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Use "UTF-8" consistently in perldelta
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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.
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35
36=head2 New \b boundaries in regular expressions
37
38=head3 qr/\b{gcb}/
39
40C<gcb> stands for Grapheme Cluster Boundary. It is a Unicode property
41that finds the boundary between sequences of characters that look like a
42single character to a native speaker of a language. Perl has long had
43the ability to deal with these through the C<\X> regular escape
44sequence. Now, there is an alternative way of handling these. See
45L<perlrebackslash/\b{}, \b, \B{}, \B> for details.
46
47=head3 qr/\b{wb}/
48
49C<wb> stands for Word Boundary. It is a Unicode property
50that finds the boundary between words. This is similar to the plain
51C<\b> (without braces) but is more suitable for natural language
01842271 52processing. It knows, for example, that apostrophes can occur in the
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53middle of words. See L<perlrebackslash/\b{}, \b, \B{}, \B> for details.
54
55=head3 qr/\b{sb}/
56
57C<sb> stands for Sentence Boundary. It is a Unicode property
58to aid in parsing natural language sentences.
59See L<perlrebackslash/\b{}, \b, \B{}, \B> for details.
60
61=head2 C<no re> covers more and is lexical
62
d140c31c 63Previously running C<no re> would turn off only a few things. Now it
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64turns off all the enabled things. For example, previously, you
65couldn't turn off debugging, once enabled, inside the same block.
66
67=head2 Non-Capturing Regular Expression Flag
68
69Regular expressions now support a C</n> flag that disables capturing
d140c31c 70and filling in C<$1>, C<$2>, etc inside of groups:
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71
72 "hello" =~ /(hi|hello)/n; # $1 is not set
73
74This is equivalent to putting C<?:> at the beginning of every capturing group.
75
76See L<perlre/"n"> for more information.
77
78=head2 C<use re 'strict'>
79
80This applies stricter syntax rules to regular expression patterns
d140c31c 81compiled within its scope. This will hopefully alert you to typos and
eabfc7bc 82other unintentional behavior that backwards-compatibility issues prevent
d140c31c 83us from reporting in normal regular expression compilations. Because the
eabfc7bc 84behavior of this is subject to change in future Perl releases as we gain
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85experience, using this pragma will raise a warning of category
86C<experimental::re_strict>.
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87See L<'strict' in re|re/'strict' mode>.
88
ce93e38b 89=head2 Unicode 7.0 (with correction) is now supported
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90
91For details on what is in this release, see
92L<http://www.unicode.org/versions/Unicode7.0.0/>.
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93The version of Unicode 7.0 that comes with Perl includes
94a correction dealing with glyph shaping in Arabic
95(see L<http://www.unicode.org/errata/#current_errata>).
96
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97
98=head2 S<C<use locale>> can restrict which locale categories are affected
99
100It is now possible to pass a parameter to S<C<use locale>> to specify
101a subset of locale categories to be locale-aware, with the remaining
102ones unaffected. See L<perllocale/The "use locale" pragma> for details.
103
01842271 104=head2 Perl now supports POSIX 2008 locale currency additions
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105
106On platforms that are able to handle POSIX.1-2008, the
107hash returned by
108L<C<POSIX::localeconv()>|perllocale/The localeconv function>
109includes the international currency fields added by that version of the
110POSIX standard. These are
111C<int_n_cs_precedes>,
112C<int_n_sep_by_space>,
113C<int_n_sign_posn>,
114C<int_p_cs_precedes>,
115C<int_p_sep_by_space>,
116and
117C<int_p_sign_posn>.
118
50ea4745 119=head2 Better heuristics on older platforms for determining locale UTF-8ness
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120
121On platforms that implement neither the C99 standard nor the POSIX 2001
50ea4745 122standard, determining if the current locale is UTF-8 or not depends on
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123heuristics. These are improved in this release.
124
125=head2 Aliasing via reference
126
127Variables and subroutines can now be aliased by assigning to a reference:
128
129 \$c = \$d;
130 \&x = \&y;
131
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132Aliasing can also be accomplished
133by using a backslash before a C<foreach> iterator variable; this is
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134perhaps the most useful idiom this feature provides:
135
136 foreach \%hash (@array_of_hash_refs) { ... }
137
138This feature is experimental and must be enabled via C<use feature
139'refaliasing'>. It will warn unless the C<experimental::refaliasing>
140warnings category is disabled.
141
142See L<perlref/Assigning to References>
143
144=head2 C<prototype> with no arguments
145
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146C<prototype()> with no arguments now infers C<$_>.
147L<[perl #123514]|https://rt.perl.org/Ticket/Display.html?id=123514>.
eabfc7bc 148
d140c31c 149=head2 New C<:const> subroutine attribute
eabfc7bc 150
d140c31c 151The C<const> attribute can be applied to an anonymous subroutine. It
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152causes the new sub to be executed immediately whenever one is created
153(i.e. when the C<sub> expression is evaluated). Its value is captured
154and used to create a new constant subroutine that is returned. This
155feature is experimental. See L<perlsub/Constant Functions>.
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156
157=head2 C<fileno> now works on directory handles
158
159When the relevant support is available in the operating system, the
160C<fileno> builtin now works on directory handles, yielding the
161underlying file descriptor in the same way as for filehandles. On
162operating systems without such support, C<fileno> on a directory handle
163continues to return the undefined value, as before, but also sets C<$!> to
164indicate that the operation is not supported.
165
166Currently, this uses either a C<dd_fd> member in the OS C<DIR>
4ec8e6f0 167structure, or a C<dirfd(3)> function as specified by POSIX.1-2008.
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168
169=head2 List form of pipe open implemented for Win32
170
171The list form of pipe:
172
173 open my $fh, "-|", "program", @arguments;
174
175is now implemented on Win32. It has the same limitations as C<system
176LIST> on Win32, since the Win32 API doesn't accept program arguments
177as a list.
178
179=head2 C<close> now sets C<$!>
180
181When an I/O error occurs, the fact that there has been an error is recorded
182in the handle. C<close> returns false for such a handle. Previously, the
183value of C<$!> would be untouched by C<close>, so the common convention of
4ec8e6f0 184writing S<C<close $fh or die $!>> did not work reliably. Now the handle
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185records the value of C<$!>, too, and C<close> restores it.
186
187=head2 Assignment to list repetition
188
189C<(...) x ...> can now be used within a list that is assigned to, as long
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190as the left-hand side is a valid lvalue. This allows S<C<(undef,undef,$foo)
191= that_function()>> to be written as S<C<((undef)x2, $foo) = that_function()>>.
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192
193=head2 Infinity and NaN (not-a-number) handling improved
194
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195Floating point values are able to hold the special values infinity, negative
196infinity, and NaN (not-a-number). Now we more robustly recognize and
197propagate the value in computations, and on output normalize them to C<Inf>,
198C<-Inf>, or C<NaN>.
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199
200See also the L<POSIX> enhancements.
201
202=head2 Floating point parsing has been improved
203
204Parsing and printing of floating point values has been improved.
205
206As a completely new feature, hexadecimal floating point literals
4ec8e6f0 207(like C<0x1.23p-4>) are now supported, and they can be output with
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208C<printf "%a">. See L<perldata/Scalar value constructors> for more
209details.
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210
211=head2 Packing infinity or not-a-number into a character is now fatal
212
213Before, when trying to pack infinity or not-a-number into a
214(signed) character, Perl would warn, and assumed you tried to
215pack C<< 0xFF >>; if you gave it as an argument to C<< chr >>,
216C<< U+FFFD >> was returned.
217
218But now, all such actions (C<< pack >>, C<< chr >>, and C<< print '%c' >>)
219result in a fatal error.
220
221=head2 Experimental C Backtrace API
2e4abf26 222
43831b1f 223Perl now supports (via a C level API) retrieving
eabfc7bc 224the C level backtrace (similar to what symbolic debuggers like gdb do).
fea59588 225
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226The backtrace returns the stack trace of the C call frames,
227with the symbol names (function names), the object names (like "perl"),
228and if it can, also the source code locations (file:line).
229
230The supported platforms are Linux and OS X (some *BSD might work at
231least partly, but they have not yet been tested).
232
233The feature needs to be enabled with C<Configure -Dusecbacktrace>.
234
eabfc7bc 235See L<perlhacktips/"C backtrace"> for more information.
83a5d6b6 236
7f9fef93 237=head1 Security
e455391f 238
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239=head2 Perl is now compiled with -fstack-protector-strong if available
240
241Perl has been compiled with the anti-stack-smashing option
242C<-fstack-protector> since 5.10.1. Now Perl uses the newer variant
243called C<-fstack-protector-strong>, if available.
244
245=head2 The L<Safe> module could allow outside packages to be replaced
246
247Critical bugfix: outside packages could be replaced. L<Safe> has
248been patched to 2.38 to address this.
249
250=head2 Perl is now always compiled with -D_FORTIFY_SOURCE=2 if available
e455391f 251
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252The 'code hardening' option called C<_FORTIFY_SOURCE>, available in
253gcc 4.*, is now always used for compiling Perl, if available.
254
255Note that this isn't necessarily a huge step since in many platforms
256the step had already been taken several years ago: many Linux
257distributions (like Fedora) have been using this option for Perl,
258and OS X has enforced the same for many years.
53902397 259
7f9fef93 260=head1 Incompatible Changes
79a77127 261
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262=head2 Subroutine signatures moved before attributes
263
264The experimental sub signatures feature, as introduced in 5.20, parsed
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265signatures after attributes. In this release, following feedback from users
266of the experimental feature, the positioning has been moved such that
267signatures occur after the subroutine name (if any) and before the attribute
268list (if any).
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269
270=head2 C<&> and C<\&> prototypes accepts only subs
271
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272The C<&> prototype character now accepts only anonymous subs (C<sub
273{...}>), things beginning with C<\&>, or an explicit C<undef>. Formerly
274it erroneously also allowed references to arrays, hashes, and lists.
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275L<[perl #4539]|https://rt.perl.org/Ticket/Display.html?id=4539>.
276L<[perl #123062]|https://rt.perl.org/Ticket/Display.html?id=123062>.
43831b1f 277L<[perl #123062]|https://rt.perl.org/Ticket/Display.html?id=123475>.
eabfc7bc 278
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279In addition, the C<\&> prototype was allowing subroutine calls, whereas
280now it only allows subroutines: C<&foo> is still permitted as an argument,
281while C<&foo()> and C<foo()> no longer are.
a75e6a3a 282L<[perl #77860]|https://rt.perl.org/Ticket/Display.html?id=77860>.
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283
284=head2 C<use encoding> is now lexical
285
286The L<encoding> pragma's effect is now limited to lexical scope. This
287pragma is deprecated, but in the meantime, it could adversely affect
288unrelated modules that are included in the same program.
289
290=head2 List slices returning empty lists
291
d140c31c 292List slices now return an empty list only if the original list was empty
eabfc7bc 293(or if there are no indices). Formerly, a list slice would return an empty
43831b1f 294list if all indices fell outside the original list; now it returns a list
d140c31c 295of undef values in that case.
a75e6a3a 296L<[perl #114498]|https://rt.perl.org/Ticket/Display.html?id=114498>.
eabfc7bc 297
01842271 298=head2 C<\N{}> with a sequence of multiple spaces is now a fatal error
eabfc7bc 299
43831b1f 300E.g. C<\N{TOO MANY SPACES}> or C<\N{TRAILING SPACE }>.
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301This has been deprecated since v5.18.
302
303=head2 S<C<use UNIVERSAL '...'>> is now a fatal error
304
305Importing functions from C<UNIVERSAL> has been deprecated since v5.12, and
d140c31c 306is now a fatal error. S<C<use UNIVERSAL>> without any arguments is still
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307allowed.
308
309=head2 In double-quotish C<\cI<X>>, I<X> must now be a printable ASCII character
310
311In prior releases, failure to do this raised a deprecation warning.
312
313=head2 Splitting the tokens C<(?> and C<(*> in regular expressions is
314now a fatal compilation error.
315
316These had been deprecated since v5.18.
317
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318=head2 C<qr/foo/x> now ignores all Unicode pattern white space
319
320The C</x> regular expression modifier allows the pattern to contain
321white space and comments (both of which are ignored) for improved
322readability. Until now, not all the white space characters that Unicode
323designates for this purpose were handled. The additional ones now
324recognized are
325
326 U+0085 NEXT LINE
327 U+200E LEFT-TO-RIGHT MARK
328 U+200F RIGHT-TO-LEFT MARK
329 U+2028 LINE SEPARATOR
330 U+2029 PARAGRAPH SEPARATOR
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331
332The use of these characters with C</x> outside bracketed character
333classes and when not preceded by a backslash has raised a deprecation
43831b1f 334warning since v5.18. Now they will be ignored.
eabfc7bc 335
43831b1f 336=head2 Comment lines within S<C<(?[ ])>> are now ended only by a C<\n>
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337
338S<C<(?[ ])>> is an experimental feature, introduced in v5.18. It operates
43831b1f 339as if C</x> is always enabled. But there was a difference: comment
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340lines (following a C<#> character) were terminated by anything matching
341C<\R> which includes all vertical whitespace, such as form feeds. For
342consistency, this is now changed to match what terminates comment lines
343outside S<C<(?[ ])>>, namely a C<\n> (even if escaped), which is the
344same as what terminates a heredoc string and formats.
345
346=head2 C<(?[...])> operators now follow standard Perl precedence
347
348This experimental feature allows set operations in regular expression patterns.
349Prior to this, the intersection operator had the same precedence as the other
350binary operators. Now it has higher precedence. This could lead to different
351outcomes than existing code expects (though the documentation has always noted
352that this change might happen, recommending fully parenthesizing the
353expressions). See L<perlrecharclass/Extended Bracketed Character Classes>.
354
4ec8e6f0 355=head2 Omitting C<%> and C<@> on hash and array names is no longer permitted
c14a43b7 356
4ec8e6f0 357Really old Perl let you omit the C<@> on array names and the C<%> on hash
eabfc7bc 358names in some spots. This has issued a deprecation warning since Perl
93780ae6 3595.000, and is no longer permitted.
c14a43b7 360
d140c31c 361=head2 C<"$!"> text is now in English outside the scope of C<use locale>
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362
363Previously, the text, unlike almost everything else, always came out
364based on the current underlying locale of the program. (Also affected
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365on some systems is C<"$^E">.) For programs that are unprepared to
366handle locale differences, this can cause garbage text to be displayed.
367It's better to display text that is translatable via some tool than
368garbage text which is much harder to figure out.
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369
370=head2 C<"$!"> text will be returned in UTF-8 when appropriate
371
372The stringification of C<$!> and C<$^E> will have the UTF-8 flag set
373when the text is actually non-ASCII UTF-8. This will enable programs
374that are set up to be locale-aware to properly output messages in the
375user's native language. Code that needs to continue the 5.20 and
376earlier behavior can do the stringification within the scopes of both
d140c31c 377S<C<use bytes>> and S<C<use locale ":messages">>. No other Perl
4ec8e6f0 378operations will
eabfc7bc 379be affected by locale; only C<$!> and C<$^E> stringification. The
d140c31c 380C<bytes> pragma causes the UTF-8 flag to not be set, just as in previous
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381Perl releases. This resolves
382L<[perl #112208]|https://rt.perl.org/Ticket/Display.html?id=112208>.
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383
384=head2 Support for C<?PATTERN?> without explicit operator has been removed
385
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386The C<m?PATTERN?> construct, which allows matching a regex only once,
387previously had an alternative form that was written directly with a question
388mark delimiter, omitting the explicit C<m> operator. This usage has produced
389a deprecation warning since 5.14.0. It is now a syntax error, so that the
390question mark can be available for use in new operators.
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391
392=head2 C<defined(@array)> and C<defined(%hash)> are now fatal errors
393
394These have been deprecated since v5.6.1 and have raised deprecation
395warnings since v5.16.
