This is a live mirror of the Perl 5 development currently hosted at https://github.com/perl/perl5
perldelta: Italicize "e.g.", "i.e."
[perl5.git] / pod / perldelta.pod
CommitLineData
44691e6f
AB
1=encoding utf8
2
3=head1 NAME
4
eabfc7bc 5perldelta - what is new for perl v5.22.0
c68523cb 6
238894db 7=head1 DESCRIPTION
c68523cb 8
f146a2b2 9This document describes differences between the 5.20.0 release and the 5.22.0
238894db 10release.
c68523cb 11
eabfc7bc
RS
12If you are upgrading from an earlier release such as 5.18.0, first read
13L<perl5200delta>, which describes differences between 5.18.0 and 5.20.0.
14
15=head1 Core Enhancements
2ec11c70 16
eabfc7bc 17=head2 New bitwise operators
b9c683b3 18
eabfc7bc
RS
19A new experimental facility has been added that makes the four standard
20bitwise operators (C<& | ^ ~>) treat their operands consistently as
21numbers, and introduces four new dotted operators (C<&. |. ^. ~.>) that
22treat their operands consistently as strings. The same applies to the
23assignment variants (C<&= |= ^= &.= |.= ^.=>).
2e4abf26 24
eabfc7bc
RS
25To use this, enable the "bitwise" feature and disable the
26"experimental::bitwise" warnings category. See L<perlop/Bitwise String
a75e6a3a
SH
27Operators> for details.
28L<[perl #123466]|https://rt.perl.org/Ticket/Display.html?id=123466>.
eabfc7bc
RS
29
30=head2 New double-diamond operator
31
32C<<< <<>> >>> is like C<< <> >> but uses three-argument C<open> to open
4ec8e6f0
KW
33each file in C<@ARGV>. This means that each element of C<@ARGV> will be treated
34as an actual file name, and C<"|foo"> won't be treated as a pipe open.
eabfc7bc
RS
35
36=head2 New \b boundaries in regular expressions
37
38=head3 qr/\b{gcb}/
39
40C<gcb> stands for Grapheme Cluster Boundary. It is a Unicode property
41that finds the boundary between sequences of characters that look like a
42single character to a native speaker of a language. Perl has long had
43the ability to deal with these through the C<\X> regular escape
44sequence. Now, there is an alternative way of handling these. See
45L<perlrebackslash/\b{}, \b, \B{}, \B> for details.
46
47=head3 qr/\b{wb}/
48
49C<wb> stands for Word Boundary. It is a Unicode property
50that finds the boundary between words. This is similar to the plain
51C<\b> (without braces) but is more suitable for natural language
01842271 52processing. It knows, for example, that apostrophes can occur in the
eabfc7bc
RS
53middle of words. See L<perlrebackslash/\b{}, \b, \B{}, \B> for details.
54
55=head3 qr/\b{sb}/
56
57C<sb> stands for Sentence Boundary. It is a Unicode property
58to aid in parsing natural language sentences.
59See L<perlrebackslash/\b{}, \b, \B{}, \B> for details.
60
eabfc7bc
RS
61=head2 Non-Capturing Regular Expression Flag
62
63Regular expressions now support a C</n> flag that disables capturing
d140c31c 64and filling in C<$1>, C<$2>, etc inside of groups:
eabfc7bc
RS
65
66 "hello" =~ /(hi|hello)/n; # $1 is not set
67
68This is equivalent to putting C<?:> at the beginning of every capturing group.
69
70See L<perlre/"n"> for more information.
71
72=head2 C<use re 'strict'>
73
74This applies stricter syntax rules to regular expression patterns
d140c31c 75compiled within its scope. This will hopefully alert you to typos and
eabfc7bc 76other unintentional behavior that backwards-compatibility issues prevent
d140c31c 77us from reporting in normal regular expression compilations. Because the
eabfc7bc 78behavior of this is subject to change in future Perl releases as we gain
d140c31c
AC
79experience, using this pragma will raise a warning of category
80C<experimental::re_strict>.
eabfc7bc
RS
81See L<'strict' in re|re/'strict' mode>.
82
ce93e38b 83=head2 Unicode 7.0 (with correction) is now supported
eabfc7bc
RS
84
85For details on what is in this release, see
86L<http://www.unicode.org/versions/Unicode7.0.0/>.
ce93e38b
KW
87The version of Unicode 7.0 that comes with Perl includes
88a correction dealing with glyph shaping in Arabic
89(see L<http://www.unicode.org/errata/#current_errata>).
90
eabfc7bc
RS
91
92=head2 S<C<use locale>> can restrict which locale categories are affected
93
94It is now possible to pass a parameter to S<C<use locale>> to specify
95a subset of locale categories to be locale-aware, with the remaining
96ones unaffected. See L<perllocale/The "use locale" pragma> for details.
97
01842271 98=head2 Perl now supports POSIX 2008 locale currency additions
eabfc7bc
RS
99
100On platforms that are able to handle POSIX.1-2008, the
101hash returned by
102L<C<POSIX::localeconv()>|perllocale/The localeconv function>
103includes the international currency fields added by that version of the
104POSIX standard. These are
105C<int_n_cs_precedes>,
106C<int_n_sep_by_space>,
107C<int_n_sign_posn>,
108C<int_p_cs_precedes>,
109C<int_p_sep_by_space>,
110and
111C<int_p_sign_posn>.
112
50ea4745 113=head2 Better heuristics on older platforms for determining locale UTF-8ness
eabfc7bc
RS
114
115On platforms that implement neither the C99 standard nor the POSIX 2001
50ea4745 116standard, determining if the current locale is UTF-8 or not depends on
eabfc7bc
RS
117heuristics. These are improved in this release.
118
119=head2 Aliasing via reference
120
121Variables and subroutines can now be aliased by assigning to a reference:
122
123 \$c = \$d;
124 \&x = \&y;
125
d140c31c
AC
126Aliasing can also be accomplished
127by using a backslash before a C<foreach> iterator variable; this is
eabfc7bc
RS
128perhaps the most useful idiom this feature provides:
129
130 foreach \%hash (@array_of_hash_refs) { ... }
131
3209f716
KW
132This feature is experimental and must be enabled via S<C<use feature
133'refaliasing'>>. It will warn unless the C<experimental::refaliasing>
eabfc7bc
RS
134warnings category is disabled.
135
136See L<perlref/Assigning to References>
137
138=head2 C<prototype> with no arguments
139
a75e6a3a
SH
140C<prototype()> with no arguments now infers C<$_>.
141L<[perl #123514]|https://rt.perl.org/Ticket/Display.html?id=123514>.
eabfc7bc 142
d140c31c 143=head2 New C<:const> subroutine attribute
eabfc7bc 144
d140c31c 145The C<const> attribute can be applied to an anonymous subroutine. It
f1c9eac6 146causes the new sub to be executed immediately whenever one is created
ff25fcfb 147(I<i.e.> when the C<sub> expression is evaluated). Its value is captured
f1c9eac6
DM
148and used to create a new constant subroutine that is returned. This
149feature is experimental. See L<perlsub/Constant Functions>.
eabfc7bc
RS
150
151=head2 C<fileno> now works on directory handles
152
153When the relevant support is available in the operating system, the
154C<fileno> builtin now works on directory handles, yielding the
155underlying file descriptor in the same way as for filehandles. On
156operating systems without such support, C<fileno> on a directory handle
157continues to return the undefined value, as before, but also sets C<$!> to
158indicate that the operation is not supported.
159
160Currently, this uses either a C<dd_fd> member in the OS C<DIR>
4ec8e6f0 161structure, or a C<dirfd(3)> function as specified by POSIX.1-2008.
eabfc7bc
RS
162
163=head2 List form of pipe open implemented for Win32
164
165The list form of pipe:
166
167 open my $fh, "-|", "program", @arguments;
168
169is now implemented on Win32. It has the same limitations as C<system
170LIST> on Win32, since the Win32 API doesn't accept program arguments
171as a list.
172
eabfc7bc
RS
173=head2 Assignment to list repetition
174
175C<(...) x ...> can now be used within a list that is assigned to, as long
4ec8e6f0
KW
176as the left-hand side is a valid lvalue. This allows S<C<(undef,undef,$foo)
177= that_function()>> to be written as S<C<((undef)x2, $foo) = that_function()>>.
eabfc7bc
RS
178
179=head2 Infinity and NaN (not-a-number) handling improved
180
d140c31c
AC
181Floating point values are able to hold the special values infinity, negative
182infinity, and NaN (not-a-number). Now we more robustly recognize and
dfd03a6a
DIM
183propagate the value in computations, and on output normalize them to the strings
184C<Inf>, C<-Inf>, and C<NaN>.
eabfc7bc
RS
185
186See also the L<POSIX> enhancements.
187
188=head2 Floating point parsing has been improved
189
190Parsing and printing of floating point values has been improved.
191
192As a completely new feature, hexadecimal floating point literals
4ec8e6f0 193(like C<0x1.23p-4>) are now supported, and they can be output with
3209f716 194S<C<printf "%a">>. See L<perldata/Scalar value constructors> for more
d140c31c 195details.
eabfc7bc
RS
196
197=head2 Packing infinity or not-a-number into a character is now fatal
198
199Before, when trying to pack infinity or not-a-number into a
200(signed) character, Perl would warn, and assumed you tried to
201pack C<< 0xFF >>; if you gave it as an argument to C<< chr >>,
202C<< U+FFFD >> was returned.
203
204But now, all such actions (C<< pack >>, C<< chr >>, and C<< print '%c' >>)
205result in a fatal error.
206
207=head2 Experimental C Backtrace API
2e4abf26 208
43831b1f 209Perl now supports (via a C level API) retrieving
eabfc7bc 210the C level backtrace (similar to what symbolic debuggers like gdb do).
fea59588 211
eabfc7bc
RS
212The backtrace returns the stack trace of the C call frames,
213with the symbol names (function names), the object names (like "perl"),
214and if it can, also the source code locations (file:line).
215
216The supported platforms are Linux and OS X (some *BSD might work at
217least partly, but they have not yet been tested).
218
219The feature needs to be enabled with C<Configure -Dusecbacktrace>.
220
eabfc7bc 221See L<perlhacktips/"C backtrace"> for more information.
83a5d6b6 222
7f9fef93 223=head1 Security
e455391f 224
eabfc7bc
RS
225=head2 Perl is now compiled with -fstack-protector-strong if available
226
227Perl has been compiled with the anti-stack-smashing option
228C<-fstack-protector> since 5.10.1. Now Perl uses the newer variant
229called C<-fstack-protector-strong>, if available.
230
231=head2 The L<Safe> module could allow outside packages to be replaced
232
233Critical bugfix: outside packages could be replaced. L<Safe> has
234been patched to 2.38 to address this.
235
236=head2 Perl is now always compiled with -D_FORTIFY_SOURCE=2 if available
e455391f 237
eabfc7bc
RS
238The 'code hardening' option called C<_FORTIFY_SOURCE>, available in
239gcc 4.*, is now always used for compiling Perl, if available.
240
241Note that this isn't necessarily a huge step since in many platforms
242the step had already been taken several years ago: many Linux
243distributions (like Fedora) have been using this option for Perl,
244and OS X has enforced the same for many years.
53902397 245
7f9fef93 246=head1 Incompatible Changes
79a77127 247
eabfc7bc
RS
248=head2 Subroutine signatures moved before attributes
249
250The experimental sub signatures feature, as introduced in 5.20, parsed
d140c31c
AC
251signatures after attributes. In this release, following feedback from users
252of the experimental feature, the positioning has been moved such that
253signatures occur after the subroutine name (if any) and before the attribute
254list (if any).
eabfc7bc
RS
255
256=head2 C<&> and C<\&> prototypes accepts only subs
257
43831b1f
DM
258The C<&> prototype character now accepts only anonymous subs (C<sub
259{...}>), things beginning with C<\&>, or an explicit C<undef>. Formerly
260it erroneously also allowed references to arrays, hashes, and lists.
a75e6a3a
SH
261L<[perl #4539]|https://rt.perl.org/Ticket/Display.html?id=4539>.
262L<[perl #123062]|https://rt.perl.org/Ticket/Display.html?id=123062>.
43831b1f 263L<[perl #123062]|https://rt.perl.org/Ticket/Display.html?id=123475>.
eabfc7bc 264
43831b1f
DM
265In addition, the C<\&> prototype was allowing subroutine calls, whereas
266now it only allows subroutines: C<&foo> is still permitted as an argument,
267while C<&foo()> and C<foo()> no longer are.
a75e6a3a 268L<[perl #77860]|https://rt.perl.org/Ticket/Display.html?id=77860>.
eabfc7bc
RS
269
270=head2 C<use encoding> is now lexical
271
272The L<encoding> pragma's effect is now limited to lexical scope. This
273pragma is deprecated, but in the meantime, it could adversely affect
274unrelated modules that are included in the same program.
275
276=head2 List slices returning empty lists
277
d140c31c 278List slices now return an empty list only if the original list was empty
eabfc7bc 279(or if there are no indices). Formerly, a list slice would return an empty
43831b1f 280list if all indices fell outside the original list; now it returns a list
3209f716 281of C<undef> values in that case.
a75e6a3a 282L<[perl #114498]|https://rt.perl.org/Ticket/Display.html?id=114498>.
eabfc7bc 283
01842271 284=head2 C<\N{}> with a sequence of multiple spaces is now a fatal error
eabfc7bc 285
3209f716 286E.g. S<C<\N{TOOE<nbsp>E<nbsp>MANY SPACES}>> or S<C<\N{TRAILING SPACE }>>.
eabfc7bc
RS
287This has been deprecated since v5.18.
288
289=head2 S<C<use UNIVERSAL '...'>> is now a fatal error
290
291Importing functions from C<UNIVERSAL> has been deprecated since v5.12, and
d140c31c 292is now a fatal error. S<C<use UNIVERSAL>> without any arguments is still
eabfc7bc
RS
293allowed.
294
295=head2 In double-quotish C<\cI<X>>, I<X> must now be a printable ASCII character
296
297In prior releases, failure to do this raised a deprecation warning.
298
d1197d77 299=head2 Splitting the tokens C<(?> and C<(*> in regular expressions is now a fatal compilation error.
eabfc7bc
RS
300
301These had been deprecated since v5.18.
302
43831b1f
DM
303=head2 C<qr/foo/x> now ignores all Unicode pattern white space
304
305The C</x> regular expression modifier allows the pattern to contain
306white space and comments (both of which are ignored) for improved
307readability. Until now, not all the white space characters that Unicode
308designates for this purpose were handled. The additional ones now
309recognized are
310
311 U+0085 NEXT LINE
312 U+200E LEFT-TO-RIGHT MARK
313 U+200F RIGHT-TO-LEFT MARK
314 U+2028 LINE SEPARATOR
315 U+2029 PARAGRAPH SEPARATOR
eabfc7bc
RS
316
317The use of these characters with C</x> outside bracketed character
318classes and when not preceded by a backslash has raised a deprecation
43831b1f 319warning since v5.18. Now they will be ignored.
eabfc7bc 320
43831b1f 321=head2 Comment lines within S<C<(?[ ])>> are now ended only by a C<\n>
eabfc7bc
RS
322
323S<C<(?[ ])>> is an experimental feature, introduced in v5.18. It operates
43831b1f 324as if C</x> is always enabled. But there was a difference: comment
eabfc7bc
RS
325lines (following a C<#> character) were terminated by anything matching
326C<\R> which includes all vertical whitespace, such as form feeds. For
327consistency, this is now changed to match what terminates comment lines
328outside S<C<(?[ ])>>, namely a C<\n> (even if escaped), which is the
329same as what terminates a heredoc string and formats.
330
331=head2 C<(?[...])> operators now follow standard Perl precedence
332
333This experimental feature allows set operations in regular expression patterns.
334Prior to this, the intersection operator had the same precedence as the other
335binary operators. Now it has higher precedence. This could lead to different
336outcomes than existing code expects (though the documentation has always noted
337that this change might happen, recommending fully parenthesizing the
338expressions). See L<perlrecharclass/Extended Bracketed Character Classes>.
339
4ec8e6f0 340=head2 Omitting C<%> and C<@> on hash and array names is no longer permitted
c14a43b7 341
4ec8e6f0 342Really old Perl let you omit the C<@> on array names and the C<%> on hash
eabfc7bc 343names in some spots. This has issued a deprecation warning since Perl
93780ae6 3445.000, and is no longer permitted.
c14a43b7 345
d140c31c 346=head2 C<"$!"> text is now in English outside the scope of C<use locale>
eabfc7bc
RS
347
348Previously, the text, unlike almost everything else, always came out
349based on the current underlying locale of the program. (Also affected
d140c31c
AC
350on some systems is C<"$^E">.) For programs that are unprepared to
351handle locale differences, this can cause garbage text to be displayed.
352It's better to display text that is translatable via some tool than
353garbage text which is much harder to figure out.
eabfc7bc
RS
354
355=head2 C<"$!"> text will be returned in UTF-8 when appropriate
356
357The stringification of C<$!> and C<$^E> will have the UTF-8 flag set
358when the text is actually non-ASCII UTF-8. This will enable programs
359that are set up to be locale-aware to properly output messages in the
360user's native language. Code that needs to continue the 5.20 and
361earlier behavior can do the stringification within the scopes of both
3b50e657
KW
362S<C<use bytes>> and S<C<use locale ":messages">>. Within these two
363scopes, no other Perl operations will
eabfc7bc 364be affected by locale; only C<$!> and C<$^E> stringification. The
d140c31c 365C<bytes> pragma causes the UTF-8 flag to not be set, just as in previous
a75e6a3a
SH
366Perl releases. This resolves
367L<[perl #112208]|https://rt.perl.org/Ticket/Display.html?id=112208>.
eabfc7bc
RS
368
369=head2 Support for C<?PATTERN?> without explicit operator has been removed
370
d140c31c
AC
371The C<m?PATTERN?> construct, which allows matching a regex only once,
372previously had an alternative form that was written directly with a question
373mark delimiter, omitting the explicit C<m> operator. This usage has produced
374a deprecation warning since 5.14.0. It is now a syntax error, so that the
375question mark can be available for use in new operators.
eabfc7bc
RS
376
377=head2 C<defined(@array)> and C<defined(%hash)> are now fatal errors
378
379These have been deprecated since v5.6.1 and have raised deprecation
380warnings since v5.16.
381
01842271 382=head2 Using a hash or an array as a reference are now fatal errors
eabfc7bc 383
43831b1f 384For example, C<< %foo->{"bar"} >> now causes a fatal compilation
eabfc7bc
RS
385error. These have been deprecated since before v5.8, and have raised
386deprecation warnings since then.
