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perldelta: Rmv some intra 5.21 changes
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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
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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
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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
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25To use this, enable the "bitwise" feature and disable the
26"experimental::bitwise" warnings category. See L<perlop/Bitwise String
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27Operators> for details.
28L<[perl #123466]|https://rt.perl.org/Ticket/Display.html?id=123466>.
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29
30=head2 New double-diamond operator
31
32C<<< <<>> >>> is like C<< <> >> but uses three-argument C<open> to open
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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 35
f0a38539 36=head2 New C<\b> boundaries in regular expressions
eabfc7bc 37
f0a38539 38=head3 C<qr/\b{gcb}/>
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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
f0a38539 47=head3 C<qr/\b{wb}/>
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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
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53middle of words. See L<perlrebackslash/\b{}, \b, \B{}, \B> for details.
54
f0a38539 55=head3 C<qr/\b{sb}/>
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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
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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:
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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
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79experience, using this pragma will raise a warning of category
80C<experimental::re_strict>.
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81See L<'strict' in re|re/'strict' mode>.
82
ce93e38b 83=head2 Unicode 7.0 (with correction) is now supported
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84
85For details on what is in this release, see
86L<http://www.unicode.org/versions/Unicode7.0.0/>.
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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
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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
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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
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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
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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
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126Aliasing can also be accomplished
127by using a backslash before a C<foreach> iterator variable; this is
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128perhaps the most useful idiom this feature provides:
129
130 foreach \%hash (@array_of_hash_refs) { ... }
131
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132This feature is experimental and must be enabled via S<C<use feature
133'refaliasing'>>. It will warn unless the C<experimental::refaliasing>
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134warnings category is disabled.
135
136See L<perlref/Assigning to References>
137
138=head2 C<prototype> with no arguments
139
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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
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148and used to create a new constant subroutine that is returned. This
149feature is experimental. See L<perlsub/Constant Functions>.
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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.
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162
163=head2 List form of pipe open implemented for Win32
164
165The list form of pipe:
166
167 open my $fh, "-|", "program", @arguments;
168
169is now implemented on Win32. It has the same limitations as C<system
170LIST> on Win32, since the Win32 API doesn't accept program arguments
171as a list.
172
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173=head2 Assignment to list repetition
174
175C<(...) x ...> can now be used within a list that is assigned to, as long
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176as the left-hand side is a valid lvalue. This allows S<C<(undef,undef,$foo)
177= that_function()>> to be written as S<C<((undef)x2, $foo) = that_function()>>.
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178
179=head2 Infinity and NaN (not-a-number) handling improved
180
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181Floating point values are able to hold the special values infinity, negative
182infinity, and NaN (not-a-number). Now we more robustly recognize and
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183propagate the value in computations, and on output normalize them to the strings
184C<Inf>, C<-Inf>, and C<NaN>.
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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.
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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
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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
f0a38539 225=head2 Perl is now compiled with C<-fstack-protector-strong> if available
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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
f0a38539 236=head2 Perl is now always compiled with C<-D_FORTIFY_SOURCE=2> if available
e455391f 237
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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
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248=head2 Subroutine signatures moved before attributes
249
250The experimental sub signatures feature, as introduced in 5.20, parsed
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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).
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255
256=head2 C<&> and C<\&> prototypes accepts only subs
257
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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.
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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
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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>.
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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 }>>.
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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
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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.
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300
301These had been deprecated since v5.18.
302
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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
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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>
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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
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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>
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347
348Previously, the text, unlike almost everything else, always came out
349based on the current underlying locale of the program. (Also affected
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350on some systems is C<"$^E">.) For programs that are unprepared to
351handle locale differences, this can cause garbage text to be displayed.
352It's better to display text that is translatable via some tool than
353garbage text which is much harder to figure out.
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354
355=head2 C<"$!"> 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
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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
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366Perl releases. This resolves
367L<[perl #112208]|https://rt.perl.org/Ticket/Display.html?id=112208>.
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368
369=head2 Support for C<?PATTERN?> without explicit operator has been removed
370
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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.
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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
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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
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391precedence over most, but not all, subroutine names. It was never
392consistent and exhibited buggy behaviour.
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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
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408This variable allows Perl scripts to be written in an encoding other than
409ASCII or UTF-8. However, it affects all modules globally, leading
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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
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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.
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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
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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
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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
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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
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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
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442 sub make_constant {
443 my $var = shift;
444 return sub () { $var }; # fine
445 }
c14a43b7 446
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447 sub make_constant_deprecated {
448 my $var;
449 $var = shift;
450 return sub () { $var }; # deprecated
451 }
c14a43b7 452
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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
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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
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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
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467changed such that inlining does not happen if the variable is modifiable
468elsewhere. Such cases should be rare.
c14a43b7 469
f0a38539 470=head2 Use of multiple C</x> regexp modifiers
c14a43b7 471
eabfc7bc 472It is now deprecated to say something like any of the following:
c14a43b7 473
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474 qr/foo/xx;
475 /(?xax:foo)/;
476 use re qw(/amxx);
be39acb2 477
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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
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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
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487This non-graphic character is essentially indistinguishable from a
488regular space, and so should not be allowed. See
489L<charnames/CUSTOM ALIASES>.
60dcce55 490
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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
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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 672It provides a new C<B::safename> function, based on the existing
f0a38539 673C<< B::GV->SAFENAME >>, that converts C<\cOPEN> to C<^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<$#{_}>.
740L<[perl #123947]|https://rt.perl.org/Ticket/Display.html?id=123947>
9189be1b 741
53ce1dd5
RS
742BEGIN blocks at the end of the enclosing scope are now deparsed in the
743right place. [perl #77452]
9189be1b 744
53ce1dd5
RS
745BEGIN blocks were sometimes deparsed as __ANON__, but are now always called
746BEGIN.
9189be1b 747
53ce1dd5 748Lexical subroutines are now fully deparsed. [perl #116553]
9189be1b 749
53ce1dd5 750C<Anything =~ y///r> with C</r> no longer omits the left-hand operand.
9189be1b 751
53ce1dd5
RS
752The op trees that make up regexp code blocks are now deparsed for real.
753Formerly, the original string that made up the regular expression was used.
754That caused problems with C<qr/(?{E<lt>E<lt>heredoc})/> and multiline code blocks,
755which were deparsed incorrectly. [perl #123217] [perl #115256]
9189be1b 756
53ce1dd5
RS
757C<$;> at the end of a statement no longer loses its semicolon.
758[perl #123357]
9189be1b 759
53ce1dd5
RS
760Some cases of subroutine declarations stored in the stash in shorthand form
761were being omitted.
9189be1b 762
53ce1dd5
RS
763Non-ASCII characters are now consistently escaped in strings, instead of
764some of the time. (There are still outstanding problems with regular
765expressions and identifiers that have not been fixed.)
9189be1b 766
ff25fcfb 767When prototype sub calls are deparsed with C<&> (I<e.g.>, under the B<-P>
53ce1dd5
RS
768option), C<scalar> is now added where appropriate, to force the scalar
769context implied by the prototype.
9189be1b 770
53ce1dd5
RS
771C<require(foo())>, C<do(foo())>, C<goto(foo())> and similar constructs with
772loop controls are now deparsed correctly. The outer parentheses are not
773optional.
9189be1b 774
53ce1dd5
RS
775Whitespace is no longer escaped in regular expressions, because it was
776getting erroneously escaped within C<(?x:...)> sections.
9189be1b 777
53ce1dd5 778C<sub foo { foo() }> is now deparsed with those mandatory parentheses.
9189be1b 779
53ce1dd5
RS
780C</@array/> is now deparsed as a regular expression, and not just
781C<@array>.
9189be1b 782
53ce1dd5
RS
783C</@{-}/>, C</@{+}/> and C<$#{1}> are now deparsed with the braces, which
784are mandatory in these cases.
9189be1b 785
f0a38539 786In deparsing feature bundles, C<B::Deparse> was emitting C<no feature;> first
53ce1dd5 787instead of C<no feature ':all';>. This has been fixed.
9189be1b 788
53ce1dd5 789C<chdir FH> is now deparsed without quotation marks.
9189be1b 790
53ce1dd5
RS
791C<\my @a> is now deparsed without parentheses. (Parenthese would flatten
792the array.)
9189be1b 793
53ce1dd5
RS
794C<system> and C<exec> followed by a block are now deparsed correctly.
795Formerly there was an erroneous C<do> before the block.
9189be1b 796
53ce1dd5
RS
797C<< use constant QR =E<gt> qr/.../flags >> followed by C<"" =~ QR> is no longer
798without the flags.
9189be1b 799
53ce1dd5
RS
800Deparsing C<BEGIN { undef &foo }> with the B<-w> switch enabled started to
801emit 'uninitialized' warnings in Perl 5.14. This has been fixed.
9189be1b 802
53ce1dd5
RS
803Deparsing calls to subs with a C<(;+)> prototype resulted in an infinite
804loop. The C<(;$>) C<(_)> and C<(;_)> prototypes were given the wrong
805precedence, causing C<foo($aE<lt>$b)> to be deparsed without the parentheses.
9189be1b 806
53ce1dd5 807Deparse now provides a defined state sub in inner subs.
9189be1b
KW
808
809=item *
810
39c78947 811L<B::Op_private> has been added.
9189be1b 812
39c78947
RS
813L<B::Op_private> provides detailed information about the flags used in the
814C<op_private> field of perl opcodes.
9189be1b
KW
815
816=item *
817
53ce1dd5 818L<bigint>, L<bignum>, L<bigrat> have been upgraded to version 0.39.
9189be1b 819
53ce1dd5
RS
820Document in CAVEATS that using strings as numbers won't always invoke
821the big number overloading, and how to invoke it. [rt.perl.org #123064]
9189be1b
KW
822
823=item *
824
39c78947 825L<Carp> has been upgraded to version 1.36.
9189be1b 826
f0a38539
KW
827C<Carp::Heavy> now ignores version mismatches with Carp if Carp is newer
828than 1.12, since C<Carp::Heavy>'s guts were merged into Carp at that
53ce1dd5
RS
829point.
830L<[perl #121574]|https://rt.perl.org/Ticket/Display.html?id=121574>
831
832Carp now handles non-ASCII platforms better.
833Off-by-one error fix for Perl E<lt> 5.14.
9189be1b
KW
834
835=item *
836
39c78947 837L<constant> has been upgraded to version 1.33.
9189be1b 838
53ce1dd5
RS
839It now accepts fully-qualified constant names, allowing constants to be defined
840in packages other than the caller.
9189be1b
KW
841
842=item *
843
39c78947 844L<CPAN> has been upgraded to version 2.11.
9189be1b 845
53ce1dd5
RS
846Add support for C<Cwd::getdcwd()> and introduce workaround for a misbehaviour
847seen on Strawberry Perl 5.20.1.
9189be1b 848
53ce1dd5 849Fix C<chdir()> after building dependencies bug.
9189be1b 850
53ce1dd5 851Introduce experimental support for plugins/hooks.
9189be1b 852
f0a38539 853Integrate the C<App::Cpan> sources.
9189be1b 854
53ce1dd5 855Do not check recursion on optional dependencies.
9189be1b 856
53ce1dd5
RS
857Sanity check F<META.yml> to contain a hash.
858L<[cpan #95271]|https://rt.cpan.org/Ticket/Display.html?id=95271>
9189be1b
KW
859
860=item *
861
39c78947 862L<CPAN::Meta::Requirements> has been upgraded to version 2.132.
9189be1b 863
f0a38539 864Works around limitations in C<version::vpp> detecting v-string magic and adds
53ce1dd5
RS
865support for forthcoming L<ExtUtils::MakeMaker> bootstrap F<version.pm> for
866Perls older than 5.10.0.
9189be1b
KW
867
868=item *
869
39c78947 870L<Data::Dumper> has been upgraded to version 2.158.
9189be1b 871
53ce1dd5
RS
872Fixes CVE-2014-4330 by adding a configuration variable/option to limit
873recursion when dumping deep data structures.
9189be1b 874
53ce1dd5
RS
875Changes to resolve Coverity issues.
876XS dumps incorrectly stored the name of code references stored in a
877GLOB.
878L<[perl #122070]|https://rt.perl.org/Ticket/Display.html?id=122070>
9189be1b
KW
879
880=item *
881
39c78947 882L<DynaLoader> has been upgraded to version 1.32.
9189be1b
KW
883
884Remove C<dl_nonlazy> global if unused in Dynaloader. [perl #122926]
885
886=item *
887
39c78947 888L<Encode> has been upgraded to version 2.72.
9189be1b 889
53ce1dd5
RS
890C<piconv> now has better error handling when the encoding name is nonexistent,
891and a build breakage when upgrading L<Encode> in perl-5.8.2 and earlier has
892been fixed.
9189be1b 893
53ce1dd5 894Building in C++ mode on Windows now works.
9189be1b
KW
895
896=item *
897
53ce1dd5 898L<Errno> has been upgraded to version 1.23.
9189be1b 899
53ce1dd5
RS
900Add C<-P> to the preprocessor command-line on GCC 5. GCC added extra
901line directives, breaking parsing of error code definitions. [rt.perl.org
902#123784]
9189be1b
KW
903
904=item *
905
39c78947 906L<experimental> has been upgraded to version 0.013.
9189be1b 907
53ce1dd5 908Hardcodes features for Perls older than 5.15.7.
9189be1b
KW
909
910=item *
911
39c78947 912L<ExtUtils::CBuilder> has been upgraded to version 0.280221.
9189be1b 913
53ce1dd5
RS
914Fixes a regression on Android.
915L<[perl #122675]|https://rt.perl.org/Ticket/Display.html?id=122675>
9189be1b
KW
916
917=item *
918
39c78947 919L<ExtUtils::Manifest> has been upgraded to version 1.70.
9189be1b 920
53ce1dd5
RS
921Fixes a bug with C<maniread()>'s handling of quoted filenames and improves
922C<manifind()> to follow symlinks.
923L<[perl #122415]|https://rt.perl.org/Ticket/Display.html?id=122415>
9189be1b
KW
924
925=item *
926
39c78947 927L<ExtUtils::ParseXS> has been upgraded to version 3.28.
9189be1b
KW
928
929Only declare C<file> unused if we actually define it.
930Improve generated C<RETVAL> code generation to avoid repeated
931references to C<ST(0)>. [perl #123278]
932Broaden and document the C</OBJ$/> to C</REF$/> typemap optimization
933for the C<DESTROY> method. [perl #123418]
934
53ce1dd5 935=item *
9189be1b 936
53ce1dd5 937L<Fcntl> has been upgraded to version 1.13.
9189be1b 938
f0a38539 939Add support for the Linux pipe buffer size C<fcntl()> commands.
9189be1b 940
53ce1dd5 941=item *
9189be1b 942
39c78947 943L<File::Find> has been upgraded to version 1.29.
9189be1b 944
53ce1dd5
RS
945C<find()> and C<finddepth()> will now warn if passed inappropriate or
946misspelled options.
9189be1b
KW
947
948=item *
949
950L<File::Glob> has been upgraded to version 1.24.