396
01842271 397=head2 Using a hash or an array as a reference are now fatal errors
eabfc7bc 398
43831b1f 399For example, C<< %foo->{"bar"} >> now causes a fatal compilation
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400error. These have been deprecated since before v5.8, and have raised
401deprecation warnings since then.
402
403=head2 Changes to the C<*> prototype
404
405The C<*> character in a subroutine's prototype used to allow barewords to take
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406precedence over most, but not all, subroutine names. It was never
407consistent and exhibited buggy behaviour.
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408
409Now it has been changed, so subroutines always take precedence over barewords,
410which brings it into conformity with similarly prototyped built-in functions:
411
412 sub splat(*) { ... }
413 sub foo { ... }
414 splat(foo); # now always splat(foo())
415 splat(bar); # still splat('bar') as before
416 close(foo); # close(foo())
417 close(bar); # close('bar')
c14a43b7 418
7f9fef93 419=head1 Deprecations
47cb8ddb 420
eabfc7bc 421=head2 Setting C<${^ENCODING}> to anything but C<undef>
c14a43b7 422
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423This variable allows Perl scripts to be written in an encoding other than
424ASCII or UTF-8. However, it affects all modules globally, leading
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425to wrong answers and segmentation faults. New scripts should be written
426in UTF-8; old scripts should be converted to UTF-8, which is easily done
726f20d2 427with the L<piconv> utility.
c14a43b7 428
eabfc7bc 429=head2 Use of non-graphic characters in single-character variable names
51c2f40f 430
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431The syntax for single-character variable names is more lenient than
432for longer variable names, allowing the one-character name to be a
433punctuation character or even invisible (a non-graphic). Perl v5.20
434deprecated the ASCII-range controls as such a name. Now, all
435non-graphic characters that formerly were allowed are deprecated.
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436The practical effect of this occurs only when not under C<S<use
437utf8>>, and affects just the C1 controls (code points 0x80 through
eabfc7bc 4380xFF), NO-BREAK SPACE, and SOFT HYPHEN.
83a5d6b6 439
eabfc7bc 440=head2 Inlining of C<sub () { $var }> with observable side-effects
abec5bed 441
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442In many cases Perl makes S<C<sub () { $var }>> into an inlinable constant
443subroutine, capturing the value of C<$var> at the time the C<sub> expression
eabfc7bc 444is evaluated. This can break the closure behaviour in those cases where
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445C<$var> is subsequently modified, since the subroutine won't return the
446changed value. (Note that this all only applies to anonymous subroutines
447with an empty prototype (C<sub ()>).)
abec5bed 448
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449This usage is now deprecated in those cases where the variable could be
450modified elsewhere. Perl detects those cases and emits a deprecation
451warning. Such code will likely change in the future and stop producing a
452constant.
abec5bed 453
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454If your variable is only modified in the place where it is declared, then
455Perl will continue to make the sub inlinable with no warnings.
c14a43b7 456
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457 sub make_constant {
458 my $var = shift;
459 return sub () { $var }; # fine
460 }
c14a43b7 461
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462 sub make_constant_deprecated {
463 my $var;
464 $var = shift;
465 return sub () { $var }; # deprecated
466 }
c14a43b7 467
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468 sub make_constant_deprecated2 {
469 my $var = shift;
470 log_that_value($var); # could modify $var
471 return sub () { $var }; # deprecated
472 }
c14a43b7 473
4ec8e6f0 474In the second example above, detecting that C<$var> is assigned to only once
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475is too hard to detect. That it happens in a spot other than the C<my>
476declaration is enough for Perl to find it suspicious.
7f9fef93 477
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478This deprecation warning happens only for a simple variable for the body of
479the sub. (A C<BEGIN> block or C<use> statement inside the sub is ignored,
480because it does not become part of the sub's body.) For more complex
4ec8e6f0 481cases, such as S<C<sub () { do_something() if 0; $var }>> the behaviour has
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482changed such that inlining does not happen if the variable is modifiable
483elsewhere. Such cases should be rare.
c14a43b7 484
eabfc7bc 485=head2 Use of multiple /x regexp modifiers
c14a43b7 486
eabfc7bc 487It is now deprecated to say something like any of the following:
c14a43b7 488
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489 qr/foo/xx;
490 /(?xax:foo)/;
491 use re qw(/amxx);
be39acb2 492
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493That is, now C<x> should only occur once in any string of contiguous
494regular expression pattern modifiers. We do not believe there are any
495occurrences of this in all of CPAN. This is in preparation for a future
d140c31c 496Perl release having C</xx> permit white-space for readability in
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497bracketed character classes (those enclosed in square brackets:
498C<[...]>).
c14a43b7 499
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500=head2 Using a NO-BREAK space in a character alias for C<\N{...}> is now
501deprecated
60dcce55 502
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503This non-graphic character is essentially indistinguishable from a
504regular space, and so should not be allowed. See
505L<charnames/CUSTOM ALIASES>.
60dcce55 506
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507=head2 A literal C<"{"> should now be escaped in a pattern
508
509If you want a literal left curly bracket (also called a left brace) in a
510regular expression pattern, you should now escape it by either
511preceding it with a backslash (C<"\{">) or enclosing it within square
512brackets C<"[{]">, or by using C<\Q>; otherwise a deprecation warning
513will be raised. This was first announced as forthcoming in the v5.16
514release; it will allow future extensions to the language to happen.
515
516=head2 Making all warnings fatal is discouraged
517
518The documentation for L<fatal warnings|warnings/Fatal Warnings> notes that
d140c31c 519C<< use warnings FATAL => 'all' >> is discouraged, and provides stronger
eabfc7bc
RS
520language about the risks of fatal warnings in general.
521
522=head1 Performance Enhancements
79a77127 523
7f9fef93 524=over 4
abec5bed
DIM
525
526=item *
527
43831b1f 528If a method or class name is known at compile time, a hash is precomputed
eabfc7bc
RS
529to speed up run-time method lookup. Also, compound method names like
530C<SUPER::new> are parsed at compile time, to save having to parse them at
531run time.
9749148e 532
eabfc7bc 533=item *
9749148e 534
eabfc7bc
RS
535Array and hash lookups (especially nested ones) that use only constants
536or simple variables as keys, are now considerably faster. See
537L</Internal Changes> for more details.
abec5bed
DIM
538
539=item *
540
eabfc7bc
RS
541C<(...)x1>, C<("constant")x0> and C<($scalar)x0> are now optimised in list
542context. If the right-hand argument is a constant 1, the repetition
543operator disappears. If the right-hand argument is a constant 0, the whole
6a3ea89b 544expression is optimised to the empty list, so long as the left-hand
d140c31c
AC
545argument is a simple scalar or constant. (That is, C<(foo())x0> is not
546subject to this optimisation.)
6bb5549b 547
eabfc7bc 548=item *
7f9fef93 549
eabfc7bc
RS
550C<substr> assignment is now optimised into 4-argument C<substr> at the end
551of a subroutine (or as the argument to C<return>). Previously, this
552optimisation only happened in void context.
abec5bed 553
eabfc7bc 554=item *
7f9fef93 555
43831b1f
DM
556In C<"\L...">, C<"\Q...">, etc., the extra "stringify" op is now optimised
557away, making these just as fast as C<lcfirst>, C<quotemeta>, etc.
2e4abf26 558
eabfc7bc 559=item *
83a5d6b6 560
eabfc7bc
RS
561Assignment to an empty list is now sometimes faster. In particular, it
562never calls C<FETCH> on tied arguments on the right-hand side, whereas it
563used to sometimes.
564
565=item *
83a5d6b6 566
d140c31c
AC
567There is a performance improvement of up to 20% when C<length> is applied to
568a non-magical, non-tied string, and either C<use bytes> is in scope or the
569string doesn't use UTF-8 internally.
338906ce 570
eabfc7bc 571=item *
5de148ee 572
d140c31c
AC
573On most perl builds with 64-bit integers, memory usage for non-magical,
574non-tied scalars containing only a floating point value has been reduced
575by between 8 and 32 bytes, depending on OS.
5de148ee 576
eabfc7bc 577=item *
5de148ee 578
d140c31c
AC
579In C<@array = split>, the assignment can be optimized away, so that C<split>
580writes directly to the array. This optimisation was happening only for
43831b1f
DM
581package arrays other than C<@_>, and only sometimes. Now this
582optimisation happens almost all the time.
5de148ee 583
eabfc7bc 584=item *
7f9fef93 585
43831b1f
DM
586C<join> is now subject to constant folding. So for example
587C<join "-", "a", "b"> is converted at compile-time to C<"a-b">.
588Moreover, C<join> with a scalar or constant for the separator and a
d140c31c 589single-item list to join is simplified to a stringification, and the
43831b1f 590separator doesn't even get evaluated.
5de148ee 591
eabfc7bc 592=item *
47cb8ddb 593
eabfc7bc 594C<qq(@array)> is implemented using two ops: a stringify op and a join op.
4ec8e6f0 595If the C<qq> contains nothing but a single array, the stringification is
eabfc7bc 596optimized away.
47cb8ddb
SH
597
598=item *
599
4ec8e6f0
KW
600S<C<our $var>> and S<C<our($s,@a,%h)>> in void context are no longer evaluated at
601run time. Even a whole sequence of S<C<our $foo;>> statements will simply be
eabfc7bc 602skipped over. The same applies to C<state> variables.
47cb8ddb 603
eabfc7bc 604=item *
47cb8ddb 605
eabfc7bc
RS
606Many internal functions have been refactored to improve performance and reduce
607their memory footprints.
eabfc7bc
RS
608L<[perl #121436]|https://rt.perl.org/Ticket/Display.html?id=121436>
609L<[perl #121906]|https://rt.perl.org/Ticket/Display.html?id=121906>
610L<[perl #121969]|https://rt.perl.org/Ticket/Display.html?id=121969>
47cb8ddb 611
eabfc7bc 612=item *
47cb8ddb 613
eabfc7bc 614C<-T> and C<-B> filetests will return sooner when an empty file is detected.
a75e6a3a 615L<[perl #121489]|https://rt.perl.org/Ticket/Display.html?id=121489>
47cb8ddb 616
eabfc7bc 617=item *
5de148ee 618
01842271 619Hash lookups where the key is a constant are faster.
be39acb2
SH
620
621=item *
622
d140c31c 623Subroutines with an empty prototype and a body containing just C<undef> are now
eabfc7bc
RS
624eligible for inlining.
625L<[perl #122728]|https://rt.perl.org/Ticket/Display.html?id=122728>
be39acb2 626
eabfc7bc 627=item *
be39acb2 628
43831b1f
DM
629Subroutines in packages no longer need to be stored in typeglobs:
630declaring a subroutine will now put a simple sub reference directly in the
631stash if possible, saving memory. The typeglob still notionally exists,
632so accessing it will cause the stash entry to be upgraded to a typeglob
633(i.e. this is just an internal implementation detail).
634This optimization does not currently apply to XSUBs or exported
635subroutines, and method calls will undo it, since they cache things in
636typeglobs.
eabfc7bc 637L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
7f9fef93 638
eabfc7bc 639=item *
be39acb2 640
eabfc7bc
RS
641The functions C<utf8::native_to_unicode()> and C<utf8::unicode_to_native()>
642(see L<utf8>) are now optimized out on ASCII platforms. There is now not even
643a minimal performance hit in writing code portable between ASCII and EBCDIC
644platforms.
be39acb2
SH
645
646=item *
647
eabfc7bc 648Win32 Perl uses 8 KB less of per-process memory than before for every perl
43831b1f 649process, because some data is now memory mapped from disk and shared
d140c31c 650between processes from the same perl binary.
be39acb2
SH
651
652=back
653
eabfc7bc 654=head1 Modules and Pragmata
83a5d6b6 655
f5b63a6e
RS
656Many of the libraries distributed with perl have been upgraded since v5.20.0.
657For a complete list of changes, run:
83a5d6b6 658
f5b63a6e 659 corelist --diff 5.20.0 5.22.0
338906ce 660
f5b63a6e 661You can substitute your favorite version in place of 5.20.0, too.
cd7bac54 662
f5b63a6e 663=head2 Removed Modules and Pragmata
391823f2 664
f5b63a6e
RS
665The following modules (and associated modules) have been removed from the core
666perl distribution:
eabfc7bc
RS
667
668=over 4
669
670=item *
671
f5b63a6e 672L<CGI>
69e954a5 673
7f9fef93 674=item *
86e0176a 675
f5b63a6e 676L<Module::Build>
69e954a5 677
e5998677 678=back
20b5e916 679
eabfc7bc
RS
680=head1 Documentation
681
682=head2 New Documentation
532ecd00 683
eabfc7bc 684=head3 L<perlunicook>
d76c14eb 685
eabfc7bc
RS
686This document, by Tom Christiansen, provides examples of handling Unicode in
687Perl.
688
689=head2 Changes to Existing Documentation
690
691=head3 L<perlapi>
d547bad0 692
e5998677 693=over 4
d547bad0 694
8a95d307
FC
695=item *
696
eabfc7bc 697Note that C<SvSetSV> doesn't do set magic.
532ecd00 698
eabfc7bc 699=item *
532ecd00 700
6ba7438b 701C<sv_usepvn_flags> - fix documentation to mention the use of C<Newx> instead of
eabfc7bc 702C<malloc>.
532ecd00 703
eabfc7bc 704L<[perl #121869]|https://rt.perl.org/Ticket/Display.html?id=121869>
532ecd00 705
eabfc7bc 706=item *
532ecd00 707
eabfc7bc 708Clarify where C<NUL> may be embedded or is required to terminate a string.
532ecd00 709
eabfc7bc 710=item *
532ecd00 711
d140c31c
AC
712Some documentation that was previously missing due to formatting errors is
713now included.
532ecd00 714
eabfc7bc 715=item *
532ecd00 716
eabfc7bc 717Entries are now organized into groups rather than by file where they are found.
532ecd00 718
eabfc7bc 719=item *
532ecd00 720
eabfc7bc
RS
721Alphabetical sorting of entries is now handled by the POD generator to make
722entries easier to find when scanning.
723
724=back
338906ce 725
eabfc7bc 726=head3 L<perldata>
338906ce 727
e5998677 728=over 4
338906ce 729
eabfc7bc 730=item *
2f304be9 731
eabfc7bc
RS
732The syntax of single-character variable names has been brought
733up-to-date and more fully explained.
9749148e 734
7f9fef93 735=back
9749148e 736
eabfc7bc 737=head3 L<perlebcdic>
47cb8ddb 738
7f9fef93 739=over 4
47cb8ddb 740
eabfc7bc 741=item *
47cb8ddb 742
eabfc7bc
RS
743This document has been significantly updated in the light of recent
744improvements to EBCDIC support.
47cb8ddb 745
7f9fef93 746=back
47cb8ddb 747
eabfc7bc 748=head3 L<perlfunc>
be39acb2 749
eabfc7bc 750=over 4
be39acb2 751
eabfc7bc 752=item *
be39acb2 753
eabfc7bc 754Mention that C<study()> is currently a no-op.
be39acb2
SH
755
756=item *
757
eabfc7bc
RS
758Calling C<delete> or C<exists> on array values is now described as "strongly
759discouraged" rather than "deprecated".
be39acb2 760
eabfc7bc 761=item *
7f9fef93 762
eabfc7bc 763Improve documentation of C<< our >>.
be39acb2 764
eabfc7bc 765=item *
be39acb2 766
eabfc7bc
RS
767C<-l> now notes that it will return false if symlinks aren't supported by the
768file system.
be39acb2 769
eabfc7bc 770L<[perl #121523]|https://rt.perl.org/Ticket/Display.html?id=121523>
be39acb2
SH
771
772=item *
773
eabfc7bc 774Note that C<exec LIST> and C<system LIST> may fall back to the shell on
d140c31c
AC
775Win32. Only the indirect-object syntax C<exec PROGRAM LIST> and
776C<system PROGRAM LIST> will reliably avoid using the shell.
eabfc7bc
RS
777
778This has also been noted in L<perlport>.
