This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
Add perldelta entries for my 5.25.1 changes
[perl5.git] / pod / perldelta.pod
CommitLineData
44691e6f
AB
1=encoding utf8
2
3=head1 NAME
4
0302547a 5perldelta - what is new for perl v5.25.1
eabfc7bc 6
2cfe9b50 7=head1 DESCRIPTION
eabfc7bc 8
0302547a 9This document describes differences between the 5.25.0 release and the 5.25.1
4b8803f0 10release.
f3ed8cbf 11
0302547a
RS
12If you are upgrading from an earlier release such as 5.24.0, first read
13L<perl5250delta>, which describes differences between 5.24.0 and 5.25.0.
eabfc7bc 14
0302547a 15=head1 Notice
fac0c351 16
0302547a
RS
17XXX Any important notices here
18
19=head1 Core Enhancements
20
21XXX New core language features go here. Summarize user-visible core language
22enhancements. Particularly prominent performance optimisations could go
23here, but most should go in the L</Performance Enhancements> section.
24
25[ List each enhancement as a =head2 entry ]
26
27=head1 Security
28
29XXX Any security-related notices go here. In particular, any security
30vulnerabilities closed should be noted here rather than in the
31L</Selected Bug Fixes> section.
32
33[ List each security issue as a =head2 entry ]
34
bf1007bc
DM
35=head2 require ::Foo::Bar is now illegal.
36
37Formerly, C<require ::Foo::Bar> would try to read F</Foo/Bar.pm>. Now any
38bareword require which starts with a double colon dies instead.
39
1656665e
KW
40=head2 Unescaped literal C<"{"> characters in regular expression
41patterns are no longer permissible
42
43You have to now say something like C<"\{"> or C<"[{]"> to specify to
44match a LEFT CURLY BRACKET. This will allow future extensions to the
45language. This restriction is not enforced, nor are there current plans
46to enforce it, if the C<"{"> is the first character in the pattern.
47
48These have been deprecated since v5.16, with a deprecation message
49displayed starting in v5.22.
50
acab2422
KW
51=head2 Literal control character variable names are no longer permissible
52
53A variable name may no longer contain a literal control character under
54any circumstances. These previously were allowed in single-character
55names on ASCII platforms, but have been deprecated there since Perl
56v5.20. This affects things like C<$I<\cT>>, where I<\cT> is a literal
57control (such as a C<NAK> or C<NEGATIVE ACKNOWLEDGE> character) in the
58source code.
0302547a 59
60108b47
KW
60=head2 C<qr//xx> is no longer permissible
61
62Using more than one C</x> regular expression pattern modifier on a
63single pattern is now forbidden. This is to allow a future enhancement
64to the language. This usage has been deprecated since v5.22.
65
61463a3e 66=head2 C<NBSP> is no longer permissible in C<\N{...}>
0302547a 67
61463a3e
KW
68The name of a character may no longer contain non-breaking spaces. It
69has been deprecated to do so since Perl v5.22.
0302547a
RS
70
71=head1 Deprecations
72
73XXX Any deprecated features, syntax, modules etc. should be listed here.
74
75=head2 Module removals
76
77XXX Remove this section if inapplicable.
78
79The following modules will be removed from the core distribution in a
80future release, and will at that time need to be installed from CPAN.
81Distributions on CPAN which require these modules will need to list them as
82prerequisites.
83
84The core versions of these modules will now issue C<"deprecated">-category
85warnings to alert you to this fact. To silence these deprecation warnings,
86install the modules in question from CPAN.
87
88Note that these are (with rare exceptions) fine modules that you are encouraged
89to continue to use. Their disinclusion from core primarily hinges on their
90necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
91not usually on concerns over their design.
92
93=over
94
95=item XXX
96
97XXX Note that deprecated modules should be listed here even if they are listed
98as an updated module in the L</Modules and Pragmata> section.