387
388=head2 Changes to the C<*> prototype
389
390The C<*> character in a subroutine's prototype used to allow barewords to take
43831b1f
DM
391precedence over most, but not all, subroutine names. It was never
392consistent and exhibited buggy behaviour.
eabfc7bc
RS
393
394Now it has been changed, so subroutines always take precedence over barewords,
395which brings it into conformity with similarly prototyped built-in functions:
396
397 sub splat(*) { ... }
398 sub foo { ... }
399 splat(foo); # now always splat(foo())
400 splat(bar); # still splat('bar') as before
401 close(foo); # close(foo())
402 close(bar); # close('bar')
c14a43b7 403
7f9fef93 404=head1 Deprecations
47cb8ddb 405
eabfc7bc 406=head2 Setting C<${^ENCODING}> to anything but C<undef>
c14a43b7 407
d140c31c
AC
408This variable allows Perl scripts to be written in an encoding other than
409ASCII or UTF-8. However, it affects all modules globally, leading
eabfc7bc
RS
410to wrong answers and segmentation faults. New scripts should be written
411in UTF-8; old scripts should be converted to UTF-8, which is easily done
726f20d2 412with the L<piconv> utility.
c14a43b7 413
eabfc7bc 414=head2 Use of non-graphic characters in single-character variable names
51c2f40f 415
eabfc7bc
RS
416The syntax for single-character variable names is more lenient than
417for longer variable names, allowing the one-character name to be a
418punctuation character or even invisible (a non-graphic). Perl v5.20
419deprecated the ASCII-range controls as such a name. Now, all
420non-graphic characters that formerly were allowed are deprecated.
d140c31c
AC
421The practical effect of this occurs only when not under C<S<use
422utf8>>, and affects just the C1 controls (code points 0x80 through
eabfc7bc 4230xFF), NO-BREAK SPACE, and SOFT HYPHEN.
83a5d6b6 424
eabfc7bc 425=head2 Inlining of C<sub () { $var }> with observable side-effects
abec5bed 426
4ec8e6f0
KW
427In many cases Perl makes S<C<sub () { $var }>> into an inlinable constant
428subroutine, capturing the value of C<$var> at the time the C<sub> expression
eabfc7bc 429is evaluated. This can break the closure behaviour in those cases where
43831b1f
DM
430C<$var> is subsequently modified, since the subroutine won't return the
431changed value. (Note that this all only applies to anonymous subroutines
3209f716 432with an empty prototype (S<C<sub ()>>).)
abec5bed 433
eabfc7bc
RS
434This usage is now deprecated in those cases where the variable could be
435modified elsewhere. Perl detects those cases and emits a deprecation
436warning. Such code will likely change in the future and stop producing a
437constant.
abec5bed 438
eabfc7bc
RS
439If your variable is only modified in the place where it is declared, then
440Perl will continue to make the sub inlinable with no warnings.
c14a43b7 441
eabfc7bc
RS
442 sub make_constant {
443 my $var = shift;
444 return sub () { $var }; # fine
445 }
c14a43b7 446
eabfc7bc
RS
447 sub make_constant_deprecated {
448 my $var;
449 $var = shift;
450 return sub () { $var }; # deprecated
451 }
c14a43b7 452
eabfc7bc
RS
453 sub make_constant_deprecated2 {
454 my $var = shift;
455 log_that_value($var); # could modify $var
456 return sub () { $var }; # deprecated
457 }
c14a43b7 458
4ec8e6f0 459In the second example above, detecting that C<$var> is assigned to only once
eabfc7bc
RS
460is too hard to detect. That it happens in a spot other than the C<my>
461declaration is enough for Perl to find it suspicious.
7f9fef93 462
eabfc7bc
RS
463This deprecation warning happens only for a simple variable for the body of
464the sub. (A C<BEGIN> block or C<use> statement inside the sub is ignored,
465because it does not become part of the sub's body.) For more complex
4ec8e6f0 466cases, such as S<C<sub () { do_something() if 0; $var }>> the behaviour has
eabfc7bc
RS
467changed such that inlining does not happen if the variable is modifiable
468elsewhere. Such cases should be rare.
c14a43b7 469
eabfc7bc 470=head2 Use of multiple /x regexp modifiers
c14a43b7 471
eabfc7bc 472It is now deprecated to say something like any of the following:
c14a43b7 473
eabfc7bc
RS
474 qr/foo/xx;
475 /(?xax:foo)/;
476 use re qw(/amxx);
be39acb2 477
eabfc7bc
RS
478That is, now C<x> should only occur once in any string of contiguous
479regular expression pattern modifiers. We do not believe there are any
480occurrences of this in all of CPAN. This is in preparation for a future
d140c31c 481Perl release having C</xx> permit white-space for readability in
eabfc7bc
RS
482bracketed character classes (those enclosed in square brackets:
483C<[...]>).
c14a43b7 484
d1197d77 485=head2 Using a NO-BREAK space in a character alias for C<\N{...}> is now deprecated
60dcce55 486
eabfc7bc
RS
487This non-graphic character is essentially indistinguishable from a
488regular space, and so should not be allowed. See
489L<charnames/CUSTOM ALIASES>.
60dcce55 490
eabfc7bc
RS
491=head2 A literal C<"{"> should now be escaped in a pattern
492
493If you want a literal left curly bracket (also called a left brace) in a
494regular expression pattern, you should now escape it by either
495preceding it with a backslash (C<"\{">) or enclosing it within square
496brackets C<"[{]">, or by using C<\Q>; otherwise a deprecation warning
497will be raised. This was first announced as forthcoming in the v5.16
498release; it will allow future extensions to the language to happen.
499
500=head2 Making all warnings fatal is discouraged
501
502The documentation for L<fatal warnings|warnings/Fatal Warnings> notes that
d140c31c 503C<< use warnings FATAL => 'all' >> is discouraged, and provides stronger
eabfc7bc
RS
504language about the risks of fatal warnings in general.
505
506=head1 Performance Enhancements
79a77127 507
7f9fef93 508=over 4
abec5bed
DIM
509
510=item *
511
43831b1f 512If a method or class name is known at compile time, a hash is precomputed
eabfc7bc
RS
513to speed up run-time method lookup. Also, compound method names like
514C<SUPER::new> are parsed at compile time, to save having to parse them at
515run time.
9749148e 516
eabfc7bc 517=item *
9749148e 518
eabfc7bc
RS
519Array and hash lookups (especially nested ones) that use only constants
520or simple variables as keys, are now considerably faster. See
521L</Internal Changes> for more details.
abec5bed
DIM
522
523=item *
524
eabfc7bc
RS
525C<(...)x1>, C<("constant")x0> and C<($scalar)x0> are now optimised in list
526context. If the right-hand argument is a constant 1, the repetition
527operator disappears. If the right-hand argument is a constant 0, the whole
6a3ea89b 528expression is optimised to the empty list, so long as the left-hand
d140c31c
AC
529argument is a simple scalar or constant. (That is, C<(foo())x0> is not
530subject to this optimisation.)
6bb5549b 531
eabfc7bc 532=item *
7f9fef93 533
eabfc7bc
RS
534C<substr> assignment is now optimised into 4-argument C<substr> at the end
535of a subroutine (or as the argument to C<return>). Previously, this
536optimisation only happened in void context.
abec5bed 537
eabfc7bc 538=item *
7f9fef93 539
43831b1f
DM
540In C<"\L...">, C<"\Q...">, etc., the extra "stringify" op is now optimised
541away, making these just as fast as C<lcfirst>, C<quotemeta>, etc.
2e4abf26 542
eabfc7bc 543=item *
83a5d6b6 544
eabfc7bc
RS
545Assignment to an empty list is now sometimes faster. In particular, it
546never calls C<FETCH> on tied arguments on the right-hand side, whereas it
547used to sometimes.
548
549=item *
83a5d6b6 550
d140c31c
AC
551There is a performance improvement of up to 20% when C<length> is applied to
552a non-magical, non-tied string, and either C<use bytes> is in scope or the
553string doesn't use UTF-8 internally.
338906ce 554
eabfc7bc 555=item *
5de148ee 556
d140c31c
AC
557On most perl builds with 64-bit integers, memory usage for non-magical,
558non-tied scalars containing only a floating point value has been reduced
559by between 8 and 32 bytes, depending on OS.
5de148ee 560
eabfc7bc 561=item *
5de148ee 562
d140c31c
AC
563In C<@array = split>, the assignment can be optimized away, so that C<split>
564writes directly to the array. This optimisation was happening only for
43831b1f
DM
565package arrays other than C<@_>, and only sometimes. Now this
566optimisation happens almost all the time.
5de148ee 567
eabfc7bc 568=item *
7f9fef93 569
43831b1f 570C<join> is now subject to constant folding. So for example
3209f716 571S<C<join "-", "a", "b">> is converted at compile-time to C<"a-b">.
43831b1f 572Moreover, C<join> with a scalar or constant for the separator and a
d140c31c 573single-item list to join is simplified to a stringification, and the
43831b1f 574separator doesn't even get evaluated.
5de148ee 575
eabfc7bc 576=item *
47cb8ddb 577
eabfc7bc 578C<qq(@array)> is implemented using two ops: a stringify op and a join op.
4ec8e6f0 579If the C<qq> contains nothing but a single array, the stringification is
eabfc7bc 580optimized away.
47cb8ddb
SH
581
582=item *
583
4ec8e6f0
KW
584S<C<our $var>> and S<C<our($s,@a,%h)>> in void context are no longer evaluated at
585run time. Even a whole sequence of S<C<our $foo;>> statements will simply be
eabfc7bc 586skipped over. The same applies to C<state> variables.
47cb8ddb 587
eabfc7bc 588=item *
47cb8ddb 589
eabfc7bc
RS
590Many internal functions have been refactored to improve performance and reduce
591their memory footprints.
eabfc7bc
RS
592L<[perl #121436]|https://rt.perl.org/Ticket/Display.html?id=121436>
593L<[perl #121906]|https://rt.perl.org/Ticket/Display.html?id=121906>
594L<[perl #121969]|https://rt.perl.org/Ticket/Display.html?id=121969>
47cb8ddb 595
eabfc7bc 596=item *
47cb8ddb 597
eabfc7bc 598C<-T> and C<-B> filetests will return sooner when an empty file is detected.
a75e6a3a 599L<[perl #121489]|https://rt.perl.org/Ticket/Display.html?id=121489>
47cb8ddb 600
eabfc7bc 601=item *
5de148ee 602
01842271 603Hash lookups where the key is a constant are faster.
be39acb2
SH
604
605=item *
606
d140c31c 607Subroutines with an empty prototype and a body containing just C<undef> are now
eabfc7bc
RS
608eligible for inlining.
609L<[perl #122728]|https://rt.perl.org/Ticket/Display.html?id=122728>
be39acb2 610
eabfc7bc 611=item *
be39acb2 612
43831b1f
DM
613Subroutines in packages no longer need to be stored in typeglobs:
614declaring a subroutine will now put a simple sub reference directly in the
615stash if possible, saving memory. The typeglob still notionally exists,
616so accessing it will cause the stash entry to be upgraded to a typeglob
ff25fcfb 617(I<i.e.> this is just an internal implementation detail).
43831b1f
DM
618This optimization does not currently apply to XSUBs or exported
619subroutines, and method calls will undo it, since they cache things in
620typeglobs.
eabfc7bc 621L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
7f9fef93 622
eabfc7bc 623=item *
be39acb2 624
eabfc7bc
RS
625The functions C<utf8::native_to_unicode()> and C<utf8::unicode_to_native()>
626(see L<utf8>) are now optimized out on ASCII platforms. There is now not even
627a minimal performance hit in writing code portable between ASCII and EBCDIC
628platforms.
be39acb2
SH
629
630=item *
631
eabfc7bc 632Win32 Perl uses 8 KB less of per-process memory than before for every perl
43831b1f 633process, because some data is now memory mapped from disk and shared
d140c31c 634between processes from the same perl binary.
be39acb2
SH
635
636=back
637
eabfc7bc 638=head1 Modules and Pragmata
83a5d6b6 639
9189be1b
KW
640=head2 Updated Modules and Pragmata
641
f5b63a6e
RS
642Many of the libraries distributed with perl have been upgraded since v5.20.0.
643For a complete list of changes, run:
83a5d6b6 644
f5b63a6e 645 corelist --diff 5.20.0 5.22.0
338906ce 646
f5b63a6e 647You can substitute your favorite version in place of 5.20.0, too.
cd7bac54 648
9189be1b
KW
649Some notable changes include:
650
651=over 4
652
653=item *
654
39c78947 655L<Archive::Tar> has been upgraded to version 2.04.
9189be1b 656
53ce1dd5 657Tests can now be run in parallel.
9189be1b
KW
658
659=item *
660
39c78947 661L<attributes> has been upgraded to version 0.27.
9189be1b 662
53ce1dd5
RS
663The usage of C<memEQs> in the XS has been corrected.
664L<[perl #122701]|https://rt.perl.org/Ticket/Display.html?id=122701>
9189be1b 665
53ce1dd5 666Avoid reading beyond the end of a buffer. [perl #122629]
9189be1b
KW
667
668=item *
669
39c78947 670L<B> has been upgraded to version 1.58.
9189be1b 671
53ce1dd5
RS
672It provides a new C<B::safename> function, based on the existing
673C<< B::GV->SAFENAME >>, that converts "\cOPEN" to "^OPEN".
9189be1b 674
53ce1dd5 675Nulled COPs are now of class C<B::COP>, rather than C<B::OP>.
9189be1b 676
53ce1dd5
RS
677C<B::REGEXP> objects now provide a C<qr_anoncv> method for accessing the
678implicit CV associated with C<qr//> things containing code blocks, and a
679C<compflags> method that returns the pertinent flags originating from the
680C<qr//blahblah> op.
9189be1b 681
53ce1dd5
RS
682C<B::PMOP> now provides a C<pmregexp> method returning a C<B::REGEXP> object.
683Two new classes, C<B::PADNAME> and C<B::PADNAMELIST>, have been introduced.
9189be1b 684
53ce1dd5
RS
685A bug where, after an ithread creation or psuedofork, special/immortal SVs in
686the child ithread/psuedoprocess did not have the correct class of
687C<B::SPECIAL>, has been fixed.
688The C<id> and C<outid> PADLIST methods have been added.
9189be1b
KW
689
690=item *
691
39c78947 692L<B::Concise> has been upgraded to version 0.996.
9189be1b 693
53ce1dd5
RS
694Null ops that are part of the execution chain are now given sequence
695numbers.
696
697Private flags for nulled ops are now dumped with mnemonics as they would be
698for the non-nulled counterparts.
9189be1b
KW
699
700=item *
701
53ce1dd5 702L<B::Deparse> has been upgraded to version 1.35.
9189be1b 703
53ce1dd5
RS
704It now deparses C<+sub : attr { ... }> correctly at the start of a
705statement. Without the initial C<+>, C<sub> would be a statement label.
9189be1b 706
53ce1dd5
RS
707C<BEGIN> blocks are now emitted in the right place most of the time, but
708the change unfortunately introduced a regression, in that C<BEGIN> blocks
709occurring just before the end of the enclosing block may appear below it
2fe1cb6b 710instead.
9189be1b 711
53ce1dd5
RS
712C<B::Deparse> no longer puts erroneous C<local> here and there, such as for
713C<LIST = tr/a//d>. [perl #119815]
9189be1b 714
53ce1dd5
RS
715Adjacent C<use> statements are no longer accidentally nested if one
716contains a C<do> block. [perl #115066]
9189be1b 717
53ce1dd5 718Parenthesised arrays in lists passed to C<\> are now correctly deparsed
ff25fcfb 719with parentheses (I<e.g.>, C<\(@a, (@b), @c)> now retains the parentheses
53ce1dd5
RS
720around @b), this preserving the flattening behaviour of referenced
721parenthesised arrays. Formerly, it only worked for one array: C<\(@a)>.
9189be1b 722
53ce1dd5 723C<local our> is now deparsed correctly, with the C<our> included.
9189be1b 724
53ce1dd5
RS
725C<for($foo; !$bar; $baz) {...}> was deparsed without the C<!> (or C<not>).
726This has been fixed.
9189be1b 727
53ce1dd5
RS
728Core keywords that conflict with lexical subroutines are now deparsed with
729the C<CORE::> prefix.
9189be1b 730
53ce1dd5
RS
731C<foreach state $x (...) {...}> now deparses correctly with C<state> and
732not C<my>.
9189be1b 733
53ce1dd5
RS
734C<our @array = split(...)> now deparses correctly with C<our> in those
735cases where the assignment is optimized away.
9189be1b 736
53ce1dd5 737It now deparses C<our(I<LIST>)> and typed lexical (C<my Dog $spot>) correctly.
9189be1b 738
53ce1dd5
RS
739Deparse C<$#_> as that instead of as C<$#{_}>.
740L<[perl #123947]|https://rt.perl.org/Ticket/Display.html?id=123947>
9189be1b 741
53ce1dd5 742C<< <<>> >> is now correctly deparsed.
9189be1b 743
53ce1dd5
RS
744BEGIN blocks at the end of the enclosing scope are now deparsed in the
745right place. [perl #77452]
9189be1b 746
53ce1dd5
RS
747BEGIN blocks were sometimes deparsed as __ANON__, but are now always called
748BEGIN.
9189be1b 749
53ce1dd5 750Lexical subroutines are now fully deparsed. [perl #116553]
9189be1b 751
53ce1dd5
RS
752Deparsing of C<$lexical =~ //> was accidentally broken in 1.30 (perl
7535.21.6), omitting the C<$lexical =~>, but has now been fixed.
9189be1b 754
53ce1dd5 755C<Anything =~ y///r> with C</r> no longer omits the left-hand operand.
9189be1b 756
53ce1dd5
RS
757The op trees that make up regexp code blocks are now deparsed for real.
758Formerly, the original string that made up the regular expression was used.
759That caused problems with C<qr/(?{E<lt>E<lt>heredoc})/> and multiline code blocks,
760which were deparsed incorrectly. [perl #123217] [perl #115256]
9189be1b 761
53ce1dd5
RS
762C<$;> at the end of a statement no longer loses its semicolon.
763[perl #123357]
9189be1b 764
53ce1dd5
RS
765Some cases of subroutine declarations stored in the stash in shorthand form
766were being omitted.
9189be1b 767
53ce1dd5
RS
768Non-ASCII characters are now consistently escaped in strings, instead of
769some of the time. (There are still outstanding problems with regular
770expressions and identifiers that have not been fixed.)
9189be1b 771
ff25fcfb 772When prototype sub calls are deparsed with C<&> (I<e.g.>, under the B<-P>
53ce1dd5
RS
773option), C<scalar> is now added where appropriate, to force the scalar
774context implied by the prototype.
9189be1b 775
53ce1dd5
RS
776C<require(foo())>, C<do(foo())>, C<goto(foo())> and similar constructs with
777loop controls are now deparsed correctly. The outer parentheses are not
778optional.
9189be1b 779
53ce1dd5
RS
780Whitespace is no longer escaped in regular expressions, because it was
781getting erroneously escaped within C<(?x:...)> sections.
9189be1b 782
53ce1dd5 783C<sub foo { foo() }> is now deparsed with those mandatory parentheses.
9189be1b 784
53ce1dd5
RS
785C</@array/> is now deparsed as a regular expression, and not just
786C<@array>.
9189be1b 787
53ce1dd5
RS
788C</@{-}/>, C</@{+}/> and C<$#{1}> are now deparsed with the braces, which
789are mandatory in these cases.
9189be1b 790
53ce1dd5
RS
791In deparsing feature bundles, B::Deparse was emitting C<no feature;> first
792instead of C<no feature ':all';>. This has been fixed.
9189be1b 793
53ce1dd5 794C<chdir FH> is now deparsed without quotation marks.
9189be1b 795
53ce1dd5
RS
796C<\my @a> is now deparsed without parentheses. (Parenthese would flatten
797the array.)
