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perldelta: Standardize references to Perl
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1=encoding utf8
2
3=head1 NAME
4
2c8edc25 5perldelta - what is new for perl v5.26.0
eabfc7bc 6
2cfe9b50 7=head1 DESCRIPTION
eabfc7bc 8
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9This document describes the differences between the 5.24.0 release and the
105.26.0 release.
11
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12=head1 Notice
13
16beba24 14This release includes three updates with widespread effects:
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15
16=over 4
17
df48f9a4 18=item * C<"."> no longer in C<@INC>
89853d76 19
df48f9a4 20For security reasons, the current directory (C<".">) is no longer included
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21by default at the end of the module search path (C<@INC>). This may have
22widespread implications for the building, testing and installing of
23modules, and for the execution of scripts. See the section
48e85ff2 24L<< Removal of the current directory (C<".">) from C<@INC> >>
8ab76fe6 25for the full details.
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26
27=item * C<do> may now warn
28
8928e7db 29C<do> now gives a deprecation warning when it fails to load a file which
df48f9a4 30it would have loaded had C<"."> been in C<@INC>.
89853d76 31
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32=item * In regular expression patterns, a literal left brace C<"{">
33should be escaped
34
35See L</Unescaped literal C<"{"> characters in regular expression patterns are no longer permissible>.
36
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37=back
38
2c8edc25 39=head1 Core Enhancements
f3ed8cbf 40
22a7b456 41=head2 Lexical subroutines are no longer experimental
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43Using the C<lexical_subs> feature introduced in v5.18 no longer emits a warning. Existing
44code that disables the C<experimental::lexical_subs> warning category
45that the feature previously used will continue to work. The
46C<lexical_subs> feature has no effect; all Perl code can use lexical
47subroutines, regardless of what feature declarations are in scope.
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48
49=head2 Indented Here-documents
50
df48f9a4 51This adds a new modifier C<"~"> to here-docs that tells the parser
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52that it should look for /^\s*$DELIM\n/ as the closing delimiter.
53
54These syntaxes are all supported:
55
56 <<~EOF;
57 <<~\EOF;
58 <<~'EOF';
59 <<~"EOF";
60 <<~`EOF`;
61 <<~ 'EOF';
62 <<~ "EOF";
63 <<~ `EOF`;
64
df48f9a4 65The C<"~"> modifier will strip, from each line in the here-doc, the
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66same whitespace that appears before the delimiter.
67
fce64130 68Newlines will be copied as-is, and lines that don't include the
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69proper beginning whitespace will cause perl to croak.
70
71For example:
72
73 if (1) {
74 print <<~EOF;
75 Hello there
76 EOF
77 }
78
79prints "Hello there\n" with no leading whitespace.
80
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81=head2 New regular expression modifier C</xx>
82
df48f9a4 83Specifying two C<"x"> characters to modify a regular expression pattern
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84does everything that a single one does, but additionally TAB and SPACE
85characters within a bracketed character class are generally ignored and
86can be added to improve readability, like
87S<C</[ ^ A-Z d-f p-x ]/xx>>. Details are at
88L<perlre/E<sol>x and E<sol>xx>.
89
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90=head2 @{^CAPTURE}, %{^CAPTURE}, and %{^CAPTURE_ALL}
91
92C<@{^CAPTURE}> exposes the capture buffers of the last match as an
95b17558 93array. So C<$1> is C<${^CAPTURE}[0]>. This is a more efficient equivalent
95013431 94to code like C<substr($matched_string,$-[0],$+[0]-$-[0])>, and you don't
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95have to keep track of the C<$matched_string> either. This variable has no
96single character equivalent. Note, like the other regex magic variables
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97the contents of this variable is dynamic, if you wish to store it beyond
98the lifetime of the match you must copy it to another array.
2c8edc25 99
95b17558 100C<%{^CAPTURE}> is the equivalent to C<%+> (I<i.e.>, named captures). Other than
95013431 101being more self documenting there is no difference between the two forms.
2c8edc25 102
fce64130 103C<%{^CAPTURE_ALL}> is the equivalent to C<%-> (I<i.e.>, all named captures).
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104Other than being more self documenting there is no difference between the
105two forms.
2c8edc25 106
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107=head2 Declaring a reference to a variable
108
109As an experimental feature, Perl now allows the referencing operator to come
110after L<C<my()>|perlfunc/my>, L<C<state()>|perlfunc/state>,
111L<C<our()>|perlfunc/our>, or L<C<local()>|perlfunc/local>. This syntax must
112be enabled with C<use feature 'declared_refs'>. It is experimental, and will
113warn by default unless C<no warnings 'experimental::refaliasing'> is in effect.
114It is intended mainly for use in assignments to references. For example:
115
116 use experimental 'refaliasing', 'declared_refs';
117 my \$a = \$b;
118
119See L<perlref/Assigning to References> for more details.
120
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121=head2 Unicode 9.0 is now supported
122
123A list of changes is at L<http://www.unicode.org/versions/Unicode9.0.0/>.
124Modules that are shipped with core Perl but not maintained by p5p do not
125necessarily support Unicode 9.0. L<Unicode::Normalize> does work on 9.0.
126
127=head2 Use of C<\p{I<script>}> uses the improved Script_Extensions property
128
129Unicode 6.0 introduced an improved form of the Script (C<sc>) property, and
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130called it Script_Extensions (C<scx>). Perl now uses this improved
131version when a property is specified as just C<\p{I<script>}>. This
132should make programs be more accurate when determining if a character is
133used in a given script, but there is a slight chance of breakage for
134programs that very specifically needed the old behavior. The meaning of
135compound forms, like C<\p{sc=I<script>}> are unchanged. See
136L<perlunicode/Scripts>.
2c8edc25 137
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138=head2 Perl can now do default collation in UTF-8 locales on platforms
139that support it
a049258c 140
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141Some platforms natively do a reasonable job of collating and sorting in
142UTF-8 locales. Perl now works with those. For portability and full
143control, L<Unicode::Collate> is still recommended, but now you may
144not need to do anything special to get good-enough results, depending on
145your application. See
146L<perllocale/Category C<LC_COLLATE>: Collation: Text Comparisons and Sorting>.
147
148=head2 Better locale collation of strings containing embedded C<NUL>
149characters
150
fce64130 151In locales that have multi-level character weights, C<NUL>s are now
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152ignored at the higher priority ones. There are still some gotchas in
153some strings, though. See
154L<perllocale/Collation of strings containing embedded C<NUL> characters>.
155
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156=head2 C<CORE> subroutines for hash and array functions callable via
157reference
158
159The hash and array functions in the C<CORE> namespace--C<keys>, C<each>,
160C<values>, C<push>, C<pop>, C<shift>, C<unshift> and C<splice>--, can now
161be called with ampersand syntax (C<&CORE::keys(\%hash>) and via reference
e6abae1c 162(C<< my $k = \&CORE::keys; $k-E<gt>(\%hash) >>). Previously they could only be
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163used when inlined.
164
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165=head2 New Hash Function For 64-bit Builds
166
167We have switched to a hybrid hash function to better balance
168performance for short and long keys.
169
170For short keys, 16 bytes and under, we use an optimised variant of
171One At A Time Hard, and for longer keys we use Siphash 1-3. For very
172long keys this is a big improvement in performance. For shorter keys
173there is a modest improvement.
174
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175=head1 Security
176
df48f9a4 177=head2 Removal of the current directory (C<".">) from C<@INC>
2c8edc25 178
95b17558 179The perl binary includes a default set of paths in C<@INC>. Historically
df48f9a4 180it has also included the current directory (C<".">) as the final entry,
95b17558 181unless run with taint mode enabled (C<perl -T>). While convenient, this has
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182security implications: for example, where a script attempts to load an
183optional module when its current directory is untrusted (such as F</tmp>),
184it could load and execute code from under that directory.
185
df48f9a4 186Starting with v5.26, C<"."> is always removed by default, not just under
95b17558 187tainting. This has major implications for installing modules and executing
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188scripts.
189
190The following new features have been added to help ameliorate these
191issues.
192
193=over
194
195=item * C<Configure -Udefault_inc_excludes_dot>
196
197There is a new C<Configure> option, C<default_inc_excludes_dot> (enabled
df48f9a4 198by default) which builds a perl executable without C<".">; unsetting this
95b17558 199option using C<-U> reverts perl to the old behaviour. This may fix your
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200path issues but will reintroduce all the security concerns, so don't
201build a perl executable like this unless you're I<really> confident that
202such issues are not a concern in your environment.
203
409c12ef 204=item * C<PERL_USE_UNSAFE_INC>
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205
206There is a new environment variable recognised by the perl interpreter.
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207If this variable has the value 1 when the perl interpreter starts up,
208then C<"."> will be automatically appended to C<@INC> (except under tainting).
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209
210This allows you restore the old perl interpreter behaviour on a
95b17558 211case-by-case basis. But note that this is intended to be a temporary crutch,
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212and this feature will likely be removed in some future perl version.
213It is currently set by the C<cpan> utility and C<Test::Harness> to
fce64130 214ease installation of CPAN modules which have not been updated to handle the
95b17558 215lack of dot. Once again, don't use this unless you are sure that this
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216will not reintroduce any security concerns.
217
218=item * A new mandatory warning issued by C<do>.
219
220While it is well-known that C<use> and C<require> use C<@INC> to search
221for the file to load, many people don't realise that C<do "file"> also
df48f9a4 222searches C<@INC> if the file is a relative path. With the removal of C<".">,
89853d76 223a simple C<do "file.pl"> will fail to read in and execute C<file.pl> from
95b17558 224the current directory. Since this is commonly expected behaviour, a new
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225mandatory warning is now issued whenever C<do> fails to load a file which
226it otherwise would have found if dot had been in C<@INC>.
227
228=back
229
230Here are some things script and module authors may need to do to make
231their software work in the new regime.
232
233=over
234
235=item * Script authors
236
237If the issue is within your own code (rather than within included
95b17558 238modules), then you have two main options. Firstly, if you are confident
89853d76 239that your script will only be run within a trusted directory (under which
df48f9a4 240you expect to find trusted files and modules), then add C<"."> back into the
fce64130 241path; I<e.g.>:
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242
243 BEGIN {
244 my $dir = "/some/trusted/directory";
245 chdir $dir or die "Can't chdir to $dir: $!\n";
246 # safe now
247 push @INC, '.';
248 }
249 use "Foo::Bar"; # may load /some/trusted/directory/Foo/Bar.pm
250 do "config.pl"; # may load /some/trusted/directory/config.pl
251
252On the other hand, if your script is intended to be run from within
253untrusted directories (such as F</tmp>), then your script suddenly failing
95b17558 254to load files may be indicative of a security issue. You most likely want
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255to replace any relative paths with full paths; for example,
256
257 do ".foo_config.pl"
258
259might become
260
261 do "$ENV{HOME}/.foo_config.pl"
262
263If you are absolutely certain that you want your script to load and
264execute a file from the current directory, then use a C<./> prefix; for
265example:
266
267 do "./.foo_config.pl"
268
269=item * Installing and using CPAN modules
270
271If you install a CPAN module using an automatic tool like C<cpan>, then
272this tool will itself set the C<PERL_USE_UNSAFE_INC> environment variable
273while building and testing the module, which may be sufficient to install
274a distribution which hasn't been updated to be dot-aware. If you want to
275install such a module manually, then you'll need to replace the
276traditional invocation:
277
278 perl Makefile.PL && make && make test && make install
279
280with something like
281
282 (export PERL_USE_UNSAFE_INC=1; \
283 perl Makefile.PL && make && make test && make install)
284
95b17558 285Note that this only helps build and install an unfixed module. It's
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286possible for the tests to pass (since they were run under
287C<PERL_USE_UNSAFE_INC=1>), but for the module itself to fail to perform
95b17558 288correctly in production. In this case you may have to temporarily modify
0f275d26 289your script until such time as a fixed version of the module is released.
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290For example:
291
292 use Foo::Bar;
293 {
294 local @INC = (@INC, '.');
295 # assuming read_config() needs '.' in @INC
296 $config = Foo::Bar->read_config();
297 }
298
95b17558 299This is only rarely expected to be necessary. Again, if doing this,
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300assess the resultant risks first.
301
302=item * Module Authors
303
304If you maintain a CPAN distribution, it may need updating to run in
95b17558 305a dotless environment. Although C<cpan> and other such tools will
0f275d26 306currently set the C<PERL_USE_UNSAFE_INC> during module build, this is a
df48f9a4 307temporary workaround for the set of modules which rely on C<"."> being in
95b17558 308C<@INC> for installation and testing, and this may mask deeper issues. It
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309could result in a module which passes tests and installs, but which
310fails at run time.
311
312During build, test and install, it will normally be the case that any perl
313processes will be executing directly within the root directory of the
95b17558 314untarred distribution, or a known subdirectory of that, such as F<t/>. It
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315may well be that F<Makefile.PL> or F<t/foo.t> will attempt to include
316local modules and configuration files using their direct relative
317filenames, which will now fail.
318
319However, as described above, automatic tools like F<cpan> will (for now)
320set the C<PERL_USE_UNSAFE_INC> environment variable, which introduces
321dot during build.
322
323This makes it likely that your existing build and test code will work, but
324this may mask issues with your code which only manifest when used after
95b17558 325install. It is prudent to try and run your build process with that
89853d76 326variable explicitly disabled:
0f275d26 327
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328 (export PERL_USE_UNSAFE_INC=0; \
329 perl Makefile.PL && make && make test && make install)
330
331This is more likely to show up any potential problems with your module's
95b17558 332build process, or even with the module itself. Fixing such issues will
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333ensure both that your module can again be installed manually, and that
334it will still build once the C<PERL_USE_UNSAFE_INC> crutch goes away.
335
336When fixing issues in tests due to the removal of dot from C<@INC>,
337reinsertion of dot into C<@INC> should be performed with caution, for this
95b17558 338too may suppress real errors in your runtime code. You are encouraged
89853d76 339wherever possible to apply the aforementioned approaches with explicit
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340absolute/relative paths, or to relocate your needed files into a
341subdirectory and insert that subdirectory into C<@INC> instead.
