowledgements
461 XXX Generate this with:
463 perl Porting/acknowledgements.pl v5.19.1..HEAD
465 =head1 Reporting Bugs
467 If you find what you think is a bug, you might check the articles recently
468 posted to the comp.lang.perl.misc newsgroup and the perl bug database at
469 http://rt.perl.org/perlbug/ . There may also be information at
470 http://www.perl.org/ , the Perl Home Page.
472 If you believe you have an unreported bug, please run the L<perlbug> program
473 included with your release. Be sure to trim your bug down to a tiny but
474 sufficient test case. Your bug report, along with the output of C<perl -V>,
475 will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
477 If the bug you are reporting has security implications, which make it
478 inappropriate to send to a publicly archived mailing list, then please send it
479 to perl5-security-report@perl.org. This points to a closed subscription
480 unarchived mailing list, which includes all the core committers, who will be
481 able to help assess the impact of issues, figure out a resolution, and help
482 co-ordinate the release of patches to mitigate or fix the problem across all
483 platforms on which Perl is supported. Please only use this address for
484 security issues in the Perl core, not for modules independently distributed on
489 The F<Changes> file for an explanation of how to view exhaustive details on
492 The F<INSTALL> file for how to build Perl.
494 The F<README> file for general stuff.
496 The F<Artistic> and F<Copying> files for copyright information.