9189be1b 798
53ce1dd5
RS
799C<system> and C<exec> followed by a block are now deparsed correctly.
800Formerly there was an erroneous C<do> before the block.
9189be1b 801
53ce1dd5
RS
802C<< use constant QR =E<gt> qr/.../flags >> followed by C<"" =~ QR> is no longer
803without the flags.
9189be1b 804
53ce1dd5
RS
805Deparsing C<BEGIN { undef &foo }> with the B<-w> switch enabled started to
806emit 'uninitialized' warnings in Perl 5.14. This has been fixed.
9189be1b 807
53ce1dd5
RS
808Deparsing calls to subs with a C<(;+)> prototype resulted in an infinite
809loop. The C<(;$>) C<(_)> and C<(;_)> prototypes were given the wrong
810precedence, causing C<foo($aE<lt>$b)> to be deparsed without the parentheses.
9189be1b 811
53ce1dd5
RS
812Deparse now provides a defined state sub in inner subs.
813Since version Perl 5.21.6, Deparse would croak on special constants, but
814this has now been fixed.
9189be1b
KW
815
816=item *
817
39c78947 818L<B::Op_private> has been added.
9189be1b 819
39c78947
RS
820L<B::Op_private> provides detailed information about the flags used in the
821C<op_private> field of perl opcodes.
9189be1b
KW
822
823=item *
824
53ce1dd5 825L<bigint>, L<bignum>, L<bigrat> have been upgraded to version 0.39.
9189be1b 826
53ce1dd5
RS
827Document in CAVEATS that using strings as numbers won't always invoke
828the big number overloading, and how to invoke it. [rt.perl.org #123064]
9189be1b
KW
829
830=item *
831
39c78947 832L<Carp> has been upgraded to version 1.36.
9189be1b 833
53ce1dd5
RS
834Carp::Heavy now ignores version mismatches with Carp if Carp is newer
835than 1.12, since Carp::Heavy's guts were merged into Carp at that
836point.
837L<[perl #121574]|https://rt.perl.org/Ticket/Display.html?id=121574>
838
839Carp now handles non-ASCII platforms better.
840Off-by-one error fix for Perl E<lt> 5.14.
9189be1b
KW
841
842=item *
843
39c78947 844L<constant> has been upgraded to version 1.33.
9189be1b 845
53ce1dd5
RS
846It now accepts fully-qualified constant names, allowing constants to be defined
847in packages other than the caller.
9189be1b
KW
848
849=item *
850
39c78947 851L<CPAN> has been upgraded to version 2.11.
9189be1b 852
53ce1dd5
RS
853Add support for C<Cwd::getdcwd()> and introduce workaround for a misbehaviour
854seen on Strawberry Perl 5.20.1.
9189be1b 855
53ce1dd5 856Fix C<chdir()> after building dependencies bug.
9189be1b 857
53ce1dd5 858Introduce experimental support for plugins/hooks.
9189be1b 859
53ce1dd5 860Integrate the App::Cpan sources.
9189be1b 861
53ce1dd5 862Do not check recursion on optional dependencies.
9189be1b 863
53ce1dd5
RS
864Sanity check F<META.yml> to contain a hash.
865L<[cpan #95271]|https://rt.cpan.org/Ticket/Display.html?id=95271>
9189be1b
KW
866
867=item *
868
39c78947 869L<CPAN::Meta::Requirements> has been upgraded to version 2.132.
9189be1b 870
53ce1dd5
RS
871Works around limitations in version::vpp detecting v-string magic and adds
872support for forthcoming L<ExtUtils::MakeMaker> bootstrap F<version.pm> for
873Perls older than 5.10.0.
9189be1b
KW
874
875=item *
876
39c78947 877L<Data::Dumper> has been upgraded to version 2.158.
9189be1b 878
53ce1dd5
RS
879Fixes CVE-2014-4330 by adding a configuration variable/option to limit
880recursion when dumping deep data structures.
9189be1b 881
53ce1dd5
RS
882Changes to resolve Coverity issues.
883XS dumps incorrectly stored the name of code references stored in a
884GLOB.
885L<[perl #122070]|https://rt.perl.org/Ticket/Display.html?id=122070>
9189be1b
KW
886
887=item *
888
39c78947 889L<DynaLoader> has been upgraded to version 1.32.
9189be1b
KW
890
891Remove C<dl_nonlazy> global if unused in Dynaloader. [perl #122926]
892
893=item *
894
39c78947 895L<Encode> has been upgraded to version 2.72.
9189be1b 896
53ce1dd5
RS
897C<piconv> now has better error handling when the encoding name is nonexistent,
898and a build breakage when upgrading L<Encode> in perl-5.8.2 and earlier has
899been fixed.
9189be1b 900
53ce1dd5 901Building in C++ mode on Windows now works.
9189be1b
KW
902
903=item *
904
53ce1dd5 905L<Errno> has been upgraded to version 1.23.
9189be1b 906
53ce1dd5
RS
907Add C<-P> to the preprocessor command-line on GCC 5. GCC added extra
908line directives, breaking parsing of error code definitions. [rt.perl.org
909#123784]
9189be1b
KW
910
911=item *
912
39c78947 913L<experimental> has been upgraded to version 0.013.
9189be1b 914
53ce1dd5 915Hardcodes features for Perls older than 5.15.7.
9189be1b
KW
916
917=item *
918
39c78947 919L<ExtUtils::CBuilder> has been upgraded to version 0.280221.
9189be1b 920
53ce1dd5
RS
921Fixes a regression on Android.
922L<[perl #122675]|https://rt.perl.org/Ticket/Display.html?id=122675>
9189be1b
KW
923
924=item *
925
39c78947 926L<ExtUtils::Manifest> has been upgraded to version 1.70.
9189be1b 927
53ce1dd5
RS
928Fixes a bug with C<maniread()>'s handling of quoted filenames and improves
929C<manifind()> to follow symlinks.
930L<[perl #122415]|https://rt.perl.org/Ticket/Display.html?id=122415>
9189be1b
KW
931
932=item *
933
39c78947 934L<ExtUtils::ParseXS> has been upgraded to version 3.28.
9189be1b
KW
935
936Only declare C<file> unused if we actually define it.
937Improve generated C<RETVAL> code generation to avoid repeated
938references to C<ST(0)>. [perl #123278]
939Broaden and document the C</OBJ$/> to C</REF$/> typemap optimization
940for the C<DESTROY> method. [perl #123418]
941
53ce1dd5 942=item *
9189be1b 943
53ce1dd5 944L<Fcntl> has been upgraded to version 1.13.
9189be1b 945
53ce1dd5 946Add support for the Linux pipe buffer size fcntl() commands.
9189be1b 947
53ce1dd5 948=item *
9189be1b 949
39c78947 950L<File::Find> has been upgraded to version 1.29.
9189be1b 951
53ce1dd5
RS
952C<find()> and C<finddepth()> will now warn if passed inappropriate or
953misspelled options.
9189be1b
KW
954
955=item *
956
957L<File::Glob> has been upgraded to version 1.24.
958
959Avoid SvIV() expanding to call get_sv() three times in a few
960places. [perl #123606]
961
962=item *
963
39c78947 964L<HTTP::Tiny> has been upgraded to version 0.054.
9189be1b 965
53ce1dd5 966C<keep_alive> is now fork-safe and thread-safe.
9189be1b
KW
967
968=item *
969
39c78947 970L<IO> has been upgraded to version 1.35.
9189be1b 971
53ce1dd5 972The XS implementation has been fixed for the sake of older Perls.
9189be1b
KW
973
974=item *
975
53ce1dd5 976L<IO::Socket> has been upgraded to version 1.38.
9189be1b 977
53ce1dd5 978Document the limitations of the connected() method. [perl #123096]
9189be1b 979
53ce1dd5 980=item *
9189be1b 981
39c78947 982L<IO::Socket::IP> has been upgraded to version 0.37.
9189be1b 983
53ce1dd5
RS
984A better fix for subclassing C<connect()>.
985L<[cpan #95983]|https://rt.cpan.org/Ticket/Display.html?id=95983>
986L<[cpan #97050]|https://rt.cpan.org/Ticket/Display.html?id=97050>
9189be1b 987
53ce1dd5
RS
988Implements Timeout for C<connect()>.
989L<[cpan #92075]|https://rt.cpan.org/Ticket/Display.html?id=92075>
9189be1b 990
53ce1dd5 991=item *
9189be1b 992
39c78947 993The libnet collection of modules has been upgraded to version 3.05.
9189be1b 994
53ce1dd5
RS
995Support for IPv6 and SSL to Net::FTP, Net::NNTP, Net::POP3 and Net::SMTP.
996Improvements in Net::SMTP authentication.
9189be1b 997
53ce1dd5 998=item *
9189be1b 999
39c78947 1000L<Locale::Codes> has been upgraded to version 3.34.
9189be1b 1001
53ce1dd5
RS
1002Fixed a bug in the scripts used to extract data from spreadsheets that
1003prevented the SHP currency code from being found.
1004L<[cpan #94229]|https://rt.cpan.org/Ticket/Display.html?id=94229>
9189be1b 1005
53ce1dd5 1006New codes have been added.
9189be1b 1007
53ce1dd5 1008=item *
9189be1b 1009
39c78947 1010L<Math::BigInt> has been upgraded to version 1.9997.
9189be1b 1011
53ce1dd5
RS
1012Synchronize POD changes from the CPAN release.
1013C<< Math::BigFloat->blog(x) >> would sometimes return blog(2*x) when
1014the accuracy was greater than 70 digits.
1015The result of C<< Math::BigFloat->bdiv() >> in list context now
1016satisfies C<< x = quotient * divisor + remainder >>.
9189be1b 1017
53ce1dd5
RS
1018Correct handling of subclasses.
1019L<[cpan #96254]|https://rt.cpan.org/Ticket/Display.html?id=96254>
1020L<[cpan #96329]|https://rt.cpan.org/Ticket/Display.html?id=96329>
9189be1b 1021
53ce1dd5 1022=item *
9189be1b 1023
39c78947 1024L<Module::Metadata> has been upgraded to version 1.000026.
9189be1b 1025
53ce1dd5
RS
1026Support installations on older perls with an L<ExtUtils::MakeMaker> earlier
1027than 6.63_03
9189be1b 1028
53ce1dd5 1029=item *
9189be1b 1030
39c78947 1031L<overload> has been upgraded to version 1.26.
9189be1b 1032
53ce1dd5 1033A redundant C<ref $sub> check has been removed.
9189be1b 1034
53ce1dd5 1035=item *
9189be1b 1036
39c78947 1037The PathTools module collection has been upgraded to version 3.56.
9189be1b 1038
53ce1dd5 1039A warning from the B<gcc> compiler is now avoided when building the XS.
9189be1b 1040
53ce1dd5 1041Don't turn leading C<//> into C</> on Cygwin. [perl #122635]
9189be1b 1042
53ce1dd5 1043=item *
9189be1b 1044
53ce1dd5 1045L<perl5db.pl> has been upgraded to version 1.49.
9189be1b 1046
53ce1dd5
RS
1047The debugger would cause an assertion failure.
1048L<[perl #124127]|https://rt.perl.org/Ticket/Display.html?id=124127>
9189be1b 1049
53ce1dd5
RS
1050C<fork()> in the debugger under C<tmux> will now create a new window for
1051the forked process. L<[perl
1052#121333]|https://rt.perl.org/Ticket/Display.html?id=121333>
9189be1b 1053
53ce1dd5
RS
1054The debugger now saves the current working directory on startup and
1055restores it when you restart your program with C<R> or C<rerun>. L<[perl
1056#121509]|https://rt.perl.org/Ticket/Display.html?id=121509>
9189be1b 1057
53ce1dd5 1058=item *
9189be1b 1059
53ce1dd5 1060L<PerlIO::scalar> has been upgraded to version 0.22.
9189be1b 1061
53ce1dd5
RS
1062Reading from a position well past the end of the scalar now correctly
1063returns end of file. [perl #123443]
9189be1b 1064
53ce1dd5
RS
1065Seeking to a negative position still fails, but no longer leaves the
1066file position set to a negation location.
9189be1b 1067
53ce1dd5
RS
1068C<eof()> on a C<PerlIO::scalar> handle now properly returns true when
1069the file position is past the 2GB mark on 32-bit systems.
1070
1071Attempting to write at file positions impossible for the platform now
1072fail early rather than wrapping at 4GB.
9189be1b
KW
1073
1074=item *
1075
39c78947 1076L<Pod::Perldoc> has been upgraded to version 3.25.
9189be1b 1077
53ce1dd5
RS
1078Filehandles opened for reading or writing now have C<:encoding(UTF-8)> set.
1079L<[cpan #98019]|https://rt.cpan.org/Ticket/Display.html?id=98019>
9189be1b
KW
1080
1081=item *
1082
39c78947 1083L<POSIX> has been upgraded to version 1.53.
9189be1b 1084
53ce1dd5
RS
1085The C99 math functions and constants (for example C<acosh>, C<isinf>, C<isnan>, C<round>,
1086C<trunc>; C<M_E>, C<M_SQRT2>, C<M_PI>) have been added.
9189be1b 1087
53ce1dd5 1088POSIX::tmpnam() now produces a deprecation warning. [perl #122005]
9189be1b
KW
1089
1090=item *
1091
53ce1dd5 1092L<Safe> has been upgraded to version 2.39.
9189be1b 1093
53ce1dd5 1094C<reval> was not propagating void context properly.
9189be1b 1095
53ce1dd5
RS
1096=item *
1097
1098Scalar-List-Utils has been upgraded to version 1.41.
1099
1100A new module, L<Sub::Util>, has been added, containing functions related to
1101CODE refs, including C<subname> (inspired by Sub::Identity) and C<set_subname>
1102(copied and renamed from Sub::Name).
1103The use of C<GetMagic> in C<List::Util::reduce()> has also been fixed.
1104L<[cpan #63211]|https://rt.cpan.org/Ticket/Display.html?id=63211>
9189be1b
KW
1105
1106=item *
1107
53ce1dd5 1108L<SDBM_File> has been upgraded to version 1.13.
9189be1b 1109
53ce1dd5 1110Simplified the build process. [perl #123413]
9189be1b
KW
1111
1112=item *
1113
53ce1dd5 1114L<Time::Piece> has been upgraded to version 1.29.
9189be1b 1115
53ce1dd5 1116When pretty printing negative Time::Seconds, the "minus" is no longer lost.
9189be1b 1117
53ce1dd5 1118=item *
9189be1b 1119
39c78947 1120L<Unicode::Collate> has been upgraded to version 1.12.
9189be1b 1121
53ce1dd5
RS
1122Version 0.67's improved discontiguous contractions is invalidated by default
1123and is supported as a parameter 'long_contraction'.
1124
1125=item *
1126
1127L<Unicode::Normalize> has been upgraded to version 1.18.
1128
1129The XSUB implementation has been removed in favour of pure Perl.
9189be1b
KW
1130
1131=item *
1132
1133L<Unicode::UCD> has been upgraded to version 0.61.
1134
1135A new function L<property_values()|Unicode::UCD/prop_values()>
1136has been added to return a given property's possible values.
1137
1138A new function L<charprop()|Unicode::UCD/charprop()>
1139has been added to return the value of a given property for a given code
1140point.
1141
1142A new function L<charprops_all()|Unicode::UCD/charprops_all()>
1143has been added to return the values of all Unicode properties for a
1144given code point.
1145
1146A bug has been fixed so that L<propaliases()|Unicode::UCD/prop_aliases()>
1147returns the correct short and long names for the Perl extensions where
1148it was incorrect.
1149
1150A bug has been fixed so that
1151L<prop_value_aliases()|Unicode::UCD/prop_value_aliases()>
1152returns C<undef> instead of a wrong result for properties that are Perl
1153extensions.
1154
1155This module now works on EBCDIC platforms.
1156
1157=item *
1158
53ce1dd5
RS
1159L<UNIVERSAL> has been upgraded to version 1.12.
1160
53ce1dd5
RS
1161=item *
1162
1163L<utf8> has been upgraded to version 1.17
1164
1165A mismatch between the documentation and the code in utf8::downgrade()
1166was fixed in favour of the documentation. The optional second argument
1167is now correctly treated as a perl boolean (true/false semantics) and
1168not as an integer.
1169
1170=item *
1171
1172L<version> has been upgraded to version 0.9909.
1173
1174Numerous changes. See the F<Changes> file in the CPAN distribution for
1175details.
1176
1177=item *
1178
9189be1b
KW
1179L<Win32> has been upgraded to version 0.51.
1180
1181GetOSName() now supports Windows 8.1, and building in C++ mode now works.
1182
1183=item *
1184
1185L<Win32API::File> has been upgraded to version 0.1202
1186
1187Building in C++ mode now works.
1188
53ce1dd5
RS
1189=item *
1190
39c78947 1191L<XSLoader> has been upgraded to version 0.20.
53ce1dd5
RS
1192
1193Allow XSLoader to load modules from a different namespace.
1194[perl #122455]
1195
9189be1b
KW
1196=back
1197
f5b63a6e 1198=head2 Removed Modules and Pragmata
391823f2 1199
f5b63a6e
RS
1200The following modules (and associated modules) have been removed from the core
1201perl distribution:
eabfc7bc
RS
1202
1203=over 4
1204
1205=item *
1206
f5b63a6e 1207L<CGI>
69e954a5 1208
7f9fef93 1209=item *
86e0176a 1210
f5b63a6e 1211L<Module::Build>
69e954a5 1212
e5998677 1213=back
20b5e916 1214
eabfc7bc
RS
1215=head1 Documentation
1216
1217=head2 New Documentation
532ecd00 1218
eabfc7bc 1219=head3 L<perlunicook>
d76c14eb 1220
eabfc7bc
RS
1221This document, by Tom Christiansen, provides examples of handling Unicode in
1222Perl.
1223
1224=head2 Changes to Existing Documentation
1225
7595828f
KW
1226=head3 L<perlaix>
1227
1228=over 4
1229
1230=item *
1231
1232A note on long doubles has been added.
1233
1234=back
1235
1236
eabfc7bc 1237=head3 L<perlapi>
d547bad0 1238
e5998677 1239=over 4
d547bad0 1240
8a95d307
FC
1241=item *
1242
eabfc7bc 1243Note that C<SvSetSV> doesn't do set magic.
532ecd00 1244
eabfc7bc 1245=item *
532ecd00 1246
6ba7438b 1247C<sv_usepvn_flags> - fix documentation to mention the use of C<Newx> instead of
eabfc7bc 1248C<malloc>.
532ecd00 1249
eabfc7bc 1250L<[perl #121869]|https://rt.perl.org/Ticket/Display.html?id=121869>
532ecd00 1251
eabfc7bc 1252=item *
532ecd00 1253
eabfc7bc 1254Clarify where C<NUL> may be embedded or is required to terminate a string.
532ecd00 1255
eabfc7bc 1256=item *
532ecd00 1257
d140c31c
AC
1258Some documentation that was previously missing due to formatting errors is
1259now included.
532ecd00 1260
eabfc7bc 1261=item *
532ecd00 1262
3b50e657
KW
1263Entries are now organized into groups rather than by the file where they
1264are found.