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342
343If your runtime code has problems under the dotless C<@INC>, then the comments
95b17558 344above on how to fix for script authors will mostly apply here too. Bear in
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345mind though that it is considered bad form for a module to globally add dot to
346C<@INC>, since it introduces both a security risk and hides issues of
347accidentally requiring dot in C<@INC>, as explained above.
348
349=back
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350
351=head2 "Escaped" colons and relative paths in PATH
352
353On Unix systems, Perl treats any relative paths in the PATH environment
354variable as tainted when starting a new process. Previously, it was
355allowing a backslash to escape a colon (unlike the OS), consequently
356allowing relative paths to be considered safe if the PATH was set to
357something like C</\:.>. The check has been fixed to treat C<.> as tainted
358in that example.
359
360=head2 C<-Di> switch is now required for PerlIO debugging output
361
362Previously PerlIO debugging output would be sent to the file specified
363by the C<PERLIO_DEBUG> environment variable if perl wasn't running
364setuid and the C<-T> or C<-t> switches hadn't been parsed yet.
365
366If perl performed output at a point where it hadn't yet parsed its
367switches this could result in perl creating or overwriting the file
368named by C<PERLIO_DEBUG> even when the C<-T> switch had been supplied.
369
370Perl now requires the C<-Di> switch to produce PerlIO debugging
371output. By default this is written to C<stderr>, but can optionally
372be redirected to a file by setting the C<PERLIO_DEBUG> environment
373variable.
a049258c 374
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375If perl is running setuid or the C<-T> switch has supplied
376C<PERLIO_DEBUG> is ignored and the debugging output is sent to
377C<stderr> as for any other C<-D> switch.
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378
379=head1 Incompatible Changes
380
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381=head2 Unescaped literal C<"{"> characters in regular expression
382patterns are no longer permissible
a049258c 383
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384You have to now say something like C<"\{"> or C<"[{]"> to specify to
385match a LEFT CURLY BRACKET; otherwise it is a fatal pattern compilation
386error. This change will allow future extensions to the language.
387
388These have been deprecated since v5.16, with a deprecation message
389raised for some uses starting in v5.22. Unfortunately, the code added
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390to raise the message was buggy, and failed to warn in some cases where
391it should have. Therefore, enforcement of this ban for these cases is
392deferred until Perl 5.30, but the code has been fixed to raise a
393default-on deprecation message for them in the meantime.
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394
395Some uses of literal C<"{"> occur in contexts where we do not foresee
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396the meaning ever being anything but the literal, such as the very first
397character in the pattern, or after a C<"|"> meaning alternation. Thus
398
399 qr/{fee|{fie/
400
401matches either of the strings C<{fee> or C<{fie>. To avoid forcing
402unnecessary code changes, these uses do not need to be escaped, and no
403warning is raised about them, and there are no current plans to change this.
404
405But it is always correct to escape C<"{">, and the simple rule to
406remember is to always do so.
a049258c 407
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408=head2 C<scalar(%hash)> return signature changed
409
410The value returned for C<scalar(%hash)> will no longer show information about
411the buckets allocated in the hash. It will simply return the count of used
412keys. It is thus equivalent to C<0+keys(%hash)>.
413
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414A form of backwards compatibility is provided via
415L<C<Hash::Util::bucket_ratio()>|Hash::Util/bucket_ratio> which provides
416the same behavior as
417C<scalar(%hash)> provided in Perl 5.24 and earlier.
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418
419=head2 C<keys> returned from an lvalue subroutine
420
421C<keys> returned from an lvalue subroutine can no longer be assigned
422to in list context.
423
424 sub foo : lvalue { keys(%INC) }
425 (foo) = 3; # death
426 sub bar : lvalue { keys(@_) }
427 (bar) = 3; # also an error
428
429This makes the lvalue sub case consistent with C<(keys %hash) = ...> and
430C<(keys @_) = ...>, which are also errors. [perl #128187]
a049258c 431
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432=head2 C<${^ENCODING}> has been removed
433
434Consequently, the L<encoding> pragma's default mode is no longer supported. If
435you still need to write your source code in encodings other than UTF-8, use a
436source filter such as L<Filter::Encoding> on CPAN or L<encoding>'s C<Filter>
437option.
438
439=head2 POSIX::tmpnam() has been removed
440
441The fundamentally unsafe C<tmpnam()> interface was deprecated in
53799a91 442Perl 5.22 and has now been removed. In its place you can use,
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443for example, the L<File::Temp> interfaces.
444
445=head2 require ::Foo::Bar is now illegal.
446
95b17558 447Formerly, C<require ::Foo::Bar> would try to read F</Foo/Bar.pm>. Now any
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448bareword require which starts with a double colon dies instead.
449
450=head2 Literal control character variable names are no longer permissible
451
452A variable name may no longer contain a literal control character under
453any circumstances. These previously were allowed in single-character
454names on ASCII platforms, but have been deprecated there since Perl
4555.20. This affects things like C<$I<\cT>>, where I<\cT> is a literal
456control (such as a C<NAK> or C<NEGATIVE ACKNOWLEDGE> character) in the
457source code.
458
459=head2 C<NBSP> is no longer permissible in C<\N{...}>
460
461The name of a character may no longer contain non-breaking spaces. It
53799a91 462has been deprecated to do so since Perl 5.22.
8d25d2f3 463
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464=head1 Deprecations
465
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466=head2 String delimiters that aren't stand-alone graphemes are now deprecated
467
468In order for Perl to eventually allow string delimiters to be Unicode
469grapheme clusters (which look like a single character, but may be
0f275d26 470a sequence of several ones), we have to stop allowing a single character
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471delimiter that isn't a grapheme by itself. These are unlikely to exist
472in actual code, as they would typically display as attached to the
473character in front of them.
474
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475=head2 C<\cI<X>> that maps to a printable is no longer deprecated
476
477This means we have no plans to remove this feature. It still raises a
478warning, but only if syntax warnings are enabled. The feature was
479originally intended to be a way to express non-printable characters that
480don't have a mnemonic (C<\t> and C<\n> are mnemonics for two
481non-printable characters, but most non-printables don't have a
482mnemonic.) But the feature can be used to specify a few printable
483characters, though those are more clearly expressed as the printable
484itself. See
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485L<http://www.nntp.perl.org/group/perl.perl5.porters/2017/02/msg242944.html>.
486
2c8edc25 487=head1 Performance Enhancements
a049258c 488
2c8edc25 489=over 4
a049258c 490
2c8edc25 491=item *
a049258c 492
fce64130 493A hash in boolean context is now sometimes faster, I<e.g.>
a049258c 494
2c8edc25 495 if (!%h) { ... }
a049258c 496
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497This was already special-cased, but some cases were missed (such as
498C<grep %$_, @AoH>, and even the ones which weren't have been improved.
a049258c 499
2c8edc25 500=item * New Faster Hash Function on 64 bit builds
a049258c 501
95b17558 502We use a different hash function for short and long keys. This should
2c8edc25 503improve performance and security, especially for long keys.
a049258c 504
2c8edc25 505=item * readline is faster
a049258c 506
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507Reading from a file line-by-line with C<readline()> or C<< E<lt>E<gt> >> should
508now typically be faster due to a better implementation of the code that
509searches for the next newline character.
510
511=item *
a049258c 512
2c8edc25 513Reduce cost of SvVALID().
a049258c 514
2c8edc25 515=item *
ad5c8857 516
2c8edc25 517C<$ref1 = $ref2> has been optimized.
5e50eae4 518
4b99a68c 519=item *
f4b40f11 520
fce64130 521Array and hash assignment are now faster, I<e.g.>
ec34c8a4 522
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523 (..., @a) = (...);
524 (..., %h) = (...);
f4b40f11 525
2c8edc25 526especially when the RHS is empty.
ec34c8a4 527
2c8edc25 528=item *
a049258c 529
2c8edc25 530Reduce the number of odd special cases for the C<SvSCREAM> flag.
e770df11 531
2c8edc25 532=item *
a049258c 533
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534Avoid sv_catpvn() in do_vop() when unneeded.
535
536=item *
537
538Enhancements in Regex concat COW implementation.
539
540=item *
541
8928e7db
DM
542Better optimise array and hash assignment: where an array or hash appears
543in the LHS of a list assignment, such as C<(..., @a) = (...);>, it's
544likely to be considerably faster, especially if it involves emptying the
545array/hash. For example this code runs about 1/3 faster compared to
d3972b39 546Perl 5.24.0:
d053832c
AB
547
548 my @a;
8928e7db 549 for my $i (1..10_000_000) {
d053832c
AB
550 @a = (1,2,3);
551 @a = ();
552 }
553
2c8edc25
S
554
555=item *
556
557Converting a single-digit string to a number is now substantially faster.
558
559=item *
560
561The internal op implementing the C<split> builtin has been simplified and
95b17558
KW
562sped up. Firstly, it no longer requires a subsidiary internal C<pushre> op
563to do its work. Secondly, code of the form C<my @x = split(...)> is now
2c8edc25
S
564optimised in the same way as C<@x = split(...)>, and is therefore a few
565percent faster.
566
567=item *
568
569The rather slow implementation for the experimental subroutine signatures
570feature has been made much faster; it is now comparable in speed with the
571old-style C<my ($a, $b, @c) = @_>.
7ca0bfc4 572
fbe3f407
S
573=item *
574
2c8edc25 575Bareword constant strings are now permitted to take part in constant
95b17558 576folding. They were originally exempted from constant folding in August 1999,
2c8edc25 577during the development of Perl 5.6, to ensure that C<use strict "subs">
95b17558 578would still apply to bareword constants. That has now been accomplished a
2c8edc25
S
579different way, so barewords, like other constants, now gain the performance
580benefits of constant folding.
581
582This also means that void-context warnings on constant expressions of
583barewords now report the folded constant operand, rather than the operation;
584this matches the behaviour for non-bareword constants.
a049258c
S
585
586=back
587
2c8edc25
S
588=head1 Modules and Pragmata
589
a049258c
S
590=head2 Updated Modules and Pragmata
591
592=over 4
fbe3f407 593
759020c9 594=item *
7ca0bfc4 595
0cc8c746
S
596L<Archive::Tar> has been upgraded from version 2.04 to 2.24.
597
598=item *
599
600L<arybase> has been upgraded from version 0.11 to 0.12.
601
602=item *
603
604L<attributes> has been upgraded from version 0.27 to 0.29.
a049258c 605
2c8edc25 606The deprecation message for the C<:unique> and C<:locked> attributes
0f275d26 607now mention that they will disappear in Perl 5.28.
a049258c 608
2c8edc25 609=item *
a049258c 610
0cc8c746
S
611L<B> has been upgraded from version 1.62 to 1.68.
612
613=item *
614
615L<B::Concise> has been upgraded from version 0.996 to 0.999.
2c8edc25
S
616
617Its output is now more descriptive for C<op_private> flags.
d5c7a4fc 618
759020c9
S
619=item *
620
0cc8c746
S
621L<B::Debug> has been upgraded from version 1.23 to 1.24.
622
623=item *
624
625L<B::Deparse> has been upgraded from version 1.37 to 1.40.
626
627=item *
628
2c8edc25 629L<B::Xref> has been upgraded from version 1.05 to 1.06.
a049258c 630
2c8edc25 631It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]
a049258c 632
2c8edc25 633=item *
a049258c 634
0cc8c746
S
635L<base> has been upgraded from version 2.23 to 2.25.
636
637=item *
638
639L<bignum> has been upgraded from version 0.42 to 0.47.
640
641=item *
642
643L<Carp> has been upgraded from version 1.40 to 1.42.
644
645=item *
646
647L<charnames> has been upgraded from version 1.43 to 1.44.
648
649=item *
650
651L<Compress::Raw::Bzip2> has been upgraded from version 2.069 to 2.074.
652
653=item *
654
655L<Compress::Raw::Zlib> has been upgraded from version 2.069 to 2.074.
656
657=item *
658
659L<Config::Perl::V> has been upgraded from version 0.25 to 0.28.
660
661=item *
662
663L<CPAN> has been upgraded from version 2.11 to 2.18.
664
665=item *
666
667L<CPAN::Meta> has been upgraded from version 2.150005 to 2.150010.
668
669=item *
670
671L<Data::Dumper> has been upgraded from version 2.160 to 2.167.
a049258c 672
2c8edc25 673The XS implementation now supports Deparse.
a049258c 674
2c8edc25 675This fixes a stack management bug. [perl #130487].
a049258c 676
2c8edc25 677=item *
a049258c 678
0cc8c746
S
679L<DB_File> has been upgraded from version 1.835 to 1.840.
680
681=item *
682
683L<Devel::Peek> has been upgraded from version 1.23 to 1.26.
684
685=item *
686
687L<Devel::PPPort> has been upgraded from version 3.32 to 3.35.
688
689=item *
690
2c8edc25 691L<Devel::SelfStubber> has been upgraded from version 1.05 to 1.06.
a049258c 692
2c8edc25 693It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]
a049258c 694
2c8edc25 695=item *
a049258c 696
0cc8c746 697L<diagnostics> has been upgraded from version 1.34 to 1.36.
a049258c 698
2c8edc25 699It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]
7ca0bfc4 700
ad5c8857 701=item *
7ca0bfc4 702
0cc8c746
S
703L<Digest> has been upgraded from version 1.17 to 1.17_01.
704
705=item *
706
707L<Digest::MD5> has been upgraded from version 2.54 to 2.55.
708
709=item *
710
711L<Digest::SHA> has been upgraded from version 5.95 to 5.96.
712
713=item *
714
715L<DynaLoader> has been upgraded from version 1.38 to 1.42.
716
717=item *
718
719L<Encode> has been upgraded from version 2.80 to 2.88.
720
721=item *
722
723L<encoding> has been upgraded from version 2.17 to 2.19.