99
100=back
101
102[ List each other deprecation as a =head2 entry ]
103
104=head1 Performance Enhancements
105
106XXX Changes which enhance performance without changing behaviour go here.
107There may well be none in a stable release.
108
109[ List each enhancement as a =item entry ]
110
111=over 4
112
113=item *
114
4de751aa
AC
115Bareword constant strings are now permitted to take part in constant
116folding. They were originally exempted from constant folding in August 1999,
117during the development of Perl 5.6, to ensure that C<use strict "subs">
118would still apply to bareword constants. That has now been accomplished a
119different way, so barewords, like other constants, now gain the performance
120benefits of constant folding.
121
122This also means that void-context warnings on constant expressions of
123barewords now report the folded constant operand, rather than the operation;
124this matches the behaviour for non-bareword constants.
0302547a
RS
125
126=back
127
128=head1 Modules and Pragmata
129
130XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
131go here. If Module::CoreList is updated, generate an initial draft of the
132following sections using F<Porting/corelist-perldelta.pl>. A paragraph summary
133for important changes should then be added by hand. In an ideal world,
134dual-life modules would have a F<Changes> file that could be cribbed.
135
136[ Within each section, list entries as a =item entry ]
137
138=head2 New Modules and Pragmata
139
140=over 4
141
142=item *
143
144XXX
145
146=back
147
148=head2 Updated Modules and Pragmata
149
150=over 4
151
152=item *
153
4de751aa
AC
154=item *
155
156L<POSIX> has been upgraded from version 1.68 to 1.69. This remedies several
157defects in making its symbols exportable. [perl #127821]
0302547a
RS
158
159=back
160
161=head2 Removed Modules and Pragmata
162
163=over 4
164
165=item *
166
167XXX
168
169=back
170
171=head1 Documentation
172
173XXX Changes to files in F<pod/> go here. Consider grouping entries by
174file and be sure to link to the appropriate page, e.g. L<perlfunc>.
175
176=head2 New Documentation
177
178XXX Changes which create B<new> files in F<pod/> go here.
179
180=head3 L<XXX>
181
182XXX Description of the purpose of the new file here
183
184=head2 Changes to Existing Documentation
185
186XXX Changes which significantly change existing files in F<pod/> go here.
187However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
188section.
189
190=head3 L<XXX>
191
192=over 4
193
194=item *
195
196XXX Description of the change here
197
198=back
199
200=head1 Diagnostics
201
202The following additions or changes have been made to diagnostic output,
203including warnings and fatal error messages. For the complete list of
204diagnostic messages, see L<perldiag>.
205
206XXX New or changed warnings emitted by the core's C<C> code go here. Also
207include any changes in L<perldiag> that reconcile it to the C<C> code.
208
209=head2 New Diagnostics
210
211XXX Newly added diagnostic messages go under here, separated into New Errors
212and New Warnings
213
214=head3 New Errors
215
216=over 4
217
218=item *
219
bf1007bc
DM
220L<Bareword in require contains "%s"|perldiag/"Bareword in require contains "%s"">
221
222=item *
223
224L<Bareword in require maps to empty filename|perldiag/"Bareword in require maps to empty filename">
225
226=item *
227
228L<Bareword in require maps to disallowed filename "%s"|perldiag/"Bareword in require maps to disallowed filename "%s"">
229
230=item *
231
232L<Bareword in require must not start with a double-colon: "%s"|perldiag/"Bareword in require must not start with a double-colon: "%s"">
0302547a
RS
233
234=back
235
236=head3 New Warnings
237
238=over 4
239
240=item *
241
242XXX L<message|perldiag/"message">
243
244=back
e1ad135d 245
0302547a 246=head2 Changes to Existing Diagnostics
be2c0c65 247
0302547a 248XXX Changes (i.e. rewording) of diagnostic messages go here
be2c0c65 249
0302547a
RS
250=over 4
251
252=item *
253
4de751aa
AC
254Code like C<$x = $x . "a"> was incorrectly failing to yield a
255L<use of uninitialized value|perldiag/"Use of uninitialized value%s">
256warning when C<$x> was a lexical variable with an undefined value. That has
257now been fixed. [perl #127877]
0302547a
RS
258
259=back
260
261=head1 Utility Changes
262
263XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
264Most of these are built within the directory F<utils>.