532ecd00 1265
eabfc7bc 1266=item *
532ecd00 1267
3b50e657
KW
1268Alphabetical sorting of entries is now done consistently (automatically
1269by the POD generator) to make entries easier to find when scanning.
eabfc7bc
RS
1270
1271=back
338906ce 1272
eabfc7bc 1273=head3 L<perldata>
338906ce 1274
e5998677 1275=over 4
338906ce 1276
eabfc7bc 1277=item *
2f304be9 1278
eabfc7bc
RS
1279The syntax of single-character variable names has been brought
1280up-to-date and more fully explained.
9749148e 1281
7595828f
KW
1282=item *
1283
1284Hexadecimal floating point numbers are described, as are infinity and
1285NaN.
1286
7f9fef93 1287=back
9749148e 1288
eabfc7bc 1289=head3 L<perlebcdic>
47cb8ddb 1290
7f9fef93 1291=over 4
47cb8ddb 1292
eabfc7bc 1293=item *
47cb8ddb 1294
eabfc7bc
RS
1295This document has been significantly updated in the light of recent
1296improvements to EBCDIC support.
47cb8ddb 1297
7f9fef93 1298=back
47cb8ddb 1299
7595828f
KW
1300=head3 L<perlfilter>
1301
1302=over 4
1303
1304=item *
1305
1306Added a L<LIMITATIONS|perlfilter/LIMITATIONS> section.
1307
1308=back
1309
1310
eabfc7bc 1311=head3 L<perlfunc>
be39acb2 1312
eabfc7bc 1313=over 4
be39acb2 1314
eabfc7bc 1315=item *
be39acb2 1316
eabfc7bc 1317Mention that C<study()> is currently a no-op.
be39acb2
SH
1318
1319=item *
1320
eabfc7bc
RS
1321Calling C<delete> or C<exists> on array values is now described as "strongly
1322discouraged" rather than "deprecated".
be39acb2 1323
eabfc7bc 1324=item *
7f9fef93 1325
eabfc7bc 1326Improve documentation of C<< our >>.
be39acb2 1327
eabfc7bc 1328=item *
be39acb2 1329
eabfc7bc
RS
1330C<-l> now notes that it will return false if symlinks aren't supported by the
1331file system.
be39acb2 1332
eabfc7bc 1333L<[perl #121523]|https://rt.perl.org/Ticket/Display.html?id=121523>
be39acb2
SH
1334
1335=item *
1336
eabfc7bc 1337Note that C<exec LIST> and C<system LIST> may fall back to the shell on
d140c31c
AC
1338Win32. Only the indirect-object syntax C<exec PROGRAM LIST> and
1339C<system PROGRAM LIST> will reliably avoid using the shell.
eabfc7bc
RS
1340
1341This has also been noted in L<perlport>.
1342
1343L<[perl #122046]|https://rt.perl.org/Ticket/Display.html?id=122046>
be39acb2 1344
7f9fef93 1345=back
be39acb2 1346
eabfc7bc
RS
1347=head3 L<perlguts>
1348
1349=over 4
1350
1351=item *
1352
1353The OOK example has been updated to account for COW changes and a change in the
1354storage of the offset.
1355
1356=item *
be39acb2 1357
eabfc7bc 1358Details on C level symbols and libperl.t added.
be39acb2 1359
ce93e38b
KW
1360=item *
1361
1362Information on Unicode handling has been added
1363
1364=item *
1365
1366Information on EBCDIC handling has been added
1367
eabfc7bc
RS
1368=back
1369
7595828f
KW
1370=head3 L<perlhack>
1371
1372=over 4
1373
1374=item *
1375
1376A note has been added about running on platforms with non-ASCII
1377character sets
1378
1379=item *
1380
1381A note has been added about performance testing
1382
1383=back
1384
eabfc7bc 1385=head3 L<perlhacktips>
7f9fef93
SH
1386
1387=over 4
be39acb2
SH
1388
1389=item *
1390
d140c31c
AC
1391Documentation has been added illustrating the perils of assuming that
1392there is no change to the contents of static memory pointed to by the
1393return values of Perl's wrappers for C library functions.
eabfc7bc
RS
1394
1395=item *
1396
d140c31c
AC
1397Replacements for C<tmpfile>, C<atoi>, C<strtol>, and C<strtoul> are now
1398recommended.
eabfc7bc
RS
1399
1400=item *
1401
1402Updated documentation for the C<test.valgrind> C<make> target.
1403
1404L<[perl #121431]|https://rt.perl.org/Ticket/Display.html?id=121431>
be39acb2 1405
7595828f
KW
1406=item *
1407
1408Information is given about writing test files portably to non-ASCII
1409platforms.
1410
1411=item *
1412
1413A note has been added about how to get a C language stack backtrace.
1414
1415=back
1416
1417=head3 L<perlhpux>
1418
1419=over 4
1420
1421=item *
1422
1423Note that the message "Redeclaration of "sendpath" with a different
1424storage class specifier" is harmless.
1425
1426=back
1427
1428=head3 L<perllocale>
1429
1430=over 4
1431
1432=item *
1433
1434Updated for the enhancements in v5.22, along with some clarifications.
1435
a9c3e753 1436=back
ea13b07e 1437
eabfc7bc 1438=head3 L<perlmodstyle>
0d42058e 1439
7f9fef93
SH
1440=over 4
1441
1442=item *
2a7a05b4 1443
eabfc7bc
RS
1444Instead of pointing to the module list, we are now pointing to
1445L<PrePAN|http://prepan.org/>.
2a7a05b4 1446
7f9fef93
SH
1447=back
1448
7595828f
KW
1449=head3 L<perlop>
1450
1451=over 4
1452
1453=item *
1454
1455Updated for the enhancements in v5.22, along with some clarifications.
1456
1457=back
1458
1459=head3 L<perlpodspec>
1460
1461=over 4
1462
1463=item *
1464
1465The specification of the pod language is changing so that the default
1466encoding of pods that aren't in UTF-8 (unless otherwise indicated) is
1467CP1252 instead of ISO 8859-1 (Latin1).
1468
1469=back
1470
eabfc7bc
RS
1471=head3 L<perlpolicy>
1472
1473=over 4
1474
1475=item *
1476
1477We now have a code of conduct for the I<< p5p >> mailing list, as documented
1478in L<< perlpolicy/STANDARDS OF CONDUCT >>.
2a7a05b4 1479
eabfc7bc
RS
1480=item *
1481
1482The conditions for marking an experimental feature as non-experimental are now
1483set out.
1484
7595828f
KW
1485=item *
1486
1487Clarification has been made as to what sorts of changes are permissible in
1488maintenance releases.
1489
eabfc7bc
RS
1490=back
1491
1492=head3 L<perlport>
1493
1494=over 4
1495
1496=item *
1497
d140c31c 1498Out-of-date VMS-specific information has been fixed and/or simplified.
eabfc7bc 1499
ce93e38b
KW
1500=item *
1501
1502Notes about EBCDIC have been added.
1503
eabfc7bc
RS
1504=back
1505
1506=head3 L<perlre>
1507
1508=over 4
1509
1510=item *
1511
d140c31c 1512The description of the C</x> modifier has been clarified to note that
7595828f
KW
1513comments cannot be continued onto the next line by escaping them; and
1514there is now a list of all the characters that are considered whitespace
1515by this modifier.
1516
1517=item *
1518
1519The new C</n> modifier is described.
1520
1521=item *
1522
1523A note has been added on how to make bracketed character class ranges
1524portable to non-ASCII machines.
eabfc7bc
RS
1525
1526=back
1527
1528=head3 L<perlrebackslash>
1529
1530=over 4
1531
1532=item *
1533
1534Added documentation of C<\b{sb}>, C<\b{wb}>, C<\b{gcb}>, and C<\b{g}>.
1535
1536=back
1537
1538=head3 L<perlrecharclass>
1539
1540=over 4
1541
1542=item *
1543
1544Clarifications have been added to L<perlrecharclass/Character Ranges>
3b50e657 1545to the effect C<[A-Z]>, C<[a-z]>, C<[0-9]> and
eabfc7bc
RS
1546any subranges thereof in regular expression bracketed character classes
1547are guaranteed to match exactly what a naive English speaker would
1548expect them to match, even on platforms (such as EBCDIC) where special
1549handling is required to accomplish this.
1550
1551=item *
1552
1553The documentation of Bracketed Character Classes has been expanded to cover the
1554improvements in C<qr/[\N{named sequence}]/> (see under L</Selected Bug Fixes>).
1555
1556=back
1557
7595828f
KW
1558=head3 L<perlref>
1559
1560=over 4
1561
1562=item *
1563
1564A new section has been added
1565L<Assigning to References|perlref/Assigning to References>
1566
1567=back
1568
eabfc7bc
RS
1569=head3 L<perlsec>
1570
1571=over 4
1572
1573=item *
1574
1575Comments added on algorithmic complexity and tied hashes.
1576
1577=back
1578
1579=head3 L<perlsyn>
1580
1581=over 4
1582
1583=item *
1584
1585An ambiguity in the documentation of the C<...> statement has been corrected.
1586L<[perl #122661]|https://rt.perl.org/Ticket/Display.html?id=122661>
1587
1588=item *
1589
1590The empty conditional in C<< for >> and C<< while >> is now documented
1591in L<< perlsyn >>.
1592
1593=back
1594
1595=head3 L<perlunicode>
1596
1597=over 4
1598
1599=item *
1600
ce93e38b 1601This has had extensive revisions to bring it up-to-date with current
7595828f
KW
1602Unicode support and to make it more readable. Notable is that Unicode
16037.0 changed what it should do with non-characters. Perl retains the old
1604way of handling for reasons of backward compatibility. See
1605L<perlunicode/Noncharacter code points>.
eabfc7bc
RS
1606
1607=back
1608
1609=head3 L<perluniintro>
1610
1611=over 4
1612
1613=item *
1614
1615Advice for how to make sure your strings and regular expression patterns are
ce93e38b 1616interpreted as Unicode has been updated.
eabfc7bc
RS
1617
1618=back
1619
1620=head3 L<perlvar>
1621
1622=over 4
1623
1624=item *
1625
7595828f
KW
1626C<$]> is no longer listed as being deprecated. Instead, discussion has
1627been added on the advantages and disadvantages of using it versus
1628C<$^V>.
1629
1630=item *
1631
1632C<${^ENCODING}> is now marked as deprecated.
1633
1634=item *
1635
1636The entry for C<%^H> has been clarified to indicate it can only handle
1637simple values.
eabfc7bc
RS
1638
1639=back
1640
1641=head3 L<perlvms>
1642
1643=over 4
1644
1645=item *
1646
1647Out-of-date and/or incorrect material has been removed.
1648
1649=item *
1650
1651Updated documentation on environment and shell interaction in VMS.
1652
1653=back
1654
1655=head3 L<perlxs>
1656
1657=over 4
1658
1659=item *
1660
1661Added a discussion of locale issues in XS code.
1662
1663=back
1664
1665=head1 Diagnostics
1666
1667The following additions or changes have been made to diagnostic output,
1668including warnings and fatal error messages. For the complete list of
1669diagnostic messages, see L<perldiag>.
1670
1671=head2 New Diagnostics
1672
1673=head3 New Errors
1674
1675=over 4
1676
1677=item *
1678
1679L<Bad symbol for scalar|perldiag/"Bad symbol for scalar">
1680
1681(P) An internal request asked to add a scalar entry to something that
1682wasn't a symbol table entry.
1683
1684=item *
1685
1686L<Can't use a hash as a reference|perldiag/"Can't use a hash as a reference">
1687
1688(F) You tried to use a hash as a reference, as in
1689C<< %foo->{"bar"} >> or C<< %$ref->{"hello"} >>. Versions of perl E<lt>= 5.6.1
1690used to allow this syntax, but shouldn't have.
1691
1692=item *
1693
1694L<Can't use an array as a reference|perldiag/"Can't use an array as a reference">
1695
1696(F) You tried to use an array as a reference, as in
1697C<< @foo->[23] >> or C<< @$ref->[99] >>. Versions of perl E<lt>= 5.6.1 used to
1698allow this syntax, but shouldn't have.
1699
1700=item *
1701
1702L<Can't use 'defined(@array)' (Maybe you should just omit the defined()?)|perldiag/"Can't use 'defined(@array)' (Maybe you should just omit the defined()?)">
1703
4ec8e6f0 1704(F) C<defined()> is not useful on arrays because it
eabfc7bc 1705checks for an undefined I<scalar> value. If you want to see if the
4ec8e6f0 1706array is empty, just use S<C<if (@array) { # not empty }>> for example.
eabfc7bc
RS
1707
1708=item *
1709
1710L<Can't use 'defined(%hash)' (Maybe you should just omit the defined()?)|perldiag/"Can't use 'defined(%hash)' (Maybe you should just omit the defined()?)">
1711
1712(F) C<defined()> is not usually right on hashes.
1713
4ec8e6f0 1714Although S<C<defined %hash>> is false on a plain not-yet-used hash, it
eabfc7bc 1715becomes true in several non-obvious circumstances, including iterators,
4ec8e6f0
KW
1716weak references, stash names, even remaining true after S<C<undef %hash>>.
1717These things make S<C<defined %hash>> fairly useless in practice, so it now
eabfc7bc
RS
1718generates a fatal error.
1719
1720If a check for non-empty is what you wanted then just put it in boolean
1721context (see L<perldata/Scalar values>):
1722
1723 if (%hash) {
1724 # not empty
1725 }
1726
4ec8e6f0 1727If you had S<C<defined %Foo::Bar::QUUX>> to check whether such a package
eabfc7bc
RS
1728variable exists then that's never really been reliable, and isn't
1729a good way to enquire about the features of a package, or whether
1730it's loaded, etc.
1731
1732=item *
1733
1734L<Cannot chr %f|perldiag/"Cannot chr %f">
1735
c21a1c59
RS
1736(F) You passed an invalid number (like an infinity or not-a-number) to
1737C<chr>.
1738
eabfc7bc
RS
1739=item *
1740
1741L<Cannot compress %f in pack|perldiag/"Cannot compress %f in pack">
1742
c21a1c59
RS
1743(F) You tried converting an infinity or not-a-number to an unsigned
1744character, which makes no sense.
1745
eabfc7bc
RS
1746=item *
1747
1748L<Cannot pack %f with '%c'|perldiag/"Cannot pack %f with '%c'">
1749
c21a1c59
RS
1750(F) You tried converting an infinity or not-a-number to a character,
1751which makes no sense.
1752
eabfc7bc
RS
1753=item *
1754
1755L<Cannot print %f with '%c'|perldiag/"Cannot printf %f with '%c'">
1756
4ec8e6f0
KW
1757(F) You tried printing an infinity or not-a-number as a character (C<%c>),
1758which makes no sense. Maybe you meant C<'%s'>, or just stringifying it?
c21a1c59 1759
eabfc7bc
RS
1760=item *
1761
1762L<charnames alias definitions may not contain a sequence of multiple spaces|perldiag/"charnames alias definitions may not contain a sequence of multiple spaces">
1763
1764(F) You defined a character name which had multiple space
1765characters in a row. Change them to single spaces. Usually these
1766names are defined in the C<:alias> import argument to C<use charnames>, but
1767they could be defined by a translator installed into C<$^H{charnames}>.
1768See L<charnames/CUSTOM ALIASES>.
1769
1770=item *
1771
1772L<charnames alias definitions may not contain trailing white-space|perldiag/"charnames alias definitions may not contain trailing white-space">
1773
1774(F) You defined a character name which ended in a space
1775character. Remove the trailing space(s). Usually these names are
1776defined in the C<:alias> import argument to C<use charnames>, but they
1777could be defined by a translator installed into C<$^H{charnames}>.
1778See L<charnames/CUSTOM ALIASES>.
1779
1780=item *
1781
1782L<:const is not permitted on named subroutines|perldiag/":const is not permitted on named subroutines">
1783
1784(F) The "const" attribute causes an anonymous subroutine to be run and
f5b97b22 1785its value captured at the time that it is cloned. Named subroutines are
eabfc7bc
RS
1786not cloned like this, so the attribute does not make sense on them.
1787
1788=item *
1789
1790L<Hexadecimal float: internal error|perldiag/"Hexadecimal float: internal error">
1791
1792(F) Something went horribly bad in hexadecimal float handling.
1793
1794=item *
1795
1796L<Hexadecimal float: unsupported long double format|perldiag/"Hexadecimal float: unsupported long double format">
1797
1798(F) You have configured Perl to use long doubles but
1799the internals of the long double format are unknown,
1800therefore the hexadecimal float output is impossible.
1801
1802=item *
1803
1804L<Illegal suidscript|perldiag/"Illegal suidscript">
1805
1806(F) The script run under suidperl was somehow illegal.
1807
1808=item *
1809
1810L<In '(?...)', the '(' and '?' must be adjacent in regex; marked by S<<-- HERE> in mE<sol>%sE<sol>|perldiag/"In '(?...)', the '(' and '?' must be adjacent in regex; marked by <-- HERE in m/%s/">
1811
1812(F) The two-character sequence C<"(?"> in
1813this context in a regular expression pattern should be an
1814indivisible token, with nothing intervening between the C<"(">
1815and the C<"?">, but you separated them.
1816
1817=item *
1818
1819L<In '(*VERB...)', the '(' and '*' must be adjacent in regex; marked by S<<-- HERE> in mE<sol>%sE<sol>|perldiag/"In '(*VERB...)', the '(' and '*' must be adjacent in regex; marked by <-- HERE in m/%s/">
1820
1821(F) The two-character sequence C<"(*"> in
1822this context in a regular expression pattern should be an
1823indivisible token, with nothing intervening between the C<"(">
1824and the C<"*">, but you separated them.
1825
1826=item *
1827
1828L<Invalid quantifier in {,} in regex; marked by <-- HERE in mE<sol>%sE<sol>|perldiag/"Invalid quantifier in {,} in regex; marked by <-- HERE in m/%s/">
1829
1830(F) The pattern looks like a {min,max} quantifier, but the min or max could not
1831be parsed as a valid number - either it has leading zeroes, or it represents
1832too big a number to cope with. The S<<-- HERE> shows where in the regular
1833expression the problem was discovered. See L<perlre>.
1834
eaa8dfa2
KW
1835=item *
1836
1837L<'%s' is an unknown bound type in regex|perldiag/"'%s' is an unknown bound type in regex; marked by <-- HERE in m/%s/">
1838
1839(F) You used C<\b{...}> or C<\B{...}> and the C<...> is not known to
1840Perl. The current valid ones are given in
1841L<perlrebackslash/\b{}, \b, \B{}, \B>.
1842
1843=item *
1844
1845L<Missing or undefined argument to require|perldiag/Missing or undefined argument to require>
1846
1847(F) You tried to call C<require> with no argument or with an undefined
1848value as an argument. C<require> expects either a package name or a
1849file-specification as an argument. See L<perlfunc/require>.
1850
1851Formerly, C<require> with no argument or C<undef> warned about a Null filename.
1852
eabfc7bc
RS
1853=back
1854
1855=head3 New Warnings
1856
1857=over 4
1858
1859=item *
1860
43831b1f
DM
1861L<\C is deprecated in regex|perldiag/"\C is deprecated in regex; marked by <-- HERE in m/%s/">
1862
1863(D deprecated) The C<< /\C/ >> character class was deprecated in v5.20, and
1864now emits a warning. It is intended that it will become an error in v5.24.