8f7edc68 724
ee8180b8 725This module's default mode is no longer supported. It now
2c8edc25 726dies when imported, unless the C<Filter> option is being used.
d5c7a4fc 727
2c8edc25 728=item *
d5c7a4fc 729
2c8edc25 730L<encoding::warnings> has been upgraded from version 0.12 to 0.13.
a049258c 731
ee8180b8 732This module is no longer supported. It emits a warning to
2c8edc25 733that effect and then does nothing.
a049258c 734
2c8edc25 735=item *
d5c7a4fc 736
0cc8c746 737L<Errno> has been upgraded from version 1.25 to 1.28.
a049258c 738
2c8edc25 739Document that using C<%!> loads Errno for you.
d5c7a4fc 740
2c8edc25 741It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]
3abe9611 742
c714fb1f 743=item *
3ce6a296 744
2c8edc25 745L<ExtUtils::Embed> has been upgraded from version 1.33 to 1.34.
a049258c 746
2c8edc25 747It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]
a049258c 748
2c8edc25 749=item *
a049258c 750
0cc8c746
S
751L<ExtUtils::MakeMaker> has been upgraded from version 7.10_01 to 7.24.
752
753=item *
754
755L<ExtUtils::Miniperl> has been upgraded from version 1.05 to 1.06.
756
757=item *
758
759L<ExtUtils::ParseXS> has been upgraded from version 3.31 to 3.34.
760
761=item *
762
763L<ExtUtils::Typemaps> has been upgraded from version 3.31 to 3.34.
764
765=item *
766
767L<feature> has been upgraded from version 1.42 to 1.47.
2c8edc25
S
768
769Fixes the Unicode Bug in the range operator.
a049258c
S
770
771=item *
5c92a635 772
0cc8c746
S
773L<File::Copy> has been upgraded from version 2.31 to 2.32.
774
775=item *
776
777L<File::Fetch> has been upgraded from version 0.48 to 0.52.
778
779=item *
780
781L<File::Glob> has been upgraded from version 1.26 to 1.28.
d5c7a4fc 782
2c8edc25 783Issue a deprecation message for C<File::Glob::glob()>.
d5c7a4fc 784
2c8edc25 785=item *
d5c7a4fc 786
0cc8c746
S
787L<File::Spec> has been upgraded from version 3.63 to 3.67.
788
789=item *
790
791L<FileHandle> has been upgraded from version 2.02 to 2.03.
792
793=item *
794
2c8edc25 795L<Filter::Simple> has been upgraded from version 0.92 to 0.93.
a049258c 796
2c8edc25
S
797It no longer treats C<no MyFilter> immediately following C<use MyFilter> as
798end-of-file. [perl #107726]
64afbd29
DM
799
800=item *
801
0cc8c746
S
802L<Getopt::Long> has been upgraded from version 2.48 to 2.49.
803
804=item *
805
806L<Getopt::Std> has been upgraded from version 1.11 to 1.12.
807
808=item *
809
810L<Hash::Util> has been upgraded from version 0.19 to 0.22.
811
812=item *
813
814L<HTTP::Tiny> has been upgraded from version 0.056 to 0.070.
a049258c 815
2c8edc25 816Internal 599-series errors now include the redirect history.
a049258c 817
2c8edc25 818=item *
a049258c 819
0cc8c746 820L<I18N::LangTags> has been upgraded from version 0.40 to 0.42.
a049258c 821
2c8edc25 822It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]
a049258c 823
2c8edc25 824=item *
a049258c 825
0cc8c746
S
826L<IO> has been upgraded from version 1.36 to 1.38.
827
828=item *
829
601d9a87 830IO-Compress has been upgraded from version 2.069 to 2.074.
0cc8c746
S
831
832=item *
833
834L<IO::Socket::IP> has been upgraded from version 0.37 to 0.38.
835
836=item *
837
838L<IPC::Cmd> has been upgraded from version 0.92 to 0.96.
839
840=item *
841
842L<IPC::SysV> has been upgraded from version 2.06_01 to 2.07.
843
844=item *
845
846L<JSON::PP> has been upgraded from version 2.27300 to 2.27400_02.
847
848=item *
849
2c8edc25
S
850L<lib> has been upgraded from version 0.63 to 0.64.
851
852It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]
faab9793 853
c714fb1f 854=item *
ad5c8857 855
0cc8c746
S
856L<List::Util> has been upgraded from version 1.42_02 to 1.46_02.
857
858=item *
859
860L<Locale::Codes> has been upgraded from version 3.37 to 3.42.
861
862=item *
863
864L<Locale::Maketext> has been upgraded from version 1.26 to 1.28.
865
866=item *
867
868L<Locale::Maketext::Simple> has been upgraded from version 0.21 to 0.21_01.
869
870=item *
871
872L<Math::BigInt> has been upgraded from version 1.999715 to 1.999806.
ad5c8857 873
2c8edc25 874There have also been some core customizations.
ad5c8857 875
2c8edc25 876=item *
2e0dcc12 877
0cc8c746
S
878L<Math::BigInt::FastCalc> has been upgraded from version 0.40 to 0.5005.
879
880=item *
881
882L<Math::BigRat> has been upgraded from version 0.260802 to 0.2611.
883
884=item *
885
886L<Math::Complex> has been upgraded from version 1.59 to 1.5901.
887
888=item *
889
890L<Memoize> has been upgraded from version 1.03 to 1.03_01.
891
892=item *
893
894L<Module::CoreList> has been upgraded from version 5.20170420 to 5.20170520.
895
896=item *
897
898L<Module::Load::Conditional> has been upgraded from version 0.64 to 0.68.
899
900=item *
901
902L<Module::Metadata> has been upgraded from version 1.000031 to 1.000033.
903
904=item *
905
906L<mro> has been upgraded from version 1.18 to 1.20.
907
908=item *
909
910L<Net::Ping> has been upgraded from version 2.43 to 2.55.
d5c7a4fc 911
2c8edc25
S
912IPv6 addresses and C<AF_INET6> sockets are now supported, along with several
913other enhancements.
d5c7a4fc 914
2c8edc25
S
915Remove sudo from 500_ping_icmp.t.
916
917Avoid stderr noise in tests
918
0f275d26 919Check for echo in new L<Net::Ping> tests.
d5c7a4fc 920
a049258c 921=item *
d5c7a4fc 922
0cc8c746
S
923L<NEXT> has been upgraded from version 0.65 to 0.67.
924
925=item *
926
927L<Opcode> has been upgraded from version 1.34 to 1.39.
928
929=item *
930
931L<open> has been upgraded from version 1.10 to 1.11.
932
933=item *
934
2c8edc25 935L<OS2::Process> has been upgraded from version 1.11 to 1.12.
a049258c 936
2c8edc25 937It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]
a049258c 938
2c8edc25 939=item *
a049258c 940
2c8edc25 941L<overload> has been upgraded from version 1.26 to 1.28.
a049258c 942
2c8edc25 943Its compilation speed has been improved slightly.
a049258c 944
2c8edc25
S
945=item *
946
0cc8c746
S
947L<parent> has been upgraded from version 0.234 to 0.236.
948
949=item *
950
2c8edc25
S
951L<perl5db.pl> has been upgraded from version 1.50 to 1.51.
952
953Ignore F</dev/tty> on non-Unix systems. [perl #113960]
954
955=item *
956
0cc8c746
S
957L<Perl::OSType> has been upgraded from version 1.009 to 1.010.
958
959=item *
960
961L<perlfaq> has been upgraded from version 5.021010 to 5.021011.
962
963=item *
964
965L<PerlIO> has been upgraded from version 1.09 to 1.10.
966
967=item *
968
969L<PerlIO::encoding> has been upgraded from version 0.24 to 0.25.
970
971=item *
972
973L<PerlIO::scalar> has been upgraded from version 0.24 to 0.26.
974
975=item *
976
977L<Pod::Checker> has been upgraded from version 1.60 to 1.73.
978
979=item *
980
981L<Pod::Functions> has been upgraded from version 1.10 to 1.11.
982
983=item *
984
985L<Pod::Html> has been upgraded from version 1.22 to 1.2202.
986
987=item *
988
989L<Pod::Perldoc> has been upgraded from version 3.25_02 to 3.28.
990
991=item *
992
993L<Pod::Simple> has been upgraded from version 3.32 to 3.35.
994
995=item *
996
997L<Pod::Usage> has been upgraded from version 1.68 to 1.69.
998
999=item *
1000
95b17558 1001L<POSIX> has been upgraded from version 1.65 to 1.76. This remedies several
2c8edc25
S
1002defects in making its symbols exportable. [perl #127821]
1003The C<POSIX::tmpnam()> interface has been removed,
1004see L</"POSIX::tmpnam() has been removed">.
1005Trying to import POSIX subs that have no real implementations
1006(like C<POSIX::atend()>) now fails at import time, instead of
1007waiting until runtime.
1008
1009=item *
1010
0cc8c746 1011L<re> has been upgraded from version 0.32 to 0.34
2c8edc25
S
1012
1013This adds support for the new L<C<E<47>xx>|perlre/E<sol>x and E<sol>xx>
1014regular expression pattern modifier, and a change to the L<S<C<use re
1015'strict'>>|re/'strict' mode> experimental feature. When S<C<re
1016'strict'>> is enabled, a warning now will be generated for all
df48f9a4 1017unescaped uses of the two characters C<"}"> and C<"]"> in regular
2c8edc25 1018expression patterns (outside bracketed character classes) that are taken
df48f9a4 1019literally. This brings them more in line with the C<")"> character which
2c8edc25
S
1020is always a metacharacter unless escaped. Being a metacharacter only
1021sometimes, depending on action at a distance, can lead to silently
1022having the pattern mean something quite different than was intended,
1023which the S<C<re 'strict'>> mode is intended to minimize.
1024
1025=item *
1026
0cc8c746
S
1027L<Safe> has been upgraded from version 2.39 to 2.40.
1028
1029=item *
1030
1031L<Scalar::Util> has been upgraded from version 1.42_02 to 1.46_02.
1032
1033=item *
1034
1035L<Storable> has been upgraded from version 2.56 to 2.62.
2c8edc25
S
1036
1037Fixes [perl #130098].
1038
1039=item *
1040
0cc8c746
S
1041L<Symbol> has been upgraded from version 1.07 to 1.08.
1042
1043=item *
1044
1045L<Sys::Syslog> has been upgraded from version 0.33 to 0.35.
1046
1047=item *
1048
1049L<Term::ANSIColor> has been upgraded from version 4.04 to 4.06.
1050
1051=item *
1052
2c8edc25
S
1053L<Term::ReadLine> has been upgraded from version 1.15 to 1.16.
1054
1055It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]
1056
1057=item *
1058
0cc8c746 1059L<Test> has been upgraded from version 1.28 to 1.30.
2c8edc25
S
1060
1061It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]
1062
1063=item *
1064
0cc8c746
S
1065L<Test::Harness> has been upgraded from version 3.36 to 3.38.
1066
1067=item *
1068
1069L<Test::Simple> has been upgraded from version 1.001014 to 1.302073.
1070
1071=item *
1072
1073L<Thread::Queue> has been upgraded from version 3.09 to 3.12.
1074
1075=item *
1076
2c8edc25
S
1077L<Thread::Semaphore> has been upgraded from 2.12 to 2.13.
1078
1079Added the C<down_timed> method.
1080
1081=item *
1082
0cc8c746 1083L<threads> has been upgraded from version 2.07 to 2.15.
2c8edc25
S
1084
1085Compatibility with 5.8 has been restored.
1086
1087Fixes [perl #130469].
1088
1089=item *
1090
0cc8c746 1091L<threads::shared> has been upgraded from version 1.51 to 1.56.
2c8edc25
S
1092
1093This fixes [cpan #119529], [perl #130457]
1094
1095=item *
1096
0cc8c746
S
1097L<Tie::Hash::NamedCapture> has been upgraded from version 0.09 to 0.10.
1098
1099=item *
1100
1101L<Time::HiRes> has been upgraded from version 1.9733 to 1.9741.
2c8edc25
S
1102
1103It now builds on systems with C++11 compilers (such as G++ 6 and Clang++
11043.9).
1105
1106Now uses C<clockid_t>.
1107
1108=item *
1109
0cc8c746
S
1110L<Time::Local> has been upgraded from version 1.2300 to 1.25.
1111
1112=item *
1113
1114L<Unicode::Collate> has been upgraded from version 1.14 to 1.19.
1115
1116=item *
1117
1118L<Unicode::UCD> has been upgraded from version 0.64 to 0.68.
2c8edc25
S
1119
1120It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]
1121
1122=item *
1123
0cc8c746
S
1124L<version> has been upgraded from version 0.9916 to 0.9917.
1125
1126=item *
1127
1128L<VMS::DCLsym> has been upgraded from version 1.06 to 1.08.
2c8edc25
S
1129
1130It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]
a049258c
S
1131
1132=item *
1133
0cc8c746
S
1134L<warnings> has been upgraded from version 1.36 to 1.37.
1135
1136=item *
1137
1138L<XS::Typemap> has been upgraded from version 0.14 to 0.15.
1139
1140=item *
1141
1142L<XSLoader> has been upgraded from version 0.21 to 0.27.
2c8edc25
S
1143
1144Fixed a security hole in which binary files could be loaded from a path
1145outside of L<C<@INC>|perlvar/@INC>.
1146
1147It now uses 3-arg C<open()> instead of 2-arg C<open()>. [perl #130122]
a049258c
S
1148
1149=back
1150
2c8edc25
S
1151=head1 Documentation
1152
1153=head2 New Documentation
a049258c 1154
2c8edc25 1155=head3 L<perldeprecation>
a049258c 1156
2c8edc25 1157This file documents all upcoming deprecations, and some of the deprecations
95b17558 1158which already have been removed. The purpose of this documentation is
2c8edc25
S
1159two-fold: document what will disappear, and by which version, and serve
1160as a guide for people dealing with code which has features that no longer
1161work after an upgrade of their perl.
a049258c 1162
2c8edc25 1163=head2 Changes to Existing Documentation
a049258c 1164
b10de59c
KW
1165We have attempted to update the documentation to reflect the changes
1166listed in this document. If you find any we have missed, send email to
1167L<mailto:perlbug@perl.org>.
a049258c 1168
b10de59c
KW
1169Additionally all references to Usenet have been removed, and the
1170following selected changes have been made:
2c8edc25 1171
b10de59c 1172=head3 L<perlfunc>
a049258c 1173
b10de59c 1174=over 4
a049258c 1175
2c8edc25
S
1176=item *
1177
b10de59c
KW
1178Removed obsolete text about L<C<defined()>|perlfunc/defined>
1179on aggregates that should have been deleted earlier, when the feature
1180was removed.