265
266[ List utility changes as a =head2 entry for each utility and =item
267entries for each change
268Use L<XXX> with program names to get proper documentation linking. ]
269
4de751aa 270=head2 L<perlbug>
0302547a
RS
271
272=over 4
273
274=item *
275
4de751aa
AC
276Long lines in the message body are now wrapped at 900 characters, to stay
277well within the 1000-character limit imposed by SMTP mail transfer agents.
278This is particularly likely to be important for the list of arguments to
279C<Configure>, which can readily exceed the limit if, for example, it names
280several non-default installation paths. This change also adds the first unit
281tests for perlbug. [perl #128020]
0302547a
RS
282
283=back
284
285=head1 Configuration and Compilation
286
287XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
288go here. Any other changes to the Perl build process should be listed here.
289However, any platform-specific changes should be listed in the
290L</Platform Support> section, instead.
291
292[ List changes as a =item entry ].
293
294=over 4
295
296=item *
297
83a177d5
TC
298C<Configure> now builds C<miniperl> and C<generate_uudmap> if you
299invoke it with C<-Dusecrosscompiler> but not C<-Dtargethost=somehost>.
300This means you can supply your target platform C<config.sh>, generate
301the headers and proceed to build your cross-target perl. [perl #127234]
0302547a 302
f54530a4
TC
303=item *
304
305Builds with C<-Accflags=-DPERL_TRACE_OPS> now only dump the operator
306counts when the environment variable C<PERL_TRACE_OPS> to be set to a
307non-zero integer. This allows C<make test> to pass on such a build.
308
4de751aa
AC
309=item *
310
311When building with GCC 6 and link-time optimization (the C<-flto> option to
312C<gcc>), C<Configure> was treating all probed symbols as present on the
313system, regardless of whether they actually exist. This has been fixed.
314[perl #128131]
315
316=item *
317
318The F<t/test.pl> library is used for internal testing of Perl itself, and
319also copied by several CPAN modules. Some of those modules must work on
320older versions of Perl, so F<t/test.pl> must in turn avoid newer Perl
321features. Compatibility with Perl 5.8 was inadvertently removed some time
322ago; it has now been restored. [perl #128052]
323
324=item *
325
326The build process no longer emits an extra blank line before building each
327"simple" extension (those with only F<*.pm> and F<*.pod> files).
328
0302547a
RS
329=back
330
331=head1 Testing
332
333XXX Any significant changes to the testing of a freshly built perl should be
334listed here. Changes which create B<new> files in F<t/> go here as do any
335large changes to the testing harness (e.g. when parallel testing was added).
336Changes to existing files in F<t/> aren't worth summarizing, although the bugs
337that they represent may be covered elsewhere.
338
339[ List each test improvement as a =item entry ]
340
341=over 4
342
343=item *
344
345XXX
346
347=back
348
349=head1 Platform Support
350
351XXX Any changes to platform support should be listed in the sections below.
352
353[ Within the sections, list each platform as a =item entry with specific
354changes as paragraphs below it. ]
355
356=head2 New Platforms
357
358XXX List any platforms that this version of perl compiles on, that previous
359versions did not. These will either be enabled by new files in the F<hints/>
360directories, or new subdirectories and F<README> files at the top level of the
361source tree.
362
363=over 4
364
365=item XXX-some-platform
366
367XXX
368
369=back
370
371=head2 Discontinued Platforms
372
373XXX List any platforms that this version of perl no longer compiles on.