1865This character class matches a single byte even if it appears within a
50ea4745 1866multi-byte character, breaks encapsulation, and can corrupt UTF-8
43831b1f
DM
1867strings.
1868
1869=item *
1870
eabfc7bc
RS
1871L<"%s" is more clearly written simply as "%s" in regex; marked by E<lt>-- HERE in mE<sol>%sE<sol>|perldiag/"%s" is more clearly written simply as "%s" in regex; marked by <-- HERE in mE<sol>%sE<sol>>
1872
1873(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1874
1875You specified a character that has the given plainer way of writing it,
1876and which is also portable to platforms running with different character
1877sets.
1878
1879=item *
1880
1881L<Argument "%s" treated as 0 in increment (++)|perldiag/"Argument "%s" treated
1882as 0 in increment (++)">
1883
1884(W numeric) The indicated string was fed as an argument to the C<++> operator
1885which expects either a number or a string matching C</^[a-zA-Z]*[0-9]*\z/>.
1886See L<perlop/Auto-increment and Auto-decrement> for details.
1887
1888=item *
1889
1890L<Both or neither range ends should be Unicode in regex; marked by E<lt>-- HERE in mE<sol>%sE<sol>|perldiag/"Both or neither range ends should be Unicode in regex; marked by <-- HERE in m/%s/">
1891
1892(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1893
1894In a bracketed character class in a regular expression pattern, you
1895had a range which has exactly one end of it specified using C<\N{}>, and
1896the other end is specified using a non-portable mechanism. Perl treats
1897the range as a Unicode range, that is, all the characters in it are
1898considered to be the Unicode characters, and which may be different code
1899points on some platforms Perl runs on. For example, C<[\N{U+06}-\x08]>
1900is treated as if you had instead said C<[\N{U+06}-\N{U+08}]>, that is it
1901matches the characters whose code points in Unicode are 6, 7, and 8.
1902But that C<\x08> might indicate that you meant something different, so
1903the warning gets raised.
1904
1905=item *
1906
e6205aca
KW
1907L<Can't do %s("%s") on non-UTF-8 locale; resolved to "%s".|perldiag/Can't do %s("%s") on non-UTF-8 locale; resolved to "%s".>
1908
1909(W locale) You are 1) running under "C<use locale>"; 2) the current
1910locale is not a UTF-8 one; 3) you tried to do the designated case-change
1911operation on the specified Unicode character; and 4) the result of this
1912operation would mix Unicode and locale rules, which likely conflict.
1913
1bc134bc
KW
1914The warnings category C<locale> is new.
1915
e6205aca
KW
1916=item *
1917
eabfc7bc
RS
1918L<:const is experimental|perldiag/":const is experimental">
1919
1920(S experimental::const_attr) The "const" attribute is experimental.
1921If you want to use the feature, disable the warning with C<no warnings
1922'experimental::const_attr'>, but know that in doing so you are taking
1923the risk that your code may break in a future Perl version.
1924
1925=item *
1926
1927L<gmtime(%f) failed|perldiag/"gmtime(%f) failed">
1928
1929(W overflow) You called C<gmtime> with a number that it could not handle:
1930too large, too small, or NaN. The returned value is C<undef>.
1931
1932=item *
1933
1934L<Hexadecimal float: exponent overflow|perldiag/"Hexadecimal float: exponent overflow">
1935
1936(W overflow) The hexadecimal floating point has larger exponent
1937than the floating point supports.
1938
1939=item *
1940
1941L<Hexadecimal float: exponent underflow|perldiag/"Hexadecimal float: exponent underflow">
1942
1943(W overflow) The hexadecimal floating point has smaller exponent
1944than the floating point supports.
1945
1946=item *
1947
1948L<Hexadecimal float: mantissa overflow|perldiag/"Hexadecimal float: mantissa overflow">
1949
1950(W overflow) The hexadecimal floating point literal had more bits in
1951the mantissa (the part between the 0x and the exponent, also known as
1952the fraction or the significand) than the floating point supports.
1953
1954=item *
1955
1956L<Hexadecimal float: precision loss|perldiag/"Hexadecimal float: precision loss">
1957
1958(W overflow) The hexadecimal floating point had internally more
1959digits than could be output. This can be caused by unsupported
1960long double formats, or by 64-bit integers not being available
1961(needed to retrieve the digits under some configurations).
1962
eabfc7bc
RS
1963=item *
1964
e6205aca
KW
1965L<Locale '%s' may not work well.%s|perldiag/Locale '%s' may not work well.%s>
1966
1967(W locale) You are using the named locale, which is a non-UTF-8 one, and
1968which perl has determined is not fully compatible with what it can
1969handle. The second C<%s> gives a reason.
1970
1bc134bc
KW
1971The warnings category C<locale> is new.
1972
e6205aca
KW
1973=item *
1974
eabfc7bc
RS
1975L<localtime(%f) failed|perldiag/"localtime(%f) failed">
1976
1977(W overflow) You called C<localtime> with a number that it could not handle:
1978too large, too small, or NaN. The returned value is C<undef>.
1979
1980=item *
1981
1982L<Negative repeat count does nothing|perldiag/"Negative repeat count does nothing">
1983
1984(W numeric) You tried to execute the
1985L<C<x>|perlop/Multiplicative Operators> repetition operator fewer than 0
1986times, which doesn't make sense.
1987
1988=item *
1989
1990L<NO-BREAK SPACE in a charnames alias definition is deprecated|perldiag/"NO-BREAK SPACE in a charnames alias definition is deprecated">
1991
1992(D deprecated) You defined a character name which contained a no-break
1993space character. Change it to a regular space. Usually these names are
1994defined in the C<:alias> import argument to C<use charnames>, but they
1995could be defined by a translator installed into C<$^H{charnames}>. See
1996L<charnames/CUSTOM ALIASES>.
1997
1998=item *
1999
2000L<Non-finite repeat count does nothing|perldiag/"Non-finite repeat count does nothing">
2001
2002(W numeric) You tried to execute the
2003L<C<x>|perlop/Multiplicative Operators> repetition operator C<Inf> (or
3209f716 2004C<-Inf>) or NaN times, which doesn't make sense.
eabfc7bc
RS
2005
2006=item *
2007
2008L<PerlIO layer ':win32' is experimental|perldiag/"PerlIO layer ':win32' is experimental">
2009
2010(S experimental::win32_perlio) The C<:win32> PerlIO layer is
2011experimental. If you want to take the risk of using this layer,
2012simply disable this warning:
2013
2014 no warnings "experimental::win32_perlio";
2015
2016=item *
2017
2018L<Ranges of ASCII printables should be some subset of "0-9", "A-Z", or "a-z" in regex; marked by E<lt>-- HERE in mE<sol>%sE<sol>|perldiag/"Ranges of ASCII printables should be some subset of "0-9", "A-Z", or "a-z" in regex; marked by <-- HERE in mE<sol>%sE<sol>">
2019
2020(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
2021
2022Stricter rules help to find typos and other errors. Perhaps you didn't
2023even intend a range here, if the C<"-"> was meant to be some other
2024character, or should have been escaped (like C<"\-">). If you did
2025intend a range, the one that was used is not portable between ASCII and
2026EBCDIC platforms, and doesn't have an obvious meaning to a casual
2027reader.
2028
2029 [3-7] # OK; Obvious and portable
2030 [d-g] # OK; Obvious and portable
2031 [A-Y] # OK; Obvious and portable
2032 [A-z] # WRONG; Not portable; not clear what is meant
2033 [a-Z] # WRONG; Not portable; not clear what is meant
2034 [%-.] # WRONG; Not portable; not clear what is meant
2035 [\x41-Z] # WRONG; Not portable; not obvious to non-geek
2036
2037(You can force portability by specifying a Unicode range, which means that
2038the endpoints are specified by
2039L<C<\N{...}>|perlrecharclass/Character Ranges>, but the meaning may
2040still not be obvious.)
2041The stricter rules require that ranges that start or stop with an ASCII
93780ae6 2042character that is not a control have all their endpoints be a literal
eabfc7bc
RS
2043character, and not some escape sequence (like C<"\x41">), and the ranges
2044must be all digits, or all uppercase letters, or all lowercase letters.
2045
2046=item *
2047
2048L<Ranges of digits should be from the same group in regex; marked by E<lt>-- HERE in mE<sol>%sE<sol>|perldiag/"Ranges of digits should be from the same group in regex; marked by <-- HERE in m/%s/">
2049
2050(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
2051
2052Stricter rules help to find typos and other errors. You included a
2053range, and at least one of the end points is a decimal digit. Under the
2054stricter rules, when this happens, both end points should be digits in
2055the same group of 10 consecutive digits.
2056
2057=item *
2058
2059L<Redundant argument in %s|perldiag/Redundant argument in %s>
2060
f5b97b22
DM
2061(W redundant) You called a function with more arguments than were
2062needed, as indicated by information within other arguments you supplied
ff25fcfb 2063(I<e.g>. a printf format). Currently only emitted when a printf-type format
f5b97b22 2064required fewer arguments than were supplied, but might be used in the
ff25fcfb 2065future for I<e.g.> L<perlfunc/pack>.
eabfc7bc 2066
a75e6a3a
SH
2067The warnings category C<< redundant >> is new. See also
2068L<[perl #121025]|https://rt.perl.org/Ticket/Display.html?id=121025>.
eabfc7bc
RS
2069
2070=item *
2071
e6205aca
KW
2072L<Replacement list is longer than search list|perldiag/Replacement list is longer than search list>
2073
2074This is not a new diagnostic, but in earlier releases was accidentally
2075not displayed if the transliteration contained wide characters. This is
2076now fixed, so that you may see this diagnostic in places where you
2077previously didn't (but should have).
2078
2079=item *
2080
eabfc7bc
RS
2081L<Use of \b{} for non-UTF-8 locale is wrong. Assuming a UTF-8 locale|perldiag/"Use of \b{} for non-UTF-8 locale is wrong. Assuming a UTF-8 locale">
2082
a2c7aad0 2083(W locale) You are matching a regular expression using locale rules,
eabfc7bc
RS
2084and a Unicode boundary is being matched, but the locale is not a Unicode
2085one. This doesn't make sense. Perl will continue, assuming a Unicode
2086(UTF-8) locale, but the results could well be wrong except if the locale
2087happens to be ISO-8859-1 (Latin1) where this message is spurious and can
2088be ignored.
2089
1bc134bc
KW
2090The warnings category C<locale> is new.
2091
eabfc7bc
RS
2092=item *
2093
2094L<< Using E<sol>u for '%s' instead of E<sol>%s in regex; marked by E<lt>-- HERE in mE<sol>%sE<sol>|perldiag/"Using E<sol>u for '%s' instead of E<sol>%s in regex; marked by <-- HERE in mE<sol>%sE<sol>" >>
2095
a2c7aad0 2096(W regexp) You used a Unicode boundary (C<\b{...}> or C<\B{...}>) in a
eabfc7bc
RS
2097portion of a regular expression where the character set modifiers C</a>
2098or C</aa> are in effect. These two modifiers indicate an ASCII
2099interpretation, and this doesn't make sense for a Unicode definition.
2100The generated regular expression will compile so that the boundary uses
2101all of Unicode. No other portion of the regular expression is affected.
2102
2103=item *
2104
2105L<The bitwise feature is experimental|perldiag/"The bitwise feature is experimental">
2106
a2c7aad0 2107(S experimental::bitwise) This warning is emitted if you use bitwise
eabfc7bc
RS
2108operators (C<& | ^ ~ &. |. ^. ~.>) with the "bitwise" feature enabled.
2109Simply suppress the warning if you want to use the feature, but know
2110that in doing so you are taking the risk of using an experimental
2111feature which may change or be removed in a future Perl version:
2112
2113 no warnings "experimental::bitwise";
2114 use feature "bitwise";
2115 $x |.= $y;
2116
2117=item *
2118
2119L<Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in mE<sol>%sE<sol>|perldiag/"Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/%s/">
2120
2121(D deprecated, regexp) You used a literal C<"{"> character in a regular
2122expression pattern. You should change to use C<"\{"> instead, because a future
2123version of Perl (tentatively v5.26) will consider this to be a syntax error. If
2124the pattern delimiters are also braces, any matching right brace
2125(C<"}">) should also be escaped to avoid confusing the parser, for
2126example,
2127
2128 qr{abc\{def\}ghi}
2129
2130=item *
2131
2132L<Use of literal non-graphic characters in variable names is deprecated|perldiag/"Use of literal non-graphic characters in variable names is deprecated">
2133
b0511669
DM
2134(D deprecated) Using literal non-graphic (including control)
2135characters in the source to refer to the ^FOO variables, like C<$^X> and
2136C<${^GLOBAL_PHASE}> is now deprecated.
2137
eabfc7bc
RS
2138=item *
2139
2140L<Useless use of attribute "const"|perldiag/Useless use of attribute "const">
2141
2142(W misc) The "const" attribute has no effect except
2143on anonymous closure prototypes. You applied it to
2144a subroutine via L<attributes.pm|attributes>. This is only useful
2145inside an attribute handler for an anonymous subroutine.
2146
2147=item *
2148
e6205aca
KW
2149L<Useless use of E<sol>d modifier in transliteration operator|perldiag/"Useless use of /d modifier in transliteration operator">
2150
2151This is not a new diagnostic, but in earlier releases was accidentally
2152not displayed if the transliteration contained wide characters. This is
2153now fixed, so that you may see this diagnostic in places where you
2154previously didn't (but should have).
2155
2156=item *
2157
eabfc7bc
RS
2158L<E<quot>use re 'strict'E<quot> is experimental|perldiag/"use re 'strict'" is experimental>
2159
2160(S experimental::re_strict) The things that are different when a regular
2161expression pattern is compiled under C<'strict'> are subject to change
3b50e657
KW
2162in future Perl releases in incompatible ways; there are also proposals
2163to change how to enable strict checking instead of using this subpragma.
2164This means that a pattern that compiles today may not in a future Perl
2165release. This warning is to alert you to that risk.
eabfc7bc
RS
2166
2167=item *
2168
caa16dbd
TC
2169L<Warning: unable to close filehandle properly: %s|perldiag/"Warning: unable to close filehandle properly: %s">
2170
eabfc7bc
RS
2171L<Warning: unable to close filehandle %s properly: %s|perldiag/"Warning: unable to close filehandle %s properly: %s">
2172
3b50e657 2173(S io) Previously, perl silently ignored any errors when doing an implicit
ff25fcfb
KW
2174close of a filehandle, I<i.e.> where the reference count of the filehandle
2175reached zero and the user's code hadn't already called C<close()>; I<e.g.>
b0511669
DM
2176
2177 {
2178 open my $fh, '>', $file or die "open: '$file': $!\n";
2179 print $fh, $data or die;
2180 } # implicit close here
2181
3b50e657 2182In a situation such as disk full, due to buffering, the error may only be
b0511669
DM
2183detected during the final close, so not checking the result of the close is
2184dangerous.
2185
2186So perl now warns in such situations.
caa16dbd 2187
eabfc7bc
RS
2188=item *
2189
2190L<Wide character (U+%X) in %s|perldiag/"Wide character (U+%X) in %s">
2191
2192(W locale) While in a single-byte locale (I<i.e.>, a non-UTF-8
2193one), a multi-byte character was encountered. Perl considers this
50ea4745 2194character to be the specified Unicode code point. Combining non-UTF-8
eabfc7bc
RS
2195locales and Unicode is dangerous. Almost certainly some characters
2196will have two different representations. For example, in the ISO 8859-7
2197(Greek) locale, the code point 0xC3 represents a Capital Gamma. But so
2198also does 0x393. This will make string comparisons unreliable.
2199
2200You likely need to figure out how this multi-byte character got mixed up
2201with your single-byte locale (or perhaps you thought you had a UTF-8
2202locale, but Perl disagrees).
2203
1bc134bc
KW
2204The warnings category C<locale> is new.
2205
eabfc7bc
RS
2206=back
2207
2208=head2 Changes to Existing Diagnostics
2209
2210=over 4
2211
2212=item *
2213
2214<> should be quotes
2215
2216This warning has been changed to
2217L<< <> at require-statement should be quotes|perldiag/"<> at require-statement should be quotes" >>
2218to make the issue more identifiable.
2219
2220=item *
2221
2222L<Argument "%s" isn't numeric%s|perldiag/"Argument "%s" isn't numeric%s">
b0511669
DM
2223
2224The L<perldiag> entry for this warning has added this clarifying note:
eabfc7bc 2225
4ec8e6f0 2226 Note that for the Inf and NaN (infinity and not-a-number) the
77c2376a
KW
2227 definition of "numeric" is somewhat unusual: the strings themselves
2228 (like "Inf") are considered numeric, and anything following them is
2229 considered non-numeric.
eabfc7bc
RS
2230
2231=item *
2232
2233L<Global symbol "%s" requires explicit package name|perldiag/"Global symbol "%s" requires explicit package name (did you forget to declare "my %s"?)">
2234
2235This message has had '(did you forget to declare "my %s"?)' appended to it, to
2236make it more helpful to new Perl programmers.
2237L<[perl #121638]|https://rt.perl.org/Ticket/Display.html?id=121638>
2238
2239=item *
2240
2241'"my" variable &foo::bar can't be in a package' has been reworded to say
2242'subroutine' instead of 'variable'.
2243
2244=item *
2245
b0511669
DM
2246L<<< \N{} in character class restricted to one character in regex; marked by
2247S<< <-- HERE >> in mE<sol>%sE<sol>|perldiag/"\N{} in inverted character
2248class or as a range end-point is restricted to one character in regex;
2249marked by <-- HERE in m/%s/" >>>
eabfc7bc 2250
b0511669
DM
2251This message has had I<character class> changed to I<inverted character
2252class or as a range end-point is> to reflect improvements in
2253C<qr/[\N{named sequence}]/> (see under L</Selected Bug Fixes>).
eabfc7bc
RS
2254
2255=item *
2256
2257L<panic: frexp|perldiag/"panic: frexp: %f">
2258
b0511669
DM
2259This message has had ': C<%f>' appended to it, to show what the offending
2260floating point number is.
eabfc7bc
RS
2261
2262=item *
2263
b0511669 2264I<Possible precedence problem on bitwise %c operator> reworded as
eabfc7bc
RS
2265L<Possible precedence problem on bitwise %s operator|perldiag/"Possible precedence problem on bitwise %s operator">.
2266
2267=item *
2268
eabfc7bc
RS
2269L<Unsuccessful %s on filename containing newline|perldiag/"Unsuccessful %s on filename containing newline">
2270
2271This warning is now only produced when the newline is at the end of
2272the filename.
2273
2274=item *
2275
4ec8e6f0 2276"Variable C<%s> will not stay shared" has been changed to say "Subroutine"
eabfc7bc
RS
2277when it is actually a lexical sub that will not stay shared.
2278
2279=item *
2280
2281L<Variable length lookbehind not implemented in regex mE<sol>%sE<sol>|perldiag/"Variable length lookbehind not implemented in regex m/%s/">
2282
b0511669
DM
2283The L<perldiag> entry for this warning has had information about Unicode
2284behaviour added.
eabfc7bc
RS
2285
2286=back
2287
2288=head2 Diagnostic Removals
2289
2290=over
2291
2292=item *
2293
2294"Ambiguous use of -foo resolved as -&foo()"
2295
2296There is actually no ambiguity here, and this impedes the use of negated
ff25fcfb 2297constants; I<e.g.>, C<-Inf>.
eabfc7bc
RS
2298
2299=item *
2300
2301"Constant is not a FOO reference"
2302
ff25fcfb 2303Compile-time checking of constant dereferencing (I<e.g.>, C<< my_constant->() >>)
eabfc7bc
RS
2304has been removed, since it was not taking overloading into account.