2c8edc25
S
1181
1182=item *
1183
b10de59c
KW
1184Corrected documentation of L<C<eval()>|perlfunc/eval>,
1185and L<C<evalbytes()>|perlfunc/evalbytes>.
a049258c 1186
2c8edc25 1187=item *
a049258c 1188
b10de59c
KW
1189Clarified documentation of L<C<seek()>|perlfunc/seek>,
1190L<C<tell()>|perlfunc/tell> and L<C<sysseek()>|perlfunc/sysseek>
1191regarding that positions are in bytes vs. characters.
1192L<[perl #128607]|https://rt.perl.org/Public/Bug/Display.html?id=128607>
2c8edc25
S
1193
1194=item *
1195
b10de59c
KW
1196Clarified documentation of L<C<sort()>|perlfunc/sort LIST> concerning
1197the variables C<$a> and C<$b>.
2c8edc25
S
1198
1199=item *
a049258c 1200
b10de59c 1201In L<C<split()>|perlfunc/split> added a caution about its use in Perls
d3972b39 1202before v5.11, and noted that certain pattern modifiers are legal in it.
a049258c 1203
2c8edc25 1204=item *
a049258c 1205
b10de59c
KW
1206Removed obsolete documentation of L<C<study()>|perlfunc/study>, noting
1207that it is now a no-op.
2c8edc25
S
1208
1209=item *
1210
b10de59c
KW
1211Noted that L<C<vec()>|perlfunc/vec> doesn't work well when the string
1212contains characters whose code points are above 255.
a049258c 1213
2c8edc25 1214=back
a049258c 1215
b10de59c 1216=head3 L<perlguts>
a049258c
S
1217
1218=over 4
1219
1220=item *
1221
b10de59c
KW
1222Added advice on
1223L<formatted printing of operands of C<Size_t> and C<SSize_t>|perlguts/Formatted Printing of Size_t and SSize_t>
a049258c
S
1224
1225=back
1226
b10de59c 1227=head3 L<perlhack>
2c8edc25
S
1228
1229=over 4
1230
1231=item *
1232
b10de59c
KW
1233Clariy indentation rules, and note that we are migrating away from using
1234tabs to indent, replacing them with sequences of SPACE characters.
2c8edc25
S
1235
1236=back
a049258c 1237
b10de59c 1238=head3 L<perlhacktips>
a049258c
S
1239
1240=over 4
1241
1242=item *
1243
b10de59c 1244Give another reason to use C<cBOOL> to cast an expression to boolean.
2c8edc25
S
1245
1246=item *
1247
b10de59c
KW
1248Note that there are macros C<TRUE> and C<FALSE> available to express
1249boolean values.
a049258c 1250
2c8edc25 1251=back
a049258c 1252
2c8edc25 1253=head3 L<perlinterp>
a049258c
S
1254
1255=over 4
1256
1257=item *
1258
2c8edc25
S
1259L<perlinterp> has been expanded to give a more detailed example of how to
1260hunt around in the parser for how a given operator is handled.
a049258c
S
1261
1262=back
1263
2c8edc25 1264=head3 L<perllocale>
a049258c
S
1265
1266=over 4
1267
a6733086
S
1268=item *
1269
b10de59c
KW
1270Some locales aren't compatible with Perl. Note that these can cause
1271core dumps.
a049258c
S
1272
1273=back
1274
2c8edc25
S
1275=head3 L<perlmodinstall>
1276
1277=over 4
1278
1279=item *
1280
b10de59c 1281Various clarifications have been added.
2c8edc25
S
1282
1283=back
1284
1285=head3 L<perlmodlib>
1286
1287=over 4
1288
1289=item *
1290
b10de59c 1291Updated the site mirror list.
2c8edc25
S
1292
1293=back
1294
1295=head3 L<perlobj>
1296
1297=over 4
1298
1299=item *
1300
1301Added a section on calling methods using their fully qualified names.
1302
1303=item *
1304
1305Do not discourage manual @ISA.
1306
1307=back
1308
1309=head3 L<perlootut>
1310
1311=over 4
1312
1313=item *
1314
2c8edc25
S
1315Mention C<Moo> more.
1316
1317=back
1318
1319=head3 L<perlop>
1320
1321=over 4
1322
1323=item *
1324
0f275d26 1325Clarify behavior of single quote regexps.
2c8edc25
S
1326
1327=back
1328
1329=head3 L<perlre>
1330
1331=over 4
1332
1333=item *
1334
1c34b59a
KW
1335The first part was extensively rewritten to incorporate various basic
1336points, that in earlier versions were mentioned in sort of an appendix
1337on Version 8 regular expressions.
1338
b10de59c
KW
1339Note that it is common to have the C</x> modifier and forget that this
1340means that C<"#"> has to be escaped.
2c8edc25
S
1341
1342=back
1343
b10de59c 1344=head3 L<perlretut>
2c8edc25
S
1345
1346=over 4
1347
1348=item *
1349
b10de59c 1350Add introductory material
2c8edc25
S
1351
1352=item *
1353
b10de59c
KW
1354Note that a metacharacter occurring in a context where it can't mean
1355that, silently loses its meta-ness and matches literally.
1356L<C<use re 'strict'>|re/'strict' mode> can catch some of these.
2c8edc25
S
1357
1358=back
1359
1360=head3 L<perlunicode>
1361
1362=over 4
1363
1364=item *
1365
b10de59c 1366Corrected the text about Unicode BYTE ORDER MARK handling.
2c8edc25
S
1367
1368=item *
1369
1370Updated the text to correspond with changes in Unicode UTS#18, concerning
1371regular expressions, and Perl compatibility with what it says.
1372
1373=back
1374
1375=head3 L<perlvar>
1376
1377=over 4
1378
1379=item *
1380
95b17558 1381Document C<@ISA>. Was documented other places, not not in L<perlvar>.
2c8edc25
S
1382
1383=back
1384
1385=head1 Diagnostics
1386
1387=head2 New Diagnostics
1388
1389=head3 New Errors
1390
1391=over 4
1392
1393=item *
1394
df48f9a4 1395Since C<"."> is now removed from C<@INC> by default, C<do> will now trigger
2c8edc25
S
1396a warning recommending to fix the C<do> statement:
1397
1398L<do "%s" failed, '.' is no longer in @INC|perldiag/do "%s" failed, '.' is no longer in @INC; did you mean do ".E<sol>%s"?>
1399
1400=item *
1401
1402Using the empty pattern (which re-executes the last successfully-matched
1403pattern) inside a code block in another regex, as in C</(?{ s!!new! })/>, has
95b17558 1404always previously yielded a segfault. It now produces an error:
4f73c567 1405L<Infinite recursion in regex|perldiag/"Infinite recursion in regex">.
2c8edc25
S
1406
1407=item *
1408
1409L<The experimental declared_refs feature is not enabled|perldiag/"The experimental declared_refs feature is not enabled">
1410
1411(F) To declare references to variables, as in C<my \%x>, you must first enable
1412the feature:
1413
1414 no warnings "experimental::declared_refs";
1415 use feature "declared_refs";
1416
1417=item *
1418
1419L<Version control conflict marker|perldiag/"Version control conflict marker">
1420
e6abae1c 1421(F) The parser found a line starting with C<E<lt>E<lt>E<lt>E<lt>E<lt>E<lt>E<lt>>,
95b17558 1422C<E<gt>E<gt>E<gt>E<gt>E<gt>E<gt>E<gt>>, or C<=======>. These may be left by a
2c8edc25
S
1423version control system to mark conflicts after a failed merge operation.
1424
1425=item *
1426
1427L<%s: command not found|perldiag/"%s: command not found">
1428
1429(A) You've accidentally run your script through B<bash> or another shell
1430instead of Perl. Check the #! line, or manually feed your script into
1431Perl yourself. The #! line at the top of your file could look like:
1432
1433 #!/usr/bin/perl
1434
1435=item *
1436
1437L<%s: command not found: %s|perldiag/"%s: command not found: %s">
1438
1439(A) You've accidentally run your script through B<zsh> or another shell
1440instead of Perl. Check the #! line, or manually feed your script into
1441Perl yourself. The #! line at the top of your file could look like:
1442
1443 #!/usr/bin/perl
1444
1445=item *
1446
a6733086 1447L<Unescaped left brace in regex is illegal here|perldiag/Unescaped left brace in regex is illegal here in regex; marked by S<E<lt>-- HERE> in mE<sol>%sE<sol>>
2c8edc25 1448
d8362e1b
KW
1449Unescaped left braces are now illegal in some contexts in regular expression
1450patterns. In other contexts, they are still just deprecated; they will
1451be illegal in Perl 5.30.
2c8edc25
S
1452
1453=item *
1454
1455L<Bareword in require contains "%s"|perldiag/"Bareword in require contains "%s"">
1456
1457=item *
1458
1459L<Bareword in require maps to empty filename|perldiag/"Bareword in require maps to empty filename">
1460
1461=item *
1462
1463L<Bareword in require maps to disallowed filename "%s"|perldiag/"Bareword in require maps to disallowed filename "%s"">
1464
1465=item *
1466
1467L<Bareword in require must not start with a double-colon: "%s"|perldiag/"Bareword in require must not start with a double-colon: "%s"">
1468
1469=back
1470
1471=head3 New Warnings
1472
1473=over 4
1474
1475=item *
1476
4f73c567 1477L<Use of unassigned code point or non-standalone grapheme for a delimiter will be a fatal error starting in Perl 5.30|perldiag/"Use of unassigned code point or non-standalone grapheme for a delimiter will be a fatal error starting in Perl 5.30">
2c8edc25
S
1478
1479See L</Deprecations>
1480
1481=item *
1482
1483L<Declaring references is experimental|perldiag/"Declaring references is experimental">
1484
1485(S experimental::declared_refs) This warning is emitted if you use a reference
1486constructor on the right-hand side of C<my()>, C<state()>, C<our()>, or
1487C<local()>. Simply suppress the warning if you want to use the feature, but
1488know that in doing so you are taking the risk of using an experimental feature
1489which may change or be removed in a future Perl version:
1490
1491 no warnings "experimental::declared_refs";
1492 use feature "declared_refs";
1493 $fooref = my \$foo;
1494
1495=item *
1496
4f73c567 1497L<C<${^ENCODING}> is no longer supported. Its use will be fatal in Perl 5.28|perldiag/"${^ENCODING} is no longer supported. Its use will be fatal in Perl 5.28">
2c8edc25 1498
0f275d26 1499The special variable C<${^ENCODING}>, formerly used to implement
53799a91 1500the C<encoding> pragma, is no longer supported as of Perl 5.26.
2c8edc25 1501
89853d76
DH
1502=item *
1503
df48f9a4 1504Since C<"."> is now removed from C<@INC> by default, C<do> will now trigger
89853d76
DH
1505a warning recommending to fix the C<do> statement:
1506
fc902710 1507L<do "%s" failed, '.' is no longer in @INC|perldiag/do "%s" failed, '.' is no longer in @INC; did you mean do ".E<sol>%s"?>
89853d76 1508
2c8edc25
S
1509=back
1510
1511=head2 Changes to Existing Diagnostics
1512
1513=over 4
1514
1515=item *
1516
1517When a C<require> fails, we now do not provide C<@INC> when the C<require>
1518is for a file instead of a module.
1519
1520=item *
1521
1522When C<@INC> is not scanned for a C<require> call, we no longer display
1523C<@INC> to avoid confusion.
1524
1525=item *
1526
1527Attribute "locked" is deprecated, and will disappear in Perl 5.28
1528
1529=item *
1530
1531Attribute "unique" is deprecated, and will disappear in Perl 5.28
1532
1533=item *
1534
1535Constants from lexical variables potentially modified elsewhere are
1536deprecated. This will not be allowed in Perl 5.32
1537
1538=item *
1539
1540Deprecated use of my() in false conditional. This will be a fatal error
1541in Perl 5.30
1542
1543=item *
1544
1545dump() better written as CORE::dump(). dump() will no longer be available
1546in Perl 5.30
1547
1548=item *
1549
1550${^ENCODING} is no longer supported. Its use will be fatal in Perl 5.28
1551
1552=item *
1553
1554File::Glob::glob() will disappear in perl 5.30. Use File::Glob::bsd_glob()
1555instead.
1556
1557=item *
1558
1559%s() is deprecated on :utf8 handles. This will be a fatal error in Perl 5.30
1560
1561=item *
1562
1563$* is no longer supported. Its use will be fatal in Perl 5.30
1564
1565=item *
1566
1567$* is no longer supported. Its use will be fatal in Perl 5.30
1568
1569=item *
1570
1571Opening dirhandle %s also as a file. This will be a fatal error in Perl 5.28
1572
1573=item *
1574
1575Opening filehandle %s also as a directory. This will be a fatal
1576error in Perl 5.28
1577
1578=item *
1579
1580Setting $/ to a reference to %s as a form of slurp is deprecated,
1581treating as undef. This will be fatal in Perl 5.28
1582
1583=item *
1584
1585Unescaped left brace in regex is deprecated here (and will be fatal
1586in Perl 5.30), passed through in regex; marked by S<< E<lt>-- HERE >> in m/%s/
1587
1588=item *
1589
1590Unknown charname '' is deprecated. Its use will be fatal in Perl 5.28
1591
1592=item *
1593
1594Use of bare E<lt>E<lt> to mean E<lt>E<lt>"" is deprecated. Its use will be fatal in Perl 5.28
1595
1596=item *
1597
1598Use of code point 0x%s is deprecated; the permissible max is 0x%s.