951
f0a38539 952Avoid C<SvIV()> expanding to call C<get_sv()> three times in a few
9189be1b
KW
953places. [perl #123606]
954
955=item *
956
39c78947 957L<HTTP::Tiny> has been upgraded to version 0.054.
9189be1b 958
53ce1dd5 959C<keep_alive> is now fork-safe and thread-safe.
9189be1b
KW
960
961=item *
962
39c78947 963L<IO> has been upgraded to version 1.35.
9189be1b 964
53ce1dd5 965The XS implementation has been fixed for the sake of older Perls.
9189be1b
KW
966
967=item *
968
53ce1dd5 969L<IO::Socket> has been upgraded to version 1.38.
9189be1b 970
f0a38539 971Document the limitations of the C<connected()> method. [perl #123096]
9189be1b 972
53ce1dd5 973=item *
9189be1b 974
39c78947 975L<IO::Socket::IP> has been upgraded to version 0.37.
9189be1b 976
53ce1dd5
RS
977A better fix for subclassing C<connect()>.
978L<[cpan #95983]|https://rt.cpan.org/Ticket/Display.html?id=95983>
979L<[cpan #97050]|https://rt.cpan.org/Ticket/Display.html?id=97050>
9189be1b 980
53ce1dd5
RS
981Implements Timeout for C<connect()>.
982L<[cpan #92075]|https://rt.cpan.org/Ticket/Display.html?id=92075>
9189be1b 983
53ce1dd5 984=item *
9189be1b 985
39c78947 986The libnet collection of modules has been upgraded to version 3.05.
9189be1b 987
f0a38539
KW
988Support for IPv6 and SSL to C<Net::FTP>, C<Net::NNTP>, C<Net::POP3> and C<Net::SMTP>.
989Improvements in C<Net::SMTP> authentication.
9189be1b 990
53ce1dd5 991=item *
9189be1b 992
39c78947 993L<Locale::Codes> has been upgraded to version 3.34.
9189be1b 994
53ce1dd5
RS
995Fixed a bug in the scripts used to extract data from spreadsheets that
996prevented the SHP currency code from being found.
997L<[cpan #94229]|https://rt.cpan.org/Ticket/Display.html?id=94229>
9189be1b 998
53ce1dd5 999New codes have been added.
9189be1b 1000
53ce1dd5 1001=item *
9189be1b 1002
39c78947 1003L<Math::BigInt> has been upgraded to version 1.9997.
9189be1b 1004
53ce1dd5 1005Synchronize POD changes from the CPAN release.
f0a38539 1006C<< Math::BigFloat->blog(x) >> would sometimes return C<blog(2*x)> when
53ce1dd5
RS
1007the accuracy was greater than 70 digits.
1008The result of C<< Math::BigFloat->bdiv() >> in list context now
1009satisfies C<< x = quotient * divisor + remainder >>.
9189be1b 1010
53ce1dd5
RS
1011Correct handling of subclasses.
1012L<[cpan #96254]|https://rt.cpan.org/Ticket/Display.html?id=96254>
1013L<[cpan #96329]|https://rt.cpan.org/Ticket/Display.html?id=96329>
9189be1b 1014
53ce1dd5 1015=item *
9189be1b 1016
39c78947 1017L<Module::Metadata> has been upgraded to version 1.000026.
9189be1b 1018
53ce1dd5
RS
1019Support installations on older perls with an L<ExtUtils::MakeMaker> earlier
1020than 6.63_03
9189be1b 1021
53ce1dd5 1022=item *
9189be1b 1023
39c78947 1024L<overload> has been upgraded to version 1.26.
9189be1b 1025
53ce1dd5 1026A redundant C<ref $sub> check has been removed.
9189be1b 1027
53ce1dd5 1028=item *
9189be1b 1029
39c78947 1030The PathTools module collection has been upgraded to version 3.56.
9189be1b 1031
53ce1dd5 1032A warning from the B<gcc> compiler is now avoided when building the XS.
9189be1b 1033
53ce1dd5 1034Don't turn leading C<//> into C</> on Cygwin. [perl #122635]
9189be1b 1035
53ce1dd5 1036=item *
9189be1b 1037
53ce1dd5 1038L<perl5db.pl> has been upgraded to version 1.49.
9189be1b 1039
53ce1dd5
RS
1040The debugger would cause an assertion failure.
1041L<[perl #124127]|https://rt.perl.org/Ticket/Display.html?id=124127>
9189be1b 1042
53ce1dd5
RS
1043C<fork()> in the debugger under C<tmux> will now create a new window for
1044the forked process. L<[perl
1045#121333]|https://rt.perl.org/Ticket/Display.html?id=121333>
9189be1b 1046
53ce1dd5
RS
1047The debugger now saves the current working directory on startup and
1048restores it when you restart your program with C<R> or C<rerun>. L<[perl
1049#121509]|https://rt.perl.org/Ticket/Display.html?id=121509>
9189be1b 1050
53ce1dd5 1051=item *
9189be1b 1052
53ce1dd5 1053L<PerlIO::scalar> has been upgraded to version 0.22.
9189be1b 1054
53ce1dd5
RS
1055Reading from a position well past the end of the scalar now correctly
1056returns end of file. [perl #123443]
9189be1b 1057
53ce1dd5
RS
1058Seeking to a negative position still fails, but no longer leaves the
1059file position set to a negation location.
9189be1b 1060
53ce1dd5
RS
1061C<eof()> on a C<PerlIO::scalar> handle now properly returns true when
1062the file position is past the 2GB mark on 32-bit systems.
1063
1064Attempting to write at file positions impossible for the platform now
1065fail early rather than wrapping at 4GB.
9189be1b
KW
1066
1067=item *
1068
39c78947 1069L<Pod::Perldoc> has been upgraded to version 3.25.
9189be1b 1070
53ce1dd5
RS
1071Filehandles opened for reading or writing now have C<:encoding(UTF-8)> set.
1072L<[cpan #98019]|https://rt.cpan.org/Ticket/Display.html?id=98019>
9189be1b
KW
1073
1074=item *
1075
39c78947 1076L<POSIX> has been upgraded to version 1.53.
9189be1b 1077
53ce1dd5
RS
1078The C99 math functions and constants (for example C<acosh>, C<isinf>, C<isnan>, C<round>,
1079C<trunc>; C<M_E>, C<M_SQRT2>, C<M_PI>) have been added.
9189be1b 1080
f0a38539 1081C<POSIX::tmpnam()> now produces a deprecation warning. [perl #122005]
9189be1b
KW
1082
1083=item *
1084
53ce1dd5 1085L<Safe> has been upgraded to version 2.39.
9189be1b 1086
53ce1dd5 1087C<reval> was not propagating void context properly.
9189be1b 1088
53ce1dd5
RS
1089=item *
1090
1091Scalar-List-Utils has been upgraded to version 1.41.
1092
1093A new module, L<Sub::Util>, has been added, containing functions related to
f0a38539
KW
1094CODE refs, including C<subname> (inspired by C<Sub::Identity>) and C<set_subname>
1095(copied and renamed from C<Sub::Name>).
53ce1dd5
RS
1096The use of C<GetMagic> in C<List::Util::reduce()> has also been fixed.
1097L<[cpan #63211]|https://rt.cpan.org/Ticket/Display.html?id=63211>
9189be1b
KW
1098
1099=item *
1100
53ce1dd5 1101L<SDBM_File> has been upgraded to version 1.13.
9189be1b 1102
53ce1dd5 1103Simplified the build process. [perl #123413]
9189be1b
KW
1104
1105=item *
1106
53ce1dd5 1107L<Time::Piece> has been upgraded to version 1.29.
9189be1b 1108
f0a38539 1109When pretty printing negative C<Time::Seconds>, the "minus" is no longer lost.
9189be1b 1110
53ce1dd5 1111=item *
9189be1b 1112
39c78947 1113L<Unicode::Collate> has been upgraded to version 1.12.
9189be1b 1114
53ce1dd5 1115Version 0.67's improved discontiguous contractions is invalidated by default
f0a38539 1116and is supported as a parameter C<long_contraction>.
53ce1dd5
RS
1117
1118=item *
1119
1120L<Unicode::Normalize> has been upgraded to version 1.18.
1121
1122The XSUB implementation has been removed in favour of pure Perl.
9189be1b
KW
1123
1124=item *
1125
1126L<Unicode::UCD> has been upgraded to version 0.61.
1127
1128A new function L<property_values()|Unicode::UCD/prop_values()>
1129has been added to return a given property's possible values.
1130
1131A new function L<charprop()|Unicode::UCD/charprop()>
1132has been added to return the value of a given property for a given code
1133point.
1134
1135A new function L<charprops_all()|Unicode::UCD/charprops_all()>
1136has been added to return the values of all Unicode properties for a
1137given code point.
1138
1139A bug has been fixed so that L<propaliases()|Unicode::UCD/prop_aliases()>
1140returns the correct short and long names for the Perl extensions where
1141it was incorrect.
1142
1143A bug has been fixed so that
1144L<prop_value_aliases()|Unicode::UCD/prop_value_aliases()>
1145returns C<undef> instead of a wrong result for properties that are Perl
1146extensions.
1147
1148This module now works on EBCDIC platforms.
1149
1150=item *
1151
53ce1dd5
RS
1152L<UNIVERSAL> has been upgraded to version 1.12.
1153
53ce1dd5
RS
1154=item *
1155
1156L<utf8> has been upgraded to version 1.17
1157
f0a38539 1158A mismatch between the documentation and the code in C<utf8::downgrade()>
53ce1dd5
RS
1159was fixed in favour of the documentation. The optional second argument
1160is now correctly treated as a perl boolean (true/false semantics) and
1161not as an integer.
1162
1163=item *
1164
1165L<version> has been upgraded to version 0.9909.
1166
1167Numerous changes. See the F<Changes> file in the CPAN distribution for
1168details.
1169
1170=item *
1171
9189be1b
KW
1172L<Win32> has been upgraded to version 0.51.
1173
f0a38539 1174C<GetOSName()> now supports Windows 8.1, and building in C++ mode now works.
9189be1b
KW
1175
1176=item *
1177
1178L<Win32API::File> has been upgraded to version 0.1202
1179
1180Building in C++ mode now works.
1181
53ce1dd5
RS
1182=item *
1183
39c78947 1184L<XSLoader> has been upgraded to version 0.20.
53ce1dd5
RS
1185
1186Allow XSLoader to load modules from a different namespace.
1187[perl #122455]
1188
9189be1b
KW
1189=back
1190
f5b63a6e 1191=head2 Removed Modules and Pragmata
391823f2 1192
f5b63a6e
RS
1193The following modules (and associated modules) have been removed from the core
1194perl distribution:
eabfc7bc
RS
1195
1196=over 4
1197
1198=item *
1199
f5b63a6e 1200L<CGI>
69e954a5 1201
7f9fef93 1202=item *
86e0176a 1203
f5b63a6e 1204L<Module::Build>
69e954a5 1205
e5998677 1206=back
20b5e916 1207
eabfc7bc
RS
1208=head1 Documentation
1209
1210=head2 New Documentation
532ecd00 1211
eabfc7bc 1212=head3 L<perlunicook>
d76c14eb 1213
eabfc7bc
RS
1214This document, by Tom Christiansen, provides examples of handling Unicode in
1215Perl.
1216
1217=head2 Changes to Existing Documentation
1218
7595828f
KW
1219=head3 L<perlaix>
1220
1221=over 4
1222
1223=item *
1224
1225A note on long doubles has been added.
1226
1227=back
1228
1229
eabfc7bc 1230=head3 L<perlapi>
d547bad0 1231
e5998677 1232=over 4
d547bad0 1233
8a95d307
FC
1234=item *
1235
eabfc7bc 1236Note that C<SvSetSV> doesn't do set magic.
532ecd00 1237
eabfc7bc 1238=item *
532ecd00 1239
6ba7438b 1240C<sv_usepvn_flags> - fix documentation to mention the use of C<Newx> instead of
eabfc7bc 1241C<malloc>.
532ecd00 1242
eabfc7bc 1243L<[perl #121869]|https://rt.perl.org/Ticket/Display.html?id=121869>
532ecd00 1244
eabfc7bc 1245=item *
532ecd00 1246
eabfc7bc 1247Clarify where C<NUL> may be embedded or is required to terminate a string.
532ecd00 1248
eabfc7bc 1249=item *
532ecd00 1250
d140c31c
AC
1251Some documentation that was previously missing due to formatting errors is
1252now included.
532ecd00 1253
eabfc7bc 1254=item *
532ecd00 1255
3b50e657
KW
1256Entries are now organized into groups rather than by the file where they
1257are found.
532ecd00 1258
eabfc7bc 1259=item *
532ecd00 1260
3b50e657
KW
1261Alphabetical sorting of entries is now done consistently (automatically
1262by the POD generator) to make entries easier to find when scanning.
eabfc7bc
RS
1263
1264=back
338906ce 1265
eabfc7bc 1266=head3 L<perldata>
338906ce 1267
e5998677 1268=over 4
338906ce 1269
eabfc7bc 1270=item *
2f304be9 1271
eabfc7bc
RS
1272The syntax of single-character variable names has been brought
1273up-to-date and more fully explained.
9749148e 1274
7595828f
KW
1275=item *
1276
1277Hexadecimal floating point numbers are described, as are infinity and
1278NaN.
1279
7f9fef93 1280=back
9749148e 1281
eabfc7bc 1282=head3 L<perlebcdic>
47cb8ddb 1283
7f9fef93 1284=over 4
47cb8ddb 1285
eabfc7bc 1286=item *
47cb8ddb 1287
eabfc7bc
RS
1288This document has been significantly updated in the light of recent
1289improvements to EBCDIC support.
47cb8ddb 1290
7f9fef93 1291=back
47cb8ddb 1292
7595828f
KW
1293=head3 L<perlfilter>
1294
1295=over 4
1296
1297=item *
1298
1299Added a L<LIMITATIONS|perlfilter/LIMITATIONS> section.
1300
1301=back
1302
1303
eabfc7bc 1304=head3 L<perlfunc>
be39acb2 1305
eabfc7bc 1306=over 4
be39acb2 1307
eabfc7bc 1308=item *
be39acb2 1309
eabfc7bc 1310Mention that C<study()> is currently a no-op.
be39acb2
SH
1311
1312=item *
1313
eabfc7bc
RS
1314Calling C<delete> or C<exists> on array values is now described as "strongly
1315discouraged" rather than "deprecated".
be39acb2 1316
eabfc7bc 1317=item *
7f9fef93 1318
eabfc7bc 1319Improve documentation of C<< our >>.
be39acb2 1320
eabfc7bc 1321=item *
be39acb2 1322
eabfc7bc
RS
1323C<-l> now notes that it will return false if symlinks aren't supported by the
1324file system.
be39acb2 1325
eabfc7bc 1326L<[perl #121523]|https://rt.perl.org/Ticket/Display.html?id=121523>
be39acb2
SH
1327
1328=item *
1329
eabfc7bc 1330Note that C<exec LIST> and C<system LIST> may fall back to the shell on
d140c31c
AC
1331Win32. Only the indirect-object syntax C<exec PROGRAM LIST> and
1332C<system PROGRAM LIST> will reliably avoid using the shell.
eabfc7bc
RS
1333
1334This has also been noted in L<perlport>.