2305L<[perl #69456]|https://rt.perl.org/Ticket/Display.html?id=69456>
2306L<[perl #122607]|https://rt.perl.org/Ticket/Display.html?id=122607>
2307
2308=back
2309
2310=head1 Utility Changes
2311
b0511669 2312=head2 F<find2perl>, F<s2p> and F<a2p> removal
eabfc7bc
RS
2313
2314=over 4
2315
2316=item *
2317
2318The F<x2p/> directory has been removed from the Perl core.
2319
2320This removes find2perl, s2p and a2p. They have all been released to CPAN as
2321separate distributions (App::find2perl, App::s2p, App::a2p).
2322
2323=back
2324
2325=head2 L<h2ph>
2326
2327=over 4
2328
2329=item *
2330
2331F<h2ph> now handles hexadecimal constants in the compiler's predefined
a75e6a3a
SH
2332macro definitions, as visible in C<$Config{cppsymbols}>.
2333L<[perl #123784]|https://rt.perl.org/Ticket/Display.html?id=123784>.
eabfc7bc
RS
2334
2335=back
2336
2337=head2 L<encguess>
2338
2339=over 4
2340
2341=item *
2342
f1c9eac6 2343No longer depends on non-core modules.
eabfc7bc
RS
2344
2345=back
2346
2347=head1 Configuration and Compilation
2348
2349=over 4
2350
2351=item *
2352
b0511669
DM
2353F<Configure> now checks for C<lrintl()>, C<lroundl()>, C<llrintl()>, and
2354C<llroundl()>.
eabfc7bc
RS
2355
2356=item *
2357
a75e6a3a
SH
2358F<Configure> with C<-Dmksymlinks> should now be faster.
2359L<[perl #122002]|https://rt.perl.org/Ticket/Display.html?id=122002>.
eabfc7bc
RS
2360
2361=item *
2362
b0511669
DM
2363The C<pthreads> and C<cl> libraries will be linked by default if present.
2364This allows XS modules that require threading to work on non-threaded
2365perls. Note that you must still pass C<-Dusethreads> if you want a
2366threaded perl.
eabfc7bc
RS
2367
2368=item *
2369
2370For long doubles (to get more precision and range for floating point numbers)
2371one can now use the GCC quadmath library which implements the quadruple
f1c9eac6
DM
2372precision floating point numbers on x86 and IA-64 platforms. See
2373F<INSTALL> for details.
eabfc7bc
RS
2374
2375=item *
2376
2377MurmurHash64A and MurmurHash64B can now be configured as the internal hash
2378function.
2379
2380=item *
2381
2382C<make test.valgrind> now supports parallel testing.
2383
2384For example:
2385
2386 TEST_JOBS=9 make test.valgrind
2387
2388See L<perlhacktips/valgrind> for more information.
2389
2390L<[perl #121431]|https://rt.perl.org/Ticket/Display.html?id=121431>
2391
2392=item *
2393
2394The MAD (Misc Attribute Decoration) build option has been removed
2395
2396This was an unmaintained attempt at preserving
2397the Perl parse tree more faithfully so that automatic conversion of
2398Perl 5 to Perl 6 would have been easier.
2399
2400This build-time configuration option had been unmaintained for years,
2401and had probably seriously diverged on both Perl 5 and Perl 6 sides.
2402
2403=item *
2404
2405A new compilation flag, C<< -DPERL_OP_PARENT >> is available. For details,
2406see the discussion below at L<< /Internal Changes >>.
2407
43831b1f
DM
2408=item *
2409
2410Pathtools no longer tries to load XS on miniperl. This speeds up building perl
2411slightly.
2412
eabfc7bc
RS
2413=back
2414
2415=head1 Testing
2416
2417=over 4
2418
2419=item *
2420
2421F<t/porting/re_context.t> has been added to test that L<utf8> and its
2422dependencies only use the subset of the C<$1..$n> capture vars that
b0511669
DM
2423C<Perl_save_re_context()> is hard-coded to localize, because that function
2424has no efficient way of determining at runtime what vars to localize.
eabfc7bc
RS
2425
2426=item *
2427
2428Tests for performance issues have been added in the file F<t/perf/taint.t>.
2429
2430=item *
2431
2432Some regular expression tests are written in such a way that they will
2433run very slowly if certain optimizations break. These tests have been
2434moved into new files, F<< t/re/speed.t >> and F<< t/re/speed_thr.t >>,
2435and are run with a C<< watchdog() >>.
2436
2437=item *
2438
2439C<< test.pl >> now allows C<< plan skip_all => $reason >>, to make it
2440more compatible with C<< Test::More >>.
2441
2442=item *
2443
3b50e657 2444A new test script, F<op/infnan.t>, has been added to test if infinity and NaN are
eabfc7bc
RS
2445working correctly. See L</Infinity and NaN (not-a-number) handling improved>.
2446
2447=back
2448
2449=head1 Platform Support
2450
2451=head2 Regained Platforms
2452
2453=over 4
2454
2455=item IRIX and Tru64 platforms are working again.
2456
2457(Some C<make test> failures remain.)
2458
2459=item z/OS running EBCDIC Code Page 1047
2460
2461Core perl now works on this EBCDIC platform. Earlier perls also worked, but,
2462even though support wasn't officially withdrawn, recent perls would not compile
2463and run well. Perl 5.20 would work, but had many bugs which have now been
2464fixed. Many CPAN modules that ship with Perl still fail tests, including
2465Pod::Simple. However the version of Pod::Simple currently on CPAN should work;
2466it was fixed too late to include in Perl 5.22. Work is under way to fix many
2467of the still-broken CPAN modules, which likely will be installed on CPAN when
2468completed, so that you may not have to wait until Perl 5.24 to get a working
2469version.
2470
2471=back
2472
2473=head2 Discontinued Platforms
2474
2475=over 4
2476
2477=item NeXTSTEP/OPENSTEP
2478
f1c9eac6
DM
2479NeXTSTEP was a proprietary operating system bundled with NeXT's
2480workstations in the early to mid 90s; OPENSTEP was an API specification
2481that provided a NeXTSTEP-like environment on a non-NeXTSTEP system. Both
2482are now long dead, so support for building Perl on them has been removed.
eabfc7bc
RS
2483
2484=back
2485
2486=head2 Platform-Specific Notes
2487
2488=over 4
2489
2490=item EBCDIC
2491
3b50e657
KW
2492Special handling is required of the perl interpreter on EBCDIC platforms
2493to get C<qr/[i-j]/> to match only C<"i"> and C<"j">, since there are 7
2494characters between the
eabfc7bc
RS
2495code points for C<"i"> and C<"j">. This special handling had only been
2496invoked when both ends of the range are literals. Now it is also
2497invoked if any of the C<\N{...}> forms for specifying a character by
2498name or Unicode code point is used instead of a literal. See
2499L<perlrecharclass/Character Ranges>.
2500
2501=item HP-UX
2502
2503The archname now distinguishes use64bitint from use64bitall.
2504
2505=item Android
2506
2507Build support has been improved for cross-compiling in general and for
2508Android in particular.
2509
2510=item VMS
2511
2512=over 4
2513
2514=item *
2515
2516When spawning a subprocess without waiting, the return value is now
2517the correct PID.
2518
2519=item *
2520
2521Fix a prototype so linking doesn't fail under the VMS C++ compiler.
2522
2523=item *
2524
2525C<finite>, C<finitel>, and C<isfinite> detection has been added to
2526C<configure.com>, environment handling has had some minor changes, and
2527a fix for legacy feature checking status.
2528
2529=back
2530
2531=item Win32
2532
2533=over 4
2534
2535=item *
2536
2537F<miniperl.exe> is now built with C<-fno-strict-aliasing>, allowing 64-bit
2538builds to complete on GCC 4.8.
2539L<[perl #123976]|https://rt.perl.org/Ticket/Display.html?id=123976>
2540
2541=item *
2542
17fcdc49
TC
2543C<nmake minitest> now works on Win32. Due to dependency issues you
2544need to build C<nmake test-prep> first, and a small number of the
2545tests fail.
2546L<[perl #123394]|https://rt.perl.org/Ticket/Display.html?id=123394>
2547
2548=item *
2549
eabfc7bc
RS
2550Perl can now be built in C++ mode on Windows by setting the makefile macro
2551C<USE_CPLUSPLUS> to the value "define".
2552
2553=item *
2554
d140c31c 2555The list form of piped open has been implemented for Win32. Note: unlike
00eebae1 2556C<system LIST> this does not fall back to the shell.
18f4cc8e 2557L<[perl #121159]|https://rt.perl.org/Ticket/Display.html?id=121159>
eabfc7bc
RS
2558
2559=item *
2560
eabfc7bc
RS
2561New C<DebugSymbols> and C<DebugFull> configuration options added to
2562Windows makefiles.
2563
2564=item *
2565
f1c9eac6 2566Previously compiling XS modules (including CPAN ones) using Visual C++ for
b0511669 2567Win64 resulted in around a dozen warnings per file from F<hv_func.h>. These
f1c9eac6 2568warnings have been silenced.
eabfc7bc
RS
2569
2570=item *
2571
2572Support for building without PerlIO has been removed from the Windows
2573makefiles. Non-PerlIO builds were all but deprecated in Perl 5.18.0 and are
2574already not supported by F<Configure> on POSIX systems.
2575
2576=item *
2577
d140c31c
AC
2578Between 2 and 6 milliseconds and seven I/O calls have been saved per attempt
2579to open a perl module for each path in C<@INC>.
eabfc7bc
RS
2580
2581=item *
2582
2583Intel C builds are now always built with C99 mode on.
2584
2585=item *
2586
2587C<%I64d> is now being used instead of C<%lld> for MinGW.
2588
2589=item *
2590
2591In the experimental C<:win32> layer, a crash in C<open> was fixed. Also
3209f716 2592opening F</dev/null> (which works under Win32 Perl's default C<:unix>
d140c31c 2593layer) was implemented for C<:win32>.
eabfc7bc
RS
2594L<[perl #122224]|https://rt.perl.org/Ticket/Display.html?id=122224>
2595
2596=item *
2597
2598A new makefile option, C<USE_LONG_DOUBLE>, has been added to the Windows
2599dmake makefile for gcc builds only. Set this to "define" if you want perl to
2600use long doubles to give more accuracy and range for floating point numbers.
2601
2602=back
2603
2604=item OpenBSD
2605
2606On OpenBSD, Perl will now default to using the system C<malloc> due to the
2607security features it provides. Perl's own malloc wrapper has been in use
2608since v5.14 due to performance reasons, but the OpenBSD project believes
2609the tradeoff is worth it and would prefer that users who need the speed
2610specifically ask for it.
2611
2612L<[perl #122000]|https://rt.perl.org/Ticket/Display.html?id=122000>.
2613
2614=item Solaris
2615
2616=over 4
2617
2618=item *
2619
2620We now look for the Sun Studio compiler in both F</opt/solstudio*> and
2621F</opt/solarisstudio*>.
2622
2623=item *
2624
2625Builds on Solaris 10 with C<-Dusedtrace> would fail early since make
2626didn't follow implied dependencies to build C<perldtrace.h>. Added an
2627explicit dependency to C<depend>.
2628L<[perl #120120]|https://rt.perl.org/Ticket/Display.html?id=120120>
2629
2630=item *
2631
d140c31c
AC
2632C<c99> options have been cleaned up; hints look for C<solstudio>
2633as well as C<SUNWspro>; and support for native C<setenv> has been added.
eabfc7bc
RS
2634
2635=back
2636
2637=back
2638
2639=head1 Internal Changes
2640
2641=over 4
2642
2643=item *
2644
bad0181b
DM
2645Experimental support has been added to allow ops in the optree to locate
2646their parent, if any. This is enabled by the non-default build option
2647C<-DPERL_OP_PARENT>. It is envisaged that this will eventually become
b0511669 2648enabled by default, so XS code which directly accesses the C<op_sibling>
bad0181b 2649field of ops should be updated to be future-proofed.
eabfc7bc
RS
2650
2651On C<PERL_OP_PARENT> builds, the C<op_sibling> field has been renamed
bad0181b
DM
2652C<op_sibparent> and a new flag, C<op_moresib>, added. On the last op in a
2653sibling chain, C<op_moresib> is false and C<op_sibparent> points to the
b0511669 2654parent (if any) rather than being C<NULL>.
bad0181b 2655
b0511669 2656To make existing code work transparently whether using C<PERL_OP_PARENT>
bad0181b
DM
2657or not, a number of new macros and functions have been added that should
2658be used, rather than directly manipulating C<op_sibling>.
2659
2660For the case of just reading C<op_sibling> to determine the next sibling,
2661two new macros have been added. A simple scan through a sibling chain
2662like this:
2663
b0511669 2664 for (; kid->op_sibling; kid = kid->op_sibling) { ... }
bad0181b
DM
2665
2666should now be written as:
2667
b0511669 2668 for (; OpHAS_SIBLING(kid); kid = OpSIBLING(kid)) { ... }
bad0181b 2669
d140c31c 2670For altering optrees, a general-purpose function C<op_sibling_splice()>
bad0181b
DM
2671has been added, which allows for manipulation of a chain of sibling ops.
2672By analogy with the Perl function C<splice()>, it allows you to cut out
2673zero or more ops from a sibling chain and replace them with zero or more
2674new ops. It transparently handles all the updating of sibling, parent,
2675op_last pointers etc.
2676
2677If you need to manipulate ops at a lower level, then three new macros,
2678C<OpMORESIB_set>, C<OpLASTSIB_set> and C<OpMAYBESIB_set> are intended to
2679be a low-level portable way to set C<op_sibling> / C<op_sibparent> while
2680also updating C<op_moresib>. The first sets the sibling pointer to a new
2681sibling, the second makes the op the last sibling, and the third
2682conditionally does the first or second action. Note that unlike
2683C<op_sibling_splice()> these macros won't maintain consistency in the
ff25fcfb 2684parent at the same time (I<e.g.> by updating C<op_first> and C<op_last> where
bad0181b
DM
2685appropriate).
2686
d140c31c 2687A C-level C<Perl_op_parent()> function and a Perl-level C<B::OP::parent()>
bad0181b 2688method have been added. The C function only exists under
b0511669 2689C<PERL_OP_PARENT> builds (using it is build-time error on vanilla
bad0181b 2690perls). C<B::OP::parent()> exists always, but on a vanilla build it
b0511669 2691always returns C<NULL>. Under C<PERL_OP_PARENT>, they return the parent
bad0181b
DM
2692of the current op, if any. The variable C<$B::OP::does_parent> allows you
2693to determine whether C<B> supports retrieving an op's parent.
2694
b0511669 2695C<PERL_OP_PARENT> was introduced in 5.21.2, but the interface was
bad0181b
DM
2696changed considerably in 5.21.11. If you updated your code before the
26975.21.11 changes, it may require further revision. The main changes after
26985.21.2 were:
eabfc7bc 2699
bad0181b 2700=over 4
eabfc7bc
RS
2701
2702=item *
2703
bad0181b
DM
2704The C<OP_SIBLING> and C<OP_HAS_SIBLING> macros have been renamed
2705C<OpSIBLING> and C<OpHAS_SIBLING> for consistency with other
2706op-manipulating macros.
eabfc7bc
RS
2707
2708=item *
2709
bad0181b
DM
2710The C<op_lastsib> field has been renamed C<op_moresib>, and its meaning
2711inverted.
eabfc7bc
RS
2712
2713=item *
2714
bad0181b 2715The macro C<OpSIBLING_set> has been removed, and has been superseded by
ff25fcfb 2716C<OpMORESIB_set> I<et al>.
eabfc7bc
RS
2717
2718=item *
2719
bad0181b
DM
2720The C<op_sibling_splice()> function now accepts a null C<parent> argument
2721where the splicing doesn't affect the first or last ops in the sibling
2722chain
eabfc7bc
RS
2723
2724=back
2725
2726=item *
2727
2728Macros have been created to allow XS code to better manipulate the POSIX locale
2729category C<LC_NUMERIC>. See L<perlapi/Locale-related functions and macros>.
2730
2731=item *
2732
ff25fcfb 2733The previous C<atoi> I<et al> replacement function, C<grok_atou>, has now been
eabfc7bc
RS
2734superseded by C<grok_atoUV>. See L<perlclib> for details.
2735
2736=item *
2737
b0511669
DM
2738A new function, C<Perl_sv_get_backrefs()>, has been added which allows you
2739retrieve the weak references, if any, which point at an SV.
eabfc7bc
RS
2740
2741=item *
2742
b0511669 2743The C<screaminstr()> function has been removed. Although marked as
f1c9eac6
DM
2744public API, it was undocumented and had no usage in CPAN modules. Calling
2745it has been fatal since 5.17.0.
eabfc7bc
RS
2746
2747=item *
2748
b0511669
DM
2749The C<newDEFSVOP()>, C<block_start()>, C<block_end()> and C<intro_my()>
2750functions have been added to the API.
eabfc7bc
RS
2751
2752=item *
2753
2754The internal C<convert> function in F<op.c> has been renamed
2755C<op_convert_list> and added to the API.
2756
2757=item *
2758
b0511669
DM
2759The C<sv_magic()> function no longer forbids "ext" magic on read-only
2760values. After all, perl can't know whether the custom magic will modify
2761the SV or not.
a75e6a3a 2762L<[perl #123103]|https://rt.perl.org/Ticket/Display.html?id=123103>.
eabfc7bc
RS
2763
2764=item *
2765
d140c31c
AC
2766Accessing L<perlapi/CvPADLIST> on an XSUB is now forbidden.
2767
cca58a48
DM
2768The C<CvPADLIST> field has been reused for a different internal purpose
2769for XSUBs. So in particular, you can no longer rely on it being NULL as a
2770test of whether a CV is an XSUB. Use C<CvISXSUB()> instead.
2771
eabfc7bc
RS
2772=item *
2773
b0511669 2774SVs of type C<SVt_NV> are now sometimes bodiless when the build
cca58a48 2775configuration and platform allow it: specifically, when C<< sizeof(NV) <=
b0511669 2776sizeof(IV) >>. "Bodiless" means that the NV value is stored directly in
cca58a48
DM
2777the head of an SV, without requiring a separate body to be allocated. This
2778trick has already been used for IVs since 5.9.2 (though in the case of
2779IVs, it is always used, regardless of platform and build configuration).
eabfc7bc
RS
2780
2781=item *
2782
b0511669 2783The C<$DB::single>, C<$DB::signal> and C<$DB::trace> variables now have set- and
d140c31c 2784get-magic that stores their values as IVs, and those IVs are used when
b0511669 2785testing their values in C<pp_dbstate()>. This prevents perl from
f1c9eac6 2786recursing infinitely if an overloaded object is assigned to any of those
a75e6a3a
SH
2787variables.