1599This will be fatal in Perl 5.28
1600
1601=item *
1602
1603Use of comma-less variable list is deprecated. Its use will be fatal
1604in Perl 5.28
1605
1606=item *
1607
1608Use of inherited AUTOLOAD for non-method %s() is deprecated. This
1609will be fatal in Perl 5.28
1610
1611=item *
1612
1613Use of strings with code points over 0xFF as arguments to %s operator
1614is deprecated. This will be a fatal error in Perl 5.28
1615
1616=item *
1617
1618Improve error for missing tie() package/method. This brings the error messages
1619in line with the ones used for normal method calls, despite not using
1620call_method().
1621
1622=item *
1623
1624Make the sysread()/syswrite/() etc :utf8 handle warnings default. These
1625warnings were under 'deprecated' previously.
1626
1627=item *
1628
1629'do' errors now refer to 'do' (not 'require').
1630
1631=item *
1632
1633Details as to the exact problem have been added to the diagnostics that
1634occur when malformed UTF-8 is encountered when trying to convert to a
1635code point.
1636
1637=item *
1638
1639Executing C<undef $x> where C<$x> is tied or magical no longer incorrectly
1640blames the variable for an uninitialized-value warning encountered by the
1641tied/magical code.
1642
1643=item *
1644
2c8edc25
S
1645Code like C<$x = $x . "a"> was incorrectly failing to yield a
1646L<use of uninitialized value|perldiag/"Use of uninitialized value%s">
1647warning when C<$x> was a lexical variable with an undefined value. That has
1648now been fixed. [perl #127877]
1649
1650=item *
1651
1652When the error "Experimental push on scalar is now forbidden" is raised for
1653the hash functions C<keys>, C<each>, and C<values>, it is now followed by
1654the more helpful message, "Type of arg 1 to whatever must be hash or
1655array". [perl #127976]
1656
1657=item *
1658
1659C<undef *_; shift> or C<undef *_; pop> inside a subroutine, with no
53799a91 1660argument to C<shift> or C<pop>, began crashing in Perl 5.14, but has now
2c8edc25
S
1661been fixed.
1662
1663=item *
1664
1665C<< "string$scalar-E<gt>$*" >> now correctly prefers concat overloading to
1666string overloading if C<< $scalar-E<gt>$* >> returns an overloaded object,
1667bringing it into consistency with C<$$scalar>.
1668
1669=item *
1670
1671C<< /@0{0*-E<gt>@*/*0 >> and similar contortions used to crash, but no longer
1672do, but merely produce a syntax error. [perl #128171]
1673
1674=item *
1675
1676C<do> or C<require> with a reference or typeglob which, when stringified,
53799a91 1677contains a null character started crashing in Perl 5.20, but has now been
2c8edc25
S
1678fixed. [perl #128182]
1679
1680=back
1681
1682=head1 Utility Changes
1683
1684=head2 F<c2ph> and F<pstruct>
1685
1686=over 4
1687
1688=item *
1689
1690These old utilities have long since superceded by L<h2xs>, and are
1691now gone from the distribution.
1692
1693=back
1694
1695=head2 F<Porting/pod_lib.pl>
1696
1697=over 4
1698
1699=item *
1700
1701Removed spurious executable bit.
1702
1703=item *
1704
1705Account for possibility of DOS file endings.
1706
1707=back
1708
1709=head2 F<Porting/sync-with-cpan>
1710
1711=over 4
1712
1713=item *
1714
1715Many improvements
1716
1717=back
1718
1719=head2 F<perf/benchmarks>
1720
1721=over 4
1722
1723=item *
1724
1725Tidy file, rename some symbols.
1726
1727=back
1728
1729=head2 F<Porting/checkAUTHORS.pl>
1730
1731=over 4
1732
1733=item *
1734
0f275d26 1735Replace obscure character range with C<\w>.
2c8edc25
S
1736
1737=back
1738
1739=head2 F<t/porting/regen.t>
1740
1741=over 4
1742
1743=item *
1744
1745try to be more helpful when tests fail.
1746
1747=back
1748
1749=head2 F<utils/h2xs.PL>
1750
1751=over 4
1752
1753=item *
1754
1755Avoid infinite loop for enums.
1756
1757=back
1758
1759=head2 L<perlbug>
1760
1761=over 4
1762
1763=item *
1764
1765Long lines in the message body are now wrapped at 900 characters, to stay
1766well within the 1000-character limit imposed by SMTP mail transfer agents.
1767This is particularly likely to be important for the list of arguments to
1768C<Configure>, which can readily exceed the limit if, for example, it names
95b17558 1769several non-default installation paths. This change also adds the first unit
2c8edc25
S
1770tests for perlbug. [perl #128020]
1771
1772=back
1773
1774=head1 Configuration and Compilation
1775
1776=over 4
1777
1778=item *
1779
89853d76 1780C<-Ddefault_inc_excludes_dot> has been turned on by default.
2c8edc25
S
1781
1782=item *
1783
1784The C<dtrace> build process has further changes:
1785
1786=over
1787
1788=item *
1789
1790If the C<-xnolibs> is available, use that so a F<dtrace> perl can be
1791built within a FreeBSD jail.
1792
1793=item *
1794
1795On systems that build a dtrace object file (FreeBSD, Solaris and
1796SystemTap's dtrace emulation), copy the input objects to a separate
1797directory and process them there, and use those objects in the link,
1798since C<dtrace -G> also modifies these objects.
1799
1800=item *
1801
1802Add libelf to the build on FreeBSD 10.x, since dtrace adds references
1803to libelf symbols.
1804
1805=item *
1806
1807Generate a dummy dtrace_main.o if C<dtrace -G> fails to build it. A
1808default build on Solaris generates probes from the unused inline
1809functions, while they don't on FreeBSD, which causes C<dtrace -G> to
1810fail.
1811
1812=back
1813
1814[perl #130108]
1815
1816=item *
1817
1818You can now disable perl's use of the PERL_HASH_SEED and
1819PERL_PERTURB_KEYS environment variables by configuring perl with
1820C<-Accflags=NO_PERL_HASH_ENV>.
1821
1822=item *
1823
1824You can now disable perl's use of the PERL_HASH_SEED_DEBUG environment
1825variable by configuring perl with
1826C<-Accflags=-DNO_PERL_HASH_SEED_DEBUG>.
1827
1828=item *
1829
1830Zero out the alignment bytes when calculating the bytes for 80-bit C<NaN>
1831and C<Inf> to make builds more reproducible. [perl #130133]
1832
1833=item *
1834
d3972b39 1835Since v5.18 for testing purposes we have included support for
2c8edc25 1836building perl with a variety of non-standard, and non-recommended
95b17558
KW
1837hash functions. Since we do not recommend the use of these functions
1838we have removed them and their corresponding build options. Specifically
2c8edc25
S
1839this includes the following build options:
1840
1841 PERL_HASH_FUNC_SDBM
1842 PERL_HASH_FUNC_DJB2
1843 PERL_HASH_FUNC_SUPERFAST
1844 PERL_HASH_FUNC_MURMUR3
1845 PERL_HASH_FUNC_ONE_AT_A_TIME
1846 PERL_HASH_FUNC_ONE_AT_A_TIME_OLD
1847 PERL_HASH_FUNC_MURMUR_HASH_64A
1848 PERL_HASH_FUNC_MURMUR_HASH_64B
1849
1850=item *
1851
1852Remove "Warning: perl appears in your path"
1853
1854This install warning is more or less obsolete, since most platforms already
1855*will* have a /usr/bin/perl or similar provided by the OS.
1856
1857=item *
1858
1859Reduce verbosity of "make install.man"
1860
1861Previously, two progress messages were emitted for each manpage: one by
1862installman itself, and one by the function in install_lib.pl that it calls to
95b17558 1863actually install the file. Disabling the second of those in each case saves
2c8edc25
S
1864over 750 lines of unhelpful output.
1865
1866=item *
1867
1868Cleanup for clang -Weverything support. [perl 129961]
1869
1870=item *
1871
1872Configure: signbit scan was assuming too much, stop assuming negative 0.
1873
1874=item *
1875
1876Various compiler warnings have been silenced.
1877
1878=item *
1879
1880Several smaller changes have been made to remove impediments to compiling under
1881C++11.
1882
1883=item *
1884
1885Builds using C<USE_PAD_RESET> now work again; this configuration had
1886bit-rotted.
1887
1888=item *
1889
1890A probe for C<gai_strerror> was added to F<Configure> that checks if the
1891the gai_strerror() routine is available and can be used to
1892translate error codes returned by getaddrinfo() into human
1893readable strings.
1894
1895=item *
1896
1897F<Configure> now aborts if both "-Duselongdouble" and "-Dusequadmath" are
1898requested.
1899L<[perl #126203]|https://rt.perl.org/Public/Bug/Display.html?id=126203>
1900
1901=item *
1902
1903Fixed a bug in which F<Configure> could append "-quadmath" to the archname even
1904if it was already present.
1905L<[perl #128538]|https://rt.perl.org/Public/Bug/Display.html?id=128538>
1906
1907=item *
1908
1909Clang builds with "-DPERL_GLOBAL_STRUCT" or "-DPERL_GLOBAL_STRUCT_PRIVATE" have
1910been fixed (by disabling Thread Safety Analysis for these configurations).
1911
1912=item *
1913
1914F<make_ext.pl> no longer updates a module's F<pm_to_blib> file when no
1915files require updates. This could cause dependencies, F<perlmain.c>
1916in particular, to be rebuilt unnecessarily. [perl #126710]
1917
1918=item *
1919
1920The output of C<perl -V> has been reformatted so that each configuration
1921and compile-time option is now listed one per line, to improve
1922readability.
1923
1924=item *
1925
1926C<Configure> now builds C<miniperl> and C<generate_uudmap> if you
1927invoke it with C<-Dusecrosscompiler> but not C<-Dtargethost=somehost>.
1928This means you can supply your target platform C<config.sh>, generate
1929the headers and proceed to build your cross-target perl. [perl #127234]
1930
1931=item *
1932
1933Builds with C<-Accflags=-DPERL_TRACE_OPS> now only dump the operator
1934counts when the environment variable C<PERL_TRACE_OPS> to be set to a
1935non-zero integer. This allows C<make test> to pass on such a build.
1936
1937=item *
1938
1939When building with GCC 6 and link-time optimization (the C<-flto> option to
1940C<gcc>), C<Configure> was treating all probed symbols as present on the
95b17558 1941system, regardless of whether they actually exist. This has been fixed.
2c8edc25
S
1942[perl #128131]
1943
1944=item *
1945
1946The F<t/test.pl> library is used for internal testing of Perl itself, and
95b17558 1947also copied by several CPAN modules. Some of those modules must work on
2c8edc25 1948older versions of Perl, so F<t/test.pl> must in turn avoid newer Perl
95b17558 1949features. Compatibility with Perl 5.8 was inadvertently removed some time
2c8edc25
S
1950ago; it has now been restored. [perl #128052]
1951
1952=item *
1953
1954The build process no longer emits an extra blank line before building each
1955"simple" extension (those with only F<*.pm> and F<*.pod> files).
1956
1957=back
1958
1959=head1 Testing
1960
dd84ba97
KW
1961Tests were added and changed to reflect the other additions and changes
1962in this release. In addition, these substantive changes were made:
1963
2c8edc25
S
1964=over 4
1965
1966=item *
1967
dd84ba97
KW
1968A new test script, F<comp/parser_run.t>, has been added to test
1969reads through invalid pointers.
2c8edc25
S
1970
1971=item *
1972
1973Tests for locales were erroneously using locales incompatible with Perl.
1974
1975=item *
1976
1977Some parts of the test suite that try to exhaustively test edge cases in the
1978regex implementation have been restricted to running for a maximum of five
95b17558 1979minutes. On slow systems they could otherwise take several hours, without
2c8edc25
S
1980significantly improving our understanding of the correctness of the code
1981under test.
1982
1983In addition, some of those test cases have been split into more files, to
1984allow them to be run in parallel on suitable systems.
1985
1986=item *
1987
1988A new internal facility allows analysing the time taken by the individual
1989tests in Perl's own test suite; see F<Porting/harness-timer-report.pl>.
1990
1991=item *
1992
1993F<t/re/regexp_nonull.t> has been added to test that the regular expression
1994engine can handle scalars that do not have a null byte just past the end of
1995the string.
1996
1997=item *
1998
1999A new test script, F<t/op/decl-refs.t>, has been added to test the new feature,
2000"Declaring a reference to a variable".
2001
2002=item *
2003
dd84ba97
KW
2004A new test script, F<t/re/keep_tabs.t> has been added to contain tests
2005where C<\t> characters should not be expanded into spaces.
2006
2007=item *
2008
2c8edc25
S
2009A new test script, F<t/re/anyof.t>, has been added to test that the ANYOF nodes
2010generated by bracketed character classes are as expected.
2011
2012=item *
2013
dd84ba97
KW
2014There is now more extensive testing of the Unicode-related API macros
2015and functions.
2016
2017=item *
2018
2019Several of the longer running API test files have been split into
2020multiple test files so that they can be run in parallel.
2021
2022=item *
2023
2c8edc25
S
2024F<t/harness> now tries really hard not to run tests outside of the Perl
2025source tree. [perl #124050]
2026
2027=back
2028
2029=head1 Platform Support
2030
2031=head2 New Platforms
2032
2033=over 4
2034
2035=item NetBSD/VAX
2036
2037Perl now compiles under NetBSD on VAX machines. However, it's not
2038possible for that platform to implement floating-point infinities and
2039NaNs compatibly with most modern systems, which implement the IEEE-754
2040floating point standard. The hexadecimal floating point (C<0x...p[+-]n>
2041literals, C<printf %a>) is not implemented, either.
2042The C<make test> passes 98% of tests.
2043
2044=over 4
2045
2046=item *
2047
2048Test fixes and minor updates.
2049
2050=item *
2051
2052Account for lack of C<inf>, C<nan>, and C<-0.0> support.
2053
2054=back
2055
2056=back
2057
2058=head2 Platform-Specific Notes
2059
2060=over 4
2061
2062=item Darwin
2063
2064don't treat -Dprefix=/usr as special, instead require an extra option
2065-Ddarwin_distribution to produce the same results.
2066
2067=item POSIX
2068
2069Finish removing POSIX deprecated functions.