779
780L<[perl #122046]|https://rt.perl.org/Ticket/Display.html?id=122046>
be39acb2 781
7f9fef93 782=back
be39acb2 783
eabfc7bc
RS
784=head3 L<perlguts>
785
786=over 4
787
788=item *
789
790The OOK example has been updated to account for COW changes and a change in the
791storage of the offset.
792
793=item *
be39acb2 794
eabfc7bc 795Details on C level symbols and libperl.t added.
be39acb2 796
ce93e38b
KW
797=item *
798
799Information on Unicode handling has been added
800
801=item *
802
803Information on EBCDIC handling has been added
804
eabfc7bc
RS
805=back
806
807=head3 L<perlhacktips>
7f9fef93
SH
808
809=over 4
be39acb2
SH
810
811=item *
812
d140c31c
AC
813Documentation has been added illustrating the perils of assuming that
814there is no change to the contents of static memory pointed to by the
815return values of Perl's wrappers for C library functions.
eabfc7bc
RS
816
817=item *
818
d140c31c
AC
819Replacements for C<tmpfile>, C<atoi>, C<strtol>, and C<strtoul> are now
820recommended.
eabfc7bc
RS
821
822=item *
823
824Updated documentation for the C<test.valgrind> C<make> target.
825
826L<[perl #121431]|https://rt.perl.org/Ticket/Display.html?id=121431>
be39acb2 827
a9c3e753 828=back
ea13b07e 829
eabfc7bc 830=head3 L<perlmodstyle>
0d42058e 831
7f9fef93
SH
832=over 4
833
834=item *
2a7a05b4 835
eabfc7bc
RS
836Instead of pointing to the module list, we are now pointing to
837L<PrePAN|http://prepan.org/>.
2a7a05b4 838
7f9fef93
SH
839=back
840
eabfc7bc
RS
841=head3 L<perlpolicy>
842
843=over 4
844
845=item *
846
847We now have a code of conduct for the I<< p5p >> mailing list, as documented
848in L<< perlpolicy/STANDARDS OF CONDUCT >>.
2a7a05b4 849
eabfc7bc
RS
850=item *
851
852The conditions for marking an experimental feature as non-experimental are now
853set out.
854
855=back
856
857=head3 L<perlport>
858
859=over 4
860
861=item *
862
d140c31c 863Out-of-date VMS-specific information has been fixed and/or simplified.
eabfc7bc 864
ce93e38b
KW
865=item *
866
867Notes about EBCDIC have been added.
868
eabfc7bc
RS
869=back
870
871=head3 L<perlre>
872
873=over 4
874
875=item *
876
d140c31c
AC
877The description of the C</x> modifier has been clarified to note that
878comments cannot be continued onto the next line by escaping them.
eabfc7bc
RS
879
880=back
881
882=head3 L<perlrebackslash>
883
884=over 4
885
886=item *
887
888Added documentation of C<\b{sb}>, C<\b{wb}>, C<\b{gcb}>, and C<\b{g}>.
889
890=back
891
892=head3 L<perlrecharclass>
893
894=over 4
895
896=item *
897
898Clarifications have been added to L<perlrecharclass/Character Ranges>
899to the effect that Perl guarantees that C<[A-Z]>, C<[a-z]>, C<[0-9]> and
900any subranges thereof in regular expression bracketed character classes
901are guaranteed to match exactly what a naive English speaker would
902expect them to match, even on platforms (such as EBCDIC) where special
903handling is required to accomplish this.
904
905=item *
906
907The documentation of Bracketed Character Classes has been expanded to cover the
908improvements in C<qr/[\N{named sequence}]/> (see under L</Selected Bug Fixes>).
909
910=back
911
912=head3 L<perlsec>
913
914=over 4
915
916=item *
917
918Comments added on algorithmic complexity and tied hashes.
919
920=back
921
922=head3 L<perlsyn>
923
924=over 4
925
926=item *
927
928An ambiguity in the documentation of the C<...> statement has been corrected.
929L<[perl #122661]|https://rt.perl.org/Ticket/Display.html?id=122661>
930
931=item *
932
933The empty conditional in C<< for >> and C<< while >> is now documented
934in L<< perlsyn >>.
935
936=back
937
938=head3 L<perlunicode>
939
940=over 4
941
942=item *
943
ce93e38b
KW
944This has had extensive revisions to bring it up-to-date with current
945Unicode support and to make it more readable.
eabfc7bc
RS
946
947=back
948
949=head3 L<perluniintro>
950
951=over 4
952
953=item *
954
955Advice for how to make sure your strings and regular expression patterns are
ce93e38b 956interpreted as Unicode has been updated.
eabfc7bc
RS
957
958=back
959
960=head3 L<perlvar>
961
962=over 4
963
964=item *
965
966Further clarify version number representations and usage.
967
968=back
969
970=head3 L<perlvms>
971
972=over 4
973
974=item *
975
976Out-of-date and/or incorrect material has been removed.
977
978=item *
979
980Updated documentation on environment and shell interaction in VMS.
981
982=back
983
984=head3 L<perlxs>
985
986=over 4
987
988=item *
989
990Added a discussion of locale issues in XS code.
991
992=back
993
994=head1 Diagnostics
995
996The following additions or changes have been made to diagnostic output,
997including warnings and fatal error messages. For the complete list of
998diagnostic messages, see L<perldiag>.
999
1000=head2 New Diagnostics
1001
1002=head3 New Errors
1003
1004=over 4
1005
1006=item *
1007
1008L<Bad symbol for scalar|perldiag/"Bad symbol for scalar">
1009
1010(P) An internal request asked to add a scalar entry to something that
1011wasn't a symbol table entry.
1012
1013=item *
1014
1015L<Can't use a hash as a reference|perldiag/"Can't use a hash as a reference">
1016
1017(F) You tried to use a hash as a reference, as in
1018C<< %foo->{"bar"} >> or C<< %$ref->{"hello"} >>. Versions of perl E<lt>= 5.6.1
1019used to allow this syntax, but shouldn't have.
1020
1021=item *
1022
1023L<Can't use an array as a reference|perldiag/"Can't use an array as a reference">
1024
1025(F) You tried to use an array as a reference, as in
1026C<< @foo->[23] >> or C<< @$ref->[99] >>. Versions of perl E<lt>= 5.6.1 used to
1027allow this syntax, but shouldn't have.
1028
1029=item *
1030
1031L<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()?)">
1032
4ec8e6f0 1033(F) C<defined()> is not useful on arrays because it
eabfc7bc 1034checks for an undefined I<scalar> value. If you want to see if the
4ec8e6f0 1035array is empty, just use S<C<if (@array) { # not empty }>> for example.
eabfc7bc
RS
1036
1037=item *
1038
1039L<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()?)">
1040
1041(F) C<defined()> is not usually right on hashes.
1042
4ec8e6f0 1043Although S<C<defined %hash>> is false on a plain not-yet-used hash, it
eabfc7bc 1044becomes true in several non-obvious circumstances, including iterators,
4ec8e6f0
KW
1045weak references, stash names, even remaining true after S<C<undef %hash>>.
1046These things make S<C<defined %hash>> fairly useless in practice, so it now
eabfc7bc
RS
1047generates a fatal error.
1048
1049If a check for non-empty is what you wanted then just put it in boolean
1050context (see L<perldata/Scalar values>):
1051
1052 if (%hash) {
1053 # not empty
1054 }
1055
4ec8e6f0 1056If you had S<C<defined %Foo::Bar::QUUX>> to check whether such a package
eabfc7bc
RS
1057variable exists then that's never really been reliable, and isn't
1058a good way to enquire about the features of a package, or whether
1059it's loaded, etc.
1060
1061=item *
1062
1063L<Cannot chr %f|perldiag/"Cannot chr %f">
1064
c21a1c59
RS
1065(F) You passed an invalid number (like an infinity or not-a-number) to
1066C<chr>.
1067
eabfc7bc
RS
1068=item *
1069
1070L<Cannot compress %f in pack|perldiag/"Cannot compress %f in pack">
1071
c21a1c59
RS
1072(F) You tried converting an infinity or not-a-number to an unsigned
1073character, which makes no sense.
1074
eabfc7bc
RS
1075=item *
1076
1077L<Cannot pack %f with '%c'|perldiag/"Cannot pack %f with '%c'">
1078
c21a1c59
RS
1079(F) You tried converting an infinity or not-a-number to a character,
1080which makes no sense.
1081
eabfc7bc
RS
1082=item *
1083
1084L<Cannot print %f with '%c'|perldiag/"Cannot printf %f with '%c'">
1085
4ec8e6f0
KW
1086(F) You tried printing an infinity or not-a-number as a character (C<%c>),
1087which makes no sense. Maybe you meant C<'%s'>, or just stringifying it?
c21a1c59 1088
eabfc7bc
RS
1089=item *
1090
1091L<charnames alias definitions may not contain a sequence of multiple spaces|perldiag/"charnames alias definitions may not contain a sequence of multiple spaces">
1092
1093(F) You defined a character name which had multiple space
1094characters in a row. Change them to single spaces. Usually these
1095names are defined in the C<:alias> import argument to C<use charnames>, but
1096they could be defined by a translator installed into C<$^H{charnames}>.
1097See L<charnames/CUSTOM ALIASES>.
1098
1099=item *
1100
1101L<charnames alias definitions may not contain trailing white-space|perldiag/"charnames alias definitions may not contain trailing white-space">
1102
1103(F) You defined a character name which ended in a space
1104character. Remove the trailing space(s). Usually these names are
1105defined in the C<:alias> import argument to C<use charnames>, but they
1106could be defined by a translator installed into C<$^H{charnames}>.
1107See L<charnames/CUSTOM ALIASES>.
1108
1109=item *
1110
1111L<:const is not permitted on named subroutines|perldiag/":const is not permitted on named subroutines">
1112
1113(F) The "const" attribute causes an anonymous subroutine to be run and
f5b97b22 1114its value captured at the time that it is cloned. Named subroutines are
eabfc7bc
RS
1115not cloned like this, so the attribute does not make sense on them.
1116
1117=item *
1118
1119L<Hexadecimal float: internal error|perldiag/"Hexadecimal float: internal error">
1120
1121(F) Something went horribly bad in hexadecimal float handling.
1122
1123=item *
1124
1125L<Hexadecimal float: unsupported long double format|perldiag/"Hexadecimal float: unsupported long double format">
1126
1127(F) You have configured Perl to use long doubles but
1128the internals of the long double format are unknown,
1129therefore the hexadecimal float output is impossible.
1130
1131=item *
1132
1133L<Illegal suidscript|perldiag/"Illegal suidscript">
1134
1135(F) The script run under suidperl was somehow illegal.
1136
1137=item *
1138
1139L<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/">
1140
1141(F) The two-character sequence C<"(?"> in
1142this context in a regular expression pattern should be an
1143indivisible token, with nothing intervening between the C<"(">
1144and the C<"?">, but you separated them.
1145
1146=item *
1147
1148L<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/">
1149
1150(F) The two-character sequence C<"(*"> in
1151this context in a regular expression pattern should be an
1152indivisible token, with nothing intervening between the C<"(">
1153and the C<"*">, but you separated them.
1154
1155=item *
1156
1157L<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/">
1158
1159(F) The pattern looks like a {min,max} quantifier, but the min or max could not
1160be parsed as a valid number - either it has leading zeroes, or it represents
1161too big a number to cope with. The S<<-- HERE> shows where in the regular
1162expression the problem was discovered. See L<perlre>.
1163
1164=back
1165
1166=head3 New Warnings
1167
1168=over 4
1169
1170=item *
1171
43831b1f
DM
1172L<\C is deprecated in regex|perldiag/"\C is deprecated in regex; marked by <-- HERE in m/%s/">
1173
1174(D deprecated) The C<< /\C/ >> character class was deprecated in v5.20, and
1175now emits a warning. It is intended that it will become an error in v5.24.
1176This character class matches a single byte even if it appears within a
50ea4745 1177multi-byte character, breaks encapsulation, and can corrupt UTF-8
43831b1f
DM
1178strings.
1179
1180=item *
1181
eabfc7bc
RS
1182L<'%s' is an unknown bound type in regex|perldiag/"'%s' is an unknown bound type in regex; marked by <-- HERE in m/%s/">
1183
1184You used C<\b{...}> or C<\B{...}> and the C<...> is not known to
1185Perl. The current valid ones are given in
1186L<perlrebackslash/\b{}, \b, \B{}, \B>.
1187
1188=item *
1189
1190L<"%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>>
1191
1192(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1193
1194You specified a character that has the given plainer way of writing it,
1195and which is also portable to platforms running with different character
1196sets.
1197
1198=item *
1199
1200L<Argument "%s" treated as 0 in increment (++)|perldiag/"Argument "%s" treated
1201as 0 in increment (++)">
1202
1203(W numeric) The indicated string was fed as an argument to the C<++> operator
1204which expects either a number or a string matching C</^[a-zA-Z]*[0-9]*\z/>.
1205See L<perlop/Auto-increment and Auto-decrement> for details.
1206
1207=item *
1208
1209L<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/">
1210
1211(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1212
1213In a bracketed character class in a regular expression pattern, you
1214had a range which has exactly one end of it specified using C<\N{}>, and
1215the other end is specified using a non-portable mechanism. Perl treats
1216the range as a Unicode range, that is, all the characters in it are
1217considered to be the Unicode characters, and which may be different code
1218points on some platforms Perl runs on. For example, C<[\N{U+06}-\x08]>
1219is treated as if you had instead said C<[\N{U+06}-\N{U+08}]>, that is it
1220matches the characters whose code points in Unicode are 6, 7, and 8.
1221But that C<\x08> might indicate that you meant something different, so
1222the warning gets raised.
1223
1224=item *
1225
eabfc7bc
RS
1226L<:const is experimental|perldiag/":const is experimental">
1227
1228(S experimental::const_attr) The "const" attribute is experimental.
1229If you want to use the feature, disable the warning with C<no warnings
1230'experimental::const_attr'>, but know that in doing so you are taking
1231the risk that your code may break in a future Perl version.
1232
1233=item *
1234
1235L<gmtime(%f) failed|perldiag/"gmtime(%f) failed">
1236
1237(W overflow) You called C<gmtime> with a number that it could not handle:
1238too large, too small, or NaN. The returned value is C<undef>.
1239
1240=item *
1241
1242L<Hexadecimal float: exponent overflow|perldiag/"Hexadecimal float: exponent overflow">
1243
1244(W overflow) The hexadecimal floating point has larger exponent
1245than the floating point supports.
1246
1247=item *
1248
1249L<Hexadecimal float: exponent underflow|perldiag/"Hexadecimal float: exponent underflow">
1250
1251(W overflow) The hexadecimal floating point has smaller exponent
1252than the floating point supports.
1253
1254=item *
1255
1256L<Hexadecimal float: mantissa overflow|perldiag/"Hexadecimal float: mantissa overflow">
1257
1258(W overflow) The hexadecimal floating point literal had more bits in
1259the mantissa (the part between the 0x and the exponent, also known as
1260the fraction or the significand) than the floating point supports.
1261
1262=item *
1263
1264L<Hexadecimal float: precision loss|perldiag/"Hexadecimal float: precision loss">
1265
1266(W overflow) The hexadecimal floating point had internally more
1267digits than could be output. This can be caused by unsupported
1268long double formats, or by 64-bit integers not being available
1269(needed to retrieve the digits under some configurations).
1270
eabfc7bc
RS
1271=item *
1272
1273L<localtime(%f) failed|perldiag/"localtime(%f) failed">
1274
1275(W overflow) You called C<localtime> with a number that it could not handle:
1276too large, too small, or NaN. The returned value is C<undef>.