1335
1336L<[perl #122046]|https://rt.perl.org/Ticket/Display.html?id=122046>
be39acb2 1337
7f9fef93 1338=back
be39acb2 1339
eabfc7bc
RS
1340=head3 L<perlguts>
1341
1342=over 4
1343
1344=item *
1345
1346The OOK example has been updated to account for COW changes and a change in the
1347storage of the offset.
1348
1349=item *
be39acb2 1350
eabfc7bc 1351Details on C level symbols and libperl.t added.
be39acb2 1352
ce93e38b
KW
1353=item *
1354
1355Information on Unicode handling has been added
1356
1357=item *
1358
1359Information on EBCDIC handling has been added
1360
eabfc7bc
RS
1361=back
1362
7595828f
KW
1363=head3 L<perlhack>
1364
1365=over 4
1366
1367=item *
1368
1369A note has been added about running on platforms with non-ASCII
1370character sets
1371
1372=item *
1373
1374A note has been added about performance testing
1375
1376=back
1377
eabfc7bc 1378=head3 L<perlhacktips>
7f9fef93
SH
1379
1380=over 4
be39acb2
SH
1381
1382=item *
1383
d140c31c
AC
1384Documentation has been added illustrating the perils of assuming that
1385there is no change to the contents of static memory pointed to by the
1386return values of Perl's wrappers for C library functions.
eabfc7bc
RS
1387
1388=item *
1389
d140c31c
AC
1390Replacements for C<tmpfile>, C<atoi>, C<strtol>, and C<strtoul> are now
1391recommended.
eabfc7bc
RS
1392
1393=item *
1394
1395Updated documentation for the C<test.valgrind> C<make> target.
1396
1397L<[perl #121431]|https://rt.perl.org/Ticket/Display.html?id=121431>
be39acb2 1398
7595828f
KW
1399=item *
1400
1401Information is given about writing test files portably to non-ASCII
1402platforms.
1403
1404=item *
1405
1406A note has been added about how to get a C language stack backtrace.
1407
1408=back
1409
1410=head3 L<perlhpux>
1411
1412=over 4
1413
1414=item *
1415
1416Note that the message "Redeclaration of "sendpath" with a different
1417storage class specifier" is harmless.
1418
1419=back
1420
1421=head3 L<perllocale>
1422
1423=over 4
1424
1425=item *
1426
1427Updated for the enhancements in v5.22, along with some clarifications.
1428
a9c3e753 1429=back
ea13b07e 1430
eabfc7bc 1431=head3 L<perlmodstyle>
0d42058e 1432
7f9fef93
SH
1433=over 4
1434
1435=item *
2a7a05b4 1436
eabfc7bc
RS
1437Instead of pointing to the module list, we are now pointing to
1438L<PrePAN|http://prepan.org/>.
2a7a05b4 1439
7f9fef93
SH
1440=back
1441
7595828f
KW
1442=head3 L<perlop>
1443
1444=over 4
1445
1446=item *
1447
1448Updated for the enhancements in v5.22, along with some clarifications.
1449
1450=back
1451
1452=head3 L<perlpodspec>
1453
1454=over 4
1455
1456=item *
1457
1458The specification of the pod language is changing so that the default
1459encoding of pods that aren't in UTF-8 (unless otherwise indicated) is
1460CP1252 instead of ISO 8859-1 (Latin1).
1461
1462=back
1463
eabfc7bc
RS
1464=head3 L<perlpolicy>
1465
1466=over 4
1467
1468=item *
1469
1470We now have a code of conduct for the I<< p5p >> mailing list, as documented
1471in L<< perlpolicy/STANDARDS OF CONDUCT >>.
2a7a05b4 1472
eabfc7bc
RS
1473=item *
1474
1475The conditions for marking an experimental feature as non-experimental are now
1476set out.
1477
7595828f
KW
1478=item *
1479
1480Clarification has been made as to what sorts of changes are permissible in
1481maintenance releases.
1482
eabfc7bc
RS
1483=back
1484
1485=head3 L<perlport>
1486
1487=over 4
1488
1489=item *
1490
d140c31c 1491Out-of-date VMS-specific information has been fixed and/or simplified.
eabfc7bc 1492
ce93e38b
KW
1493=item *
1494
1495Notes about EBCDIC have been added.
1496
eabfc7bc
RS
1497=back
1498
1499=head3 L<perlre>
1500
1501=over 4
1502
1503=item *
1504
d140c31c 1505The description of the C</x> modifier has been clarified to note that
7595828f
KW
1506comments cannot be continued onto the next line by escaping them; and
1507there is now a list of all the characters that are considered whitespace
1508by this modifier.
1509
1510=item *
1511
1512The new C</n> modifier is described.
1513
1514=item *
1515
1516A note has been added on how to make bracketed character class ranges
1517portable to non-ASCII machines.
eabfc7bc
RS
1518
1519=back
1520
1521=head3 L<perlrebackslash>
1522
1523=over 4
1524
1525=item *
1526
1527Added documentation of C<\b{sb}>, C<\b{wb}>, C<\b{gcb}>, and C<\b{g}>.
1528
1529=back
1530
1531=head3 L<perlrecharclass>
1532
1533=over 4
1534
1535=item *
1536
1537Clarifications have been added to L<perlrecharclass/Character Ranges>
3b50e657 1538to the effect C<[A-Z]>, C<[a-z]>, C<[0-9]> and
eabfc7bc
RS
1539any subranges thereof in regular expression bracketed character classes
1540are guaranteed to match exactly what a naive English speaker would
1541expect them to match, even on platforms (such as EBCDIC) where special
1542handling is required to accomplish this.
1543
1544=item *
1545
1546The documentation of Bracketed Character Classes has been expanded to cover the
1547improvements in C<qr/[\N{named sequence}]/> (see under L</Selected Bug Fixes>).
1548
1549=back
1550
7595828f
KW
1551=head3 L<perlref>
1552
1553=over 4
1554
1555=item *
1556
1557A new section has been added
1558L<Assigning to References|perlref/Assigning to References>
1559
1560=back
1561
eabfc7bc
RS
1562=head3 L<perlsec>
1563
1564=over 4
1565
1566=item *
1567
1568Comments added on algorithmic complexity and tied hashes.
1569
1570=back
1571
1572=head3 L<perlsyn>
1573
1574=over 4
1575
1576=item *
1577
1578An ambiguity in the documentation of the C<...> statement has been corrected.
1579L<[perl #122661]|https://rt.perl.org/Ticket/Display.html?id=122661>
1580
1581=item *
1582
1583The empty conditional in C<< for >> and C<< while >> is now documented
1584in L<< perlsyn >>.
1585
1586=back
1587
1588=head3 L<perlunicode>
1589
1590=over 4
1591
1592=item *
1593
ce93e38b 1594This has had extensive revisions to bring it up-to-date with current
7595828f
KW
1595Unicode support and to make it more readable. Notable is that Unicode
15967.0 changed what it should do with non-characters. Perl retains the old
1597way of handling for reasons of backward compatibility. See
1598L<perlunicode/Noncharacter code points>.
eabfc7bc
RS
1599
1600=back
1601
1602=head3 L<perluniintro>
1603
1604=over 4
1605
1606=item *
1607
1608Advice for how to make sure your strings and regular expression patterns are
ce93e38b 1609interpreted as Unicode has been updated.
eabfc7bc
RS
1610
1611=back
1612
1613=head3 L<perlvar>
1614
1615=over 4
1616
1617=item *
1618
7595828f
KW
1619C<$]> is no longer listed as being deprecated. Instead, discussion has
1620been added on the advantages and disadvantages of using it versus
1621C<$^V>.
1622
1623=item *
1624
1625C<${^ENCODING}> is now marked as deprecated.
1626
1627=item *
1628
1629The entry for C<%^H> has been clarified to indicate it can only handle
1630simple values.
eabfc7bc
RS
1631
1632=back
1633
1634=head3 L<perlvms>
1635
1636=over 4
1637
1638=item *
1639
1640Out-of-date and/or incorrect material has been removed.
1641
1642=item *
1643
1644Updated documentation on environment and shell interaction in VMS.
1645
1646=back
1647
1648=head3 L<perlxs>
1649
1650=over 4
1651
1652=item *
1653
1654Added a discussion of locale issues in XS code.
1655
1656=back
1657
1658=head1 Diagnostics
1659
1660The following additions or changes have been made to diagnostic output,
1661including warnings and fatal error messages. For the complete list of
1662diagnostic messages, see L<perldiag>.
1663
1664=head2 New Diagnostics
1665
1666=head3 New Errors
1667
1668=over 4
1669
1670=item *
1671
1672L<Bad symbol for scalar|perldiag/"Bad symbol for scalar">
1673
1674(P) An internal request asked to add a scalar entry to something that
1675wasn't a symbol table entry.
1676
1677=item *
1678
1679L<Can't use a hash as a reference|perldiag/"Can't use a hash as a reference">
1680
1681(F) You tried to use a hash as a reference, as in
1682C<< %foo->{"bar"} >> or C<< %$ref->{"hello"} >>. Versions of perl E<lt>= 5.6.1
1683used to allow this syntax, but shouldn't have.
1684
1685=item *
1686
1687L<Can't use an array as a reference|perldiag/"Can't use an array as a reference">
1688
1689(F) You tried to use an array as a reference, as in
1690C<< @foo->[23] >> or C<< @$ref->[99] >>. Versions of perl E<lt>= 5.6.1 used to
1691allow this syntax, but shouldn't have.
1692
1693=item *
1694
1695L<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()?)">
1696
4ec8e6f0 1697(F) C<defined()> is not useful on arrays because it
eabfc7bc 1698checks for an undefined I<scalar> value. If you want to see if the
4ec8e6f0 1699array is empty, just use S<C<if (@array) { # not empty }>> for example.
eabfc7bc
RS
1700
1701=item *
1702
1703L<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()?)">
1704
1705(F) C<defined()> is not usually right on hashes.
1706
4ec8e6f0 1707Although S<C<defined %hash>> is false on a plain not-yet-used hash, it
eabfc7bc 1708becomes true in several non-obvious circumstances, including iterators,
4ec8e6f0
KW
1709weak references, stash names, even remaining true after S<C<undef %hash>>.
1710These things make S<C<defined %hash>> fairly useless in practice, so it now
eabfc7bc
RS
1711generates a fatal error.
1712
1713If a check for non-empty is what you wanted then just put it in boolean
1714context (see L<perldata/Scalar values>):
1715
1716 if (%hash) {
1717 # not empty
1718 }
1719
4ec8e6f0 1720If you had S<C<defined %Foo::Bar::QUUX>> to check whether such a package
eabfc7bc
RS
1721variable exists then that's never really been reliable, and isn't
1722a good way to enquire about the features of a package, or whether
1723it's loaded, etc.
1724
1725=item *
1726
1727L<Cannot chr %f|perldiag/"Cannot chr %f">
1728
c21a1c59
RS
1729(F) You passed an invalid number (like an infinity or not-a-number) to
1730C<chr>.
1731
eabfc7bc
RS
1732=item *
1733
1734L<Cannot compress %f in pack|perldiag/"Cannot compress %f in pack">
1735
c21a1c59
RS
1736(F) You tried converting an infinity or not-a-number to an unsigned
1737character, which makes no sense.
1738
eabfc7bc
RS
1739=item *
1740
1741L<Cannot pack %f with '%c'|perldiag/"Cannot pack %f with '%c'">
1742
c21a1c59
RS
1743(F) You tried converting an infinity or not-a-number to a character,
1744which makes no sense.
1745
eabfc7bc
RS
1746=item *
1747
1748L<Cannot print %f with '%c'|perldiag/"Cannot printf %f with '%c'">
1749
4ec8e6f0
KW
1750(F) You tried printing an infinity or not-a-number as a character (C<%c>),
1751which makes no sense. Maybe you meant C<'%s'>, or just stringifying it?
c21a1c59 1752
eabfc7bc
RS
1753=item *
1754
1755L<charnames alias definitions may not contain a sequence of multiple spaces|perldiag/"charnames alias definitions may not contain a sequence of multiple spaces">
1756
1757(F) You defined a character name which had multiple space
1758characters in a row. Change them to single spaces. Usually these
1759names are defined in the C<:alias> import argument to C<use charnames>, but
1760they could be defined by a translator installed into C<$^H{charnames}>.
1761See L<charnames/CUSTOM ALIASES>.
1762
1763=item *
1764
1765L<charnames alias definitions may not contain trailing white-space|perldiag/"charnames alias definitions may not contain trailing white-space">
1766
1767(F) You defined a character name which ended in a space
1768character. Remove the trailing space(s). Usually these names are
1769defined in the C<:alias> import argument to C<use charnames>, but they
1770could be defined by a translator installed into C<$^H{charnames}>.
1771See L<charnames/CUSTOM ALIASES>.
1772
1773=item *
1774
1775L<:const is not permitted on named subroutines|perldiag/":const is not permitted on named subroutines">
1776
f0a38539 1777(F) The C<const> attribute causes an anonymous subroutine to be run and
f5b97b22 1778its value captured at the time that it is cloned. Named subroutines are
eabfc7bc
RS
1779not cloned like this, so the attribute does not make sense on them.
1780
1781=item *
1782
1783L<Hexadecimal float: internal error|perldiag/"Hexadecimal float: internal error">
1784
1785(F) Something went horribly bad in hexadecimal float handling.
1786
1787=item *
1788
1789L<Hexadecimal float: unsupported long double format|perldiag/"Hexadecimal float: unsupported long double format">
1790
1791(F) You have configured Perl to use long doubles but
1792the internals of the long double format are unknown,
1793therefore the hexadecimal float output is impossible.
1794
1795=item *
1796
1797L<Illegal suidscript|perldiag/"Illegal suidscript">
1798
1799(F) The script run under suidperl was somehow illegal.
1800
1801=item *
1802
1803L<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/">
1804
1805(F) The two-character sequence C<"(?"> in
1806this context in a regular expression pattern should be an
1807indivisible token, with nothing intervening between the C<"(">
1808and the C<"?">, but you separated them.
1809
1810=item *
1811
1812L<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/">
1813
1814(F) The two-character sequence C<"(*"> in
1815this context in a regular expression pattern should be an
1816indivisible token, with nothing intervening between the C<"(">
1817and the C<"*">, but you separated them.
1818
1819=item *
1820
1821L<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/">
1822
1823(F) The pattern looks like a {min,max} quantifier, but the min or max could not
1824be parsed as a valid number - either it has leading zeroes, or it represents
1825too big a number to cope with. The S<<-- HERE> shows where in the regular
1826expression the problem was discovered. See L<perlre>.
1827
eaa8dfa2
KW
1828=item *
1829
1830L<'%s' is an unknown bound type in regex|perldiag/"'%s' is an unknown bound type in regex; marked by <-- HERE in m/%s/">
1831
1832(F) You used C<\b{...}> or C<\B{...}> and the C<...> is not known to
1833Perl. The current valid ones are given in
1834L<perlrebackslash/\b{}, \b, \B{}, \B>.
1835
1836=item *
1837
1838L<Missing or undefined argument to require|perldiag/Missing or undefined argument to require>
1839
1840(F) You tried to call C<require> with no argument or with an undefined
1841value as an argument. C<require> expects either a package name or a
1842file-specification as an argument. See L<perlfunc/require>.