2070
2071=item OS X
2072
29ce4d71 2073OS X El Capitan doesn't implement the clock_gettime() or clock_getres() APIs;
2c8edc25
S
2074emulate them as necessary.
2075
2076=item macOS
2077
2078Deprecated syscall(2) on macOS 10.12.
2079
2080=item EBCDIC
2081
2082Several tests have been updated to work (or be skipped) on EBCDIC platforms.
2083
2084=item HP-UX
2085
2086L<Net::Ping> UDP test is skipped on HP-UX.
2087
2088=item Hurd
2089
2090The hints for Hurd have been improved enabling malloc wrap and reporting the
2091GNU libc used (previously it was an empty string when reported).
2092
2093=item VAX
2094
29ce4d71 2095VAX floating point formats are now supported on NetBSD.
2c8edc25
S
2096
2097=item VMS
2098
2099=over 4
2100
2101=item *
2102
2103The path separator for the C<PERL5LIB> and C<PERLLIB> environment entries is
df48f9a4
KW
2104now a colon (C<":">) when running under a Unix shell. There is no change when
2105running under DCL (it's still C<"|">).
2c8edc25
S
2106
2107=item *
2108
29ce4d71
CB
2109C<configure.com> now recognizes the VSI-branded C compiler and no longer
2110recognizes the "DEC"-branded C compiler (as there hasn't been such a thing for
211115 or more years).
2c8edc25
S
2112
2113=back
2114
2115=item Windows
2116
2117=over 4
2118
2119=item *
2120
2121Support for compiling perl on Windows using Microsoft Visual Studio 2015
2122(containing Visual C++ 14.0) has been added.
2123
2124This version of VC++ includes a completely rewritten C run-time library, some
2125of the changes in which mean that work done to resolve a socket close() bug in
2126perl #120091 and perl #118059 is not workable in its current state with this
2127version of VC++. Therefore, we have effectively reverted that bug fix for
2128VS2015 onwards on the basis that being able to build with VS2015 onwards is
2129more important than keeping the bug fix. We may revisit this in the future to
2130attempt to fix the bug again in a way that is compatible with VS2015.
2131
2132These changes do not affect compilation with GCC or with Visual Studio versions
fce64130 2133up to and including VS2013, I<i.e.>, the bug fix is retained (unchanged) for those
2c8edc25
S
2134compilers.
2135
2136Note that you may experience compatibility problems if you mix a perl built
2137with GCC or VS E<lt>= VS2013 with XS modules built with VS2015, or if you mix a
2138perl built with VS2015 with XS modules built with GCC or VS E<lt>= VS2013.
2139Some incompatibility may arise because of the bug fix that has been reverted
2140for VS2015 builds of perl, but there may well be incompatibility anyway because
fce64130 2141of the rewritten CRT in VS2015 (I<e.g.>, see discussion at
2c8edc25
S
2142http://stackoverflow.com/questions/30412951).
2143
2144=back
2145
2146=item Win32
2147
2148=over 4
2149
2150=item *
2151
95b17558 2152Tweaks for Win32 VC vs GCC detection makefile code. This fixes issue that CCHOME
2c8edc25 2153depends on CCTYPE, which in auto detect mode is set after CCHOME, so CCHOME uses
95b17558 2154the uninit CCTYPE var. Also fix else vs .ELSE in makefile.mk
2c8edc25
S
2155
2156=item *
2157
2158fp definitions have been updated.
2159
2160=back
2161
2c8edc25
S
2162=item Linux
2163
2164Drop support for Linux a.out Linux has used ELF for over twenty years.
2165
2166=item OpenBSD 6
2167
2168OpenBSD 6 still does not support returning pid, gid or uid with SA_SIGINFO.
2169Make sure this is accounted for.
2170
2171=item FreeBSD
2172
2173t/uni/overload.t: Skip hanging test on FreeBSD.
2174
2175=back
2176
2177=head1 Internal Changes
2178
2179=over 4
2180
2181=item *
2182
c2ef64b1
DM
2183A new API function C<sv_setvpv_bufsize()> allows simultaneously setting the
2184length and allocated size of the buffer in an C<SV>, growing the buffer if
2185necessary.
2c8edc25
S
2186
2187=item *
2188
c2ef64b1
DM
2189A new API macro C<SvPVCLEAR()> sets its C<SV> argument to an empty string,
2190like Perl-space C<$x = ''>, but with several optimisations.
2c8edc25
S
2191
2192=item *
2193
c11f9206
DM
2194Several new macros and functions for dealing with Unicode and
2195UTF-8-encoded strings have been added to the API, as well some changes in
2196functionality of existing functions (see L<perlapi/Unicode Support> for
2197more details):
2198
2199=over
2200
2201=item *
2202
2c8edc25
S
2203New versions of macros like C<isALPHA_utf8> and C<toLOWER_utf8> have
2204been added, each with the
2205suffix C<_safe>, like C<isSPACE_utf8_safe>. These take an extra
2206parameter, giving an upper limit of how far into the string it is safe
2207to read. Using the old versions could cause attempts to read beyond the
2208end of the input buffer if the UTF-8 is not well-formed, and their use
2209now raises a deprecation warning. Details are at
2210L<perlapi/Character classification>.
2211
2212=item *
2213
2214Calling macros like C<isALPHA_utf8> on malformed UTF-8 have issued a
53799a91 2215deprecation warning since Perl 5.18. They now die.
2c8edc25
S
2216Similarly, macros like C<toLOWER_utf8> on malformed UTF-8 now die.
2217
2218=item *
2219
c11f9206
DM
2220Several new macros for analysing the validity of utf8 sequences. These
2221are:
2222
2223C<L<perlapi/UTF8_GOT_ABOVE_31_BIT>>
2224C<L<perlapi/UTF8_GOT_CONTINUATION>>
2225C<L<perlapi/UTF8_GOT_EMPTY>>
2226C<L<perlapi/UTF8_GOT_LONG>>
2227C<L<perlapi/UTF8_GOT_NONCHAR>>
2228C<L<perlapi/UTF8_GOT_NON_CONTINUATION>>
2229C<L<perlapi/UTF8_GOT_OVERFLOW>>
2230C<L<perlapi/UTF8_GOT_SHORT>>
2231C<L<perlapi/UTF8_GOT_SUPER>>
2232C<L<perlapi/UTF8_GOT_SURROGATE>>
2233C<L<perlapi/UTF8_IS_INVARIANT>>
2234C<L<perlapi/UTF8_IS_NONCHAR>>
2235C<L<perlapi/UTF8_IS_SUPER>>
2236C<L<perlapi/UTF8_IS_SURROGATE>>
2237C<L<perlapi/UVCHR_IS_INVARIANT>>
2238C<L<perlapi/isUTF8_CHAR_flags>>
2239C<L<perlapi/isSTRICT_UTF8_CHAR>>
2240C<L<perlapi/isC9_STRICT_UTF8_CHAR>>
2c8edc25
S
2241
2242=item *
2243
c11f9206
DM
2244Functions that are all extensions of the C<is_utf8_string_*()> functions,
2245that apply various restrictions to the UTF-8 recognized as valid:
2246
2247C<L<perlapi/is_strict_utf8_string>>,
2248C<L<perlapi/is_strict_utf8_string_loc>>,
2249C<L<perlapi/is_strict_utf8_string_loclen>>,
2250
2251C<L<perlapi/is_c9strict_utf8_string>>,
2252C<L<perlapi/is_c9strict_utf8_string_loc>>,
2253C<L<perlapi/is_c9strict_utf8_string_loclen>>,
2254
2255C<L<perlapi/is_utf8_string_flags>>,
2256C<L<perlapi/is_utf8_string_loc_flags>>,
2257C<L<perlapi/is_utf8_string_loclen_flags>>,
2258
2259C<L<perlapi/is_utf8_fixed_width_buf_flags>>,
2260C<L<perlapi/is_utf8_fixed_width_buf_loc_flags>>,
2261C<L<perlapi/is_utf8_fixed_width_buf_loclen_flags>>.
2262
2263C<L<perlapi/is_utf8_invariant_string>>.
2264C<L<perlapi/is_utf8_valid_partial_char>>.
2265C<L<perlapi/is_utf8_valid_partial_char_flags>>.
2c8edc25
S
2266
2267=item *
2268
c11f9206
DM
2269The functions C<L<perlapi/utf8n_to_uvchr>> and its derivatives have had
2270several changes of behaviour.
2271
2272Calling them, while passing a string length of 0 is now asserted against
2273in DEBUGGING builds, and otherwise returns the Unicode REPLACEMENT
2274CHARACTER. If you have nothing to decode, you shouldn't call the decode
2275function.
2276
2277They now return the Unicode REPLACEMENT CHARACTER if called with UTF-8
2278that has the overlong malformation, and that malformation is allowed by
2279the input parameters. This malformation is where the UTF-8 looks valid
2280syntactically, but there is a shorter sequence that yields the same code
2281point. This has been forbidden since Unicode version 3.1.
2282
2283They now accept an input
2c8edc25
S
2284flag to allow the overflow malformation. This malformation is when the
2285UTF-8 may be syntactically valid, but the code point it represents is
2286not capable of being represented in the word length on the platform.
2287What "allowed" means in this case is that the function doesn't return an
2288error, and advances the parse pointer to beyond the UTF-8 in question,
2289but it returns the Unicode REPLACEMENT CHARACTER as the value of the
2290code point (since the real value is not representable).
2291
c11f9206 2292C<utf8n_to_uvchr> has been changed to not
2c8edc25
S
2293abandon searching for other malformations when the first one is
2294encountered. A call to it thus can generate multiple diagnostics,
2295instead of just one.
2296
2297=item *
2298
c11f9206
DM
2299C<valid_utf8_to_uvchr()> has been added to the API (although it was
2300present in core earlier). Like C<utf8_to_uvchr_buf()>, but assumes that
2301the next character is well-formed.
2302
2303=item *
2304
2c8edc25
S
2305A new function, C<L<perlapi/utf8n_to_uvchr_error>>, has been added for
2306use by modules that need to know the details of UTF-8 malformations
2307beyond pass/fail. Previously, the only ways to know why a sequence was
2308ill-formed was to capture and parse the generated diagnostics, or to do
2309your own analysis.
2310
2311=item *
2312
c11f9206
DM
2313There is now a safer version of utf8_hop(), called utf8_hop_safe().
2314Unlike utf8_hop(), utf8_hop_safe() won't navigate before the beginning or
2315after the end of the supplied buffer.
2c8edc25
S
2316
2317=item *
2318
c11f9206
DM
2319Two new functions, C<utf8_hop_forward()> and C<utf8_hop_back()> are
2320similar to C<utf8_hop_safe()> but are for when you know which direction
2321you wish to travel.
2c8edc25
S
2322
2323=item *
2324
c11f9206
DM
2325Two new macros which return useful utf8 byte sequences:
2326
2327C<L<perlapi/BOM_UTF8>>
2328C<L<perlapi/REPLACEMENT_CHARACTER_UTF8>>
2329
2330=back
c2ef64b1
DM
2331
2332=item *
2333
2334Perl is now built with the C<PERL_OP_PARENT> compiler define enabled by
2335default. To disable it, use the C<PERL_NO_OP_PARENT> compiler define.
2336This flag alters how the C<op_sibling> field is used in C<OP> structures,
2337and has been available optionally since perl 5.22.
2338
2339See L<perl5220delta/"Internal Changes"> for more details of what this
2340build option does.
2341
2342=item *
2343
2344Three new ops, C<OP_ARGELEM>, C<OP_ARGDEFELEM> and C<OP_ARGCHECK> have
2345been added. These are intended principally to implement the individual
2346elements of a subroutine signature, plus any overall checking required.
2347
2348=item *
2349
2350The C<op_class()> API function has been added. This is like the existing
2351C<OP_CLASS()> macro, but can more accurately determine what struct an op
2352has been allocated as. For example C<OP_CLASS()> might return
2353C<OA_BASEOP_OR_UNOP> indicating that ops of this type are usually
2354allocated as an C<OP> or C<UNOP>; while C<op_class()> will return
2355C<OPclass_BASEOP> or C<OPclass_UNOP> as appropriate.
2c8edc25
S
2356
2357=item *
2358
2359All parts of the internals now agree that the C<sassign> op is a C<BINOP>;
2360previously it was listed as a C<BASEOP> in F<regen/opcodes>, which meant
2361that several parts of the internals had to be special-cased to accommodate
95b17558 2362it. This oddity's original motivation was to handle code like C<$x ||= 1>;
2c8edc25
S
2363that is now handled in a simpler way.
2364
2365=item *
2366
c2ef64b1
DM
2367The output format of the C<op_dump()> function (as used by C<perl -Dx>)
2368has changed: it now displays an "ASCII-art" tree structure, and shows more
2369low-level details about each op, such as its address and class.
2c8edc25
S
2370
2371=item *
2372
c2ef64b1
DM
2373The C<PADOFFSET> type has changed from being unsigned to signed, and
2374several pad-related variables such as C<PL_padix> have changed from being
2375of type C<I32> to type C<PADOFFSET>.
2c8edc25
S
2376
2377=item *
2378
c2ef64b1
DM
2379The C<DEBUGGING>-mode output for regex compilation and execution has been
2380enhanced.
2c8edc25
S
2381
2382=item *
2383
74ca8c9e
DM
2384Several obscure SV flags have been eliminated, sometimes along with the
2385macros which manipulate them: C<SVpbm_VALID>, C<SVpbm_TAIL>, C<SvTAIL_on>,
2386C<SvTAIL_off>, C<SVrepl_EVAL>, C<SvEVALED>
2c8edc25
S
2387
2388=item *
2389
74ca8c9e
DM
2390An OP op_private flag has been eliminated: C<OPpRUNTIME>. This used to
2391often get set on C<PMOP>s, but had become meaningless over time.