2788L<[perl #122445]|https://rt.perl.org/Ticket/Display.html?id=122445>.
eabfc7bc
RS
2789
2790=item *
2791
b0511669 2792C<Perl_tmps_grow()>, which is marked as public API but is undocumented, has
d140c31c 2793been removed from the public API. This change does not affect XS code that
b0511669 2794uses the C<EXTEND_MORTAL> macro to pre-extend the mortal stack.
eabfc7bc
RS
2795
2796=item *
2797
b0511669
DM
2798Perl's internals no longer sets or uses the C<SVs_PADMY> flag.
2799C<SvPADMY()> now returns a true value for anything not marked C<PADTMP>
2800and C<SVs_PADMY> is now defined as 0.
eabfc7bc
RS
2801
2802=item *
2803
d140c31c 2804The macros C<SETsv> and C<SETsvUN> have been removed. They were no longer used
b0511669
DM
2805in the core since commit 6f1401dc2a five years ago, and have not been
2806found present on CPAN.
eabfc7bc
RS
2807
2808=item *
2809
2810The C<< SvFAKE >> bit (unused on HVs) got informally reserved by
2811David Mitchell for future work on vtables.
2812
2813=item *
2814
b0511669 2815The C<sv_catpvn_flags()> function accepts C<SV_CATBYTES> and C<SV_CATUTF8>
50ea4745 2816flags, which specify whether the appended string is bytes or UTF-8,
b0511669
DM
2817respectively. (These flags have in fact been present since 5.16.0, but
2818were formerly not regarded as part of the API.)
eabfc7bc
RS
2819
2820=item *
2821
f1c9eac6 2822A new opcode class, C<< METHOP >>, has been introduced. It holds
d140c31c 2823information used at runtime for improve the performance
eabfc7bc
RS
2824of class/object method calls.
2825
d140c31c 2826C<< OP_METHOD >> and C<< OP_METHOD_NAMED >> have changed from being
eabfc7bc
RS
2827C<< UNOP/SVOP >> to being C<< METHOP >>.
2828
2829=item *
2830
b0511669
DM
2831C<cv_name()> is a new API function that can be passed a CV or GV. It
2832returns an SV containing the name of the subroutine, for use in
2833diagnostics.
eabfc7bc 2834
eabfc7bc
RS
2835L<[perl #116735]|https://rt.perl.org/Ticket/Display.html?id=116735>
2836L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
2837
2838=item *
2839
b0511669
DM
2840C<cv_set_call_checker_flags()> is a new API function that works like
2841C<cv_set_call_checker()>, except that it allows the caller to specify
2842whether the call checker requires a full GV for reporting the subroutine's
2843name, or whether it could be passed a CV instead. Whatever value is
2844passed will be acceptable to C<cv_name()>. C<cv_set_call_checker()>
2845guarantees there will be a GV, but it may have to create one on the fly,
2846which is inefficient.
eabfc7bc
RS
2847L<[perl #116735]|https://rt.perl.org/Ticket/Display.html?id=116735>
2848
2849=item *
2850
2851C<CvGV> (which is not part of the API) is now a more complex macro, which may
b0511669 2852call a function and reify a GV. For those cases where it has been used as a
eabfc7bc
RS
2853boolean, C<CvHASGV> has been added, which will return true for CVs that
2854notionally have GVs, but without reifying the GV. C<CvGV> also returns a GV
2855now for lexical subs.
2856L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
2857
2858=item *
2859
d140c31c
AC
2860The L<perlapi/sync_locale> function has been added to the public API.
2861Changing the program's locale should be avoided by XS code. Nevertheless,
2862certain non-Perl libraries called from XS need to do so, such as C<Gtk>.
2863When this happens, Perl needs to be told that the locale has
eabfc7bc
RS
2864changed. Use this function to do so, before returning to Perl.
2865
2866=item *
2867
2868The defines and labels for the flags in the C<op_private> field of OPs are now
2869auto-generated from data in F<regen/op_private>. The noticeable effect of this
2870is that some of the flag output of C<Concise> might differ slightly, and the
3209f716 2871flag output of S<C<perl -Dx>> may differ considerably (they both use the same set
d140c31c
AC
2872of labels now). Also, debugging builds now have a new assertion in
2873C<op_free()> to ensure that the op doesn't have any unrecognized flags set in
eabfc7bc
RS
2874C<op_private>.
2875
2876=item *
2877
eabfc7bc
RS
2878The deprecated variable C<PL_sv_objcount> has been removed.
2879
2880=item *
2881
2882Perl now tries to keep the locale category C<LC_NUMERIC> set to "C"
2883except around operations that need it to be set to the program's
2884underlying locale. This protects the many XS modules that cannot cope
2885with the decimal radix character not being a dot. Prior to this
2886release, Perl initialized this category to "C", but a call to
2887C<POSIX::setlocale()> would change it. Now such a call will change the
2888underlying locale of the C<LC_NUMERIC> category for the program, but the
ce93e38b
KW
2889locale exposed to XS code will remain "C". There are new macros
2890to manipulate the LC_NUMERIC locale, including
2891C<STORE_LC_NUMERIC_SET_TO_NEEDED> and
2892C<STORE_LC_NUMERIC_FORCE_TO_UNDERLYING>.
2893See L<perlapi/Locale-related functions and macros>.
eabfc7bc
RS
2894
2895=item *
2896
2897A new macro L<C<isUTF8_CHAR>|perlapi/isUTF8_CHAR> has been written which
2898efficiently determines if the string given by its parameters begins
2899with a well-formed UTF-8 encoded character.
2900
2901=item *
2902
b0511669 2903The following private API functions had their context parameter removed:
eabfc7bc
RS
2904C<Perl_cast_ulong>, C<Perl_cast_i32>, C<Perl_cast_iv>, C<Perl_cast_uv>,
2905C<Perl_cv_const_sv>, C<Perl_mg_find>, C<Perl_mg_findext>, C<Perl_mg_magical>,
2906C<Perl_mini_mktime>, C<Perl_my_dirfd>, C<Perl_sv_backoff>, C<Perl_utf8_hop>.
2907
cca58a48
DM
2908Note that the prefix-less versions of those functions that are part of the
2909public API, such as C<cast_i32()>, remain unaffected.
eabfc7bc
RS
2910
2911=item *
2912
b0511669
DM
2913The C<PADNAME> and C<PADNAMELIST> types are now separate types, and no
2914longer simply aliases for SV and AV.
a75e6a3a 2915L<[perl #123223]|https://rt.perl.org/Ticket/Display.html?id=123223>.
eabfc7bc
RS
2916
2917=item *
2918
50ea4745 2919Pad names are now always UTF-8. The C<PadnameUTF8> macro always returns
eabfc7bc
RS
2920true. Previously, this was effectively the case already, but any support
2921for two different internal representations of pad names has now been
2922removed.
2923
2924=item *
2925
eabfc7bc
RS
2926A new op class, C<UNOP_AUX>, has been added. This is a subclass of
2927C<UNOP> with an C<op_aux> field added, which points to an array of unions
2928of C<UV>, C<SV*> etc. It is intended for where an op needs to store more data
2929than a simple C<op_sv> or whatever. Currently the only op of this type is
2930C<OP_MULTIDEREF> (see below).
2931
2932=item *
2933
2934A new op has been added, C<OP_MULTIDEREF>, which performs one or more
2935nested array and hash lookups where the key is a constant or simple
2936variable. For example the expression C<$a[0]{$k}[$i]>, which previously
2937involved ten C<rv2Xv>, C<Xelem>, C<gvsv> and C<const> ops is now performed
2938by a single C<multideref> op. It can also handle C<local>, C<exists> and
2939C<delete>. A non-simple index expression, such as C<[$i+1]> is still done
77c2376a 2940using C<aelem>/C<helem>, and single-level array lookup with a small constant
eabfc7bc
RS
2941index is still done using C<aelemfast>.
2942
2943=back
2944
2945=head1 Selected Bug Fixes
2946
2947=over 4
2948
2949=item *
2950
2f737055
RS
2951C<close> now sets C<$!>
2952
2953When an I/O error occurs, the fact that there has been an error is recorded
2954in the handle. C<close> returns false for such a handle. Previously, the
2955value of C<$!> would be untouched by C<close>, so the common convention of
2956writing S<C<close $fh or die $!>> did not work reliably. Now the handle
2957records the value of C<$!>, too, and C<close> restores it.
2958
2959=item *
2960
d6d147bf
KW
2961C<no re> now can turn off everything that C<use re> enables
2962
2963Previously, running C<no re> would turn off only a few things. Now it
2964can turn off all the enabled things. For example, the only way to
2965stop debugging, once enabled, was to exit the enclosing block; that is
2966now fixed.
2967
2968=item *
2969
33ca8d3c
DM
2970C<pack("D", $x)> and C<pack("F", $x)> now zero the padding on x86 long
2971double builds. Under some build options on GCC 4.8 and later, they used
2972to either overwrite the zero-initialized padding, or bypass the
2973initialized buffer entirely. This caused F<op/pack.t> to fail.
eabfc7bc
RS
2974L<[perl #123971]|https://rt.perl.org/Ticket/Display.html?id=123971>
2975
2976=item *
2977
2978Extending an array cloned from a parent thread could result in "Modification of
2979a read-only value attempted" errors when attempting to modify the new elements.
2980L<[perl #124127]|https://rt.perl.org/Ticket/Display.html?id=124127>
2981
2982=item *
2983
2984An assertion failure and subsequent crash with C<< *x=<y> >> has been fixed.
2985L<[perl #123790]|https://rt.perl.org/Ticket/Display.html?id=123790>
2986
2987=item *
2988
33ca8d3c
DM
2989A possible crashing/looping bug related to compiling lexical subs has been
2990fixed.
eabfc7bc
RS
2991L<[perl #124099]|https://rt.perl.org/Ticket/Display.html?id=124099>
2992
2993=item *
2994
d140c31c
AC
2995UTF-8 now works correctly in function names, in unquoted HERE-document
2996terminators, and in variable names used as array indexes.
eabfc7bc
RS
2997L<[perl #124113]|https://rt.perl.org/Ticket/Display.html?id=124113>
2998
2999=item *
3000
3001Repeated global pattern matches in scalar context on large tainted strings were
3002exponentially slow depending on the current match position in the string.
3003L<[perl #123202]|https://rt.perl.org/Ticket/Display.html?id=123202>
3004
3005=item *
3006
3007Various crashes due to the parser getting confused by syntax errors have been
3008fixed.
3009L<[perl #123801]|https://rt.perl.org/Ticket/Display.html?id=123801>
3010L<[perl #123802]|https://rt.perl.org/Ticket/Display.html?id=123802>
3011L<[perl #123955]|https://rt.perl.org/Ticket/Display.html?id=123955>
3012L<[perl #123995]|https://rt.perl.org/Ticket/Display.html?id=123995>
3013
3014=item *
3015
d140c31c 3016C<split> in the scope of lexical C<$_> has been fixed not to fail assertions.
eabfc7bc
RS
3017L<[perl #123763]|https://rt.perl.org/Ticket/Display.html?id=123763>
3018
3019=item *
3020
3021C<my $x : attr> syntax inside various list operators no longer fails
3022assertions.
3023L<[perl #123817]|https://rt.perl.org/Ticket/Display.html?id=123817>
3024
3025=item *
3026
4ec8e6f0 3027An C<@> sign in quotes followed by a non-ASCII digit (which is not a valid
33ca8d3c
DM
3028identifier) would cause the parser to crash, instead of simply trying the
3029C<@> as literal. This has been fixed.
eabfc7bc
RS
3030L<[perl #123963]|https://rt.perl.org/Ticket/Display.html?id=123963>
3031
3032=item *
3033
3034C<*bar::=*foo::=*glob_with_hash> has been crashing since Perl 5.14, but no
3035longer does.
3036L<[perl #123847]|https://rt.perl.org/Ticket/Display.html?id=123847>
3037
3038=item *
3039
3040C<foreach> in scalar context was not pushing an item on to the stack, resulting
33ca8d3c
DM
3041in bugs. (S<C<print 4, scalar do { foreach(@x){} } + 1>> would print 5.)
3042It has been fixed to return C<undef>.
eabfc7bc
RS
3043L<[perl #124004]|https://rt.perl.org/Ticket/Display.html?id=124004>
3044
3045=item *
3046
eabfc7bc
RS
3047Several cases of data used to store environment variable contents in core C
3048code being potentially overwritten before being used have been fixed.
3049L<[perl #123748]|https://rt.perl.org/Ticket/Display.html?id=123748>
3050
3051=item *
3052
33ca8d3c
DM
3053Some patterns starting with C</.*..../> matched against long strings have
3054been slow since v5.8, and some of the form C</.*..../i> have been slow
3055since v5.18. They are now all fast again.
a75e6a3a 3056L<[perl #123743]|https://rt.perl.org/Ticket/Display.html?id=123743>.
eabfc7bc
RS
3057
3058=item *
3059
3060The original visible value of C<$/> is now preserved when it is set to
3061an invalid value. Previously if you set C<$/> to a reference to an
3062array, for example, perl would produce a runtime error and not set
3063C<PL_rs>, but perl code that checked C<$/> would see the array
a75e6a3a
SH
3064reference.
3065L<[perl #123218]|https://rt.perl.org/Ticket/Display.html?id=123218>.
eabfc7bc
RS
3066
3067=item *
3068
3069In a regular expression pattern, a POSIX class, like C<[:ascii:]>, must
93780ae6 3070be inside a bracketed character class, like C<qr/[[:ascii:]]/>. A
eabfc7bc
RS
3071warning is issued when something looking like a POSIX class is not
3072inside a bracketed class. That warning wasn't getting generated when
3073the POSIX class was negated: C<[:^ascii:]>. This is now fixed.
3074
3075=item *
3076
3209f716 3077Perl 5.14.0 introduced a bug whereby S<C<eval { LABEL: }>> would crash. This
a75e6a3a
SH
3078has been fixed.
3079L<[perl #123652]|https://rt.perl.org/Ticket/Display.html?id=123652>.
eabfc7bc
RS
3080
3081=item *
3082
3083Various crashes due to the parser getting confused by syntax errors have
a75e6a3a
SH
3084been fixed.
3085L<[perl #123617]|https://rt.perl.org/Ticket/Display.html?id=123617>.
3086L<[perl #123737]|https://rt.perl.org/Ticket/Display.html?id=123737>.
3087L<[perl #123753]|https://rt.perl.org/Ticket/Display.html?id=123753>.
3088L<[perl #123677]|https://rt.perl.org/Ticket/Display.html?id=123677>.
eabfc7bc
RS
3089
3090=item *
3091
3092Code like C</$a[/> used to read the next line of input and treat it as
3093though it came immediately after the opening bracket. Some invalid code
3094consequently would parse and run, but some code caused crashes, so this is
a75e6a3a
SH
3095now disallowed.
3096L<[perl #123712]|https://rt.perl.org/Ticket/Display.html?id=123712>.
eabfc7bc
RS
3097
3098=item *
3099
a75e6a3a
SH
3100Fix argument underflow for C<pack>.
3101L<[perl #123874]|https://rt.perl.org/Ticket/Display.html?id=123874>.
eabfc7bc
RS
3102
3103=item *
3104
3105Fix handling of non-strict C<\x{}>. Now C<\x{}> is equivalent to C<\x{0}>
3106instead of faulting.
3107
3108=item *
3109
3110C<stat -t> is now no longer treated as stackable, just like C<-t stat>.
a75e6a3a 3111L<[perl #123816]|https://rt.perl.org/Ticket/Display.html?id=123816>.
eabfc7bc
RS
3112
3113=item *
3114
3115The following no longer causes a SEGV: C<qr{x+(y(?0))*}>.
3116
3117=item *
3118
3119Fixed infinite loop in parsing backrefs in regexp patterns.
3120
3121=item *
3122
3b50e657
KW
3123Several minor bug fixes in behavior of Infinity and NaN, including
3124warnings when stringifying Infinity-like or NaN-like strings. For example,
eabfc7bc
RS
3125"NaNcy" doesn't numify to NaN anymore.
3126
3127=item *
3128
eabfc7bc
RS
3129A bug in regular expression patterns that could lead to segfaults and
3130other crashes has been fixed. This occurred only in patterns compiled
d140c31c
AC
3131with C</i> while taking into account the current POSIX locale (which usually
3132means they have to be compiled within the scope of C<S<use locale>>),
eabfc7bc 3133and there must be a string of at least 128 consecutive bytes to match.
a75e6a3a 3134L<[perl #123539]|https://rt.perl.org/Ticket/Display.html?id=123539>.
eabfc7bc
RS
3135
3136=item *
3137
33ca8d3c
DM
3138C<s///g> now works on very long strings (where there are more than 2
3139billion iterations) instead of dying with 'Substitution loop'.
a75e6a3a
SH
3140L<[perl #103260]|https://rt.perl.org/Ticket/Display.html?id=103260>.
3141L<[perl #123071]|https://rt.perl.org/Ticket/Display.html?id=123071>.
eabfc7bc
RS
3142
3143=item *
3144
a75e6a3a
SH
3145C<gmtime> no longer crashes with not-a-number values.
3146L<[perl #123495]|https://rt.perl.org/Ticket/Display.html?id=123495>.
eabfc7bc
RS
3147
3148=item *
3149
33ca8d3c
DM
3150C<\()> (a reference to an empty list), and C<y///> with lexical C<$_> in
3151scope, could both do a bad write past the end of the stack. They have
3152both been fixed to extend the stack first.
eabfc7bc
RS
3153
3154=item *
3155
3156C<prototype()> with no arguments used to read the previous item on the
3209f716
KW
3157stack, so S<C<print "foo", prototype()>> would print foo's prototype.
3158It has been fixed to infer C<$_> instead.
a75e6a3a 3159L<[perl #123514]|https://rt.perl.org/Ticket/Display.html?id=123514>.
eabfc7bc
RS
3160
3161=item *
3162
33ca8d3c
DM
3163Some cases of lexical state subs declared inside predeclared subs could
3164crash, for example when evalling a string including the name of an outer
3165variable, but no longer do.
eabfc7bc
RS
3166
3167=item *
3168
3169Some cases of nested lexical state subs inside anonymous subs could cause
d140c31c 3170'Bizarre copy' errors or possibly even crashes.
eabfc7bc
RS
3171
3172=item *
3173
3174When trying to emit warnings, perl's default debugger (F<perl5db.pl>) was
3175sometimes giving 'Undefined subroutine &DB::db_warn called' instead. This
a75e6a3a
SH
3176bug, which started to occur in Perl 5.18, has been fixed.
3177L<[perl #123553]|https://rt.perl.org/Ticket/Display.html?id=123553>.
eabfc7bc
RS
3178
3179=item *
3180
d140c31c 3181Certain syntax errors in substitutions, such as C<< s/${<>{})// >>, would
eabfc7bc
RS
3182crash, and had done so since Perl 5.10. (In some cases the crash did not
3183start happening till 5.16.) The crash has, of course, been fixed.
a75e6a3a 3184L<[perl #123542]|https://rt.perl.org/Ticket/Display.html?id=123542>.
eabfc7bc
RS
3185
3186=item *
3187
33ca8d3c 3188Fix a couple of string grow size calculation overflows; in particular,
3209f716 3189a repeat expression like S<C<33 x ~3>> could cause a large buffer
eabfc7bc 3190overflow since the new output buffer size was not correctly handled by
3209f716 3191C<SvGROW()>. An expression like this now properly produces a memory wrap
a75e6a3a
SH
3192panic.