1843
1844Formerly, C<require> with no argument or C<undef> warned about a Null filename.
1845
eabfc7bc
RS
1846=back
1847
1848=head3 New Warnings
1849
1850=over 4
1851
1852=item *
1853
43831b1f
DM
1854L<\C is deprecated in regex|perldiag/"\C is deprecated in regex; marked by <-- HERE in m/%s/">
1855
1856(D deprecated) The C<< /\C/ >> character class was deprecated in v5.20, and
1857now emits a warning. It is intended that it will become an error in v5.24.
1858This character class matches a single byte even if it appears within a
50ea4745 1859multi-byte character, breaks encapsulation, and can corrupt UTF-8
43831b1f
DM
1860strings.
1861
1862=item *
1863
eabfc7bc
RS
1864L<"%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>>
1865
1866(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1867
1868You specified a character that has the given plainer way of writing it,
1869and which is also portable to platforms running with different character
1870sets.
1871
1872=item *
1873
1874L<Argument "%s" treated as 0 in increment (++)|perldiag/"Argument "%s" treated
1875as 0 in increment (++)">
1876
1877(W numeric) The indicated string was fed as an argument to the C<++> operator
1878which expects either a number or a string matching C</^[a-zA-Z]*[0-9]*\z/>.
1879See L<perlop/Auto-increment and Auto-decrement> for details.
1880
1881=item *
1882
1883L<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/">
1884
1885(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1886
1887In a bracketed character class in a regular expression pattern, you
1888had a range which has exactly one end of it specified using C<\N{}>, and
1889the other end is specified using a non-portable mechanism. Perl treats
1890the range as a Unicode range, that is, all the characters in it are
1891considered to be the Unicode characters, and which may be different code
1892points on some platforms Perl runs on. For example, C<[\N{U+06}-\x08]>
1893is treated as if you had instead said C<[\N{U+06}-\N{U+08}]>, that is it
1894matches the characters whose code points in Unicode are 6, 7, and 8.
1895But that C<\x08> might indicate that you meant something different, so
1896the warning gets raised.
1897
1898=item *
1899
e6205aca
KW
1900L<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".>
1901
1902(W locale) You are 1) running under "C<use locale>"; 2) the current
1903locale is not a UTF-8 one; 3) you tried to do the designated case-change
1904operation on the specified Unicode character; and 4) the result of this
1905operation would mix Unicode and locale rules, which likely conflict.
1906
1bc134bc
KW
1907The warnings category C<locale> is new.
1908
e6205aca
KW
1909=item *
1910
eabfc7bc
RS
1911L<:const is experimental|perldiag/":const is experimental">
1912
f0a38539 1913(S experimental::const_attr) The C<const> attribute is experimental.
eabfc7bc
RS
1914If you want to use the feature, disable the warning with C<no warnings
1915'experimental::const_attr'>, but know that in doing so you are taking
1916the risk that your code may break in a future Perl version.
1917
1918=item *
1919
1920L<gmtime(%f) failed|perldiag/"gmtime(%f) failed">
1921
1922(W overflow) You called C<gmtime> with a number that it could not handle:
1923too large, too small, or NaN. The returned value is C<undef>.
1924
1925=item *
1926
1927L<Hexadecimal float: exponent overflow|perldiag/"Hexadecimal float: exponent overflow">
1928
1929(W overflow) The hexadecimal floating point has larger exponent
1930than the floating point supports.
1931
1932=item *
1933
1934L<Hexadecimal float: exponent underflow|perldiag/"Hexadecimal float: exponent underflow">
1935
1936(W overflow) The hexadecimal floating point has smaller exponent
1937than the floating point supports.
1938
1939=item *
1940
1941L<Hexadecimal float: mantissa overflow|perldiag/"Hexadecimal float: mantissa overflow">
1942
1943(W overflow) The hexadecimal floating point literal had more bits in
f0a38539 1944the mantissa (the part between the C<0x> and the exponent, also known as
eabfc7bc
RS
1945the fraction or the significand) than the floating point supports.
1946
1947=item *
1948
1949L<Hexadecimal float: precision loss|perldiag/"Hexadecimal float: precision loss">
1950
1951(W overflow) The hexadecimal floating point had internally more
1952digits than could be output. This can be caused by unsupported
1953long double formats, or by 64-bit integers not being available
1954(needed to retrieve the digits under some configurations).
1955
eabfc7bc
RS
1956=item *
1957
e6205aca
KW
1958L<Locale '%s' may not work well.%s|perldiag/Locale '%s' may not work well.%s>
1959
1960(W locale) You are using the named locale, which is a non-UTF-8 one, and
1961which perl has determined is not fully compatible with what it can
1962handle. The second C<%s> gives a reason.
1963
1bc134bc
KW
1964The warnings category C<locale> is new.
1965
e6205aca
KW
1966=item *
1967
eabfc7bc
RS
1968L<localtime(%f) failed|perldiag/"localtime(%f) failed">
1969
1970(W overflow) You called C<localtime> with a number that it could not handle:
1971too large, too small, or NaN. The returned value is C<undef>.
1972
1973=item *
1974
1975L<Negative repeat count does nothing|perldiag/"Negative repeat count does nothing">
1976
1977(W numeric) You tried to execute the
1978L<C<x>|perlop/Multiplicative Operators> repetition operator fewer than 0
1979times, which doesn't make sense.
1980
1981=item *
1982
1983L<NO-BREAK SPACE in a charnames alias definition is deprecated|perldiag/"NO-BREAK SPACE in a charnames alias definition is deprecated">
1984
1985(D deprecated) You defined a character name which contained a no-break
1986space character. Change it to a regular space. Usually these names are
1987defined in the C<:alias> import argument to C<use charnames>, but they
1988could be defined by a translator installed into C<$^H{charnames}>. See
1989L<charnames/CUSTOM ALIASES>.
1990
1991=item *
1992
1993L<Non-finite repeat count does nothing|perldiag/"Non-finite repeat count does nothing">
1994
1995(W numeric) You tried to execute the
1996L<C<x>|perlop/Multiplicative Operators> repetition operator C<Inf> (or
3209f716 1997C<-Inf>) or NaN times, which doesn't make sense.
eabfc7bc
RS
1998
1999=item *
2000
2001L<PerlIO layer ':win32' is experimental|perldiag/"PerlIO layer ':win32' is experimental">
2002
2003(S experimental::win32_perlio) The C<:win32> PerlIO layer is
2004experimental. If you want to take the risk of using this layer,
2005simply disable this warning:
2006
2007 no warnings "experimental::win32_perlio";
2008
2009=item *
2010
2011L<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>">
2012
2013(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
2014
2015Stricter rules help to find typos and other errors. Perhaps you didn't
2016even intend a range here, if the C<"-"> was meant to be some other
2017character, or should have been escaped (like C<"\-">). If you did
2018intend a range, the one that was used is not portable between ASCII and
2019EBCDIC platforms, and doesn't have an obvious meaning to a casual
2020reader.
2021
2022 [3-7] # OK; Obvious and portable
2023 [d-g] # OK; Obvious and portable
2024 [A-Y] # OK; Obvious and portable
2025 [A-z] # WRONG; Not portable; not clear what is meant
2026 [a-Z] # WRONG; Not portable; not clear what is meant
2027 [%-.] # WRONG; Not portable; not clear what is meant
2028 [\x41-Z] # WRONG; Not portable; not obvious to non-geek
2029
2030(You can force portability by specifying a Unicode range, which means that
2031the endpoints are specified by
2032L<C<\N{...}>|perlrecharclass/Character Ranges>, but the meaning may
2033still not be obvious.)
2034The stricter rules require that ranges that start or stop with an ASCII
93780ae6 2035character that is not a control have all their endpoints be a literal
eabfc7bc
RS
2036character, and not some escape sequence (like C<"\x41">), and the ranges
2037must be all digits, or all uppercase letters, or all lowercase letters.
2038
2039=item *
2040
2041L<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/">
2042
2043(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
2044
2045Stricter rules help to find typos and other errors. You included a
2046range, and at least one of the end points is a decimal digit. Under the
2047stricter rules, when this happens, both end points should be digits in
2048the same group of 10 consecutive digits.
2049
2050=item *
2051
2052L<Redundant argument in %s|perldiag/Redundant argument in %s>
2053
f5b97b22
DM
2054(W redundant) You called a function with more arguments than were
2055needed, as indicated by information within other arguments you supplied
ff25fcfb 2056(I<e.g>. a printf format). Currently only emitted when a printf-type format
f5b97b22 2057required fewer arguments than were supplied, but might be used in the
ff25fcfb 2058future for I<e.g.> L<perlfunc/pack>.
eabfc7bc 2059
a75e6a3a
SH
2060The warnings category C<< redundant >> is new. See also
2061L<[perl #121025]|https://rt.perl.org/Ticket/Display.html?id=121025>.
eabfc7bc
RS
2062
2063=item *
2064
e6205aca
KW
2065L<Replacement list is longer than search list|perldiag/Replacement list is longer than search list>
2066
2067This is not a new diagnostic, but in earlier releases was accidentally
2068not displayed if the transliteration contained wide characters. This is
2069now fixed, so that you may see this diagnostic in places where you
2070previously didn't (but should have).
2071
2072=item *
2073
eabfc7bc
RS
2074L<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">
2075
a2c7aad0 2076(W locale) You are matching a regular expression using locale rules,
eabfc7bc
RS
2077and a Unicode boundary is being matched, but the locale is not a Unicode
2078one. This doesn't make sense. Perl will continue, assuming a Unicode
2079(UTF-8) locale, but the results could well be wrong except if the locale
2080happens to be ISO-8859-1 (Latin1) where this message is spurious and can
2081be ignored.
2082
1bc134bc
KW
2083The warnings category C<locale> is new.
2084
eabfc7bc
RS
2085=item *
2086
2087L<< 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>" >>
2088
a2c7aad0 2089(W regexp) You used a Unicode boundary (C<\b{...}> or C<\B{...}>) in a
eabfc7bc
RS
2090portion of a regular expression where the character set modifiers C</a>
2091or C</aa> are in effect. These two modifiers indicate an ASCII
2092interpretation, and this doesn't make sense for a Unicode definition.
2093The generated regular expression will compile so that the boundary uses
2094all of Unicode. No other portion of the regular expression is affected.
2095
2096=item *
2097
2098L<The bitwise feature is experimental|perldiag/"The bitwise feature is experimental">
2099
a2c7aad0 2100(S experimental::bitwise) This warning is emitted if you use bitwise
eabfc7bc
RS
2101operators (C<& | ^ ~ &. |. ^. ~.>) with the "bitwise" feature enabled.
2102Simply suppress the warning if you want to use the feature, but know
2103that in doing so you are taking the risk of using an experimental
2104feature which may change or be removed in a future Perl version:
2105
2106 no warnings "experimental::bitwise";
2107 use feature "bitwise";
2108 $x |.= $y;
2109
2110=item *
2111
2112L<Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in mE<sol>%sE<sol>|perldiag/"Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/%s/">
2113
2114(D deprecated, regexp) You used a literal C<"{"> character in a regular
2115expression pattern. You should change to use C<"\{"> instead, because a future
2116version of Perl (tentatively v5.26) will consider this to be a syntax error. If
2117the pattern delimiters are also braces, any matching right brace
2118(C<"}">) should also be escaped to avoid confusing the parser, for
2119example,
2120
2121 qr{abc\{def\}ghi}
2122
2123=item *
2124
2125L<Use of literal non-graphic characters in variable names is deprecated|perldiag/"Use of literal non-graphic characters in variable names is deprecated">
2126
b0511669 2127(D deprecated) Using literal non-graphic (including control)
f0a38539 2128characters in the source to refer to the I<^FOO> variables, like C<$^X> and
b0511669
DM
2129C<${^GLOBAL_PHASE}> is now deprecated.
2130
eabfc7bc
RS
2131=item *
2132
2133L<Useless use of attribute "const"|perldiag/Useless use of attribute "const">
2134
f0a38539 2135(W misc) The C<const> attribute has no effect except
eabfc7bc
RS
2136on anonymous closure prototypes. You applied it to
2137a subroutine via L<attributes.pm|attributes>. This is only useful
2138inside an attribute handler for an anonymous subroutine.
2139
2140=item *
2141
e6205aca
KW
2142L<Useless use of E<sol>d modifier in transliteration operator|perldiag/"Useless use of /d modifier in transliteration operator">
2143
2144This is not a new diagnostic, but in earlier releases was accidentally
2145not displayed if the transliteration contained wide characters. This is
2146now fixed, so that you may see this diagnostic in places where you
2147previously didn't (but should have).
2148
2149=item *
2150
eabfc7bc
RS
2151L<E<quot>use re 'strict'E<quot> is experimental|perldiag/"use re 'strict'" is experimental>
2152
2153(S experimental::re_strict) The things that are different when a regular
2154expression pattern is compiled under C<'strict'> are subject to change
3b50e657
KW
2155in future Perl releases in incompatible ways; there are also proposals
2156to change how to enable strict checking instead of using this subpragma.
2157This means that a pattern that compiles today may not in a future Perl
2158release. This warning is to alert you to that risk.
eabfc7bc
RS
2159
2160=item *
2161
caa16dbd
TC
2162L<Warning: unable to close filehandle properly: %s|perldiag/"Warning: unable to close filehandle properly: %s">
2163
eabfc7bc
RS
2164L<Warning: unable to close filehandle %s properly: %s|perldiag/"Warning: unable to close filehandle %s properly: %s">
2165
3b50e657 2166(S io) Previously, perl silently ignored any errors when doing an implicit
ff25fcfb
KW
2167close of a filehandle, I<i.e.> where the reference count of the filehandle
2168reached zero and the user's code hadn't already called C<close()>; I<e.g.>
b0511669
DM
2169
2170 {
2171 open my $fh, '>', $file or die "open: '$file': $!\n";
2172 print $fh, $data or die;
2173 } # implicit close here
2174
3b50e657 2175In a situation such as disk full, due to buffering, the error may only be
b0511669
DM
2176detected during the final close, so not checking the result of the close is
2177dangerous.
2178
2179So perl now warns in such situations.
caa16dbd 2180
eabfc7bc
RS
2181=item *
2182
2183L<Wide character (U+%X) in %s|perldiag/"Wide character (U+%X) in %s">
2184
2185(W locale) While in a single-byte locale (I<i.e.>, a non-UTF-8
2186one), a multi-byte character was encountered. Perl considers this
50ea4745 2187character to be the specified Unicode code point. Combining non-UTF-8
eabfc7bc
RS
2188locales and Unicode is dangerous. Almost certainly some characters
2189will have two different representations. For example, in the ISO 8859-7
2190(Greek) locale, the code point 0xC3 represents a Capital Gamma. But so
2191also does 0x393. This will make string comparisons unreliable.
2192
2193You likely need to figure out how this multi-byte character got mixed up
2194with your single-byte locale (or perhaps you thought you had a UTF-8
2195locale, but Perl disagrees).
2196
1bc134bc
KW
2197The warnings category C<locale> is new.