2c8edc25
S
2392
2393=back
2394
2395=head1 Selected Bug Fixes
2396
2397=over 4
2398
2399=item *
2400
5573eafe
DM
2401Perl no longer panics when switching into some locales on machines with
2402buggy C<strxfrm()> implementations in their libc. [perl #121734]
2403
2404=item *
2405
2c8edc25
S
2406C< $-{$name} > would leak an C<AV> on each access if the regular
2407expression had no named captures. The same applies to access to any
2408hash tied with L<Tie::Hash::NamedCapture> and C<< all =E<gt> 1 >>. [perl
2409#130822]
2410
2411=item *
2412
2413Attempting to use the deprecated variable C<$#> as the object in an
2414indirect object method call could cause a heap use after free or
2415buffer overflow. [perl #129274]
2416
2417=item *
2418
2419When checking for an indirect object method call in some rare cases
2420the parser could reallocate the line buffer but then continue to use
2421pointers to the old buffer. [perl #129190]
2422
2423=item *
2424
2425Supplying a glob as the format argument to L<perlfunc/formline> would
2426cause an assertion failure. [perl #130722]
2427
2428=item *
2429
2430Code like C< $value1 =~ qr/.../ ~~ $value2 > would have the match
2431converted into a qr// operator, leaving extra elements on the stack to
2432confuse any surrounding expression. [perl #130705]
2433
2434=item *
2435
d3972b39 2436Since v5.24 in some obscure cases, a regex which included code blocks
fce64130 2437from multiple sources (I<e.g.>, via embedded via qr// objects) could end up
2c8edc25
S
2438with the wrong current pad and crash or give weird results. [perl #129881]
2439
2440=item *
2441
2442Occasionally C<local()>s in a code block within a patterns weren't being
2443undone when the pattern matching backtracked over the code block.
2444[perl #126697]
2445
2446=item *
2447
2448Using C<substr()> to modify a magic variable could access freed memory
2449in some cases. [perl #129340]
2450
2451=item *
2452
2c8edc25
S
2453Under C<use utf8>, the entire Perl program is now checked that the UTF-8
2454is wellformed. This resolves [perl #126310].
2455
2456=item *
2457
df48f9a4 2458The range operator C<".."> on strings now handles its arguments correctly when in
2c8edc25 2459the scope of the L<< C<unicode_strings>|feature/"The 'unicode_strings' feature" >>
95b17558 2460feature. The previous behaviour was sufficiently unexpected that we believe no
2c8edc25
S
2461correct program could have made use of it.
2462
2463=item *
2464
2465The S<split> operator did not ensure enough space was allocated for
2466its return value in scalar context. It could then write a single
2467pointer immediately beyond the end of the memory block allocated for
2468the stack. [perl #130262]
2469
2470=item *
2471
df48f9a4 2472Using a large code point with the C<"W"> pack template character with
2c8edc25
S
2473the current output position aligned at just the right point could
2474cause a write a single zero byte immediately beyond the end of an
2475allocated buffer. [perl #129149]
2476
2477=item *
2478
2479Supplying the form picture argument as part of the form argument list
2480where the picture specifies modifying the argument could cause an
2481access to the new freed compiled form. [perl #129125]
2482
2483=item *
2484
2485Fix a problem with sort's build-in compare, where it would not sort
2486correctly with 64-bit integers, and non-long doubles. [perl #130335]
2487
2488=item *
2489
2490Fix issues with /(?{ ... E<lt>E<lt>EOF })/ that broke Method-Signatures. [perl #130398]
2491
2492=item *
2493
2494Fix a macro which caused syntax error on an EBCDIC build.
2495
2496=item *
2497
2498Prevent tests from getting hung up on 'NonStop' option. [perl #130445]
2499
2500=item *
2501
2502Fixed an assertion failure with C<chop> and C<chomp>, which
2503could be triggered by C<chop(@x =~ tr/1/1/)>. [perl #130198].
2504
2505=item *
2506
2507Fixed a comment skipping error under C</x>; it could stop skipping a
2508byte early, which could be in the middle of a UTF-8 character.
2509[perl #130495].
2510
2511=item *
2512
2513F<perldb> now ignores F</dev/tty> on non-Unix systems. [perl #113960];
2514
2515=item *
2516
2517Fix assertion failure for C<{}-E<gt>$x> when C<$x> isn't defined. [perl #130496].
2518
2519=item *
2520
2521DragonFly BSD now has support for setproctitle(). [perl #130068].
2522
2523=item *
2524
2525Fix an assertion error which could be triggered when lookahead string
2526in patterns exceeded a minimum length. [perl #130522].
2527
2528=item *
2529
df48f9a4 2530Only warn once per literal about a misplaced C<"_">. [perl #70878].
2c8edc25
S
2531
2532=item *
2533
2534Ensure range-start is set after error in C<tr///>. [perl #129342].
2535
2536=item *
2537
2538Don't read past start of string for unmatched backref; otherwise,
2539we may have heap buffer overflow. [perl #129377].
2540
2541=item *
2542
2543Properly recognize mathematical digit ranges starting at U+1D7E.
2544C<use re 'strict'> is supposed to warn if you use a range whose start
95b17558 2545and end digit aren't from the same group of 10. It didn't do that
2c8edc25
S
2546for five groups of mathematical digits starting at U+1D7E.
2547
2548=item *
2549
fce64130 2550A sub containing a "forward" declaration with the same name (I<e.g.>,
2c8edc25
S
2551C<sub c { sub c; }>) could sometimes crash or loop infinitely. [perl
2552#129090]
2553
2554=item *
2555
2556A crash in executing a regex with a floating UTF-8 substring against a
2557target string that also used UTF-8 has been fixed. [perl #129350]
2558
2559=item *
2560
2561Previously, a shebang line like C<#!perl -i u> could be erroneously
95b17558 2562interpreted as requesting the C<-u> option. This has been fixed. [perl
2c8edc25
S
2563#129336]
2564
2565=item *
2566
2567The regex engine was previously producing incorrect results in some rare
2568situations when backtracking past a trie that matches only one thing; this
2569showed up as capture buffers (C<$1>, C<$2>, etc) erroneously containing data
2570from regex execution paths that weren't actually executed for the final
2571match. [perl #129897]
2572
2573=item *
2574
2575Certain regexes making use of the experimental C<regex_sets> feature could
95b17558 2576trigger an assertion failure. This has been fixed. [perl #129322]
2c8edc25
S
2577
2578=item *
2579
fce64130 2580Invalid assignments to a reference constructor (I<e.g.>, C<\eval=time>) could
2c8edc25
S
2581sometimes crash in addition to giving a syntax error. [perl #125679]
2582
2583=item *
2584
2585The parser could sometimes crash if a bareword came after C<evalbytes>.
2586[perl #129196]
2587
2588=item *
2589
2590Autoloading via a method call would warn erroneously ("Use of inherited
2591AUTOLOAD for non-method") if there was a stub present in the package into
2592which the invocant had been blessed. The warning is no longer emitted in
2593such circumstances. [perl #47047]
2594
2595=item *
2596
fce64130
KW
2597A sub containing with a "forward" declaration with the same name
2598(I<e.g.>,
2c8edc25
S
2599C<sub c { sub c; }>) could sometimes crash or loop infinitely. [perl
2600#129090]
2601
2602=item *
2603
2604The use of C<splice> on arrays with nonexistent elements could cause other
2605operators to crash. [perl #129164]
2606
2607=item *
2608
2609Fixed case where C<re_untuit_start> will overshoot the length of a utf8
2610string. [perl #129012]
2611
2612=item *
2613
2614Handle C<CXt_SUBST> better in C<Perl_deb_stack_all>, previously it wasn't
2615checking that the I<current> C<cx> is the right type, and instead was always
2616checking the base C<cx> (effectively a noop). [perl #129029]
2617
2618=item *
2619
95b17558 2620Fixed two possible use-after-free bugs in C<Perl_yylex>. C<Perl_yylex>
2c8edc25
S
2621maintains up to two pointers into the parser buffer, one of which can
2622become stale under the right conditions. [perl #129069]
2623
2624=item *
2625
2626Fixed a crash with C<s///l> where it thought it was dealing with UTF-8
2627when it wasn't. [perl #129038]
2628
2629=item *
2630
2631Fixed place where regex was not setting the syntax error correctly.
2632[perl #129122]
2633
2634=item *
2635
df48f9a4 2636The C<&.> operator (and the C<"&"> operator, when it treats its arguments as
2c8edc25
S
2637strings) were failing to append a trailing null byte if at least one string
2638was marked as utf8 internally. Many code paths (system calls, regexp
2639compilation) still expect there to be a null byte in the string buffer
2640just past the end of the logical string. An assertion failure was the
2641result. [perl #129287]
2642
2643=item *
2644
2645Check C<pack_sockaddr_un()>'s return value because C<pack_sockaddr_un()>
2646silently truncates the supplied path if it won't fit into the C<sun_path>
95b17558 2647member of C<sockaddr_un>. This may change in the future, but for now
2c8edc25
S
2648check the path in theC<sockaddr> matches the desired path, and skip if
2649it doesn't. [perl #128095]
2650
2651=item *
2652
95b17558 2653Make sure C<PL_oldoldbufptr> is preserved in C<scan_heredoc()>. In some
2c8edc25
S
2654cases this is used in building error messages. [perl #128988]
2655
2656=item *
2657
2658Check for null PL_curcop in IN_LC() [perl #129106]
2659
2660=item *
2661
2662Fixed the parser error handling for an 'C<:attr(foo>' that does not have
df48f9a4 2663an ending 'C<")">'.
2c8edc25
S
2664
2665=item *
2666
2667Fix C<Perl_delimcpy()> to handle a backslash as last char, this
2668actually fixed two bugs, [perl #129064] and [perl #129176].
2669
2670=item *
2671
2672[perl #129267] rework gv_fetchmethod_pvn_flags separator parsing to
2673prevent possible string overrun with invalid len in gv.c
2674
2675=item *
2676
2677Problems with in-place array sorts: code like C<@a = sort { ... } @a>,
2678where the source and destination of the sort are the same plain array, are
95b17558 2679optimised to do less copying around. Two side-effects of this optimisation
2c8edc25
S
2680were that the contents of C<@a> as visible to to sort routine were
2681partially sorted, and under some circumstances accessing C<@a> during the
95b17558 2682sort could crash the interpreter. Both these issues have been fixed, and
2c8edc25
S
2683Sort functions see the original value of C<@a>.
2684
2685=item *
2686
2687Non-ASCII string delimiters are now reported correctly in error messages
2688for unterminated strings. [perl #128701]
2689
2690=item *
2691
2692C<pack("p", ...)> used to emit its warning ("Attempt to pack pointer to
2693temporary value") erroneously in some cases, but has been fixed.
2694
2695=item *
2696
2697C<@DB::args> is now exempt from "used once" warnings. The warnings only
2698occurred under B<-w>, because F<warnings.pm> itself uses C<@DB::args>
2699multiple times.
2700
2701=item *
2702
2703The use of built-in arrays or hash slices in a double-quoted string no
2704longer issues a warning ("Possible unintended interpolation...") if the
2705variable has not been mentioned before. This affected code like
2706C<qq|@DB::args|> and C<qq|@SIG{'CHLD', 'HUP'}|>. (The special variables
2707C<@-> and C<@+> were already exempt from the warning.)
2708
2709=item *
2710
2711C<gethostent> and similar functions now perform a null check internally, to
d3972b39 2712avoid crashing with torsocks. This was a regression from v5.22. [perl
2c8edc25
S
2713#128740]
2714
2715=item *
2716
2717C<defined *{'!'}>, C<defined *{'['}>, and C<defined *{'-'}> no longer leak
2718memory if the typeglob in question has never been accessed before.
2719
2720=item *
2721
2c8edc25
S
2722Mentioning the same constant twice in a row (which is a syntax error) no
2723longer fails an assertion under debugging builds. This was a regression
d3972b39 2724from v5.20. [perl #126482]
2c8edc25
S
2725
2726=item *
2727
2728Many issues relating to C<printf "%a"> of hexadecimal floating point
2729were fixed. In addition, the "subnormals" (formerly known as "denormals")
2730floating point anumbers are now supported both with the plain IEEE 754
2731floating point numbers (64-bit or 128-bit) and the x86 80-bit
2732"extended precision". Note that subnormal hexadecimal floating
2733point literals will give a warning about "exponent underflow".
2734[perl #128843, #128889, #128890, #128893, #128909, #128919]
2735
2736=item *
2737
d3972b39 2738A regression in v5.24 with C<tr/\N{U+...}/foo/> when the code point was between
2c8edc25
S
2739128 and 255 has been fixed. [perl #128734].
2740
2741=item *
2742
2c8edc25
S
2743Use of a string delimiter whose code point is above 2**31 now works
2744correctly on platforms that allow this. Previously, certain characters,
2745due to truncation, would be confused with other delimiter characters
df48f9a4 2746with special meaning (such as C<"?"> in C<m?...?>), resulting
2c8edc25
S
2747in inconsistent behaviour. Note that this is non-portable,
2748and is based on Perl's extension to UTF-8, and is probably not
2749displayable nor enterable by any editor. [perl #128738]
2750
2751=item *
2752
df48f9a4 2753C<@{x> followed by a newline where C<"x"> represents a control or non-ASCII
2c8edc25
S
2754character no longer produces a garbled syntax error message or a crash.
2755[perl #128951]
2756
2757=item *
2758
2759An assertion failure with C<%: = 0> has been fixed.
2760L<[perl #128238]|https://rt.perl.org/Public/Bug/Display.html?id=128238>
2761
2762=item *
2763
2764In Perl 5.18, the parsing of C<"$foo::$bar"> was accidentally changed, such
2765that it would be treated as C<$foo."::".$bar>. The previous behavior, which
2766was to parse it as C<$foo:: . $bar>, has been restored.
2767L<[perl #128478]|https://rt.perl.org/Public/Bug/Display.html?id=128478>
2768
2769=item *
2770
2771Since Perl 5.20, line numbers have been off by one when perl is invoked with
2772the B<-x> switch. This has been fixed.
2773L<[perl #128508]|https://rt.perl.org/Public/Bug/Display.html?id=128508>
2774
2775=item *
2776
fce64130 2777Vivifying a subroutine stub in a deleted stash (I<e.g.>, C<delete $My::{"Foo::"};
2c8edc25
S
2778\&My::Foo::foo>) no longer crashes. It had begun crashing in Perl 5.18.