1277
1278=item *
1279
1280L<Negative repeat count does nothing|perldiag/"Negative repeat count does nothing">
1281
1282(W numeric) You tried to execute the
1283L<C<x>|perlop/Multiplicative Operators> repetition operator fewer than 0
1284times, which doesn't make sense.
1285
1286=item *
1287
1288L<NO-BREAK SPACE in a charnames alias definition is deprecated|perldiag/"NO-BREAK SPACE in a charnames alias definition is deprecated">
1289
1290(D deprecated) You defined a character name which contained a no-break
1291space character. Change it to a regular space. Usually these names are
1292defined in the C<:alias> import argument to C<use charnames>, but they
1293could be defined by a translator installed into C<$^H{charnames}>. See
1294L<charnames/CUSTOM ALIASES>.
1295
1296=item *
1297
1298L<Non-finite repeat count does nothing|perldiag/"Non-finite repeat count does nothing">
1299
1300(W numeric) You tried to execute the
1301L<C<x>|perlop/Multiplicative Operators> repetition operator C<Inf> (or
1302C<-Inf>) or C<NaN> times, which doesn't make sense.
1303
1304=item *
1305
1306L<PerlIO layer ':win32' is experimental|perldiag/"PerlIO layer ':win32' is experimental">
1307
1308(S experimental::win32_perlio) The C<:win32> PerlIO layer is
1309experimental. If you want to take the risk of using this layer,
1310simply disable this warning:
1311
1312 no warnings "experimental::win32_perlio";
1313
1314=item *
1315
1316L<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>">
1317
1318(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1319
1320Stricter rules help to find typos and other errors. Perhaps you didn't
1321even intend a range here, if the C<"-"> was meant to be some other
1322character, or should have been escaped (like C<"\-">). If you did
1323intend a range, the one that was used is not portable between ASCII and
1324EBCDIC platforms, and doesn't have an obvious meaning to a casual
1325reader.
1326
1327 [3-7] # OK; Obvious and portable
1328 [d-g] # OK; Obvious and portable
1329 [A-Y] # OK; Obvious and portable
1330 [A-z] # WRONG; Not portable; not clear what is meant
1331 [a-Z] # WRONG; Not portable; not clear what is meant
1332 [%-.] # WRONG; Not portable; not clear what is meant
1333 [\x41-Z] # WRONG; Not portable; not obvious to non-geek
1334
1335(You can force portability by specifying a Unicode range, which means that
1336the endpoints are specified by
1337L<C<\N{...}>|perlrecharclass/Character Ranges>, but the meaning may
1338still not be obvious.)
1339The stricter rules require that ranges that start or stop with an ASCII
93780ae6 1340character that is not a control have all their endpoints be a literal
eabfc7bc
RS
1341character, and not some escape sequence (like C<"\x41">), and the ranges
1342must be all digits, or all uppercase letters, or all lowercase letters.
1343
1344=item *
1345
1346L<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/">
1347
1348(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1349
1350Stricter rules help to find typos and other errors. You included a
1351range, and at least one of the end points is a decimal digit. Under the
1352stricter rules, when this happens, both end points should be digits in
1353the same group of 10 consecutive digits.
1354
1355=item *
1356
1357L<Redundant argument in %s|perldiag/Redundant argument in %s>
1358
f5b97b22
DM
1359(W redundant) You called a function with more arguments than were
1360needed, as indicated by information within other arguments you supplied
1361(e.g. a printf format). Currently only emitted when a printf-type format
1362required fewer arguments than were supplied, but might be used in the
1363future for e.g. L<perlfunc/pack>.
eabfc7bc 1364
a75e6a3a
SH
1365The warnings category C<< redundant >> is new. See also
1366L<[perl #121025]|https://rt.perl.org/Ticket/Display.html?id=121025>.
eabfc7bc
RS
1367
1368=item *
1369
1370L<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">
1371
1372You are matching a regular expression using locale rules,
1373and a Unicode boundary is being matched, but the locale is not a Unicode
1374one. This doesn't make sense. Perl will continue, assuming a Unicode
1375(UTF-8) locale, but the results could well be wrong except if the locale
1376happens to be ISO-8859-1 (Latin1) where this message is spurious and can
1377be ignored.
1378
1379=item *
1380
1381L<< 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>" >>
1382
1383You used a Unicode boundary (C<\b{...}> or C<\B{...}>) in a
1384portion of a regular expression where the character set modifiers C</a>
1385or C</aa> are in effect. These two modifiers indicate an ASCII
1386interpretation, and this doesn't make sense for a Unicode definition.
1387The generated regular expression will compile so that the boundary uses
1388all of Unicode. No other portion of the regular expression is affected.
1389
1390=item *
1391
1392L<The bitwise feature is experimental|perldiag/"The bitwise feature is experimental">
1393
1394This warning is emitted if you use bitwise
1395operators (C<& | ^ ~ &. |. ^. ~.>) with the "bitwise" feature enabled.
1396Simply suppress the warning if you want to use the feature, but know
1397that in doing so you are taking the risk of using an experimental
1398feature which may change or be removed in a future Perl version:
1399
1400 no warnings "experimental::bitwise";
1401 use feature "bitwise";
1402 $x |.= $y;
1403
1404=item *
1405
1406L<Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in mE<sol>%sE<sol>|perldiag/"Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/%s/">
1407
1408(D deprecated, regexp) You used a literal C<"{"> character in a regular
1409expression pattern. You should change to use C<"\{"> instead, because a future
1410version of Perl (tentatively v5.26) will consider this to be a syntax error. If
1411the pattern delimiters are also braces, any matching right brace
1412(C<"}">) should also be escaped to avoid confusing the parser, for
1413example,
1414
1415 qr{abc\{def\}ghi}
1416
1417=item *
1418
1419L<Use of literal non-graphic characters in variable names is deprecated|perldiag/"Use of literal non-graphic characters in variable names is deprecated">
1420
b0511669
DM
1421(D deprecated) Using literal non-graphic (including control)
1422characters in the source to refer to the ^FOO variables, like C<$^X> and
1423C<${^GLOBAL_PHASE}> is now deprecated.
1424
eabfc7bc
RS
1425=item *
1426
1427L<Useless use of attribute "const"|perldiag/Useless use of attribute "const">
1428
1429(W misc) The "const" attribute has no effect except
1430on anonymous closure prototypes. You applied it to
1431a subroutine via L<attributes.pm|attributes>. This is only useful
1432inside an attribute handler for an anonymous subroutine.
1433
1434=item *
1435
1436L<E<quot>use re 'strict'E<quot> is experimental|perldiag/"use re 'strict'" is experimental>
1437
1438(S experimental::re_strict) The things that are different when a regular
1439expression pattern is compiled under C<'strict'> are subject to change
1440in future Perl releases in incompatible ways. This means that a pattern
1441that compiles today may not in a future Perl release. This warning is
1442to alert you to that risk.
1443
1444=item *
1445
caa16dbd
TC
1446L<Warning: unable to close filehandle properly: %s|perldiag/"Warning: unable to close filehandle properly: %s">
1447
eabfc7bc
RS
1448L<Warning: unable to close filehandle %s properly: %s|perldiag/"Warning: unable to close filehandle %s properly: %s">
1449
b0511669
DM
1450(S io) Previously perl silently ignored any errors when doing an implicit
1451close of a filehandle, i.e. where the reference count of the filehandle
1452reached zero and the user's code hadn't already called C<close()>; e.g.
1453
1454 {
1455 open my $fh, '>', $file or die "open: '$file': $!\n";
1456 print $fh, $data or die;
1457 } # implicit close here
1458
1459In a situation such as disk full, due to buffering the error may only be
1460detected during the final close, so not checking the result of the close is
1461dangerous.
1462
1463So perl now warns in such situations.
caa16dbd 1464
eabfc7bc
RS
1465=item *
1466
1467L<Wide character (U+%X) in %s|perldiag/"Wide character (U+%X) in %s">
1468
1469(W locale) While in a single-byte locale (I<i.e.>, a non-UTF-8
1470one), a multi-byte character was encountered. Perl considers this
50ea4745 1471character to be the specified Unicode code point. Combining non-UTF-8
eabfc7bc
RS
1472locales and Unicode is dangerous. Almost certainly some characters
1473will have two different representations. For example, in the ISO 8859-7
1474(Greek) locale, the code point 0xC3 represents a Capital Gamma. But so
1475also does 0x393. This will make string comparisons unreliable.
1476
1477You likely need to figure out how this multi-byte character got mixed up
1478with your single-byte locale (or perhaps you thought you had a UTF-8
1479locale, but Perl disagrees).
1480
1481=item *
1482
1483The following two warnings for C<tr///> used to be skipped if the
1484transliteration contained wide characters, but now they occur regardless of
1485whether there are wide characters or not:
1486
1487L<Useless use of E<sol>d modifier in transliteration operator|perldiag/"Useless use of /d modifier in transliteration operator">
1488
1489L<Replacement list is longer than search list|perldiag/Replacement list is longer than search list>
1490
1491=item *
1492
1493A new C<locale> warning category has been created, with the following warning
1494messages currently in it:
1495
1496=over 4
1497
1498=item *
1499
1500L<Locale '%s' may not work well.%s|perldiag/Locale '%s' may not work well.%s>
1501
b0511669
DM
1502(W locale) You are using the named locale, which is a non-UTF-8 one, and
1503which Perl has determined is not fully compatible with Perl. The second
1504C<%s> gives a reason.
1505
eabfc7bc
RS
1506=item *
1507
1508L<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".>
1509
b0511669
DM
1510(W locale) You are 1) running under "C<use locale>"; 2) the current
1511locale is not a UTF-8 one; 3) you tried to do the designated case-change
1512operation on the specified Unicode character; and 4) the result of this
1513operation would mix Unicode and locale rules, which likely conflict.
1514
eabfc7bc
RS
1515=back
1516
b0511669
DM
1517=item *
1518
1519L<Missing or undefined argument to require|perldiag/Missing or undefined argument to require>
1520
1521(F) You tried to call require with no argument or with an undefined
1522value as an argument. Require expects either a package name or a
1523file-specification as an argument. See L<perlfunc/require>.
1524
1525Formerly, C<require> with no argument or undef warned about a Null filename.
1526
eabfc7bc
RS
1527=back
1528
1529=head2 Changes to Existing Diagnostics
1530
1531=over 4
1532
1533=item *
1534
1535<> should be quotes
1536
1537This warning has been changed to
1538L<< <> at require-statement should be quotes|perldiag/"<> at require-statement should be quotes" >>
1539to make the issue more identifiable.
1540
1541=item *
1542
1543L<Argument "%s" isn't numeric%s|perldiag/"Argument "%s" isn't numeric%s">
b0511669
DM
1544
1545The L<perldiag> entry for this warning has added this clarifying note:
eabfc7bc 1546
4ec8e6f0 1547 Note that for the Inf and NaN (infinity and not-a-number) the
77c2376a
KW
1548 definition of "numeric" is somewhat unusual: the strings themselves
1549 (like "Inf") are considered numeric, and anything following them is
1550 considered non-numeric.
eabfc7bc
RS
1551
1552=item *
1553
1554L<Global symbol "%s" requires explicit package name|perldiag/"Global symbol "%s" requires explicit package name (did you forget to declare "my %s"?)">
1555
1556This message has had '(did you forget to declare "my %s"?)' appended to it, to
1557make it more helpful to new Perl programmers.
1558L<[perl #121638]|https://rt.perl.org/Ticket/Display.html?id=121638>
1559
1560=item *
1561
1562'"my" variable &foo::bar can't be in a package' has been reworded to say
1563'subroutine' instead of 'variable'.
1564
1565=item *
1566
b0511669
DM
1567L<<< \N{} in character class restricted to one character in regex; marked by
1568S<< <-- HERE >> in mE<sol>%sE<sol>|perldiag/"\N{} in inverted character
1569class or as a range end-point is restricted to one character in regex;
1570marked by <-- HERE in m/%s/" >>>
eabfc7bc 1571
b0511669
DM
1572This message has had I<character class> changed to I<inverted character
1573class or as a range end-point is> to reflect improvements in
1574C<qr/[\N{named sequence}]/> (see under L</Selected Bug Fixes>).
eabfc7bc
RS
1575
1576=item *
1577
1578L<panic: frexp|perldiag/"panic: frexp: %f">
1579
b0511669
DM
1580This message has had ': C<%f>' appended to it, to show what the offending
1581floating point number is.
eabfc7bc
RS
1582
1583=item *
1584
b0511669 1585I<Possible precedence problem on bitwise %c operator> reworded as
eabfc7bc
RS
1586L<Possible precedence problem on bitwise %s operator|perldiag/"Possible precedence problem on bitwise %s operator">.
1587
1588=item *
1589
eabfc7bc
RS
1590L<Unsuccessful %s on filename containing newline|perldiag/"Unsuccessful %s on filename containing newline">
1591
1592This warning is now only produced when the newline is at the end of
1593the filename.
1594
1595=item *
1596
4ec8e6f0 1597"Variable C<%s> will not stay shared" has been changed to say "Subroutine"
eabfc7bc
RS
1598when it is actually a lexical sub that will not stay shared.
1599
1600=item *
1601
1602L<Variable length lookbehind not implemented in regex mE<sol>%sE<sol>|perldiag/"Variable length lookbehind not implemented in regex m/%s/">
1603
b0511669
DM
1604The L<perldiag> entry for this warning has had information about Unicode
1605behaviour added.
eabfc7bc
RS
1606
1607=back
1608
1609=head2 Diagnostic Removals
1610
1611=over
1612
1613=item *
1614
1615"Ambiguous use of -foo resolved as -&foo()"
1616
1617There is actually no ambiguity here, and this impedes the use of negated
1618constants; e.g., C<-Inf>.
1619
1620=item *
1621
1622"Constant is not a FOO reference"
1623
1624Compile-time checking of constant dereferencing (e.g., C<< my_constant->() >>)
1625has been removed, since it was not taking overloading into account.
1626L<[perl #69456]|https://rt.perl.org/Ticket/Display.html?id=69456>
1627L<[perl #122607]|https://rt.perl.org/Ticket/Display.html?id=122607>
1628
1629=back
1630
1631=head1 Utility Changes
1632
b0511669 1633=head2 F<find2perl>, F<s2p> and F<a2p> removal
eabfc7bc
RS
1634
1635=over 4
1636
1637=item *
1638
1639The F<x2p/> directory has been removed from the Perl core.
1640
1641This removes find2perl, s2p and a2p. They have all been released to CPAN as
1642separate distributions (App::find2perl, App::s2p, App::a2p).
1643
1644=back
1645
1646=head2 L<h2ph>
1647
1648=over 4
1649
1650=item *
1651
1652F<h2ph> now handles hexadecimal constants in the compiler's predefined
a75e6a3a
SH
1653macro definitions, as visible in C<$Config{cppsymbols}>.
1654L<[perl #123784]|https://rt.perl.org/Ticket/Display.html?id=123784>.
eabfc7bc
RS
1655
1656=back
1657
1658=head2 L<encguess>
1659
1660=over 4
1661
1662=item *
1663
f1c9eac6 1664No longer depends on non-core modules.
eabfc7bc
RS
1665
1666=back
1667
1668=head1 Configuration and Compilation
1669
1670=over 4
1671
1672=item *
1673
b0511669
DM
1674F<Configure> now checks for C<lrintl()>, C<lroundl()>, C<llrintl()>, and
1675C<llroundl()>.
eabfc7bc
RS
1676
1677=item *
1678
a75e6a3a
SH
1679F<Configure> with C<-Dmksymlinks> should now be faster.