2198
eabfc7bc
RS
2199=back
2200
2201=head2 Changes to Existing Diagnostics
2202
2203=over 4
2204
2205=item *
2206
2207<> should be quotes
2208
2209This warning has been changed to
2210L<< <> at require-statement should be quotes|perldiag/"<> at require-statement should be quotes" >>
2211to make the issue more identifiable.
2212
2213=item *
2214
2215L<Argument "%s" isn't numeric%s|perldiag/"Argument "%s" isn't numeric%s">
b0511669
DM
2216
2217The L<perldiag> entry for this warning has added this clarifying note:
eabfc7bc 2218
4ec8e6f0 2219 Note that for the Inf and NaN (infinity and not-a-number) the
77c2376a
KW
2220 definition of "numeric" is somewhat unusual: the strings themselves
2221 (like "Inf") are considered numeric, and anything following them is
2222 considered non-numeric.
eabfc7bc
RS
2223
2224=item *
2225
2226L<Global symbol "%s" requires explicit package name|perldiag/"Global symbol "%s" requires explicit package name (did you forget to declare "my %s"?)">
2227
2228This message has had '(did you forget to declare "my %s"?)' appended to it, to
2229make it more helpful to new Perl programmers.
2230L<[perl #121638]|https://rt.perl.org/Ticket/Display.html?id=121638>
2231
2232=item *
2233
2234'"my" variable &foo::bar can't be in a package' has been reworded to say
2235'subroutine' instead of 'variable'.
2236
2237=item *
2238
b0511669
DM
2239L<<< \N{} in character class restricted to one character in regex; marked by
2240S<< <-- HERE >> in mE<sol>%sE<sol>|perldiag/"\N{} in inverted character
2241class or as a range end-point is restricted to one character in regex;
2242marked by <-- HERE in m/%s/" >>>
eabfc7bc 2243
b0511669
DM
2244This message has had I<character class> changed to I<inverted character
2245class or as a range end-point is> to reflect improvements in
2246C<qr/[\N{named sequence}]/> (see under L</Selected Bug Fixes>).
eabfc7bc
RS
2247
2248=item *
2249
2250L<panic: frexp|perldiag/"panic: frexp: %f">
2251
b0511669
DM
2252This message has had ': C<%f>' appended to it, to show what the offending
2253floating point number is.
eabfc7bc
RS
2254
2255=item *
2256
b0511669 2257I<Possible precedence problem on bitwise %c operator> reworded as
eabfc7bc
RS
2258L<Possible precedence problem on bitwise %s operator|perldiag/"Possible precedence problem on bitwise %s operator">.
2259
2260=item *
2261
eabfc7bc
RS
2262L<Unsuccessful %s on filename containing newline|perldiag/"Unsuccessful %s on filename containing newline">
2263
2264This warning is now only produced when the newline is at the end of
2265the filename.
2266
2267=item *
2268
4ec8e6f0 2269"Variable C<%s> will not stay shared" has been changed to say "Subroutine"
eabfc7bc
RS
2270when it is actually a lexical sub that will not stay shared.
2271
2272=item *
2273
2274L<Variable length lookbehind not implemented in regex mE<sol>%sE<sol>|perldiag/"Variable length lookbehind not implemented in regex m/%s/">
2275
b0511669
DM
2276The L<perldiag> entry for this warning has had information about Unicode
2277behaviour added.
eabfc7bc
RS
2278
2279=back
2280
2281=head2 Diagnostic Removals
2282
2283=over
2284
2285=item *
2286
2287"Ambiguous use of -foo resolved as -&foo()"
2288
2289There is actually no ambiguity here, and this impedes the use of negated
ff25fcfb 2290constants; I<e.g.>, C<-Inf>.
eabfc7bc
RS
2291
2292=item *
2293
2294"Constant is not a FOO reference"
2295
ff25fcfb 2296Compile-time checking of constant dereferencing (I<e.g.>, C<< my_constant->() >>)
eabfc7bc
RS
2297has been removed, since it was not taking overloading into account.
2298L<[perl #69456]|https://rt.perl.org/Ticket/Display.html?id=69456>
2299L<[perl #122607]|https://rt.perl.org/Ticket/Display.html?id=122607>
2300
2301=back
2302
2303=head1 Utility Changes
2304
b0511669 2305=head2 F<find2perl>, F<s2p> and F<a2p> removal
eabfc7bc
RS
2306
2307=over 4
2308
2309=item *
2310
2311The F<x2p/> directory has been removed from the Perl core.
2312
2313This removes find2perl, s2p and a2p. They have all been released to CPAN as
f0a38539 2314separate distributions (C<App::find2perl>, C<App::s2p>, C<App::a2p>).
eabfc7bc
RS
2315
2316=back
2317
2318=head2 L<h2ph>
2319
2320=over 4
2321
2322=item *
2323
2324F<h2ph> now handles hexadecimal constants in the compiler's predefined
a75e6a3a
SH
2325macro definitions, as visible in C<$Config{cppsymbols}>.
2326L<[perl #123784]|https://rt.perl.org/Ticket/Display.html?id=123784>.
eabfc7bc
RS
2327
2328=back
2329
2330=head2 L<encguess>
2331
2332=over 4
2333
2334=item *
2335
f1c9eac6 2336No longer depends on non-core modules.
eabfc7bc
RS
2337
2338=back
2339
2340=head1 Configuration and Compilation
2341
2342=over 4
2343
2344=item *
2345
b0511669
DM
2346F<Configure> now checks for C<lrintl()>, C<lroundl()>, C<llrintl()>, and
2347C<llroundl()>.
eabfc7bc
RS
2348
2349=item *
2350
a75e6a3a
SH
2351F<Configure> with C<-Dmksymlinks> should now be faster.
2352L<[perl #122002]|https://rt.perl.org/Ticket/Display.html?id=122002>.
eabfc7bc
RS
2353
2354=item *
2355
b0511669
DM
2356The C<pthreads> and C<cl> libraries will be linked by default if present.
2357This allows XS modules that require threading to work on non-threaded
2358perls. Note that you must still pass C<-Dusethreads> if you want a
2359threaded perl.
eabfc7bc
RS
2360
2361=item *
2362
2363For long doubles (to get more precision and range for floating point numbers)
2364one can now use the GCC quadmath library which implements the quadruple
f1c9eac6
DM
2365precision floating point numbers on x86 and IA-64 platforms. See
2366F<INSTALL> for details.
eabfc7bc
RS
2367
2368=item *
2369
2370MurmurHash64A and MurmurHash64B can now be configured as the internal hash
2371function.
2372
2373=item *
2374
2375C<make test.valgrind> now supports parallel testing.
2376
2377For example:
2378
2379 TEST_JOBS=9 make test.valgrind
2380
2381See L<perlhacktips/valgrind> for more information.
2382
2383L<[perl #121431]|https://rt.perl.org/Ticket/Display.html?id=121431>
2384
2385=item *
2386
2387The MAD (Misc Attribute Decoration) build option has been removed
2388
2389This was an unmaintained attempt at preserving
2390the Perl parse tree more faithfully so that automatic conversion of
2391Perl 5 to Perl 6 would have been easier.
2392
2393This build-time configuration option had been unmaintained for years,
2394and had probably seriously diverged on both Perl 5 and Perl 6 sides.
2395
2396=item *
2397
2398A new compilation flag, C<< -DPERL_OP_PARENT >> is available. For details,
2399see the discussion below at L<< /Internal Changes >>.
2400
43831b1f
DM
2401=item *
2402
2403Pathtools no longer tries to load XS on miniperl. This speeds up building perl
2404slightly.
2405
eabfc7bc
RS
2406=back
2407
2408=head1 Testing
2409
2410=over 4
2411
2412=item *
2413
2414F<t/porting/re_context.t> has been added to test that L<utf8> and its
2415dependencies only use the subset of the C<$1..$n> capture vars that
b0511669
DM
2416C<Perl_save_re_context()> is hard-coded to localize, because that function
2417has no efficient way of determining at runtime what vars to localize.
eabfc7bc
RS
2418
2419=item *
2420
2421Tests for performance issues have been added in the file F<t/perf/taint.t>.
2422
2423=item *
2424
2425Some regular expression tests are written in such a way that they will
2426run very slowly if certain optimizations break. These tests have been
2427moved into new files, F<< t/re/speed.t >> and F<< t/re/speed_thr.t >>,
2428and are run with a C<< watchdog() >>.
2429
2430=item *
2431
2432C<< test.pl >> now allows C<< plan skip_all => $reason >>, to make it
2433more compatible with C<< Test::More >>.
2434
2435=item *
2436
3b50e657 2437A new test script, F<op/infnan.t>, has been added to test if infinity and NaN are
eabfc7bc
RS
2438working correctly. See L</Infinity and NaN (not-a-number) handling improved>.
2439
2440=back
2441
2442=head1 Platform Support
2443
2444=head2 Regained Platforms
2445
2446=over 4
2447
2448=item IRIX and Tru64 platforms are working again.
2449
2450(Some C<make test> failures remain.)
2451
2452=item z/OS running EBCDIC Code Page 1047
2453
2454Core perl now works on this EBCDIC platform. Earlier perls also worked, but,
2455even though support wasn't officially withdrawn, recent perls would not compile
2456and run well. Perl 5.20 would work, but had many bugs which have now been
2457fixed. Many CPAN modules that ship with Perl still fail tests, including
f0a38539 2458C<Pod::Simple>. However the version of C<Pod::Simple> currently on CPAN should work;
eabfc7bc
RS
2459it was fixed too late to include in Perl 5.22. Work is under way to fix many
2460of the still-broken CPAN modules, which likely will be installed on CPAN when
2461completed, so that you may not have to wait until Perl 5.24 to get a working
2462version.
2463
2464=back
2465
2466=head2 Discontinued Platforms
2467
2468=over 4
2469
2470=item NeXTSTEP/OPENSTEP
2471
f1c9eac6
DM
2472NeXTSTEP was a proprietary operating system bundled with NeXT's
2473workstations in the early to mid 90s; OPENSTEP was an API specification
2474that provided a NeXTSTEP-like environment on a non-NeXTSTEP system. Both
2475are now long dead, so support for building Perl on them has been removed.
eabfc7bc
RS
2476
2477=back
2478
2479=head2 Platform-Specific Notes
2480
2481=over 4
2482
2483=item EBCDIC
2484
3b50e657
KW
2485Special handling is required of the perl interpreter on EBCDIC platforms
2486to get C<qr/[i-j]/> to match only C<"i"> and C<"j">, since there are 7
2487characters between the
eabfc7bc
RS
2488code points for C<"i"> and C<"j">. This special handling had only been
2489invoked when both ends of the range are literals. Now it is also
2490invoked if any of the C<\N{...}> forms for specifying a character by
2491name or Unicode code point is used instead of a literal. See
2492L<perlrecharclass/Character Ranges>.
2493
2494=item HP-UX
2495
2496The archname now distinguishes use64bitint from use64bitall.
2497
2498=item Android
2499
2500Build support has been improved for cross-compiling in general and for
2501Android in particular.
2502
2503=item VMS
2504
2505=over 4
2506
2507=item *
2508
2509When spawning a subprocess without waiting, the return value is now
2510the correct PID.
2511
2512=item *
2513
2514Fix a prototype so linking doesn't fail under the VMS C++ compiler.
2515
2516=item *
2517
2518C<finite>, C<finitel>, and C<isfinite> detection has been added to
2519C<configure.com>, environment handling has had some minor changes, and
2520a fix for legacy feature checking status.
2521
2522=back
2523
2524=item Win32
2525
2526=over 4
2527
2528=item *
2529
2530F<miniperl.exe> is now built with C<-fno-strict-aliasing>, allowing 64-bit
2531builds to complete on GCC 4.8.
2532L<[perl #123976]|https://rt.perl.org/Ticket/Display.html?id=123976>
2533
2534=item *
2535
17fcdc49
TC
2536C<nmake minitest> now works on Win32. Due to dependency issues you
2537need to build C<nmake test-prep> first, and a small number of the
2538tests fail.
2539L<[perl #123394]|https://rt.perl.org/Ticket/Display.html?id=123394>
2540
2541=item *
2542
eabfc7bc
RS
2543Perl can now be built in C++ mode on Windows by setting the makefile macro
2544C<USE_CPLUSPLUS> to the value "define".
2545
2546=item *
2547
d140c31c 2548The list form of piped open has been implemented for Win32. Note: unlike
00eebae1 2549C<system LIST> this does not fall back to the shell.
18f4cc8e 2550L<[perl #121159]|https://rt.perl.org/Ticket/Display.html?id=121159>
eabfc7bc
RS
2551
2552=item *
2553
eabfc7bc
RS
2554New C<DebugSymbols> and C<DebugFull> configuration options added to
2555Windows makefiles.
2556
2557=item *
2558
f1c9eac6 2559Previously compiling XS modules (including CPAN ones) using Visual C++ for
b0511669 2560Win64 resulted in around a dozen warnings per file from F<hv_func.h>. These
f1c9eac6 2561warnings have been silenced.
eabfc7bc
RS
2562
2563=item *
2564
2565Support for building without PerlIO has been removed from the Windows
2566makefiles. Non-PerlIO builds were all but deprecated in Perl 5.18.0 and are
2567already not supported by F<Configure> on POSIX systems.
2568
2569=item *
2570
d140c31c
AC
2571Between 2 and 6 milliseconds and seven I/O calls have been saved per attempt
2572to open a perl module for each path in C<@INC>.
eabfc7bc
RS
2573
2574=item *
2575
2576Intel C builds are now always built with C99 mode on.
2577
2578=item *
2579
2580C<%I64d> is now being used instead of C<%lld> for MinGW.
2581
2582=item *
2583
2584In the experimental C<:win32> layer, a crash in C<open> was fixed. Also
3209f716 2585opening F</dev/null> (which works under Win32 Perl's default C<:unix>
d140c31c 2586layer) was implemented for C<:win32>.
eabfc7bc
RS
2587L<[perl #122224]|https://rt.perl.org/Ticket/Display.html?id=122224>
2588
2589=item *
2590
2591A new makefile option, C<USE_LONG_DOUBLE>, has been added to the Windows
2592dmake makefile for gcc builds only. Set this to "define" if you want perl to
2593use long doubles to give more accuracy and range for floating point numbers.
2594
2595=back
2596
2597=item OpenBSD
2598
2599On OpenBSD, Perl will now default to using the system C<malloc> due to the
2600security features it provides. Perl's own malloc wrapper has been in use
2601since v5.14 due to performance reasons, but the OpenBSD project believes
2602the tradeoff is worth it and would prefer that users who need the speed
2603specifically ask for it.
2604
2605L<[perl #122000]|https://rt.perl.org/Ticket/Display.html?id=122000>.
2606
2607=item Solaris
2608
2609=over 4
2610
2611=item *
2612
2613We now look for the Sun Studio compiler in both F</opt/solstudio*> and
2614F</opt/solarisstudio*>.
2615
2616=item *
2617
2618Builds on Solaris 10 with C<-Dusedtrace> would fail early since make
2619didn't follow implied dependencies to build C<perldtrace.h>. Added an
2620explicit dependency to C<depend>.