2779L<[perl #128532]|https://rt.perl.org/Public/Bug/Display.html?id=128532>
2780
2781=item *
2782
2783Some obscure cases of subroutines and file handles being freed at the same time
2784could result in crashes, but have been fixed. The crash was introduced in Perl
27855.22.
2786L<[perl #128597]|https://rt.perl.org/Public/Bug/Display.html?id=128597>
2787
2788=item *
2789
2790Code that looks for a variable name associated with an uninitialized value
2791could cause an assertion in cases where magic is involved, such as
2792C<$ISA[0][0]>. This has now been fixed.
2793L<[perl #128253]|https://rt.perl.org/Public/Bug/Display.html?id=128253>
2794
2795=item *
2796
2797A crash caused by code generating the warning "Subroutine STASH::NAME
2798redefined" in cases such as C<sub P::f{} undef *P::; *P::f =sub{};> has been
2799fixed. In these cases, where the STASH is missing, the warning will now appear
2800as "Subroutine NAME redefined".
2801L<[perl #128257]|https://rt.perl.org/Public/Bug/Display.html?id=128257>
2802
2803=item *
2804
2805Fixed an assertion triggered by some code that handles deprecated behavior in
fce64130 2806formats, I<e.g.>, in cases like this:
2c8edc25
S
2807
2808 format STDOUT =
2809 @
2810 0"$x"
2811
2812L<[perl #128255]|https://rt.perl.org/Public/Bug/Display.html?id=128255>
2813
2814=item *
2815
2816A possible divide by zero in string transformation code on Windows has been
2817avoided, fixing a crash when collating an empty string.
2818L<[perl #128618]|https://rt.perl.org/Public/Bug/Display.html?id=128618>
2819
2820=item *
2821
2822Some regular expression parsing glitches could lead to assertion failures with
e6abae1c 2823regular expressions such as C</(?E<lt>=/> and C</(?E<lt>!/>. This has now been fixed.
2c8edc25
S
2824L<[perl #128170]|https://rt.perl.org/Public/Bug/Display.html?id=128170>
2825
2826=item *
2827
2828C< until ($x = 1) { ... } > and C< ... until $x = 1 > now properly
2829warn when syntax warnings are enabled. [perl #127333]
2830
2831=item *
2832
2833socket() now leaves the error code returned by the system in C<$!> on
2834failure. [perl #128316]
2835
2836=item *
2837
2838Assignment variants of any bitwise ops under the C<bitwise> feature would
2839crash if the left-hand side was an array or hash. [perl #128204]
2840
2841=item *
2842
2843C<require> followed by a single colon (as in C<foo() ? require : ...> is
2844now parsed correctly as C<require> with implicit $_, rather than
2845C<require "">. [perl #128307]
2846
2847=item *
2848
2849Scalar C<keys %hash> can now be assigned to consistently in all scalar
2850lvalue contexts. Previously it worked for some contexts but not others.
2851
2852=item *
2853
2854List assignment to C<vec> or C<substr> with an array or hash for its first
2855argument used to result in crashes or "Can't coerce" error messages at run
2856time, unlike scalar assignment, which would give an error at compile time.
2857List assignment now gives a compile-time error, too. [perl #128260]
2858
2859=item *
2860
2861Expressions containing an C<&&> or C<||> operator (or their synonyms C<and>
95b17558 2862and C<or>) were being compiled incorrectly in some cases. If the left-hand
2c8edc25
S
2863side consisted of either a negated bareword constant or a negated C<do {}>
2864block containing a constant expression, and the right-hand side consisted of
2865a negated non-foldable expression, one of the negations was effectively
95b17558
KW
2866ignored. The same was true of C<if> and C<unless> statement modifiers,
2867though with the left-hand and right-hand sides swapped. This long-standing
2c8edc25
S
2868bug has now been fixed. [perl #127952]
2869
2870=item *
2871
2872C<reset> with an argument no longer crashes when encountering stash entries
2873other than globs. [perl #128106]
2874
2875=item *
2876
2877Assignment of hashes to, and deletion of, typeglobs named C<*::::::> no
2878longer causes crashes. [perl #128086]
2879
2880=item *
2881
2882Handle SvIMMORTALs in LHS of list assign. [perl #129991]
2883
2884=item *
2885
2886[perl #130010] a5540cf breaks texinfo
2887
2888This involved user-defined Unicode properties.
2889
2890=item *
2891
2892Fix error message for unclosed C<\N{> in regcomp.
2893
2894An unclosed C<\N{> could give the wrong error message
2895C<"\N{NAME} must be resolved by the lexer">.
2896
2897=item *
2898
2899List assignment in list context where the LHS contained aggregates and
2900where there were not enough RHS elements, used to skip scalar lvalues.
2901Previously, C<(($a,$b,@c,$d) = (1))> in list context returned C<($a)>; now
95b17558
KW
2902it returns C<($a,$b,$d)>. C<(($a,$b,$c) = (1))> is unchanged: it still
2903returns C<($a,$b,$c)>. This can be seen in the following:
2c8edc25
S
2904
2905 sub inc { $_++ for @_ }
2906 inc(($a,$b,@c,$d) = (10))
2907
2908Formerly, the values of C<($a,$b,$d)> would be left as C<(11,undef,undef)>;
2909now they are C<(11,1,1)>.
2910
2911=item *
2912
2913[perl 129903]
2914
2915The basic problem is that code like this: /(?{ s!!! })/ can trigger infinite
2916recursion on the C stack (not the normal perl stack) when the last successful
95b17558 2917pattern in scope is itself. Since the C stack overflows this manifests as an
2c8edc25
S
2918untrappable error/segfault, which then kills perl.
2919
2920We avoid the segfault by simply forbidding the use of the empty pattern when it
2921would resolve to the currently executing pattern.
2922
2923=item *
2924
2925[perl 128997] Avoid reading beyond the end of the line buffer when there's a
2926short UTF-8 character at the end.
2927
2928=item *
2929
2930[perl 129950] fix firstchar bitmap under utf8 with prefix optimisation.
2931
2932=item *
2933
2934[perl 129954] Carp/t/arg_string.t: be liberal in f/p formats.
2935
2936=item *
2937
2938[perl 129928] make do "a\0b" fail silently instead of throwing.
2939
2940=item *
2941
2942[perl 129130] make chdir allocate the stack it needs.
2943
2944=back
2945
2946=head1 Known Problems
2947
2948=over 4
2949
2950=item *
2951
2952Some modules have been broken by the L<context stack rework|/Internal Changes>.
2953These modules were relying on non-guaranteed implementation details in perl.
2954Their maintainers have been informed, and should contact perl5-porters for
2955advice if needed. Below is a subset of these modules:
2956
2957=over 4
2958
2959=item * L<Algorithm::Permute>
2960
2961=item * L<Coro>
2962
d3972b39 2963L<Coro> and Perl 5.22 were already incompatible due to a change in the perl,
2c8edc25
S
2964and the reworking on the perl context stack creates a further incompatibility.
2965perl5-porters has L<discussed the issue on the mailing
2966list|http://www.nntp.perl.org/group/perl.perl5.porters/2016/05/msg236174.html>.
2967
2968=item * L<Data::Alias>
2969
2970=item * L<RPerl>
2971
2972=item * L<Scope::Upper>
2973
2974=item * L<TryCatch>
2975
2976=back
2977
2978=item *
2979
53799a91 2980The module L<lexical::underscore> no longer works on Perl 5.24, because perl
2c8edc25
S
2981no longer has a lexical C<$_>!
2982
2983=item *
2984
53799a91 2985C<mod_perl> has been patched for compatibility for v5.22 and later but no
2c8edc25
S
2986release has been made. The relevant patch (and other changes) can be found in
2987their source code repository, L<mirrored at
2988GitHub|https://github.com/apache/mod_perl/commit/82827132efd3c2e25cc413c85af61bb63375da6e>.
2989
2990=back
2991
2992=head1 Errata From Previous Releases
2993
2994=over 4
2995
2996=item *
2997
ee8180b8 2998Parsing bad POSIX charclasses no longer leaks memory.
2c8edc25
S
2999L<[perl #128313]|https://rt.perl.org/Public/Bug/Display.html?id=128313>
3000
3001=item *
3002
53799a91 3003Fixed issues with recursive regexes. The behavior was fixed in Perl 5.24.
2c8edc25
S
3004L<[perl #126182]|https://rt.perl.org/Public/Bug/Display.html?id=126182>
3005
3006=back
3007
3008=head1 Obituary
3009
3010Jon Portnoy (AVENJ), a prolific Perl author and admired Gentoo community
95b17558 3011member, has passed away on August 10, 2016. He will be remembered and
c94c0e4f 3012missed by all those who he came in contact with, and enriched with his
2c8edc25
S
3013intellect, wit, and spirit.
3014
c94c0e4f 3015It is with great sadness that we also note Kip Hampton's passing. Probably
2c8edc25
S
3016best known as the author of the Perl & XML column on XML.com, he was a
3017core contributor to AxKit, an XML server platform that became an Apache
95b17558
KW
3018Foundation project. He was a frequent speaker in the early days at
3019OSCON, and most recently at YAPC::NA in Madison. He was frequently on
2c8edc25
S
3020irc.perl.org as `ubu`, generally in the #axkit-dahut community, the
3021group responsible for YAPC::NA Asheville in 2011.
a049258c 3022
2c8edc25
S
3023Kip and his constant contributions to the community will be greatly
3024missed.
a049258c
S
3025
3026=head1 Acknowledgements
2e0dcc12 3027
0cc8c746 3028Perl 5.26.0 represents approximately 12 months of development since Perl 5.24.0
c2948ced 3029and contains approximately 370,000 lines of changes across 2,600 files from 86
0cc8c746
S
3030authors.
3031
3032Excluding auto-generated files, documentation and release tools, there were
3033approximately 230,000 lines of changes to 1,800 .pm, .t, .c and .h files.
3034
3035Perl continues to flourish into its third decade thanks to a vibrant community
95b17558 3036of users and developers. The following people are known to have contributed the
ad543fb2 3037improvements that became Perl 5.26.0:
0cc8c746
S
3038
3039Aaron Crane, Abigail, Ævar Arnfjörð Bjarmason, Alex Vandiver, Andreas
3040König, Andreas Voegele, Andrew Fresh, Andy Lester, Aristotle Pagaltzis, Chad
3041Granum, Chase Whitener, Chris 'BinGOs' Williams, Chris Lamb, Christian Hansen,
3042Christian Millour, Colin Newell, Craig A. Berry, Dagfinn Ilmari Mannsåker, Dan
c2948ced
S
3043Collins, Daniel Dragan, Dave Cross, Dave Rolsky, David Golden, David H.
3044Gutteridge, David Mitchell, Dominic Hargreaves, Doug Bell, E. Choroba, Ed Avis,
3045Father Chrysostomos, François Perrad, Hauke D, H.Merijn Brand, Hugo van der
3046Sanden, Ivan Pozdeev, James E Keenan, James Raspass, Jarkko Hietaniemi, Jerry
3047D. Hedden, Jim Cromie, J. Nick Koston, John Lightsey, Karen Etheridge, Karl
3048Williamson, Leon Timmermans, Lukas Mai, Matthew Horsfall, Maxwell Carey, Misty
3049De Meo, Neil Bowers, Nicholas Clark, Nicolas R., Niko Tyni, Pali, Paul
3050Marquess, Peter Avalos, Petr Písař, Pino Toscano, Rafael Garcia-Suarez, Reini
3051Urban, Renee Baecker, Ricardo Signes, Richard Levitte, Rick Delaney, Salvador
3052Fandiño, Samuel Thibault, Sawyer X, Sébastien Aperghis-Tramoni, Sergey
3053Aleynikov, Shlomi Fish, Smylers, Stefan Seifert, Steffen Müller, Stevan
3054Little, Steve Hay, Steven Humphrey, Sullivan Beck, Theo Buehler, Thomas Sibley,
3055Todd Rinaldo, Tomasz Konojacki, Tony Cook, Unicode Consortium, Yaroslav Kuzmin,
3056Yves Orton, Zefram.
0cc8c746
S
3057
3058The list above is almost certainly incomplete as it is automatically generated
95b17558 3059from version control history. In particular, it does not include the names of
0cc8c746
S
3060the (very much appreciated) contributors who reported issues to the Perl bug
3061tracker.
3062
3063Many of the changes included in this version originated in the CPAN modules
95b17558 3064included in Perl's core. We're grateful to the entire CPAN community for
0cc8c746
S
3065helping Perl to flourish.
3066
3067For a more complete list of all of Perl's historical contributors, please see
3068the F<AUTHORS> file in the Perl source distribution.
f5b73711 3069
44691e6f
AB
3070=head1 Reporting Bugs
3071
2c8edc25
S
3072If you find what you think is a bug, you might check the articles recently
3073posted to the comp.lang.perl.misc newsgroup and the perl bug database at
3074L<https://rt.perl.org/> . There may also be information at
4b8803f0 3075L<http://www.perl.org/> , the Perl Home Page.
44691e6f 3076
e08634c5
SH
3077If you believe you have an unreported bug, please run the L<perlbug> program
3078included with your release. Be sure to trim your bug down to a tiny but
3079sufficient test case. Your bug report, along with the output of C<perl -V>,
7c825fca 3080will be sent off to C<perlbug@perl.org> to be analysed by the Perl porting team.
44691e6f 3081
87c118b9
DM
3082If the bug you are reporting has security implications which make it
3083inappropriate to send to a publicly archived mailing list, then see
c0ea3294
SH
3084L<perlsec/SECURITY VULNERABILITY CONTACT INFORMATION>
3085for details of how to report the issue.
44691e6f
AB
3086
3087=head1 SEE ALSO
3088
e08634c5
SH
3089The F<Changes> file for an explanation of how to view exhaustive details on
3090what changed.
44691e6f
AB
3091
3092The F<INSTALL> file for how to build Perl.
3093
3094The F<README> file for general stuff.
3095
3096The F<Artistic> and F<Copying> files for copyright information.
3097
3098=cut