374
375=over 4
376
377=item XXX-some-platform
378
379XXX
380
381=back
382
383=head2 Platform-Specific Notes
384
385XXX List any changes for specific platforms. This could include configuration
386and compilation changes or changes in portability/compatibility. However,
387changes within modules for platforms should generally be listed in the
388L</Modules and Pragmata> section.
389
390=over 4
391
392=item XXX-some-platform
393
394XXX
395
396=back
397
398=head1 Internal Changes
399
400XXX Changes which affect the interface available to C<XS> code go here. Other
401significant internal changes for future core maintainers should be noted as
402well.
403
404[ List each change as a =item entry ]
405
406=over 4
407
408=item *
409
bf1007bc
DM
410Perl is now built with the C<PERL_OP_PARENT> compiler define enabled by
411default. To disable it, use the C<PERL_NO_OP_PARENT> compiler define.
412This flag alters how the C<op_sibling> field is used in C<OP> structures,
413and has been available optionally since perl 5.22.0.
414
415See L<perl5220delta/"Internal Changes"> for more details of what this
416build option does.
0302547a
RS
417
418=back
419
420=head1 Selected Bug Fixes
421
422XXX Important bug fixes in the core language are summarized here. Bug fixes in
423files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
424
425[ List each fix as a =item entry ]
426
427=over 4
428
429=item *
430
4de751aa
AC
431Expressions containing an C<&&> or C<||> operator (or their synonyms C<and>
432and C<or>) were being compiled incorrectly in some cases. If the left-hand
433side consisted of either a negated bareword constant or a negated C<do {}>
434block containing a constant expression, and the right-hand side consisted of
435a negated non-foldable expression, one of the negations was effectively
436ignored. The same was true of C<if> and C<unless> statement modifiers,
437though with the left-hand and right-hand sides swapped. This long-standing
438bug has now been fixed. [perl #127952]
0302547a
RS
439
440=back
441
442=head1 Known Problems
443
444XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
445tests that had to be C<TODO>ed for the release would be noted here. Unfixed
446platform specific bugs also go here.
447
448[ List each fix as a =item entry ]
449
450=over 4
451
452=item *
453
454XXX
455
456=back
457
458=head1 Errata From Previous Releases
459
460=over 4
461
462=item *
463
464XXX Add anything here that we forgot to add, or were mistaken about, in
465the perldelta of a previous release.
466
467=back
468
469=head1 Obituary
470
471XXX If any significant core contributor has died, we've added a short obituary
472here.
473
474=head1 Acknowledgements
be2c0c65 475
0302547a 476Generate this with:
be2c0c65 477
0302547a 478 perl Porting/acknowledgements.pl v5.25.1..HEAD
f5b73711 479
44691e6f
AB
480=head1 Reporting Bugs
481
e08634c5
SH
482If you find what you think is a bug, you might check the articles recently
483posted to the comp.lang.perl.misc newsgroup and the perl bug database at
4b8803f0
RS
484L<https://rt.perl.org/> . There may also be information at
485L<http://www.perl.org/> , the Perl Home Page.
44691e6f 486
e08634c5
SH
487If you believe you have an unreported bug, please run the L<perlbug> program
488included with your release. Be sure to trim your bug down to a tiny but
489sufficient test case. Your bug report, along with the output of C<perl -V>,
490will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
44691e6f 491
87c118b9
DM
492If the bug you are reporting has security implications which make it
493inappropriate to send to a publicly archived mailing list, then see
494L<perlsec/SECURITY VULNERABILITY CONTACT INFORMATION>
495for details of how to report the issue.
44691e6f
AB
496
497=head1 SEE ALSO
498
e08634c5
SH
499The F<Changes> file for an explanation of how to view exhaustive details on
500what changed.
44691e6f
AB
501
502The F<INSTALL> file for how to build Perl.
503
504The F<README> file for general stuff.
505
506The F<Artistic> and F<Copying> files for copyright information.
507
508=cut