1680L<[perl #122002]|https://rt.perl.org/Ticket/Display.html?id=122002>.
eabfc7bc
RS
1681
1682=item *
1683
b0511669
DM
1684The C<pthreads> and C<cl> libraries will be linked by default if present.
1685This allows XS modules that require threading to work on non-threaded
1686perls. Note that you must still pass C<-Dusethreads> if you want a
1687threaded perl.
eabfc7bc
RS
1688
1689=item *
1690
1691For long doubles (to get more precision and range for floating point numbers)
1692one can now use the GCC quadmath library which implements the quadruple
f1c9eac6
DM
1693precision floating point numbers on x86 and IA-64 platforms. See
1694F<INSTALL> for details.
eabfc7bc
RS
1695
1696=item *
1697
1698MurmurHash64A and MurmurHash64B can now be configured as the internal hash
1699function.
1700
1701=item *
1702
1703C<make test.valgrind> now supports parallel testing.
1704
1705For example:
1706
1707 TEST_JOBS=9 make test.valgrind
1708
1709See L<perlhacktips/valgrind> for more information.
1710
1711L<[perl #121431]|https://rt.perl.org/Ticket/Display.html?id=121431>
1712
1713=item *
1714
1715The MAD (Misc Attribute Decoration) build option has been removed
1716
1717This was an unmaintained attempt at preserving
1718the Perl parse tree more faithfully so that automatic conversion of
1719Perl 5 to Perl 6 would have been easier.
1720
1721This build-time configuration option had been unmaintained for years,
1722and had probably seriously diverged on both Perl 5 and Perl 6 sides.
1723
1724=item *
1725
1726A new compilation flag, C<< -DPERL_OP_PARENT >> is available. For details,
1727see the discussion below at L<< /Internal Changes >>.
1728
43831b1f
DM
1729=item *
1730
1731Pathtools no longer tries to load XS on miniperl. This speeds up building perl
1732slightly.
1733
eabfc7bc
RS
1734=back
1735
1736=head1 Testing
1737
1738=over 4
1739
1740=item *
1741
1742F<t/porting/re_context.t> has been added to test that L<utf8> and its
1743dependencies only use the subset of the C<$1..$n> capture vars that
b0511669
DM
1744C<Perl_save_re_context()> is hard-coded to localize, because that function
1745has no efficient way of determining at runtime what vars to localize.
eabfc7bc
RS
1746
1747=item *
1748
1749Tests for performance issues have been added in the file F<t/perf/taint.t>.
1750
1751=item *
1752
1753Some regular expression tests are written in such a way that they will
1754run very slowly if certain optimizations break. These tests have been
1755moved into new files, F<< t/re/speed.t >> and F<< t/re/speed_thr.t >>,
1756and are run with a C<< watchdog() >>.
1757
1758=item *
1759
1760C<< test.pl >> now allows C<< plan skip_all => $reason >>, to make it
1761more compatible with C<< Test::More >>.
1762
1763=item *
1764
1765A new test script, F<op/infnan.t>, has been added to test if Inf and NaN are
1766working correctly. See L</Infinity and NaN (not-a-number) handling improved>.
1767
1768=back
1769
1770=head1 Platform Support
1771
1772=head2 Regained Platforms
1773
1774=over 4
1775
1776=item IRIX and Tru64 platforms are working again.
1777
1778(Some C<make test> failures remain.)
1779
1780=item z/OS running EBCDIC Code Page 1047
1781
1782Core perl now works on this EBCDIC platform. Earlier perls also worked, but,
1783even though support wasn't officially withdrawn, recent perls would not compile
1784and run well. Perl 5.20 would work, but had many bugs which have now been
1785fixed. Many CPAN modules that ship with Perl still fail tests, including
1786Pod::Simple. However the version of Pod::Simple currently on CPAN should work;
1787it was fixed too late to include in Perl 5.22. Work is under way to fix many
1788of the still-broken CPAN modules, which likely will be installed on CPAN when
1789completed, so that you may not have to wait until Perl 5.24 to get a working
1790version.
1791
1792=back
1793
1794=head2 Discontinued Platforms
1795
1796=over 4
1797
1798=item NeXTSTEP/OPENSTEP
1799
f1c9eac6
DM
1800NeXTSTEP was a proprietary operating system bundled with NeXT's
1801workstations in the early to mid 90s; OPENSTEP was an API specification
1802that provided a NeXTSTEP-like environment on a non-NeXTSTEP system. Both
1803are now long dead, so support for building Perl on them has been removed.
eabfc7bc
RS
1804
1805=back
1806
1807=head2 Platform-Specific Notes
1808
1809=over 4
1810
1811=item EBCDIC
1812
1813Special handling is required on EBCDIC platforms to get C<qr/[i-j]/> to
1814match only C<"i"> and C<"j">, since there are 7 characters between the
1815code points for C<"i"> and C<"j">. This special handling had only been
1816invoked when both ends of the range are literals. Now it is also
1817invoked if any of the C<\N{...}> forms for specifying a character by
1818name or Unicode code point is used instead of a literal. See
1819L<perlrecharclass/Character Ranges>.
1820
1821=item HP-UX
1822
1823The archname now distinguishes use64bitint from use64bitall.
1824
1825=item Android
1826
1827Build support has been improved for cross-compiling in general and for
1828Android in particular.
1829
1830=item VMS
1831
1832=over 4
1833
1834=item *
1835
1836When spawning a subprocess without waiting, the return value is now
1837the correct PID.
1838
1839=item *
1840
1841Fix a prototype so linking doesn't fail under the VMS C++ compiler.
1842
1843=item *
1844
1845C<finite>, C<finitel>, and C<isfinite> detection has been added to
1846C<configure.com>, environment handling has had some minor changes, and
1847a fix for legacy feature checking status.
1848
1849=back
1850
1851=item Win32
1852
1853=over 4
1854
1855=item *
1856
1857F<miniperl.exe> is now built with C<-fno-strict-aliasing>, allowing 64-bit
1858builds to complete on GCC 4.8.
1859L<[perl #123976]|https://rt.perl.org/Ticket/Display.html?id=123976>
1860
1861=item *
1862
17fcdc49
TC
1863C<nmake minitest> now works on Win32. Due to dependency issues you
1864need to build C<nmake test-prep> first, and a small number of the
1865tests fail.
1866L<[perl #123394]|https://rt.perl.org/Ticket/Display.html?id=123394>
1867
1868=item *
1869
eabfc7bc
RS
1870Perl can now be built in C++ mode on Windows by setting the makefile macro
1871C<USE_CPLUSPLUS> to the value "define".
1872
1873=item *
1874
d140c31c 1875The list form of piped open has been implemented for Win32. Note: unlike
00eebae1 1876C<system LIST> this does not fall back to the shell.
18f4cc8e 1877L<[perl #121159]|https://rt.perl.org/Ticket/Display.html?id=121159>
eabfc7bc
RS
1878
1879=item *
1880
eabfc7bc
RS
1881New C<DebugSymbols> and C<DebugFull> configuration options added to
1882Windows makefiles.
1883
1884=item *
1885
f1c9eac6 1886Previously compiling XS modules (including CPAN ones) using Visual C++ for
b0511669 1887Win64 resulted in around a dozen warnings per file from F<hv_func.h>. These
f1c9eac6 1888warnings have been silenced.
eabfc7bc
RS
1889
1890=item *
1891
1892Support for building without PerlIO has been removed from the Windows
1893makefiles. Non-PerlIO builds were all but deprecated in Perl 5.18.0 and are
1894already not supported by F<Configure> on POSIX systems.
1895
1896=item *
1897
d140c31c
AC
1898Between 2 and 6 milliseconds and seven I/O calls have been saved per attempt
1899to open a perl module for each path in C<@INC>.
eabfc7bc
RS
1900
1901=item *
1902
1903Intel C builds are now always built with C99 mode on.
1904
1905=item *
1906
1907C<%I64d> is now being used instead of C<%lld> for MinGW.
1908
1909=item *
1910
1911In the experimental C<:win32> layer, a crash in C<open> was fixed. Also
d140c31c
AC
1912opening C</dev/null> (which works under Win32 Perl's default C<:unix>
1913layer) was implemented for C<:win32>.
eabfc7bc
RS
1914L<[perl #122224]|https://rt.perl.org/Ticket/Display.html?id=122224>
1915
1916=item *
1917
1918A new makefile option, C<USE_LONG_DOUBLE>, has been added to the Windows
1919dmake makefile for gcc builds only. Set this to "define" if you want perl to
1920use long doubles to give more accuracy and range for floating point numbers.
1921
1922=back
1923
1924=item OpenBSD
1925
1926On OpenBSD, Perl will now default to using the system C<malloc> due to the
1927security features it provides. Perl's own malloc wrapper has been in use
1928since v5.14 due to performance reasons, but the OpenBSD project believes
1929the tradeoff is worth it and would prefer that users who need the speed
1930specifically ask for it.
1931
1932L<[perl #122000]|https://rt.perl.org/Ticket/Display.html?id=122000>.
1933
1934=item Solaris
1935
1936=over 4
1937
1938=item *
1939
1940We now look for the Sun Studio compiler in both F</opt/solstudio*> and
1941F</opt/solarisstudio*>.
1942
1943=item *
1944
1945Builds on Solaris 10 with C<-Dusedtrace> would fail early since make
1946didn't follow implied dependencies to build C<perldtrace.h>. Added an
1947explicit dependency to C<depend>.
1948L<[perl #120120]|https://rt.perl.org/Ticket/Display.html?id=120120>
1949
1950=item *
1951
d140c31c
AC
1952C<c99> options have been cleaned up; hints look for C<solstudio>
1953as well as C<SUNWspro>; and support for native C<setenv> has been added.
eabfc7bc
RS
1954
1955=back
1956
1957=back
1958
1959=head1 Internal Changes
1960
1961=over 4
1962
1963=item *
1964
bad0181b
DM
1965Experimental support has been added to allow ops in the optree to locate
1966their parent, if any. This is enabled by the non-default build option
1967C<-DPERL_OP_PARENT>. It is envisaged that this will eventually become
b0511669 1968enabled by default, so XS code which directly accesses the C<op_sibling>
bad0181b 1969field of ops should be updated to be future-proofed.
eabfc7bc
RS
1970
1971On C<PERL_OP_PARENT> builds, the C<op_sibling> field has been renamed
bad0181b
DM
1972C<op_sibparent> and a new flag, C<op_moresib>, added. On the last op in a
1973sibling chain, C<op_moresib> is false and C<op_sibparent> points to the
b0511669 1974parent (if any) rather than being C<NULL>.
bad0181b 1975
b0511669 1976To make existing code work transparently whether using C<PERL_OP_PARENT>
bad0181b
DM
1977or not, a number of new macros and functions have been added that should
1978be used, rather than directly manipulating C<op_sibling>.
1979
1980For the case of just reading C<op_sibling> to determine the next sibling,
1981two new macros have been added. A simple scan through a sibling chain
1982like this:
1983
b0511669 1984 for (; kid->op_sibling; kid = kid->op_sibling) { ... }
bad0181b
DM
1985
1986should now be written as:
1987
b0511669 1988 for (; OpHAS_SIBLING(kid); kid = OpSIBLING(kid)) { ... }
bad0181b 1989
d140c31c 1990For altering optrees, a general-purpose function C<op_sibling_splice()>
bad0181b
DM
1991has been added, which allows for manipulation of a chain of sibling ops.
1992By analogy with the Perl function C<splice()>, it allows you to cut out
1993zero or more ops from a sibling chain and replace them with zero or more
1994new ops. It transparently handles all the updating of sibling, parent,
1995op_last pointers etc.
1996
1997If you need to manipulate ops at a lower level, then three new macros,
1998C<OpMORESIB_set>, C<OpLASTSIB_set> and C<OpMAYBESIB_set> are intended to
1999be a low-level portable way to set C<op_sibling> / C<op_sibparent> while
2000also updating C<op_moresib>. The first sets the sibling pointer to a new
2001sibling, the second makes the op the last sibling, and the third
2002conditionally does the first or second action. Note that unlike
2003C<op_sibling_splice()> these macros won't maintain consistency in the
2004parent at the same time (e.g. by updating C<op_first> and C<op_last> where
2005appropriate).
2006
d140c31c 2007A C-level C<Perl_op_parent()> function and a Perl-level C<B::OP::parent()>
bad0181b 2008method have been added. The C function only exists under
b0511669 2009C<PERL_OP_PARENT> builds (using it is build-time error on vanilla
bad0181b 2010perls). C<B::OP::parent()> exists always, but on a vanilla build it
b0511669 2011always returns C<NULL>. Under C<PERL_OP_PARENT>, they return the parent
bad0181b
DM
2012of the current op, if any. The variable C<$B::OP::does_parent> allows you
2013to determine whether C<B> supports retrieving an op's parent.
2014
b0511669 2015C<PERL_OP_PARENT> was introduced in 5.21.2, but the interface was
bad0181b
DM
2016changed considerably in 5.21.11. If you updated your code before the
20175.21.11 changes, it may require further revision. The main changes after
20185.21.2 were:
eabfc7bc 2019
bad0181b 2020=over 4
eabfc7bc
RS
2021
2022=item *
2023
bad0181b
DM
2024The C<OP_SIBLING> and C<OP_HAS_SIBLING> macros have been renamed
2025C<OpSIBLING> and C<OpHAS_SIBLING> for consistency with other
2026op-manipulating macros.
eabfc7bc
RS
2027
2028=item *
2029
bad0181b
DM
2030The C<op_lastsib> field has been renamed C<op_moresib>, and its meaning
2031inverted.
eabfc7bc
RS
2032
2033=item *
2034
bad0181b
DM
2035The macro C<OpSIBLING_set> has been removed, and has been superseded by
2036C<OpMORESIB_set> et al.
eabfc7bc
RS
2037
2038=item *
2039
bad0181b
DM
2040The C<op_sibling_splice()> function now accepts a null C<parent> argument
2041where the splicing doesn't affect the first or last ops in the sibling
2042chain
eabfc7bc
RS
2043
2044=back
2045
2046=item *
2047
2048Macros have been created to allow XS code to better manipulate the POSIX locale
2049category C<LC_NUMERIC>. See L<perlapi/Locale-related functions and macros>.
2050
2051=item *
2052
2053The previous C<atoi> et al replacement function, C<grok_atou>, has now been
2054superseded by C<grok_atoUV>. See L<perlclib> for details.
2055
2056=item *
2057
b0511669
DM
2058A new function, C<Perl_sv_get_backrefs()>, has been added which allows you
2059retrieve the weak references, if any, which point at an SV.
eabfc7bc
RS
2060
2061=item *
2062
b0511669 2063The C<screaminstr()> function has been removed. Although marked as
f1c9eac6
DM
2064public API, it was undocumented and had no usage in CPAN modules. Calling
2065it has been fatal since 5.17.0.
eabfc7bc
RS
2066
2067=item *
2068
b0511669
DM
2069The C<newDEFSVOP()>, C<block_start()>, C<block_end()> and C<intro_my()>
2070functions have been added to the API.
eabfc7bc
RS
2071
2072=item *
2073
2074The internal C<convert> function in F<op.c> has been renamed
2075C<op_convert_list> and added to the API.
2076
2077=item *
2078
b0511669
DM
2079The C<sv_magic()> function no longer forbids "ext" magic on read-only
2080values. After all, perl can't know whether the custom magic will modify
2081the SV or not.
a75e6a3a 2082L<[perl #123103]|https://rt.perl.org/Ticket/Display.html?id=123103>.
eabfc7bc
RS
2083
2084=item *
2085
d140c31c
AC
2086Accessing L<perlapi/CvPADLIST> on an XSUB is now forbidden.
2087
cca58a48
DM
2088The C<CvPADLIST> field has been reused for a different internal purpose
2089for XSUBs. So in particular, you can no longer rely on it being NULL as a
2090test of whether a CV is an XSUB. Use C<CvISXSUB()> instead.