2621L<[perl #120120]|https://rt.perl.org/Ticket/Display.html?id=120120>
2622
2623=item *
2624
f0a38539 2625C99 options have been cleaned up; hints look for C<solstudio>
d140c31c 2626as well as C<SUNWspro>; and support for native C<setenv> has been added.
eabfc7bc
RS
2627
2628=back
2629
2630=back
2631
2632=head1 Internal Changes
2633
2634=over 4
2635
2636=item *
2637
bad0181b
DM
2638Experimental support has been added to allow ops in the optree to locate
2639their parent, if any. This is enabled by the non-default build option
2640C<-DPERL_OP_PARENT>. It is envisaged that this will eventually become
b0511669 2641enabled by default, so XS code which directly accesses the C<op_sibling>
bad0181b 2642field of ops should be updated to be future-proofed.
eabfc7bc
RS
2643
2644On C<PERL_OP_PARENT> builds, the C<op_sibling> field has been renamed
bad0181b
DM
2645C<op_sibparent> and a new flag, C<op_moresib>, added. On the last op in a
2646sibling chain, C<op_moresib> is false and C<op_sibparent> points to the
b0511669 2647parent (if any) rather than being C<NULL>.
bad0181b 2648
b0511669 2649To make existing code work transparently whether using C<PERL_OP_PARENT>
bad0181b
DM
2650or not, a number of new macros and functions have been added that should
2651be used, rather than directly manipulating C<op_sibling>.
2652
2653For the case of just reading C<op_sibling> to determine the next sibling,
2654two new macros have been added. A simple scan through a sibling chain
2655like this:
2656
b0511669 2657 for (; kid->op_sibling; kid = kid->op_sibling) { ... }
bad0181b
DM
2658
2659should now be written as:
2660
b0511669 2661 for (; OpHAS_SIBLING(kid); kid = OpSIBLING(kid)) { ... }
bad0181b 2662
d140c31c 2663For altering optrees, a general-purpose function C<op_sibling_splice()>
bad0181b
DM
2664has been added, which allows for manipulation of a chain of sibling ops.
2665By analogy with the Perl function C<splice()>, it allows you to cut out
2666zero or more ops from a sibling chain and replace them with zero or more
2667new ops. It transparently handles all the updating of sibling, parent,
2668op_last pointers etc.
2669
2670If you need to manipulate ops at a lower level, then three new macros,
2671C<OpMORESIB_set>, C<OpLASTSIB_set> and C<OpMAYBESIB_set> are intended to
2672be a low-level portable way to set C<op_sibling> / C<op_sibparent> while
2673also updating C<op_moresib>. The first sets the sibling pointer to a new
2674sibling, the second makes the op the last sibling, and the third
2675conditionally does the first or second action. Note that unlike
2676C<op_sibling_splice()> these macros won't maintain consistency in the
ff25fcfb 2677parent at the same time (I<e.g.> by updating C<op_first> and C<op_last> where
bad0181b
DM
2678appropriate).
2679
d140c31c 2680A C-level C<Perl_op_parent()> function and a Perl-level C<B::OP::parent()>
bad0181b 2681method have been added. The C function only exists under
b0511669 2682C<PERL_OP_PARENT> builds (using it is build-time error on vanilla
bad0181b 2683perls). C<B::OP::parent()> exists always, but on a vanilla build it
b0511669 2684always returns C<NULL>. Under C<PERL_OP_PARENT>, they return the parent
bad0181b
DM
2685of the current op, if any. The variable C<$B::OP::does_parent> allows you
2686to determine whether C<B> supports retrieving an op's parent.
2687
b0511669 2688C<PERL_OP_PARENT> was introduced in 5.21.2, but the interface was
bad0181b
DM
2689changed considerably in 5.21.11. If you updated your code before the
26905.21.11 changes, it may require further revision. The main changes after
26915.21.2 were:
eabfc7bc 2692
bad0181b 2693=over 4
eabfc7bc
RS
2694
2695=item *
2696
bad0181b
DM
2697The C<OP_SIBLING> and C<OP_HAS_SIBLING> macros have been renamed
2698C<OpSIBLING> and C<OpHAS_SIBLING> for consistency with other
2699op-manipulating macros.
eabfc7bc
RS
2700
2701=item *
2702
bad0181b
DM
2703The C<op_lastsib> field has been renamed C<op_moresib>, and its meaning
2704inverted.
eabfc7bc
RS
2705
2706=item *
2707
bad0181b 2708The macro C<OpSIBLING_set> has been removed, and has been superseded by
ff25fcfb 2709C<OpMORESIB_set> I<et al>.
eabfc7bc
RS
2710
2711=item *
2712
bad0181b
DM
2713The C<op_sibling_splice()> function now accepts a null C<parent> argument
2714where the splicing doesn't affect the first or last ops in the sibling
2715chain
eabfc7bc
RS
2716
2717=back
2718
2719=item *
2720
2721Macros have been created to allow XS code to better manipulate the POSIX locale
2722category C<LC_NUMERIC>. See L<perlapi/Locale-related functions and macros>.
2723
2724=item *
2725
ff25fcfb 2726The previous C<atoi> I<et al> replacement function, C<grok_atou>, has now been
eabfc7bc
RS
2727superseded by C<grok_atoUV>. See L<perlclib> for details.
2728
2729=item *
2730
b0511669
DM
2731A new function, C<Perl_sv_get_backrefs()>, has been added which allows you
2732retrieve the weak references, if any, which point at an SV.
eabfc7bc
RS
2733
2734=item *
2735
b0511669 2736The C<screaminstr()> function has been removed. Although marked as
f1c9eac6
DM
2737public API, it was undocumented and had no usage in CPAN modules. Calling
2738it has been fatal since 5.17.0.
eabfc7bc
RS
2739
2740=item *
2741
b0511669
DM
2742The C<newDEFSVOP()>, C<block_start()>, C<block_end()> and C<intro_my()>
2743functions have been added to the API.
eabfc7bc
RS
2744
2745=item *
2746
2747The internal C<convert> function in F<op.c> has been renamed
2748C<op_convert_list> and added to the API.
2749
2750=item *
2751
b0511669
DM
2752The C<sv_magic()> function no longer forbids "ext" magic on read-only
2753values. After all, perl can't know whether the custom magic will modify
2754the SV or not.
a75e6a3a 2755L<[perl #123103]|https://rt.perl.org/Ticket/Display.html?id=123103>.
eabfc7bc
RS
2756
2757=item *
2758
d140c31c
AC
2759Accessing L<perlapi/CvPADLIST> on an XSUB is now forbidden.
2760
cca58a48
DM
2761The C<CvPADLIST> field has been reused for a different internal purpose
2762for XSUBs. So in particular, you can no longer rely on it being NULL as a
2763test of whether a CV is an XSUB. Use C<CvISXSUB()> instead.
2764
eabfc7bc
RS
2765=item *
2766
b0511669 2767SVs of type C<SVt_NV> are now sometimes bodiless when the build
cca58a48 2768configuration and platform allow it: specifically, when C<< sizeof(NV) <=
b0511669 2769sizeof(IV) >>. "Bodiless" means that the NV value is stored directly in
cca58a48
DM
2770the head of an SV, without requiring a separate body to be allocated. This
2771trick has already been used for IVs since 5.9.2 (though in the case of
2772IVs, it is always used, regardless of platform and build configuration).
eabfc7bc
RS
2773
2774=item *
2775
b0511669 2776The C<$DB::single>, C<$DB::signal> and C<$DB::trace> variables now have set- and
d140c31c 2777get-magic that stores their values as IVs, and those IVs are used when
b0511669 2778testing their values in C<pp_dbstate()>. This prevents perl from
f1c9eac6 2779recursing infinitely if an overloaded object is assigned to any of those
a75e6a3a
SH
2780variables.
2781L<[perl #122445]|https://rt.perl.org/Ticket/Display.html?id=122445>.
eabfc7bc
RS
2782
2783=item *
2784
b0511669 2785C<Perl_tmps_grow()>, which is marked as public API but is undocumented, has
d140c31c 2786been removed from the public API. This change does not affect XS code that
b0511669 2787uses the C<EXTEND_MORTAL> macro to pre-extend the mortal stack.
eabfc7bc
RS
2788
2789=item *
2790
b0511669
DM
2791Perl's internals no longer sets or uses the C<SVs_PADMY> flag.
2792C<SvPADMY()> now returns a true value for anything not marked C<PADTMP>
2793and C<SVs_PADMY> is now defined as 0.
eabfc7bc
RS
2794
2795=item *
2796
d140c31c 2797The macros C<SETsv> and C<SETsvUN> have been removed. They were no longer used
b0511669
DM
2798in the core since commit 6f1401dc2a five years ago, and have not been
2799found present on CPAN.
eabfc7bc
RS
2800
2801=item *
2802
2803The C<< SvFAKE >> bit (unused on HVs) got informally reserved by
2804David Mitchell for future work on vtables.
2805
2806=item *
2807
b0511669 2808The C<sv_catpvn_flags()> function accepts C<SV_CATBYTES> and C<SV_CATUTF8>
50ea4745 2809flags, which specify whether the appended string is bytes or UTF-8,
b0511669
DM
2810respectively. (These flags have in fact been present since 5.16.0, but
2811were formerly not regarded as part of the API.)
eabfc7bc
RS
2812
2813=item *
2814
f1c9eac6 2815A new opcode class, C<< METHOP >>, has been introduced. It holds
d140c31c 2816information used at runtime for improve the performance
eabfc7bc
RS
2817of class/object method calls.
2818
d140c31c 2819C<< OP_METHOD >> and C<< OP_METHOD_NAMED >> have changed from being
eabfc7bc
RS
2820C<< UNOP/SVOP >> to being C<< METHOP >>.
2821
2822=item *
2823
b0511669
DM
2824C<cv_name()> is a new API function that can be passed a CV or GV. It
2825returns an SV containing the name of the subroutine, for use in
2826diagnostics.
eabfc7bc 2827
eabfc7bc
RS
2828L<[perl #116735]|https://rt.perl.org/Ticket/Display.html?id=116735>
2829L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
2830
2831=item *
2832
b0511669
DM
2833C<cv_set_call_checker_flags()> is a new API function that works like
2834C<cv_set_call_checker()>, except that it allows the caller to specify
2835whether the call checker requires a full GV for reporting the subroutine's
2836name, or whether it could be passed a CV instead. Whatever value is
2837passed will be acceptable to C<cv_name()>. C<cv_set_call_checker()>
2838guarantees there will be a GV, but it may have to create one on the fly,
2839which is inefficient.
eabfc7bc
RS
2840L<[perl #116735]|https://rt.perl.org/Ticket/Display.html?id=116735>
2841
2842=item *
2843
2844C<CvGV> (which is not part of the API) is now a more complex macro, which may
b0511669 2845call a function and reify a GV. For those cases where it has been used as a
eabfc7bc
RS
2846boolean, C<CvHASGV> has been added, which will return true for CVs that
2847notionally have GVs, but without reifying the GV. C<CvGV> also returns a GV
2848now for lexical subs.
2849L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
2850
2851=item *
2852
d140c31c
AC
2853The L<perlapi/sync_locale> function has been added to the public API.
2854Changing the program's locale should be avoided by XS code. Nevertheless,
2855certain non-Perl libraries called from XS need to do so, such as C<Gtk>.
2856When this happens, Perl needs to be told that the locale has
eabfc7bc
RS
2857changed. Use this function to do so, before returning to Perl.
2858
2859=item *
2860
2861The defines and labels for the flags in the C<op_private> field of OPs are now
2862auto-generated from data in F<regen/op_private>. The noticeable effect of this
2863is that some of the flag output of C<Concise> might differ slightly, and the
3209f716 2864flag output of S<C<perl -Dx>> may differ considerably (they both use the same set
d140c31c
AC
2865of labels now). Also, debugging builds now have a new assertion in
2866C<op_free()> to ensure that the op doesn't have any unrecognized flags set in
eabfc7bc
RS
2867C<op_private>.
2868
2869=item *
2870
eabfc7bc
RS
2871The deprecated variable C<PL_sv_objcount> has been removed.
2872
2873=item *
2874
2875Perl now tries to keep the locale category C<LC_NUMERIC> set to "C"
2876except around operations that need it to be set to the program's
2877underlying locale. This protects the many XS modules that cannot cope
2878with the decimal radix character not being a dot. Prior to this
2879release, Perl initialized this category to "C", but a call to
2880C<POSIX::setlocale()> would change it. Now such a call will change the
2881underlying locale of the C<LC_NUMERIC> category for the program, but the
ce93e38b
KW
2882locale exposed to XS code will remain "C". There are new macros
2883to manipulate the LC_NUMERIC locale, including
2884C<STORE_LC_NUMERIC_SET_TO_NEEDED> and
2885C<STORE_LC_NUMERIC_FORCE_TO_UNDERLYING>.
2886See L<perlapi/Locale-related functions and macros>.
eabfc7bc
RS
2887
2888=item *
2889
2890A new macro L<C<isUTF8_CHAR>|perlapi/isUTF8_CHAR> has been written which
2891efficiently determines if the string given by its parameters begins
2892with a well-formed UTF-8 encoded character.
2893
2894=item *
2895
b0511669 2896The following private API functions had their context parameter removed:
eabfc7bc
RS
2897C<Perl_cast_ulong>, C<Perl_cast_i32>, C<Perl_cast_iv>, C<Perl_cast_uv>,
2898C<Perl_cv_const_sv>, C<Perl_mg_find>, C<Perl_mg_findext>, C<Perl_mg_magical>,
2899C<Perl_mini_mktime>, C<Perl_my_dirfd>, C<Perl_sv_backoff>, C<Perl_utf8_hop>.
2900
cca58a48
DM
2901Note that the prefix-less versions of those functions that are part of the
2902public API, such as C<cast_i32()>, remain unaffected.
eabfc7bc
RS
2903
2904=item *
2905
b0511669
DM
2906The C<PADNAME> and C<PADNAMELIST> types are now separate types, and no
2907longer simply aliases for SV and AV.
a75e6a3a 2908L<[perl #123223]|https://rt.perl.org/Ticket/Display.html?id=123223>.
eabfc7bc
RS
2909
2910=item *
2911
50ea4745 2912Pad names are now always UTF-8. The C<PadnameUTF8> macro always returns
eabfc7bc
RS
2913true. Previously, this was effectively the case already, but any support
2914for two different internal representations of pad names has now been
2915removed.
2916
2917=item *
2918
eabfc7bc
RS
2919A new op class, C<UNOP_AUX>, has been added. This is a subclass of
2920C<UNOP> with an C<op_aux> field added, which points to an array of unions
f0a38539 2921of UV, SV* etc. It is intended for where an op needs to store more data
eabfc7bc
RS
2922than a simple C<op_sv> or whatever. Currently the only op of this type is
2923C<OP_MULTIDEREF> (see below).
2924
2925=item *
2926
2927A new op has been added, C<OP_MULTIDEREF>, which performs one or more
2928nested array and hash lookups where the key is a constant or simple
2929variable. For example the expression C<$a[0]{$k}[$i]>, which previously
2930involved ten C<rv2Xv>, C<Xelem>, C<gvsv> and C<const> ops is now performed
2931by a single C<multideref> op. It can also handle C<local>, C<exists> and
2932C<delete>. A non-simple index expression, such as C<[$i+1]> is still done
77c2376a 2933using C<aelem>/C<helem>, and single-level array lookup with a small constant
eabfc7bc
RS
2934index is still done using C<aelemfast>.