3193L<[perl #123554]|https://rt.perl.org/Ticket/Display.html?id=123554>.
eabfc7bc
RS
3194
3195=item *
3196
3197C<< formline("@...", "a"); >> would crash. The C<FF_CHECKNL> case in
3198pp_formline() didn't set the pointer used to mark the chop position,
3199which led to the C<FF_MORE> case crashing with a segmentation fault.
a75e6a3a
SH
3200This has been fixed.
3201L<[perl #123538]|https://rt.perl.org/Ticket/Display.html?id=123538>.
eabfc7bc
RS
3202
3203=item *
3204
3205A possible buffer overrun and crash when parsing a literal pattern during
a75e6a3a
SH
3206regular expression compilation has been fixed.
3207L<[perl #123604]|https://rt.perl.org/Ticket/Display.html?id=123604>.
eabfc7bc
RS
3208
3209=item *
3210
4ec8e6f0 3211C<fchmod()> and C<futimes()> now set C<$!> when they fail due to being
a75e6a3a
SH
3212passed a closed file handle.
3213L<[perl #122703]|https://rt.perl.org/Ticket/Display.html?id=122703>.
eabfc7bc
RS
3214
3215=item *
3216
33ca8d3c
DM
3217C<op_free()> and C<scalarvoid()> no longer crash due to a stack overflow
3218when freeing a deeply recursive op tree.
a75e6a3a 3219L<[perl #108276]|https://rt.perl.org/Ticket/Display.html?id=108276>.
eabfc7bc
RS
3220
3221=item *
3222
50ea4745 3223In Perl 5.20.0, C<$^N> accidentally had the internal UTF-8 flag turned off
eabfc7bc 3224if accessed from a code block within a regular expression, effectively
50ea4745 3225UTF-8-encoding the value. This has been fixed.
a75e6a3a 3226L<[perl #123135]|https://rt.perl.org/Ticket/Display.html?id=123135>.
eabfc7bc
RS
3227
3228=item *
3229
3230A failed C<semctl> call no longer overwrites existing items on the stack,
33ca8d3c
DM
3231which means that C<(semctl(-1,0,0,0))[0]> no longer gives an
3232"uninitialized" warning.
eabfc7bc
RS
3233
3234=item *
3235
3236C<else{foo()}> with no space before C<foo> is now better at assigning the
a75e6a3a
SH
3237right line number to that statement.
3238L<[perl #122695]|https://rt.perl.org/Ticket/Display.html?id=122695>.
eabfc7bc
RS
3239
3240=item *
3241
d140c31c 3242Sometimes the assignment in C<@array = split> gets optimised so that C<split>
eabfc7bc
RS
3243itself writes directly to the array. This caused a bug, preventing this
3244assignment from being used in lvalue context. So
3245C<(@a=split//,"foo")=bar()> was an error. (This bug probably goes back to
33ca8d3c 3246Perl 3, when the optimisation was added.) It has now been fixed.
a75e6a3a 3247L<[perl #123057]|https://rt.perl.org/Ticket/Display.html?id=123057>.
eabfc7bc
RS
3248
3249=item *
3250
33ca8d3c
DM
3251When an argument list fails the checks specified by a subroutine
3252signature (which is still an experimental feature), the resulting error
3253messages now give the file and line number of the caller, not of the
3254called subroutine.
a75e6a3a 3255L<[perl #121374]|https://rt.perl.org/Ticket/Display.html?id=121374>.
eabfc7bc
RS
3256
3257=item *
3258
33ca8d3c 3259The flip-flop operators (C<..> and C<...> in scalar context) used to maintain
eabfc7bc
RS
3260a separate state for each recursion level (the number of times the
3261enclosing sub was called recursively), contrary to the documentation. Now
a75e6a3a
SH
3262each closure has one internal state for each flip-flop.
3263L<[perl #122829]|https://rt.perl.org/Ticket/Display.html?id=122829>.
eabfc7bc
RS
3264
3265=item *
3266
33ca8d3c
DM
3267The flip-flop operator (C<..> in scalar context) would return the same
3268scalar each time, unless the containing subroutine was called recursively.
3269Now it always returns a new scalar.
3270L<[perl #122829]|https://rt.perl.org/Ticket/Display.html?id=122829>.
3271
3272=item *
3273
eabfc7bc
RS
3274C<use>, C<no>, statement labels, special blocks (C<BEGIN>) and pod are now
3275permitted as the first thing in a C<map> or C<grep> block, the block after
3276C<print> or C<say> (or other functions) returning a handle, and within
a75e6a3a
SH
3277C<${...}>, C<@{...}>, etc.
3278L<[perl #122782]|https://rt.perl.org/Ticket/Display.html?id=122782>.
eabfc7bc
RS
3279
3280=item *
3281
3282The repetition operator C<x> now propagates lvalue context to its left-hand
3283argument when used in contexts like C<foreach>. That allows
4ec8e6f0 3284S<C<for(($#that_array)x2) { ... }>> to work as expected if the loop modifies
eabfc7bc
RS
3285$_.
3286
3287=item *
3288
3289C<(...) x ...> in scalar context used to corrupt the stack if one operand
d140c31c 3290was an object with "x" overloading, causing erratic behaviour.
a75e6a3a 3291L<[perl #121827]|https://rt.perl.org/Ticket/Display.html?id=121827>.
eabfc7bc
RS
3292
3293=item *
3294
33ca8d3c
DM
3295Assignment to a lexical scalar is often optimised away; for example in
3296C<my $x; $x = $y + $z>, the assign operator is optimised away and the add
3297operator writes its result directly to C<$x>. Various bugs related to
3298this optimisation have been fixed. Certain operators on the right-hand
3299side would sometimes fail to assign the value at all or assign the wrong
3300value, or would call STORE twice or not at all on tied variables. The
3301operators affected were C<$foo++>, C<$foo-->, and C<-$foo> under C<use
3302integer>, C<chomp>, C<chr> and C<setpgrp>.
eabfc7bc
RS
3303
3304=item *
3305
3306List assignments were sometimes buggy if the same scalar ended up on both
d140c31c 3307sides of the assignment due to use of C<tied>, C<values> or C<each>. The
eabfc7bc
RS
3308result would be the wrong value getting assigned.
3309
3310=item *
3311
3312C<setpgrp($nonzero)> (with one argument) was accidentally changed in 5.16
3313to mean C<setpgrp(0)>. This has been fixed.
3314
3315=item *
3316
3317C<__SUB__> could return the wrong value or even corrupt memory under the
4ec8e6f0 3318debugger (the C<-d> switch) and in subs containing C<eval $string>.
eabfc7bc
RS
3319
3320=item *
3321
4ec8e6f0 3322When S<C<sub () { $var }>> becomes inlinable, it now returns a different
eabfc7bc
RS
3323scalar each time, just as a non-inlinable sub would, though Perl still
3324optimises the copy away in cases where it would make no observable
3325difference.
3326
3327=item *
3328
4ec8e6f0 3329S<C<my sub f () { $var }>> and S<C<sub () : attr { $var }>> are no longer
eabfc7bc
RS
3330eligible for inlining. The former would crash; the latter would just
3331throw the attributes away. An exception is made for the little-known
3332":method" attribute, which does nothing much.
3333
3334=item *
3335
3336Inlining of subs with an empty prototype is now more consistent than
d140c31c
AC
3337before. Previously, a sub with multiple statements, of which all but the last
3338were optimised away, would be inlinable only if it were an anonymous sub
eabfc7bc
RS
3339containing a string C<eval> or C<state> declaration or closing over an
3340outer lexical variable (or any anonymous sub under the debugger). Now any
3341sub that gets folded to a single constant after statements have been
3342optimised away is eligible for inlining. This applies to things like C<sub
3343() { jabber() if DEBUG; 42 }>.
3344
3345Some subroutines with an explicit C<return> were being made inlinable,
3346contrary to the documentation, Now C<return> always prevents inlining.
3347
3348=item *
3349
3350On some systems, such as VMS, C<crypt> can return a non-ASCII string. If a
50ea4745
DIM
3351scalar assigned to had contained a UTF-8 string previously, then C<crypt>
3352would not turn off the UTF-8 flag, thus corrupting the return value. This
3209f716 3353would happen with S<C<$lexical = crypt ...>>.
eabfc7bc
RS
3354
3355=item *
3356
3357C<crypt> no longer calls C<FETCH> twice on a tied first argument.
3358
3359=item *
3360
3361An unterminated here-doc on the last line of a quote-like operator
3362(C<qq[${ <<END }]>, C</(?{ <<END })/>) no longer causes a double free. It
3363started doing so in 5.18.
3364
3365=item *
3366
4ec8e6f0 3367C<index()> and C<rindex()> no longer crash when used on strings over 2GB in
eabfc7bc
RS
3368size.
3369L<[perl #121562]|https://rt.perl.org/Ticket/Display.html?id=121562>.
3370
3371=item *
3372
3373A small previously intentional memory leak in PERL_SYS_INIT/PERL_SYS_INIT3 on
3374Win32 builds was fixed. This might affect embedders who repeatedly create and
3375destroy perl engines within the same process.
3376
3377=item *
3378
3379C<POSIX::localeconv()> now returns the data for the program's underlying
3380locale even when called from outside the scope of S<C<use locale>>.
3381
3382=item *
3383
3384C<POSIX::localeconv()> now works properly on platforms which don't have
3385C<LC_NUMERIC> and/or C<LC_MONETARY>, or for which Perl has been compiled
3386to disregard either or both of these locale categories. In such
3387circumstances, there are now no entries for the corresponding values in
3388the hash returned by C<localeconv()>.
3389
3390=item *
3391
3392C<POSIX::localeconv()> now marks appropriately the values it returns as
6a3ea89b 3393UTF-8 or not. Previously they were always returned as bytes, even if
eabfc7bc
RS
3394they were supposed to be encoded as UTF-8.
3395
3396=item *
3397
3398On Microsoft Windows, within the scope of C<S<use locale>>, the following
3399POSIX character classes gave results for many locales that did not
3400conform to the POSIX standard:
3401C<[[:alnum:]]>,
3402C<[[:alpha:]]>,
3403C<[[:blank:]]>,
3404C<[[:digit:]]>,
3405C<[[:graph:]]>,
3406C<[[:lower:]]>,
3407C<[[:print:]]>,
3408C<[[:punct:]]>,
3409C<[[:upper:]]>,
3410C<[[:word:]]>,
3411and
3412C<[[:xdigit:]]>.
f1c9eac6 3413This was because the underlying Microsoft implementation does not
eabfc7bc
RS
3414follow the standard. Perl now takes special precautions to correct for
3415this.
3416
3417=item *
3418
3419Many issues have been detected by L<Coverity|http://www.coverity.com/> and
3420fixed.
3421
3422=item *
3423
d140c31c 3424C<system()> and friends should now work properly on more Android builds.
eabfc7bc 3425
4ec8e6f0 3426Due to an oversight, the value specified through C<-Dtargetsh> to F<Configure>
eabfc7bc 3427would end up being ignored by some of the build process. This caused perls
4ec8e6f0 3428cross-compiled for Android to end up with defective versions of C<system()>,
d140c31c 3429C<exec()> and backticks: the commands would end up looking for C</bin/sh>
eabfc7bc
RS
3430instead of C</system/bin/sh>, and so would fail for the vast majority
3431of devices, leaving C<$!> as C<ENOENT>.
3432
3433=item *
3434
3435C<qr(...\(...\)...)>,
3436C<qr[...\[...\]...]>,
3437and
3438C<qr{...\{...\}...}>
3439now work. Previously it was impossible to escape these three
3440left-characters with a backslash within a regular expression pattern
3441where otherwise they would be considered metacharacters, and the pattern
3442opening delimiter was the character, and the closing delimiter was its
3443mirror character.
3444
3445=item *
3446
50ea4745 3447C<< s///e >> on tainted UTF-8 strings corrupted C<< pos() >>. This bug,
a75e6a3a
SH
3448introduced in 5.20, is now fixed.
3449L<[perl #122148]|https://rt.perl.org/Ticket/Display.html?id=122148>.
eabfc7bc
RS
3450
3451=item *
3452
3453A non-word boundary in a regular expression (C<< \B >>) did not always
3454match the end of the string; in particular C<< q{} =~ /\B/ >> did not
a75e6a3a
SH
3455match. This bug, introduced in perl 5.14, is now fixed.
3456L<[perl #122090]|https://rt.perl.org/Ticket/Display.html?id=122090>.
eabfc7bc
RS
3457
3458=item *
3459
3460C<< " P" =~ /(?=.*P)P/ >> should match, but did not. This is now fixed.
a75e6a3a 3461L<[perl #122171]|https://rt.perl.org/Ticket/Display.html?id=122171>.
eabfc7bc
RS
3462
3463=item *
3464
3209f716 3465Failing to compile C<use Foo> in an C<eval> could leave a spurious
eabfc7bc
RS
3466C<BEGIN> subroutine definition, which would produce a "Subroutine
3467BEGIN redefined" warning on the next use of C<use>, or other C<BEGIN>
a75e6a3a
SH
3468block.
3469L<[perl #122107]|https://rt.perl.org/Ticket/Display.html?id=122107>.
eabfc7bc
RS
3470
3471=item *
3472
3473C<method { BLOCK } ARGS> syntax now correctly parses the arguments if they
a75e6a3a
SH
3474begin with an opening brace.
3475L<[perl #46947]|https://rt.perl.org/Ticket/Display.html?id=46947>.
eabfc7bc
RS
3476
3477=item *
3478
3479External libraries and Perl may have different ideas of what the locale is.
3480This is problematic when parsing version strings if the locale's numeric
3481separator has been changed. Version parsing has been patched to ensure
a75e6a3a
SH
3482it handles the locales correctly.
3483L<[perl #121930]|https://rt.perl.org/Ticket/Display.html?id=121930>.
eabfc7bc
RS
3484
3485=item *
3486
3487A bug has been fixed where zero-length assertions and code blocks inside of a
a75e6a3a
SH
3488regex could cause C<pos> to see an incorrect value.
3489L<[perl #122460]|https://rt.perl.org/Ticket/Display.html?id=122460>.
eabfc7bc
RS
3490
3491=item *
3492
3b50e657 3493Dereferencing of constants now works correctly for typeglob constants. Previously
eabfc7bc
RS
3494the glob was stringified and its name looked up. Now the glob itself is used.
3495L<[perl #69456]|https://rt.perl.org/Ticket/Display.html?id=69456>
3496
3497=item *
3498
d140c31c 3499When parsing a sigil (C<$> C<@> C<%> C<&)> followed by braces,
4ec8e6f0 3500the parser no
eabfc7bc
RS
3501longer tries to guess whether it is a block or a hash constructor (causing a
3502syntax error when it guesses the latter), since it can only be a block.
3503
3504=item *
3505
4ec8e6f0 3506S<C<undef $reference>> now frees the referent immediately, instead of hanging on
eabfc7bc
RS
3507to it until the next statement.
3508L<[perl #122556]|https://rt.perl.org/Ticket/Display.html?id=122556>
3509
3510=item *
3511
3512Various cases where the name of a sub is used (autoload, overloading, error
3513messages) used to crash for lexical subs, but have been fixed.
3514
3515=item *
3516
3517Bareword lookup now tries to avoid vivifying packages if it turns out the
3518bareword is not going to be a subroutine name.
3519
3520=item *
3521
ff25fcfb 3522Compilation of anonymous constants (I<e.g.>, C<sub () { 3 }>) no longer deletes
eabfc7bc
RS
3523any subroutine named C<__ANON__> in the current package. Not only was
3524C<*__ANON__{CODE}> cleared, but there was a memory leak, too. This bug goes
3525back to Perl 5.8.0.
3526
3527=item *
3528
3529Stub declarations like C<sub f;> and C<sub f ();> no longer wipe out constants
3530of the same name declared by C<use constant>. This bug was introduced in Perl
35315.10.0.
3532
3533=item *
3534
33ca8d3c
DM
3535C<qr/[\N{named sequence}]/> now works properly in many instances.
3536
3537Some names
eabfc7bc
RS
3538known to C<\N{...}> refer to a sequence of multiple characters, instead of the
3539usual single character. Bracketed character classes generally only match
3540single characters, but now special handling has been added so that they can
3541match named sequences, but not if the class is inverted or the sequence is
3542specified as the beginning or end of a range. In these cases, the only
3543behavior change from before is a slight rewording of the fatal error message
3544given when this class is part of a C<?[...])> construct. When the C<[...]>
3545stands alone, the same non-fatal warning as before is raised, and only the
3546first character in the sequence is used, again just as before.
3547
3548=item *
3549
3550Tainted constants evaluated at compile time no longer cause unrelated
3551statements to become tainted.
3552L<[perl #122669]|https://rt.perl.org/Ticket/Display.html?id=122669>
3553
3554=item *
3555
33ca8d3c
DM
3556S<C<open $$fh, ...>>, which vivifies a handle with a name like
3557C<"main::_GEN_0">, was not giving the handle the right reference count, so
3558a double free could happen.
eabfc7bc
RS
3559
3560=item *
3561
3562When deciding that a bareword was a method name, the parser would get confused
4ec8e6f0
KW
3563if an C<our> sub with the same name existed, and look up the method in the
3564package of the C<our> sub, instead of the package of the invocant.
eabfc7bc
RS
3565
3566=item *
3567
3568The parser no longer gets confused by C<\U=> within a double-quoted string. It
3569used to produce a syntax error, but now compiles it correctly.
3570L<[perl #80368]|https://rt.perl.org/Ticket/Display.html?id=80368>
3571
3572=item *
3573
3574It has always been the intention for the C<-B> and C<-T> file test operators to
3575treat UTF-8 encoded files as text. (L<perlfunc|perlfunc/-X FILEHANDLE> has
3576been updated to say this.) Previously, it was possible for some files to be
3577considered UTF-8 that actually weren't valid UTF-8. This is now fixed. The
3578operators now work on EBCDIC platforms as well.
3579
3580=item *
3581
3582Under some conditions warning messages raised during regular expression pattern
3583compilation were being output more than once. This has now been fixed.
3584
3585=item *
3586
d140c31c
AC
3587Perl 5.20.0 introduced a regression in which a UTF-8 encoded regular
3588expression pattern that contains a single ASCII lowercase letter did not
3589match its uppercase counterpart. That has been fixed in both 5.20.1 and
35905.22.0.
eabfc7bc
RS
3591L<[perl #122655]|https://rt.perl.org/Ticket/Display.html?id=122655>
3592
3593=item *
3594
33ca8d3c
DM
3595Constant folding could incorrectly suppress warnings if lexical warnings
3596(C<use warnings> or C<no warnings>) were not in effect and C<$^W> were
3597false at compile time and true at run time.
eabfc7bc
RS
3598
3599=item *
3600
1e45139a 3601Loading Unicode tables during a regular expression match could cause assertion
eabfc7bc
RS
3602failures under debugging builds if the previous match used the very same
3603regular expression.
3604L<[perl #122747]|https://rt.perl.org/Ticket/Display.html?id=122747>
3605
3606=item *
3607
3608Thread cloning used to work incorrectly for lexical subs, possibly causing
3609crashes or double frees on exit.
3610