2091
eabfc7bc
RS
2092=item *
2093
b0511669 2094SVs of type C<SVt_NV> are now sometimes bodiless when the build
cca58a48 2095configuration and platform allow it: specifically, when C<< sizeof(NV) <=
b0511669 2096sizeof(IV) >>. "Bodiless" means that the NV value is stored directly in
cca58a48
DM
2097the head of an SV, without requiring a separate body to be allocated. This
2098trick has already been used for IVs since 5.9.2 (though in the case of
2099IVs, it is always used, regardless of platform and build configuration).
eabfc7bc
RS
2100
2101=item *
2102
b0511669 2103The C<$DB::single>, C<$DB::signal> and C<$DB::trace> variables now have set- and
d140c31c 2104get-magic that stores their values as IVs, and those IVs are used when
b0511669 2105testing their values in C<pp_dbstate()>. This prevents perl from
f1c9eac6 2106recursing infinitely if an overloaded object is assigned to any of those
a75e6a3a
SH
2107variables.
2108L<[perl #122445]|https://rt.perl.org/Ticket/Display.html?id=122445>.
eabfc7bc
RS
2109
2110=item *
2111
b0511669 2112C<Perl_tmps_grow()>, which is marked as public API but is undocumented, has
d140c31c 2113been removed from the public API. This change does not affect XS code that
b0511669 2114uses the C<EXTEND_MORTAL> macro to pre-extend the mortal stack.
eabfc7bc
RS
2115
2116=item *
2117
b0511669
DM
2118Perl's internals no longer sets or uses the C<SVs_PADMY> flag.
2119C<SvPADMY()> now returns a true value for anything not marked C<PADTMP>
2120and C<SVs_PADMY> is now defined as 0.
eabfc7bc
RS
2121
2122=item *
2123
d140c31c 2124The macros C<SETsv> and C<SETsvUN> have been removed. They were no longer used
b0511669
DM
2125in the core since commit 6f1401dc2a five years ago, and have not been
2126found present on CPAN.
eabfc7bc
RS
2127
2128=item *
2129
2130The C<< SvFAKE >> bit (unused on HVs) got informally reserved by
2131David Mitchell for future work on vtables.
2132
2133=item *
2134
b0511669 2135The C<sv_catpvn_flags()> function accepts C<SV_CATBYTES> and C<SV_CATUTF8>
50ea4745 2136flags, which specify whether the appended string is bytes or UTF-8,
b0511669
DM
2137respectively. (These flags have in fact been present since 5.16.0, but
2138were formerly not regarded as part of the API.)
eabfc7bc
RS
2139
2140=item *
2141
f1c9eac6 2142A new opcode class, C<< METHOP >>, has been introduced. It holds
d140c31c 2143information used at runtime for improve the performance
eabfc7bc
RS
2144of class/object method calls.
2145
d140c31c 2146C<< OP_METHOD >> and C<< OP_METHOD_NAMED >> have changed from being
eabfc7bc
RS
2147C<< UNOP/SVOP >> to being C<< METHOP >>.
2148
2149=item *
2150
b0511669
DM
2151C<cv_name()> is a new API function that can be passed a CV or GV. It
2152returns an SV containing the name of the subroutine, for use in
2153diagnostics.
eabfc7bc 2154
b0511669
DM
2155Note that after C<cv_name> was introduced in 5.21.4, it had a C<flags>
2156field added in 5.21.5 which allows the caller to specify whether the name
2157should be fully qualified. See L<perlapi/cv_name>.
eabfc7bc 2158
eabfc7bc
RS
2159L<[perl #116735]|https://rt.perl.org/Ticket/Display.html?id=116735>
2160L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
2161
2162=item *
2163
b0511669
DM
2164C<cv_set_call_checker_flags()> is a new API function that works like
2165C<cv_set_call_checker()>, except that it allows the caller to specify
2166whether the call checker requires a full GV for reporting the subroutine's
2167name, or whether it could be passed a CV instead. Whatever value is
2168passed will be acceptable to C<cv_name()>. C<cv_set_call_checker()>
2169guarantees there will be a GV, but it may have to create one on the fly,
2170which is inefficient.
eabfc7bc
RS
2171L<[perl #116735]|https://rt.perl.org/Ticket/Display.html?id=116735>
2172
2173=item *
2174
2175C<CvGV> (which is not part of the API) is now a more complex macro, which may
b0511669 2176call a function and reify a GV. For those cases where it has been used as a
eabfc7bc
RS
2177boolean, C<CvHASGV> has been added, which will return true for CVs that
2178notionally have GVs, but without reifying the GV. C<CvGV> also returns a GV
2179now for lexical subs.
2180L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
2181
2182=item *
2183
d140c31c
AC
2184The L<perlapi/sync_locale> function has been added to the public API.
2185Changing the program's locale should be avoided by XS code. Nevertheless,
2186certain non-Perl libraries called from XS need to do so, such as C<Gtk>.
2187When this happens, Perl needs to be told that the locale has
eabfc7bc
RS
2188changed. Use this function to do so, before returning to Perl.
2189
2190=item *
2191
2192The defines and labels for the flags in the C<op_private> field of OPs are now
2193auto-generated from data in F<regen/op_private>. The noticeable effect of this
2194is that some of the flag output of C<Concise> might differ slightly, and the
2195flag output of C<perl -Dx> may differ considerably (they both use the same set
d140c31c
AC
2196of labels now). Also, debugging builds now have a new assertion in
2197C<op_free()> to ensure that the op doesn't have any unrecognized flags set in
eabfc7bc
RS
2198C<op_private>.
2199
2200=item *
2201
eabfc7bc
RS
2202The deprecated variable C<PL_sv_objcount> has been removed.
2203
2204=item *
2205
2206Perl now tries to keep the locale category C<LC_NUMERIC> set to "C"
2207except around operations that need it to be set to the program's
2208underlying locale. This protects the many XS modules that cannot cope
2209with the decimal radix character not being a dot. Prior to this
2210release, Perl initialized this category to "C", but a call to
2211C<POSIX::setlocale()> would change it. Now such a call will change the
2212underlying locale of the C<LC_NUMERIC> category for the program, but the
ce93e38b
KW
2213locale exposed to XS code will remain "C". There are new macros
2214to manipulate the LC_NUMERIC locale, including
2215C<STORE_LC_NUMERIC_SET_TO_NEEDED> and
2216C<STORE_LC_NUMERIC_FORCE_TO_UNDERLYING>.
2217See L<perlapi/Locale-related functions and macros>.
eabfc7bc
RS
2218
2219=item *
2220
2221A new macro L<C<isUTF8_CHAR>|perlapi/isUTF8_CHAR> has been written which
2222efficiently determines if the string given by its parameters begins
2223with a well-formed UTF-8 encoded character.
2224
2225=item *
2226
b0511669 2227The following private API functions had their context parameter removed:
eabfc7bc
RS
2228C<Perl_cast_ulong>, C<Perl_cast_i32>, C<Perl_cast_iv>, C<Perl_cast_uv>,
2229C<Perl_cv_const_sv>, C<Perl_mg_find>, C<Perl_mg_findext>, C<Perl_mg_magical>,
2230C<Perl_mini_mktime>, C<Perl_my_dirfd>, C<Perl_sv_backoff>, C<Perl_utf8_hop>.
2231
cca58a48
DM
2232Note that the prefix-less versions of those functions that are part of the
2233public API, such as C<cast_i32()>, remain unaffected.
eabfc7bc
RS
2234
2235=item *
2236
b0511669
DM
2237The C<PADNAME> and C<PADNAMELIST> types are now separate types, and no
2238longer simply aliases for SV and AV.
a75e6a3a 2239L<[perl #123223]|https://rt.perl.org/Ticket/Display.html?id=123223>.
eabfc7bc
RS
2240
2241=item *
2242
50ea4745 2243Pad names are now always UTF-8. The C<PadnameUTF8> macro always returns
eabfc7bc
RS
2244true. Previously, this was effectively the case already, but any support
2245for two different internal representations of pad names has now been
2246removed.
2247
2248=item *
2249
eabfc7bc
RS
2250A new op class, C<UNOP_AUX>, has been added. This is a subclass of
2251C<UNOP> with an C<op_aux> field added, which points to an array of unions
2252of C<UV>, C<SV*> etc. It is intended for where an op needs to store more data
2253than a simple C<op_sv> or whatever. Currently the only op of this type is
2254C<OP_MULTIDEREF> (see below).
2255
2256=item *
2257
2258A new op has been added, C<OP_MULTIDEREF>, which performs one or more
2259nested array and hash lookups where the key is a constant or simple
2260variable. For example the expression C<$a[0]{$k}[$i]>, which previously
2261involved ten C<rv2Xv>, C<Xelem>, C<gvsv> and C<const> ops is now performed
2262by a single C<multideref> op. It can also handle C<local>, C<exists> and
2263C<delete>. A non-simple index expression, such as C<[$i+1]> is still done
77c2376a 2264using C<aelem>/C<helem>, and single-level array lookup with a small constant
eabfc7bc
RS
2265index is still done using C<aelemfast>.
2266
2267=back
2268
2269=head1 Selected Bug Fixes
2270
2271=over 4
2272
2273=item *
2274
33ca8d3c
DM
2275C<pack("D", $x)> and C<pack("F", $x)> now zero the padding on x86 long
2276double builds. Under some build options on GCC 4.8 and later, they used
2277to either overwrite the zero-initialized padding, or bypass the
2278initialized buffer entirely. This caused F<op/pack.t> to fail.
eabfc7bc
RS
2279L<[perl #123971]|https://rt.perl.org/Ticket/Display.html?id=123971>
2280
2281=item *
2282
2283Extending an array cloned from a parent thread could result in "Modification of
2284a read-only value attempted" errors when attempting to modify the new elements.
2285L<[perl #124127]|https://rt.perl.org/Ticket/Display.html?id=124127>
2286
2287=item *
2288
2289An assertion failure and subsequent crash with C<< *x=<y> >> has been fixed.
2290L<[perl #123790]|https://rt.perl.org/Ticket/Display.html?id=123790>
2291
2292=item *
2293
33ca8d3c
DM
2294A possible crashing/looping bug related to compiling lexical subs has been
2295fixed.
eabfc7bc
RS
2296L<[perl #124099]|https://rt.perl.org/Ticket/Display.html?id=124099>
2297
2298=item *
2299
d140c31c
AC
2300UTF-8 now works correctly in function names, in unquoted HERE-document
2301terminators, and in variable names used as array indexes.
eabfc7bc
RS
2302L<[perl #124113]|https://rt.perl.org/Ticket/Display.html?id=124113>
2303
2304=item *
2305
2306Repeated global pattern matches in scalar context on large tainted strings were
2307exponentially slow depending on the current match position in the string.
2308L<[perl #123202]|https://rt.perl.org/Ticket/Display.html?id=123202>
2309
2310=item *
2311
2312Various crashes due to the parser getting confused by syntax errors have been
2313fixed.
2314L<[perl #123801]|https://rt.perl.org/Ticket/Display.html?id=123801>
2315L<[perl #123802]|https://rt.perl.org/Ticket/Display.html?id=123802>
2316L<[perl #123955]|https://rt.perl.org/Ticket/Display.html?id=123955>
2317L<[perl #123995]|https://rt.perl.org/Ticket/Display.html?id=123995>
2318
2319=item *
2320
d140c31c 2321C<split> in the scope of lexical C<$_> has been fixed not to fail assertions.
eabfc7bc
RS
2322L<[perl #123763]|https://rt.perl.org/Ticket/Display.html?id=123763>
2323
2324=item *
2325
2326C<my $x : attr> syntax inside various list operators no longer fails
2327assertions.
2328L<[perl #123817]|https://rt.perl.org/Ticket/Display.html?id=123817>
2329
2330=item *
2331
4ec8e6f0 2332An C<@> sign in quotes followed by a non-ASCII digit (which is not a valid
33ca8d3c
DM
2333identifier) would cause the parser to crash, instead of simply trying the
2334C<@> as literal. This has been fixed.
eabfc7bc
RS
2335L<[perl #123963]|https://rt.perl.org/Ticket/Display.html?id=123963>
2336
2337=item *
2338
2339C<*bar::=*foo::=*glob_with_hash> has been crashing since Perl 5.14, but no
2340longer does.
2341L<[perl #123847]|https://rt.perl.org/Ticket/Display.html?id=123847>
2342
2343=item *
2344
2345C<foreach> in scalar context was not pushing an item on to the stack, resulting
33ca8d3c
DM
2346in bugs. (S<C<print 4, scalar do { foreach(@x){} } + 1>> would print 5.)
2347It has been fixed to return C<undef>.
eabfc7bc
RS
2348L<[perl #124004]|https://rt.perl.org/Ticket/Display.html?id=124004>
2349
2350=item *
2351
eabfc7bc
RS
2352Several cases of data used to store environment variable contents in core C
2353code being potentially overwritten before being used have been fixed.
2354L<[perl #123748]|https://rt.perl.org/Ticket/Display.html?id=123748>
2355
2356=item *
2357
33ca8d3c
DM
2358Some patterns starting with C</.*..../> matched against long strings have
2359been slow since v5.8, and some of the form C</.*..../i> have been slow
2360since v5.18. They are now all fast again.
a75e6a3a 2361L<[perl #123743]|https://rt.perl.org/Ticket/Display.html?id=123743>.
eabfc7bc
RS
2362
2363=item *
2364
2365The original visible value of C<$/> is now preserved when it is set to
2366an invalid value. Previously if you set C<$/> to a reference to an
2367array, for example, perl would produce a runtime error and not set
2368C<PL_rs>, but perl code that checked C<$/> would see the array
a75e6a3a
SH
2369reference.
2370L<[perl #123218]|https://rt.perl.org/Ticket/Display.html?id=123218>.
eabfc7bc
RS
2371
2372=item *
2373
2374In a regular expression pattern, a POSIX class, like C<[:ascii:]>, must
93780ae6 2375be inside a bracketed character class, like C<qr/[[:ascii:]]/>. A
eabfc7bc
RS
2376warning is issued when something looking like a POSIX class is not
2377inside a bracketed class. That warning wasn't getting generated when
2378the POSIX class was negated: C<[:^ascii:]>. This is now fixed.
2379
2380=item *
2381
eabfc7bc 2382Perl 5.14.0 introduced a bug whereby C<eval { LABEL: }> would crash. This
a75e6a3a
SH
2383has been fixed.
2384L<[perl #123652]|https://rt.perl.org/Ticket/Display.html?id=123652>.
eabfc7bc
RS
2385
2386=item *
2387
2388Various crashes due to the parser getting confused by syntax errors have
a75e6a3a
SH
2389been fixed.
2390L<[perl #123617]|https://rt.perl.org/Ticket/Display.html?id=123617>.
2391L<[perl #123737]|https://rt.perl.org/Ticket/Display.html?id=123737>.
2392L<[perl #123753]|https://rt.perl.org/Ticket/Display.html?id=123753>.
2393L<[perl #123677]|https://rt.perl.org/Ticket/Display.html?id=123677>.
eabfc7bc
RS
2394
2395=item *
2396
2397Code like C</$a[/> used to read the next line of input and treat it as
2398though it came immediately after the opening bracket. Some invalid code
2399consequently would parse and run, but some code caused crashes, so this is
a75e6a3a
SH
2400now disallowed.
2401L<[perl #123712]|https://rt.perl.org/Ticket/Display.html?id=123712>.
eabfc7bc
RS
2402
2403=item *
2404
a75e6a3a
SH
2405Fix argument underflow for C<pack>.
2406L<[perl #123874]|https://rt.perl.org/Ticket/Display.html?id=123874>.
eabfc7bc
RS
2407
2408=item *
2409
2410Fix handling of non-strict C<\x{}>. Now C<\x{}> is equivalent to C<\x{0}>
2411instead of faulting.