2935
2936=back
2937
2938=head1 Selected Bug Fixes
2939
2940=over 4
2941
2942=item *
2943
2f737055
RS
2944C<close> now sets C<$!>
2945
2946When an I/O error occurs, the fact that there has been an error is recorded
2947in the handle. C<close> returns false for such a handle. Previously, the
2948value of C<$!> would be untouched by C<close>, so the common convention of
2949writing S<C<close $fh or die $!>> did not work reliably. Now the handle
2950records the value of C<$!>, too, and C<close> restores it.
2951
2952=item *
2953
d6d147bf
KW
2954C<no re> now can turn off everything that C<use re> enables
2955
2956Previously, running C<no re> would turn off only a few things. Now it
2957can turn off all the enabled things. For example, the only way to
2958stop debugging, once enabled, was to exit the enclosing block; that is
2959now fixed.
2960
2961=item *
2962
33ca8d3c
DM
2963C<pack("D", $x)> and C<pack("F", $x)> now zero the padding on x86 long
2964double builds. Under some build options on GCC 4.8 and later, they used
2965to either overwrite the zero-initialized padding, or bypass the
2966initialized buffer entirely. This caused F<op/pack.t> to fail.
eabfc7bc
RS
2967L<[perl #123971]|https://rt.perl.org/Ticket/Display.html?id=123971>
2968
2969=item *
2970
2971Extending an array cloned from a parent thread could result in "Modification of
2972a read-only value attempted" errors when attempting to modify the new elements.
2973L<[perl #124127]|https://rt.perl.org/Ticket/Display.html?id=124127>
2974
2975=item *
2976
2977An assertion failure and subsequent crash with C<< *x=<y> >> has been fixed.
2978L<[perl #123790]|https://rt.perl.org/Ticket/Display.html?id=123790>
2979
2980=item *
2981
33ca8d3c
DM
2982A possible crashing/looping bug related to compiling lexical subs has been
2983fixed.
eabfc7bc
RS
2984L<[perl #124099]|https://rt.perl.org/Ticket/Display.html?id=124099>
2985
2986=item *
2987
d140c31c
AC
2988UTF-8 now works correctly in function names, in unquoted HERE-document
2989terminators, and in variable names used as array indexes.
eabfc7bc
RS
2990L<[perl #124113]|https://rt.perl.org/Ticket/Display.html?id=124113>
2991
2992=item *
2993
2994Repeated global pattern matches in scalar context on large tainted strings were
2995exponentially slow depending on the current match position in the string.
2996L<[perl #123202]|https://rt.perl.org/Ticket/Display.html?id=123202>
2997
2998=item *
2999
3000Various crashes due to the parser getting confused by syntax errors have been
3001fixed.
3002L<[perl #123801]|https://rt.perl.org/Ticket/Display.html?id=123801>
3003L<[perl #123802]|https://rt.perl.org/Ticket/Display.html?id=123802>
3004L<[perl #123955]|https://rt.perl.org/Ticket/Display.html?id=123955>
3005L<[perl #123995]|https://rt.perl.org/Ticket/Display.html?id=123995>
3006
3007=item *
3008
d140c31c 3009C<split> in the scope of lexical C<$_> has been fixed not to fail assertions.
eabfc7bc
RS
3010L<[perl #123763]|https://rt.perl.org/Ticket/Display.html?id=123763>
3011
3012=item *
3013
3014C<my $x : attr> syntax inside various list operators no longer fails
3015assertions.
3016L<[perl #123817]|https://rt.perl.org/Ticket/Display.html?id=123817>
3017
3018=item *
3019
4ec8e6f0 3020An C<@> sign in quotes followed by a non-ASCII digit (which is not a valid
33ca8d3c
DM
3021identifier) would cause the parser to crash, instead of simply trying the
3022C<@> as literal. This has been fixed.
eabfc7bc
RS
3023L<[perl #123963]|https://rt.perl.org/Ticket/Display.html?id=123963>
3024
3025=item *
3026
3027C<*bar::=*foo::=*glob_with_hash> has been crashing since Perl 5.14, but no
3028longer does.
3029L<[perl #123847]|https://rt.perl.org/Ticket/Display.html?id=123847>
3030
3031=item *
3032
3033C<foreach> in scalar context was not pushing an item on to the stack, resulting
33ca8d3c
DM
3034in bugs. (S<C<print 4, scalar do { foreach(@x){} } + 1>> would print 5.)
3035It has been fixed to return C<undef>.
eabfc7bc
RS
3036L<[perl #124004]|https://rt.perl.org/Ticket/Display.html?id=124004>
3037
3038=item *
3039
eabfc7bc
RS
3040Several cases of data used to store environment variable contents in core C
3041code being potentially overwritten before being used have been fixed.
3042L<[perl #123748]|https://rt.perl.org/Ticket/Display.html?id=123748>
3043
3044=item *
3045
33ca8d3c
DM
3046Some patterns starting with C</.*..../> matched against long strings have
3047been slow since v5.8, and some of the form C</.*..../i> have been slow
3048since v5.18. They are now all fast again.
a75e6a3a 3049L<[perl #123743]|https://rt.perl.org/Ticket/Display.html?id=123743>.
eabfc7bc
RS
3050
3051=item *
3052
3053The original visible value of C<$/> is now preserved when it is set to
3054an invalid value. Previously if you set C<$/> to a reference to an
3055array, for example, perl would produce a runtime error and not set
3056C<PL_rs>, but perl code that checked C<$/> would see the array
a75e6a3a
SH
3057reference.
3058L<[perl #123218]|https://rt.perl.org/Ticket/Display.html?id=123218>.
eabfc7bc
RS
3059
3060=item *
3061
3062In a regular expression pattern, a POSIX class, like C<[:ascii:]>, must
93780ae6 3063be inside a bracketed character class, like C<qr/[[:ascii:]]/>. A
eabfc7bc
RS
3064warning is issued when something looking like a POSIX class is not
3065inside a bracketed class. That warning wasn't getting generated when
3066the POSIX class was negated: C<[:^ascii:]>. This is now fixed.
3067
3068=item *
3069
3209f716 3070Perl 5.14.0 introduced a bug whereby S<C<eval { LABEL: }>> would crash. This
a75e6a3a
SH
3071has been fixed.
3072L<[perl #123652]|https://rt.perl.org/Ticket/Display.html?id=123652>.
eabfc7bc
RS
3073
3074=item *
3075
3076Various crashes due to the parser getting confused by syntax errors have
a75e6a3a
SH
3077been fixed.
3078L<[perl #123617]|https://rt.perl.org/Ticket/Display.html?id=123617>.
3079L<[perl #123737]|https://rt.perl.org/Ticket/Display.html?id=123737>.
3080L<[perl #123753]|https://rt.perl.org/Ticket/Display.html?id=123753>.
3081L<[perl #123677]|https://rt.perl.org/Ticket/Display.html?id=123677>.
eabfc7bc
RS
3082
3083=item *
3084
3085Code like C</$a[/> used to read the next line of input and treat it as
3086though it came immediately after the opening bracket. Some invalid code
3087consequently would parse and run, but some code caused crashes, so this is
a75e6a3a
SH
3088now disallowed.
3089L<[perl #123712]|https://rt.perl.org/Ticket/Display.html?id=123712>.
eabfc7bc
RS
3090
3091=item *
3092
a75e6a3a
SH
3093Fix argument underflow for C<pack>.
3094L<[perl #123874]|https://rt.perl.org/Ticket/Display.html?id=123874>.
eabfc7bc
RS
3095
3096=item *
3097
3098Fix handling of non-strict C<\x{}>. Now C<\x{}> is equivalent to C<\x{0}>
3099instead of faulting.
3100
3101=item *
3102
3103C<stat -t> is now no longer treated as stackable, just like C<-t stat>.
a75e6a3a 3104L<[perl #123816]|https://rt.perl.org/Ticket/Display.html?id=123816>.
eabfc7bc
RS
3105
3106=item *
3107
3108The following no longer causes a SEGV: C<qr{x+(y(?0))*}>.
3109
3110=item *
3111
3112Fixed infinite loop in parsing backrefs in regexp patterns.
3113
3114=item *
3115
3b50e657
KW
3116Several minor bug fixes in behavior of Infinity and NaN, including
3117warnings when stringifying Infinity-like or NaN-like strings. For example,
eabfc7bc
RS
3118"NaNcy" doesn't numify to NaN anymore.
3119
3120=item *
3121
eabfc7bc
RS
3122A bug in regular expression patterns that could lead to segfaults and
3123other crashes has been fixed. This occurred only in patterns compiled
d140c31c
AC
3124with C</i> while taking into account the current POSIX locale (which usually
3125means they have to be compiled within the scope of C<S<use locale>>),
eabfc7bc 3126and there must be a string of at least 128 consecutive bytes to match.
a75e6a3a 3127L<[perl #123539]|https://rt.perl.org/Ticket/Display.html?id=123539>.
eabfc7bc
RS
3128
3129=item *
3130
33ca8d3c
DM
3131C<s///g> now works on very long strings (where there are more than 2
3132billion iterations) instead of dying with 'Substitution loop'.
a75e6a3a
SH
3133L<[perl #103260]|https://rt.perl.org/Ticket/Display.html?id=103260>.
3134L<[perl #123071]|https://rt.perl.org/Ticket/Display.html?id=123071>.
eabfc7bc
RS
3135
3136=item *
3137
a75e6a3a
SH
3138C<gmtime> no longer crashes with not-a-number values.
3139L<[perl #123495]|https://rt.perl.org/Ticket/Display.html?id=123495>.
eabfc7bc
RS
3140
3141=item *
3142
33ca8d3c
DM
3143C<\()> (a reference to an empty list), and C<y///> with lexical C<$_> in
3144scope, could both do a bad write past the end of the stack. They have
3145both been fixed to extend the stack first.
eabfc7bc
RS
3146
3147=item *
3148
3149C<prototype()> with no arguments used to read the previous item on the
3209f716
KW
3150stack, so S<C<print "foo", prototype()>> would print foo's prototype.
3151It has been fixed to infer C<$_> instead.
a75e6a3a 3152L<[perl #123514]|https://rt.perl.org/Ticket/Display.html?id=123514>.
eabfc7bc
RS
3153
3154=item *
3155
33ca8d3c
DM
3156Some cases of lexical state subs declared inside predeclared subs could
3157crash, for example when evalling a string including the name of an outer
3158variable, but no longer do.
eabfc7bc
RS
3159
3160=item *
3161
3162Some cases of nested lexical state subs inside anonymous subs could cause
d140c31c 3163'Bizarre copy' errors or possibly even crashes.
eabfc7bc
RS
3164
3165=item *
3166
3167When trying to emit warnings, perl's default debugger (F<perl5db.pl>) was
3168sometimes giving 'Undefined subroutine &DB::db_warn called' instead. This
a75e6a3a
SH
3169bug, which started to occur in Perl 5.18, has been fixed.
3170L<[perl #123553]|https://rt.perl.org/Ticket/Display.html?id=123553>.
eabfc7bc
RS
3171
3172=item *
3173
d140c31c 3174Certain syntax errors in substitutions, such as C<< s/${<>{})// >>, would
eabfc7bc
RS
3175crash, and had done so since Perl 5.10. (In some cases the crash did not
3176start happening till 5.16.) The crash has, of course, been fixed.
a75e6a3a 3177L<[perl #123542]|https://rt.perl.org/Ticket/Display.html?id=123542>.
eabfc7bc
RS
3178
3179=item *
3180
33ca8d3c 3181Fix a couple of string grow size calculation overflows; in particular,
3209f716 3182a repeat expression like S<C<33 x ~3>> could cause a large buffer
eabfc7bc 3183overflow since the new output buffer size was not correctly handled by
3209f716 3184C<SvGROW()>. An expression like this now properly produces a memory wrap
a75e6a3a
SH
3185panic.
3186L<[perl #123554]|https://rt.perl.org/Ticket/Display.html?id=123554>.
eabfc7bc
RS
3187
3188=item *
3189
3190C<< formline("@...", "a"); >> would crash. The C<FF_CHECKNL> case in
f0a38539 3191C<pp_formline()> didn't set the pointer used to mark the chop position,
eabfc7bc 3192which led to the C<FF_MORE> case crashing with a segmentation fault.
a75e6a3a
SH
3193This has been fixed.
3194L<[perl #123538]|https://rt.perl.org/Ticket/Display.html?id=123538>.
eabfc7bc
RS
3195
3196=item *
3197
3198A possible buffer overrun and crash when parsing a literal pattern during
a75e6a3a
SH
3199regular expression compilation has been fixed.
3200L<[perl #123604]|https://rt.perl.org/Ticket/Display.html?id=123604>.
eabfc7bc
RS
3201
3202=item *
3203
4ec8e6f0 3204C<fchmod()> and C<futimes()> now set C<$!> when they fail due to being
a75e6a3a
SH
3205passed a closed file handle.
3206L<[perl #122703]|https://rt.perl.org/Ticket/Display.html?id=122703>.
eabfc7bc
RS
3207
3208=item *
3209
33ca8d3c
DM
3210C<op_free()> and C<scalarvoid()> no longer crash due to a stack overflow
3211when freeing a deeply recursive op tree.
a75e6a3a 3212L<[perl #108276]|https://rt.perl.org/Ticket/Display.html?id=108276>.
eabfc7bc
RS
3213
3214=item *
3215
50ea4745 3216In Perl 5.20.0, C<$^N> accidentally had the internal UTF-8 flag turned off
eabfc7bc 3217if accessed from a code block within a regular expression, effectively
50ea4745 3218UTF-8-encoding the value. This has been fixed.
a75e6a3a 3219L<[perl #123135]|https://rt.perl.org/Ticket/Display.html?id=123135>.
eabfc7bc
RS
3220
3221=item *
3222
3223A failed C<semctl> call no longer overwrites existing items on the stack,
33ca8d3c
DM
3224which means that C<(semctl(-1,0,0,0))[0]> no longer gives an
3225"uninitialized" warning.
eabfc7bc
RS
3226
3227=item *
3228
3229C<else{foo()}> with no space before C<foo> is now better at assigning the
a75e6a3a
SH
3230right line number to that statement.
3231L<[perl #122695]|https://rt.perl.org/Ticket/Display.html?id=122695>.
eabfc7bc
RS
3232
3233=item *
3234
d140c31c 3235Sometimes the assignment in C<@array = split> gets optimised so that C<split>
eabfc7bc
RS
3236itself writes directly to the array. This caused a bug, preventing this
3237assignment from being used in lvalue context. So
3238C<(@a=split//,"foo")=bar()> was an error. (This bug probably goes back to
33ca8d3c 3239Perl 3, when the optimisation was added.) It has now been fixed.
a75e6a3a 3240L<[perl #123057]|https://rt.perl.org/Ticket/Display.html?id=123057>.
eabfc7bc
RS
3241
3242=item *
3243
33ca8d3c
DM
3244When an argument list fails the checks specified by a subroutine
3245signature (which is still an experimental feature), the resulting error
3246messages now give the file and line number of the caller, not of the
3247called subroutine.
a75e6a3a 3248L<[perl #121374]|https://rt.perl.org/Ticket/Display.html?id=121374>.
eabfc7bc
RS
3249
3250=item *
3251
33ca8d3c 3252The flip-flop operators (C<..> and C<...> in scalar context) used to maintain
eabfc7bc
RS
3253a separate state for each recursion level (the number of times the
3254enclosing sub was called recursively), contrary to the documentation. Now
a75e6a3a
SH
3255each closure has one internal state for each flip-flop.