2412
2413=item *
2414
2415C<stat -t> is now no longer treated as stackable, just like C<-t stat>.
a75e6a3a 2416L<[perl #123816]|https://rt.perl.org/Ticket/Display.html?id=123816>.
eabfc7bc
RS
2417
2418=item *
2419
2420The following no longer causes a SEGV: C<qr{x+(y(?0))*}>.
2421
2422=item *
2423
2424Fixed infinite loop in parsing backrefs in regexp patterns.
2425
2426=item *
2427
2428Several minor bug fixes in behavior of Inf and NaN, including
2429warnings when stringifying Inf-like or NaN-like strings. For example,
2430"NaNcy" doesn't numify to NaN anymore.
2431
2432=item *
2433
eabfc7bc
RS
2434A bug in regular expression patterns that could lead to segfaults and
2435other crashes has been fixed. This occurred only in patterns compiled
d140c31c
AC
2436with C</i> while taking into account the current POSIX locale (which usually
2437means they have to be compiled within the scope of C<S<use locale>>),
eabfc7bc 2438and there must be a string of at least 128 consecutive bytes to match.
a75e6a3a 2439L<[perl #123539]|https://rt.perl.org/Ticket/Display.html?id=123539>.
eabfc7bc
RS
2440
2441=item *
2442
33ca8d3c
DM
2443C<s///g> now works on very long strings (where there are more than 2
2444billion iterations) instead of dying with 'Substitution loop'.
a75e6a3a
SH
2445L<[perl #103260]|https://rt.perl.org/Ticket/Display.html?id=103260>.
2446L<[perl #123071]|https://rt.perl.org/Ticket/Display.html?id=123071>.
eabfc7bc
RS
2447
2448=item *
2449
a75e6a3a
SH
2450C<gmtime> no longer crashes with not-a-number values.
2451L<[perl #123495]|https://rt.perl.org/Ticket/Display.html?id=123495>.
eabfc7bc
RS
2452
2453=item *
2454
33ca8d3c
DM
2455C<\()> (a reference to an empty list), and C<y///> with lexical C<$_> in
2456scope, could both do a bad write past the end of the stack. They have
2457both been fixed to extend the stack first.
eabfc7bc
RS
2458
2459=item *
2460
2461C<prototype()> with no arguments used to read the previous item on the
2462stack, so C<print "foo", prototype()> would print foo's prototype. It has
4ec8e6f0 2463been fixed to infer C<$_> instead.
a75e6a3a 2464L<[perl #123514]|https://rt.perl.org/Ticket/Display.html?id=123514>.
eabfc7bc
RS
2465
2466=item *
2467
33ca8d3c
DM
2468Some cases of lexical state subs declared inside predeclared subs could
2469crash, for example when evalling a string including the name of an outer
2470variable, but no longer do.
eabfc7bc
RS
2471
2472=item *
2473
2474Some cases of nested lexical state subs inside anonymous subs could cause
d140c31c 2475'Bizarre copy' errors or possibly even crashes.
eabfc7bc
RS
2476
2477=item *
2478
2479When trying to emit warnings, perl's default debugger (F<perl5db.pl>) was
2480sometimes giving 'Undefined subroutine &DB::db_warn called' instead. This
a75e6a3a
SH
2481bug, which started to occur in Perl 5.18, has been fixed.
2482L<[perl #123553]|https://rt.perl.org/Ticket/Display.html?id=123553>.
eabfc7bc
RS
2483
2484=item *
2485
d140c31c 2486Certain syntax errors in substitutions, such as C<< s/${<>{})// >>, would
eabfc7bc
RS
2487crash, and had done so since Perl 5.10. (In some cases the crash did not
2488start happening till 5.16.) The crash has, of course, been fixed.
a75e6a3a 2489L<[perl #123542]|https://rt.perl.org/Ticket/Display.html?id=123542>.
eabfc7bc
RS
2490
2491=item *
2492
33ca8d3c
DM
2493Fix a couple of string grow size calculation overflows; in particular,
2494a repeat expression like C<33 x ~3> could cause a large buffer
eabfc7bc
RS
2495overflow since the new output buffer size was not correctly handled by
2496SvGROW(). An expression like this now properly produces a memory wrap
a75e6a3a
SH
2497panic.
2498L<[perl #123554]|https://rt.perl.org/Ticket/Display.html?id=123554>.
eabfc7bc
RS
2499
2500=item *
2501
2502C<< formline("@...", "a"); >> would crash. The C<FF_CHECKNL> case in
2503pp_formline() didn't set the pointer used to mark the chop position,
2504which led to the C<FF_MORE> case crashing with a segmentation fault.
a75e6a3a
SH
2505This has been fixed.
2506L<[perl #123538]|https://rt.perl.org/Ticket/Display.html?id=123538>.
eabfc7bc
RS
2507
2508=item *
2509
2510A possible buffer overrun and crash when parsing a literal pattern during
a75e6a3a
SH
2511regular expression compilation has been fixed.
2512L<[perl #123604]|https://rt.perl.org/Ticket/Display.html?id=123604>.
eabfc7bc
RS
2513
2514=item *
2515
4ec8e6f0 2516C<fchmod()> and C<futimes()> now set C<$!> when they fail due to being
a75e6a3a
SH
2517passed a closed file handle.
2518L<[perl #122703]|https://rt.perl.org/Ticket/Display.html?id=122703>.
eabfc7bc
RS
2519
2520=item *
2521
33ca8d3c
DM
2522C<op_free()> and C<scalarvoid()> no longer crash due to a stack overflow
2523when freeing a deeply recursive op tree.
a75e6a3a 2524L<[perl #108276]|https://rt.perl.org/Ticket/Display.html?id=108276>.
eabfc7bc
RS
2525
2526=item *
2527
50ea4745 2528In Perl 5.20.0, C<$^N> accidentally had the internal UTF-8 flag turned off
eabfc7bc 2529if accessed from a code block within a regular expression, effectively
50ea4745 2530UTF-8-encoding the value. This has been fixed.
a75e6a3a 2531L<[perl #123135]|https://rt.perl.org/Ticket/Display.html?id=123135>.
eabfc7bc
RS
2532
2533=item *
2534
2535A failed C<semctl> call no longer overwrites existing items on the stack,
33ca8d3c
DM
2536which means that C<(semctl(-1,0,0,0))[0]> no longer gives an
2537"uninitialized" warning.
eabfc7bc
RS
2538
2539=item *
2540
2541C<else{foo()}> with no space before C<foo> is now better at assigning the
a75e6a3a
SH
2542right line number to that statement.
2543L<[perl #122695]|https://rt.perl.org/Ticket/Display.html?id=122695>.
eabfc7bc
RS
2544
2545=item *
2546
d140c31c 2547Sometimes the assignment in C<@array = split> gets optimised so that C<split>
eabfc7bc
RS
2548itself writes directly to the array. This caused a bug, preventing this
2549assignment from being used in lvalue context. So
2550C<(@a=split//,"foo")=bar()> was an error. (This bug probably goes back to
33ca8d3c 2551Perl 3, when the optimisation was added.) It has now been fixed.
a75e6a3a 2552L<[perl #123057]|https://rt.perl.org/Ticket/Display.html?id=123057>.
eabfc7bc
RS
2553
2554=item *
2555
33ca8d3c
DM
2556When an argument list fails the checks specified by a subroutine
2557signature (which is still an experimental feature), the resulting error
2558messages now give the file and line number of the caller, not of the
2559called subroutine.
a75e6a3a 2560L<[perl #121374]|https://rt.perl.org/Ticket/Display.html?id=121374>.
eabfc7bc
RS
2561
2562=item *
2563
33ca8d3c 2564The flip-flop operators (C<..> and C<...> in scalar context) used to maintain
eabfc7bc
RS
2565a separate state for each recursion level (the number of times the
2566enclosing sub was called recursively), contrary to the documentation. Now
a75e6a3a
SH
2567each closure has one internal state for each flip-flop.
2568L<[perl #122829]|https://rt.perl.org/Ticket/Display.html?id=122829>.
eabfc7bc
RS
2569
2570=item *
2571
33ca8d3c
DM
2572The flip-flop operator (C<..> in scalar context) would return the same
2573scalar each time, unless the containing subroutine was called recursively.
2574Now it always returns a new scalar.
2575L<[perl #122829]|https://rt.perl.org/Ticket/Display.html?id=122829>.
2576
2577=item *
2578
eabfc7bc
RS
2579C<use>, C<no>, statement labels, special blocks (C<BEGIN>) and pod are now
2580permitted as the first thing in a C<map> or C<grep> block, the block after
2581C<print> or C<say> (or other functions) returning a handle, and within
a75e6a3a
SH
2582C<${...}>, C<@{...}>, etc.
2583L<[perl #122782]|https://rt.perl.org/Ticket/Display.html?id=122782>.
eabfc7bc
RS
2584
2585=item *
2586
2587The repetition operator C<x> now propagates lvalue context to its left-hand
2588argument when used in contexts like C<foreach>. That allows
4ec8e6f0 2589S<C<for(($#that_array)x2) { ... }>> to work as expected if the loop modifies
eabfc7bc
RS
2590$_.
2591
2592=item *
2593
2594C<(...) x ...> in scalar context used to corrupt the stack if one operand
d140c31c 2595was an object with "x" overloading, causing erratic behaviour.
a75e6a3a 2596L<[perl #121827]|https://rt.perl.org/Ticket/Display.html?id=121827>.
eabfc7bc
RS
2597
2598=item *
2599
33ca8d3c
DM
2600Assignment to a lexical scalar is often optimised away; for example in
2601C<my $x; $x = $y + $z>, the assign operator is optimised away and the add
2602operator writes its result directly to C<$x>. Various bugs related to
2603this optimisation have been fixed. Certain operators on the right-hand
2604side would sometimes fail to assign the value at all or assign the wrong
2605value, or would call STORE twice or not at all on tied variables. The
2606operators affected were C<$foo++>, C<$foo-->, and C<-$foo> under C<use
2607integer>, C<chomp>, C<chr> and C<setpgrp>.
eabfc7bc
RS
2608
2609=item *
2610
2611List assignments were sometimes buggy if the same scalar ended up on both
d140c31c 2612sides of the assignment due to use of C<tied>, C<values> or C<each>. The
eabfc7bc
RS
2613result would be the wrong value getting assigned.
2614
2615=item *
2616
2617C<setpgrp($nonzero)> (with one argument) was accidentally changed in 5.16
2618to mean C<setpgrp(0)>. This has been fixed.
2619
2620=item *
2621
2622C<__SUB__> could return the wrong value or even corrupt memory under the
4ec8e6f0 2623debugger (the C<-d> switch) and in subs containing C<eval $string>.
eabfc7bc
RS
2624
2625=item *
2626
4ec8e6f0 2627When S<C<sub () { $var }>> becomes inlinable, it now returns a different
eabfc7bc
RS
2628scalar each time, just as a non-inlinable sub would, though Perl still
2629optimises the copy away in cases where it would make no observable
2630difference.
2631
2632=item *
2633
4ec8e6f0 2634S<C<my sub f () { $var }>> and S<C<sub () : attr { $var }>> are no longer
eabfc7bc
RS
2635eligible for inlining. The former would crash; the latter would just
2636throw the attributes away. An exception is made for the little-known
2637":method" attribute, which does nothing much.
2638
2639=item *
2640
2641Inlining of subs with an empty prototype is now more consistent than
d140c31c
AC
2642before. Previously, a sub with multiple statements, of which all but the last
2643were optimised away, would be inlinable only if it were an anonymous sub
eabfc7bc
RS
2644containing a string C<eval> or C<state> declaration or closing over an
2645outer lexical variable (or any anonymous sub under the debugger). Now any
2646sub that gets folded to a single constant after statements have been
2647optimised away is eligible for inlining. This applies to things like C<sub
2648() { jabber() if DEBUG; 42 }>.
2649
2650Some subroutines with an explicit C<return> were being made inlinable,
2651contrary to the documentation, Now C<return> always prevents inlining.
2652
2653=item *
2654
2655On some systems, such as VMS, C<crypt> can return a non-ASCII string. If a
50ea4745
DIM
2656scalar assigned to had contained a UTF-8 string previously, then C<crypt>
2657would not turn off the UTF-8 flag, thus corrupting the return value. This
eabfc7bc
RS
2658would happen with C<$lexical = crypt ...>.
2659
2660=item *
2661
2662C<crypt> no longer calls C<FETCH> twice on a tied first argument.
2663
2664=item *
2665
2666An unterminated here-doc on the last line of a quote-like operator
2667(C<qq[${ <<END }]>, C</(?{ <<END })/>) no longer causes a double free. It
2668started doing so in 5.18.
2669
2670=item *
2671
4ec8e6f0 2672C<index()> and C<rindex()> no longer crash when used on strings over 2GB in
eabfc7bc
RS
2673size.
2674L<[perl #121562]|https://rt.perl.org/Ticket/Display.html?id=121562>.
2675
2676=item *
2677
2678A small previously intentional memory leak in PERL_SYS_INIT/PERL_SYS_INIT3 on
2679Win32 builds was fixed. This might affect embedders who repeatedly create and
2680destroy perl engines within the same process.
2681
2682=item *
2683
2684C<POSIX::localeconv()> now returns the data for the program's underlying
2685locale even when called from outside the scope of S<C<use locale>>.
2686
2687=item *
2688
2689C<POSIX::localeconv()> now works properly on platforms which don't have
2690C<LC_NUMERIC> and/or C<LC_MONETARY>, or for which Perl has been compiled
2691to disregard either or both of these locale categories. In such
2692circumstances, there are now no entries for the corresponding values in
2693the hash returned by C<localeconv()>.
2694
2695=item *
2696
2697C<POSIX::localeconv()> now marks appropriately the values it returns as
6a3ea89b 2698UTF-8 or not. Previously they were always returned as bytes, even if
eabfc7bc
RS
2699they were supposed to be encoded as UTF-8.
2700
2701=item *
2702
2703On Microsoft Windows, within the scope of C<S<use locale>>, the following
2704POSIX character classes gave results for many locales that did not
2705conform to the POSIX standard:
2706C<[[:alnum:]]>,
2707C<[[:alpha:]]>,
2708C<[[:blank:]]>,
2709C<[[:digit:]]>,
2710C<[[:graph:]]>,
2711C<[[:lower:]]>,
2712C<[[:print:]]>,
2713C<[[:punct:]]>,
2714C<[[:upper:]]>,
2715C<[[:word:]]>,
2716and
2717C<[[:xdigit:]]>.
f1c9eac6 2718This was because the underlying Microsoft implementation does not
eabfc7bc
RS
2719follow the standard. Perl now takes special precautions to correct for
2720this.
2721
2722=item *
2723
2724Many issues have been detected by L<Coverity|http://www.coverity.com/> and
2725fixed.
2726
2727=item *
2728
d140c31c 2729C<system()> and friends should now work properly on more Android builds.
eabfc7bc 2730
4ec8e6f0 2731Due to an oversight, the value specified through C<-Dtargetsh> to F<Configure>
eabfc7bc 2732would end up being ignored by some of the build process. This caused perls
4ec8e6f0 2733cross-compiled for Android to end up with defective versions of C<system()>,
d140c31c 2734C<exec()> and backticks: the commands would end up looking for C</bin/sh>
eabfc7bc
RS
2735instead of C</system/bin/sh>, and so would fail for the vast majority
2736of devices, leaving C<$!> as C<ENOENT>.
2737
2738=item *
2739
2740C<qr(...\(...\)...)>,
2741C<qr[...\[...\]...]>,
2742and
2743C<qr{...\{...\}...}>
2744now work. Previously it was impossible to escape these three
2745left-characters with a backslash within a regular expression pattern
2746where otherwise they would be considered metacharacters, and the pattern
2747opening delimiter was the character, and the closing delimiter was its
2748mirror character.