3256L<[perl #122829]|https://rt.perl.org/Ticket/Display.html?id=122829>.
eabfc7bc
RS
3257
3258=item *
3259
33ca8d3c
DM
3260The flip-flop operator (C<..> in scalar context) would return the same
3261scalar each time, unless the containing subroutine was called recursively.
3262Now it always returns a new scalar.
3263L<[perl #122829]|https://rt.perl.org/Ticket/Display.html?id=122829>.
3264
3265=item *
3266
eabfc7bc
RS
3267C<use>, C<no>, statement labels, special blocks (C<BEGIN>) and pod are now
3268permitted as the first thing in a C<map> or C<grep> block, the block after
3269C<print> or C<say> (or other functions) returning a handle, and within
a75e6a3a
SH
3270C<${...}>, C<@{...}>, etc.
3271L<[perl #122782]|https://rt.perl.org/Ticket/Display.html?id=122782>.
eabfc7bc
RS
3272
3273=item *
3274
3275The repetition operator C<x> now propagates lvalue context to its left-hand
3276argument when used in contexts like C<foreach>. That allows
4ec8e6f0 3277S<C<for(($#that_array)x2) { ... }>> to work as expected if the loop modifies
f0a38539 3278C<$_>.
eabfc7bc
RS
3279
3280=item *
3281
3282C<(...) x ...> in scalar context used to corrupt the stack if one operand
d140c31c 3283was an object with "x" overloading, causing erratic behaviour.
a75e6a3a 3284L<[perl #121827]|https://rt.perl.org/Ticket/Display.html?id=121827>.
eabfc7bc
RS
3285
3286=item *
3287
33ca8d3c
DM
3288Assignment to a lexical scalar is often optimised away; for example in
3289C<my $x; $x = $y + $z>, the assign operator is optimised away and the add
3290operator writes its result directly to C<$x>. Various bugs related to
3291this optimisation have been fixed. Certain operators on the right-hand
3292side would sometimes fail to assign the value at all or assign the wrong
3293value, or would call STORE twice or not at all on tied variables. The
3294operators affected were C<$foo++>, C<$foo-->, and C<-$foo> under C<use
3295integer>, C<chomp>, C<chr> and C<setpgrp>.
eabfc7bc
RS
3296
3297=item *
3298
3299List assignments were sometimes buggy if the same scalar ended up on both
d140c31c 3300sides of the assignment due to use of C<tied>, C<values> or C<each>. The
eabfc7bc
RS
3301result would be the wrong value getting assigned.
3302
3303=item *
3304
3305C<setpgrp($nonzero)> (with one argument) was accidentally changed in 5.16
3306to mean C<setpgrp(0)>. This has been fixed.
3307
3308=item *
3309
3310C<__SUB__> could return the wrong value or even corrupt memory under the
4ec8e6f0 3311debugger (the C<-d> switch) and in subs containing C<eval $string>.
eabfc7bc
RS
3312
3313=item *
3314
4ec8e6f0 3315When S<C<sub () { $var }>> becomes inlinable, it now returns a different
eabfc7bc
RS
3316scalar each time, just as a non-inlinable sub would, though Perl still
3317optimises the copy away in cases where it would make no observable
3318difference.
3319
3320=item *
3321
4ec8e6f0 3322S<C<my sub f () { $var }>> and S<C<sub () : attr { $var }>> are no longer
eabfc7bc
RS
3323eligible for inlining. The former would crash; the latter would just
3324throw the attributes away. An exception is made for the little-known
f0a38539 3325C<:method> attribute, which does nothing much.
eabfc7bc
RS
3326
3327=item *
3328
3329Inlining of subs with an empty prototype is now more consistent than
d140c31c
AC
3330before. Previously, a sub with multiple statements, of which all but the last
3331were optimised away, would be inlinable only if it were an anonymous sub
eabfc7bc
RS
3332containing a string C<eval> or C<state> declaration or closing over an
3333outer lexical variable (or any anonymous sub under the debugger). Now any
3334sub that gets folded to a single constant after statements have been
3335optimised away is eligible for inlining. This applies to things like C<sub
3336() { jabber() if DEBUG; 42 }>.
3337
3338Some subroutines with an explicit C<return> were being made inlinable,
3339contrary to the documentation, Now C<return> always prevents inlining.
3340
3341=item *
3342
3343On some systems, such as VMS, C<crypt> can return a non-ASCII string. If a
50ea4745
DIM
3344scalar assigned to had contained a UTF-8 string previously, then C<crypt>
3345would not turn off the UTF-8 flag, thus corrupting the return value. This
3209f716 3346would happen with S<C<$lexical = crypt ...>>.
eabfc7bc
RS
3347
3348=item *
3349
3350C<crypt> no longer calls C<FETCH> twice on a tied first argument.
3351
3352=item *
3353
3354An unterminated here-doc on the last line of a quote-like operator
3355(C<qq[${ <<END }]>, C</(?{ <<END })/>) no longer causes a double free. It
3356started doing so in 5.18.
3357
3358=item *
3359
4ec8e6f0 3360C<index()> and C<rindex()> no longer crash when used on strings over 2GB in
eabfc7bc
RS
3361size.
3362L<[perl #121562]|https://rt.perl.org/Ticket/Display.html?id=121562>.
3363
3364=item *
3365
f0a38539
KW
3366A small, previously intentional, memory leak in
3367C<PERL_SYS_INIT>/C<PERL_SYS_INIT3> on Win32 builds was fixed. This might
3368affect embedders who repeatedly create and destroy perl engines within
3369the same process.
eabfc7bc
RS
3370
3371=item *
3372
3373C<POSIX::localeconv()> now returns the data for the program's underlying
3374locale even when called from outside the scope of S<C<use locale>>.
3375
3376=item *
3377
3378C<POSIX::localeconv()> now works properly on platforms which don't have
3379C<LC_NUMERIC> and/or C<LC_MONETARY>, or for which Perl has been compiled
3380to disregard either or both of these locale categories. In such
3381circumstances, there are now no entries for the corresponding values in
3382the hash returned by C<localeconv()>.
3383
3384=item *
3385
3386C<POSIX::localeconv()> now marks appropriately the values it returns as
6a3ea89b 3387UTF-8 or not. Previously they were always returned as bytes, even if
eabfc7bc
RS
3388they were supposed to be encoded as UTF-8.
3389
3390=item *
3391
3392On Microsoft Windows, within the scope of C<S<use locale>>, the following
3393POSIX character classes gave results for many locales that did not
3394conform to the POSIX standard:
3395C<[[:alnum:]]>,
3396C<[[:alpha:]]>,
3397C<[[:blank:]]>,
3398C<[[:digit:]]>,
3399C<[[:graph:]]>,
3400C<[[:lower:]]>,
3401C<[[:print:]]>,
3402C<[[:punct:]]>,
3403C<[[:upper:]]>,
3404C<[[:word:]]>,
3405and
3406C<[[:xdigit:]]>.
f1c9eac6 3407This was because the underlying Microsoft implementation does not
eabfc7bc
RS
3408follow the standard. Perl now takes special precautions to correct for
3409this.
3410
3411=item *
3412
3413Many issues have been detected by L<Coverity|http://www.coverity.com/> and
3414fixed.
3415
3416=item *
3417
d140c31c 3418C<system()> and friends should now work properly on more Android builds.
eabfc7bc 3419
4ec8e6f0 3420Due to an oversight, the value specified through C<-Dtargetsh> to F<Configure>
eabfc7bc 3421would end up being ignored by some of the build process. This caused perls
4ec8e6f0 3422cross-compiled for Android to end up with defective versions of C<system()>,
d140c31c 3423C<exec()> and backticks: the commands would end up looking for C</bin/sh>
eabfc7bc
RS
3424instead of C</system/bin/sh>, and so would fail for the vast majority
3425of devices, leaving C<$!> as C<ENOENT>.
3426
3427=item *
3428
3429C<qr(...\(...\)...)>,
3430C<qr[...\[...\]...]>,
3431and
3432C<qr{...\{...\}...}>
3433now work. Previously it was impossible to escape these three
3434left-characters with a backslash within a regular expression pattern
3435where otherwise they would be considered metacharacters, and the pattern
3436opening delimiter was the character, and the closing delimiter was its
3437mirror character.
3438
3439=item *
3440
50ea4745 3441C<< s///e >> on tainted UTF-8 strings corrupted C<< pos() >>. This bug,
a75e6a3a
SH
3442introduced in 5.20, is now fixed.
3443L<[perl #122148]|https://rt.perl.org/Ticket/Display.html?id=122148>.
eabfc7bc
RS
3444
3445=item *
3446
3447A non-word boundary in a regular expression (C<< \B >>) did not always
3448match the end of the string; in particular C<< q{} =~ /\B/ >> did not
a75e6a3a
SH
3449match. This bug, introduced in perl 5.14, is now fixed.
3450L<[perl #122090]|https://rt.perl.org/Ticket/Display.html?id=122090>.
eabfc7bc
RS
3451
3452=item *
3453
3454C<< " P" =~ /(?=.*P)P/ >> should match, but did not. This is now fixed.
a75e6a3a 3455L<[perl #122171]|https://rt.perl.org/Ticket/Display.html?id=122171>.
eabfc7bc
RS
3456
3457=item *
3458
3209f716 3459Failing to compile C<use Foo> in an C<eval> could leave a spurious
eabfc7bc
RS
3460C<BEGIN> subroutine definition, which would produce a "Subroutine
3461BEGIN redefined" warning on the next use of C<use>, or other C<BEGIN>
a75e6a3a
SH
3462block.
3463L<[perl #122107]|https://rt.perl.org/Ticket/Display.html?id=122107>.
eabfc7bc
RS
3464
3465=item *
3466
3467C<method { BLOCK } ARGS> syntax now correctly parses the arguments if they
a75e6a3a
SH
3468begin with an opening brace.
3469L<[perl #46947]|https://rt.perl.org/Ticket/Display.html?id=46947>.
eabfc7bc
RS
3470
3471=item *
3472
3473External libraries and Perl may have different ideas of what the locale is.
3474This is problematic when parsing version strings if the locale's numeric
3475separator has been changed. Version parsing has been patched to ensure
a75e6a3a
SH
3476it handles the locales correctly.
3477L<[perl #121930]|https://rt.perl.org/Ticket/Display.html?id=121930>.
eabfc7bc
RS
3478
3479=item *
3480
3481A bug has been fixed where zero-length assertions and code blocks inside of a
a75e6a3a
SH
3482regex could cause C<pos> to see an incorrect value.
3483L<[perl #122460]|https://rt.perl.org/Ticket/Display.html?id=122460>.
eabfc7bc
RS
3484
3485=item *
3486
3b50e657 3487Dereferencing of constants now works correctly for typeglob constants. Previously
eabfc7bc
RS
3488the glob was stringified and its name looked up. Now the glob itself is used.
3489L<[perl #69456]|https://rt.perl.org/Ticket/Display.html?id=69456>
3490
3491=item *
3492
d140c31c 3493When parsing a sigil (C<$> C<@> C<%> C<&)> followed by braces,
4ec8e6f0 3494the parser no
eabfc7bc
RS
3495longer tries to guess whether it is a block or a hash constructor (causing a
3496syntax error when it guesses the latter), since it can only be a block.
3497
3498=item *
3499
4ec8e6f0 3500S<C<undef $reference>> now frees the referent immediately, instead of hanging on
eabfc7bc
RS
3501to it until the next statement.
3502L<[perl #122556]|https://rt.perl.org/Ticket/Display.html?id=122556>
3503
3504=item *
3505
3506Various cases where the name of a sub is used (autoload, overloading, error
3507messages) used to crash for lexical subs, but have been fixed.
3508
3509=item *
3510
3511Bareword lookup now tries to avoid vivifying packages if it turns out the
3512bareword is not going to be a subroutine name.
3513
3514=item *
3515
ff25fcfb 3516Compilation of anonymous constants (I<e.g.>, C<sub () { 3 }>) no longer deletes
eabfc7bc
RS
3517any subroutine named C<__ANON__> in the current package. Not only was
3518C<*__ANON__{CODE}> cleared, but there was a memory leak, too. This bug goes
3519back to Perl 5.8.0.
3520
3521=item *
3522
3523Stub declarations like C<sub f;> and C<sub f ();> no longer wipe out constants
3524of the same name declared by C<use constant>. This bug was introduced in Perl
35255.10.0.
3526
3527=item *
3528
33ca8d3c
DM
3529C<qr/[\N{named sequence}]/> now works properly in many instances.
3530
3531Some names
eabfc7bc
RS
3532known to C<\N{...}> refer to a sequence of multiple characters, instead of the
3533usual single character. Bracketed character classes generally only match
3534single characters, but now special handling has been added so that they can
3535match named sequences, but not if the class is inverted or the sequence is
3536specified as the beginning or end of a range. In these cases, the only
3537behavior change from before is a slight rewording of the fatal error message
3538given when this class is part of a C<?[...])> construct. When the C<[...]>
3539stands alone, the same non-fatal warning as before is raised, and only the
3540first character in the sequence is used, again just as before.
3541
3542=item *
3543
3544Tainted constants evaluated at compile time no longer cause unrelated
3545statements to become tainted.
3546L<[perl #122669]|https://rt.perl.org/Ticket/Display.html?id=122669>
3547
3548=item *
3549
33ca8d3c
DM
3550S<C<open $$fh, ...>>, which vivifies a handle with a name like
3551C<"main::_GEN_0">, was not giving the handle the right reference count, so
3552a double free could happen.
eabfc7bc
RS
3553
3554=item *
3555
3556When deciding that a bareword was a method name, the parser would get confused
4ec8e6f0
KW
3557if an C<our> sub with the same name existed, and look up the method in the
3558package of the C<our> sub, instead of the package of the invocant.
eabfc7bc
RS
3559
3560=item *
3561
3562The parser no longer gets confused by C<\U=> within a double-quoted string. It
3563used to produce a syntax error, but now compiles it correctly.
3564L<[perl #80368]|https://rt.perl.org/Ticket/Display.html?id=80368>
3565
3566=item *
3567
3568It has always been the intention for the C<-B> and C<-T> file test operators to
3569treat UTF-8 encoded files as text. (L<perlfunc|perlfunc/-X FILEHANDLE> has
3570been updated to say this.) Previously, it was possible for some files to be
3571considered UTF-8 that actually weren't valid UTF-8. This is now fixed. The
3572operators now work on EBCDIC platforms as well.
3573
3574=item *
3575
3576Under some conditions warning messages raised during regular expression pattern
3577compilation were being output more than once. This has now been fixed.
3578
3579=item *
3580