2749
2750=item *
2751
50ea4745 2752C<< s///e >> on tainted UTF-8 strings corrupted C<< pos() >>. This bug,
a75e6a3a
SH
2753introduced in 5.20, is now fixed.
2754L<[perl #122148]|https://rt.perl.org/Ticket/Display.html?id=122148>.
eabfc7bc
RS
2755
2756=item *
2757
2758A non-word boundary in a regular expression (C<< \B >>) did not always
2759match the end of the string; in particular C<< q{} =~ /\B/ >> did not
a75e6a3a
SH
2760match. This bug, introduced in perl 5.14, is now fixed.
2761L<[perl #122090]|https://rt.perl.org/Ticket/Display.html?id=122090>.
eabfc7bc
RS
2762
2763=item *
2764
2765C<< " P" =~ /(?=.*P)P/ >> should match, but did not. This is now fixed.
a75e6a3a 2766L<[perl #122171]|https://rt.perl.org/Ticket/Display.html?id=122171>.
eabfc7bc
RS
2767
2768=item *
2769
2770Failing to compile C<use Foo> in an eval could leave a spurious
2771C<BEGIN> subroutine definition, which would produce a "Subroutine
2772BEGIN redefined" warning on the next use of C<use>, or other C<BEGIN>
a75e6a3a
SH
2773block.
2774L<[perl #122107]|https://rt.perl.org/Ticket/Display.html?id=122107>.
eabfc7bc
RS
2775
2776=item *
2777
2778C<method { BLOCK } ARGS> syntax now correctly parses the arguments if they
a75e6a3a
SH
2779begin with an opening brace.
2780L<[perl #46947]|https://rt.perl.org/Ticket/Display.html?id=46947>.
eabfc7bc
RS
2781
2782=item *
2783
2784External libraries and Perl may have different ideas of what the locale is.
2785This is problematic when parsing version strings if the locale's numeric
2786separator has been changed. Version parsing has been patched to ensure
a75e6a3a
SH
2787it handles the locales correctly.
2788L<[perl #121930]|https://rt.perl.org/Ticket/Display.html?id=121930>.
eabfc7bc
RS
2789
2790=item *
2791
2792A bug has been fixed where zero-length assertions and code blocks inside of a
a75e6a3a
SH
2793regex could cause C<pos> to see an incorrect value.
2794L<[perl #122460]|https://rt.perl.org/Ticket/Display.html?id=122460>.
eabfc7bc
RS
2795
2796=item *
2797
2798Constant dereferencing now works correctly for typeglob constants. Previously
2799the glob was stringified and its name looked up. Now the glob itself is used.
2800L<[perl #69456]|https://rt.perl.org/Ticket/Display.html?id=69456>
2801
2802=item *
2803
d140c31c 2804When parsing a sigil (C<$> C<@> C<%> C<&)> followed by braces,
4ec8e6f0 2805the parser no
eabfc7bc
RS
2806longer tries to guess whether it is a block or a hash constructor (causing a
2807syntax error when it guesses the latter), since it can only be a block.
2808
2809=item *
2810
4ec8e6f0 2811S<C<undef $reference>> now frees the referent immediately, instead of hanging on
eabfc7bc
RS
2812to it until the next statement.
2813L<[perl #122556]|https://rt.perl.org/Ticket/Display.html?id=122556>
2814
2815=item *
2816
2817Various cases where the name of a sub is used (autoload, overloading, error
2818messages) used to crash for lexical subs, but have been fixed.
2819
2820=item *
2821
2822Bareword lookup now tries to avoid vivifying packages if it turns out the
2823bareword is not going to be a subroutine name.
2824
2825=item *
2826
2827Compilation of anonymous constants (e.g., C<sub () { 3 }>) no longer deletes
2828any subroutine named C<__ANON__> in the current package. Not only was
2829C<*__ANON__{CODE}> cleared, but there was a memory leak, too. This bug goes
2830back to Perl 5.8.0.
2831
2832=item *
2833
2834Stub declarations like C<sub f;> and C<sub f ();> no longer wipe out constants
2835of the same name declared by C<use constant>. This bug was introduced in Perl
28365.10.0.
2837
2838=item *
2839
33ca8d3c
DM
2840C<qr/[\N{named sequence}]/> now works properly in many instances.
2841
2842Some names
eabfc7bc
RS
2843known to C<\N{...}> refer to a sequence of multiple characters, instead of the
2844usual single character. Bracketed character classes generally only match
2845single characters, but now special handling has been added so that they can
2846match named sequences, but not if the class is inverted or the sequence is
2847specified as the beginning or end of a range. In these cases, the only
2848behavior change from before is a slight rewording of the fatal error message
2849given when this class is part of a C<?[...])> construct. When the C<[...]>
2850stands alone, the same non-fatal warning as before is raised, and only the
2851first character in the sequence is used, again just as before.
2852
2853=item *
2854
2855Tainted constants evaluated at compile time no longer cause unrelated
2856statements to become tainted.
2857L<[perl #122669]|https://rt.perl.org/Ticket/Display.html?id=122669>
2858
2859=item *
2860
33ca8d3c
DM
2861S<C<open $$fh, ...>>, which vivifies a handle with a name like
2862C<"main::_GEN_0">, was not giving the handle the right reference count, so
2863a double free could happen.
eabfc7bc
RS
2864
2865=item *
2866
2867When deciding that a bareword was a method name, the parser would get confused
4ec8e6f0
KW
2868if an C<our> sub with the same name existed, and look up the method in the
2869package of the C<our> sub, instead of the package of the invocant.
eabfc7bc
RS
2870
2871=item *
2872
2873The parser no longer gets confused by C<\U=> within a double-quoted string. It
2874used to produce a syntax error, but now compiles it correctly.
2875L<[perl #80368]|https://rt.perl.org/Ticket/Display.html?id=80368>
2876
2877=item *
2878
2879It has always been the intention for the C<-B> and C<-T> file test operators to
2880treat UTF-8 encoded files as text. (L<perlfunc|perlfunc/-X FILEHANDLE> has
2881been updated to say this.) Previously, it was possible for some files to be
2882considered UTF-8 that actually weren't valid UTF-8. This is now fixed. The
2883operators now work on EBCDIC platforms as well.
2884
2885=item *
2886
2887Under some conditions warning messages raised during regular expression pattern
2888compilation were being output more than once. This has now been fixed.
2889
2890=item *
2891
d140c31c
AC
2892Perl 5.20.0 introduced a regression in which a UTF-8 encoded regular
2893expression pattern that contains a single ASCII lowercase letter did not
2894match its uppercase counterpart. That has been fixed in both 5.20.1 and
28955.22.0.
eabfc7bc
RS
2896L<[perl #122655]|https://rt.perl.org/Ticket/Display.html?id=122655>
2897
2898=item *
2899
33ca8d3c
DM
2900Constant folding could incorrectly suppress warnings if lexical warnings
2901(C<use warnings> or C<no warnings>) were not in effect and C<$^W> were
2902false at compile time and true at run time.
eabfc7bc
RS
2903
2904=item *
2905
50ea4745 2906Loading UTF-8 tables during a regular expression match could cause assertion
eabfc7bc
RS
2907failures under debugging builds if the previous match used the very same
2908regular expression.
2909L<[perl #122747]|https://rt.perl.org/Ticket/Display.html?id=122747>
2910
2911=item *
2912
2913Thread cloning used to work incorrectly for lexical subs, possibly causing
2914crashes or double frees on exit.
2915
2916=item *
2917
2918Since Perl 5.14.0, deleting C<$SomePackage::{__ANON__}> and then undefining an
2919anonymous subroutine could corrupt things internally, resulting in
2920L<Devel::Peek> crashing or L<B.pm|B> giving nonsensical data. This has been
2921fixed.
2922
2923=item *
2924
33ca8d3c
DM
2925S<C<(caller $n)[3]>> now reports names of lexical subs, instead of
2926treating them as C<"(unknown)">.
eabfc7bc
RS
2927
2928=item *
2929
d140c31c
AC
2930C<sort subname LIST> now supports using a lexical sub as the comparison
2931routine.
eabfc7bc
RS
2932
2933=item *
2934
2935Aliasing (e.g., via C<*x = *y>) could confuse list assignments that mention the
2936two names for the same variable on either side, causing wrong values to be
2937assigned.
2938L<[perl #15667]|https://rt.perl.org/Ticket/Display.html?id=15667>
2939
2940=item *
2941
2942Long here-doc terminators could cause a bad read on short lines of input. This
2943has been fixed. It is doubtful that any crash could have occurred. This bug
2944goes back to when here-docs were introduced in Perl 3.000 twenty-five years
2945ago.
2946
2947=item *
2948
d140c31c
AC
2949An optimization in C<split> to treat C<split /^/> like C<split /^/m> had the
2950unfortunate side-effect of also treating C<split /\A/> like C<split /^/m>,
2951which it should not. This has been fixed. (Note, however, that C<split /^x/>
2952does not behave like C<split /^x/m>, which is also considered to be a bug and
2953will be fixed in a future version.)
eabfc7bc
RS
2954L<[perl #122761]|https://rt.perl.org/Ticket/Display.html?id=122761>
2955
2956=item *
2957
4ec8e6f0 2958The little-known S<C<my Class $var>> syntax (see L<fields> and L<attributes>)
eabfc7bc
RS
2959could get confused in the scope of C<use utf8> if C<Class> were a constant
2960whose value contained Latin-1 characters.
2961
2962=item *
2963
2964Locking and unlocking values via L<Hash::Util> or C<Internals::SvREADONLY>
33ca8d3c 2965no longer has any effect on values that were read-only to begin with.
eabfc7bc
RS
2966Previously, unlocking such values could result in crashes, hangs or
2967other erratic behaviour.
2968
2969=item *
2970
eabfc7bc
RS
2971Some unterminated C<(?(...)...)> constructs in regular expressions would
2972either crash or give erroneous error messages. C</(?(1)/> is one such
2973example.
2974
2975=item *
2976
4ec8e6f0 2977S<C<pack "w", $tied>> no longer calls FETCH twice.
eabfc7bc
RS
2978
2979=item *
2980
4ec8e6f0
KW
2981List assignments like S<C<($x, $z) = (1, $y)>> now work correctly if C<$x> and
2982C<$y> have been aliased by C<foreach>.
eabfc7bc
RS
2983
2984=item *
2985
2986Some patterns including code blocks with syntax errors, such as
2987C</ (?{(^{})/>, would hang or fail assertions on debugging builds. Now
2988they produce errors.
2989
2990=item *
2991
2992An assertion failure when parsing C<sort> with debugging enabled has been
a75e6a3a
SH
2993fixed.
2994L<[perl #122771]|https://rt.perl.org/Ticket/Display.html?id=122771>.
eabfc7bc
RS
2995
2996=item *
2997
4ec8e6f0 2998S<C<*a = *b; @a = split //, $b[1]>> could do a bad read and produce junk
eabfc7bc
RS
2999results.
3000
3001=item *
3002
4ec8e6f0 3003In S<C<() = @array = split>>, the S<C<() =>> at the beginning no longer confuses
d140c31c 3004the optimizer into assuming a limit of 1.
eabfc7bc
RS
3005
3006=item *
3007
3008Fatal warnings no longer prevent the output of syntax errors.
a75e6a3a 3009L<[perl #122966]|https://rt.perl.org/Ticket/Display.html?id=122966>.
eabfc7bc
RS
3010
3011=item *
3012
d140c31c 3013Fixed a NaN double-to-long-double conversion error on VMS. For quiet NaNs
eabfc7bc
RS
3014(and only on Itanium, not Alpha) negative infinity instead of NaN was
3015produced.
3016
3017=item *
3018
d140c31c
AC
3019Fixed the issue that caused C<< make distclean >> to incorrectly leave some
3020files behind.
a75e6a3a 3021L<[perl #122820]|https://rt.perl.org/Ticket/Display.html?id=122820>.
eabfc7bc
RS
3022
3023=item *
3024
a75e6a3a
SH
3025AIX now sets the length in C<< getsockopt >> correctly.
3026L<[perl #120835]|https://rt.perl.org/Ticket/Display.html?id=120835>.
3027L<[cpan #91183]|https://rt.cpan.org/Ticket/Display.html?id=91183>.
3028L<[cpan #85570]|https://rt.cpan.org/Ticket/Display.html?id=85570>.
eabfc7bc
RS
3029
3030=item *
3031
33ca8d3c
DM
3032During the optimization phase of a regexp compilation, we no longer
3033recurse into C<GOSUB>/C<GOSTART> when the internal C<SCF_DO_SUBSTR> flag
3034is false. This prevents the optimizer from running "forever" and
3035exhausting all memory.
a75e6a3a 3036L<[perl #122283]|https://rt.perl.org/Ticket/Display.html?id=122283>.
eabfc7bc
RS
3037
3038=item *
3039
33ca8d3c
DM
3040The test script F<< t/op/crypt.t >> now uses the SHA-256 algorithm if the
3041default one is disabled, rather than giving failures.
a75e6a3a 3042L<[perl #121591]|https://rt.perl.org/Ticket/Display.html?id=121591>.
eabfc7bc
RS
3043
3044=item *
3045
d140c31c 3046Fixed an off-by-one error when setting the size of a shared array.
a75e6a3a 3047L<[perl #122950]|https://rt.perl.org/Ticket/Display.html?id=122950>.
eabfc7bc
RS
3048
3049=item *
3050
d140c31c 3051Fixed a bug that could cause perl to enter an infinite loop during
33ca8d3c
DM
3052compilation. In particular, for a C<while(1)> within a sublist, e.g.
3053
3054 sub foo { () = ($a, my $b, ($c, do { while(1) {} })) }
3055
3056The bug was introduced in 5.20.0
a75e6a3a 3057L<[perl #122995]|https://rt.perl.org/Ticket/Display.html?id=122995>.
eabfc7bc
RS
3058
3059=item *
3060
cca58a48 3061On Win32, if a variable was C<local>-ized in a pseudo-process that later
d140c31c
AC
3062forked, restoring the original value in the child pseudo-process caused
3063memory corruption and a crash in the child pseudo-process (and therefore the
3064OS process).
a75e6a3a 3065L<[perl #40565]|https://rt.perl.org/Ticket/Display.html?id=40565>.
eabfc7bc
RS
3066
3067=item *
3068
3069Calling C<write> on a format with a C<^**> field could produce a panic
4ec8e6f0 3070in C<sv_chop()> if there were insufficient arguments or if the variable
a75e6a3a
SH
3071used to fill the field was empty.
3072L<[perl #123245]|https://rt.perl.org/Ticket/Display.html?id=123245>.
eabfc7bc
RS
3073
3074=item *
3075
d140c31c
AC
3076Non-ASCII lexical sub names now appear without trailing junk when they
3077appear in error messages.
eabfc7bc
RS
3078
3079=item *
3080
3081The C<\@> subroutine prototype no longer flattens parenthesized arrays
3082(taking a reference to each element), but takes a reference to the array
a75e6a3a
SH
3083itself.
3084L<[perl #47363]|https://rt.perl.org/Ticket/Display.html?id=47363>.
eabfc7bc
RS
3085
3086=item *
3087
3088A block containing nothing except a C-style C<for> loop could corrupt the
3089stack, causing lists outside the block to lose elements or have elements
3090overwritten. This could happen with C<map { for(...){...} } ...> and with
a75e6a3a
SH
3091lists containing C<do { for(...){...} }>.
3092L<[perl #123286]|https://rt.perl.org/Ticket/Display.html?id=123286>.
eabfc7bc
RS
3093
3094=item *
3095
3096C<scalar()> now propagates lvalue context, so that
4ec8e6f0 3097S<C<for(scalar($#foo)) { ... }>> can modify C<$#foo> through C<$_>.
eabfc7bc
RS
3098
3099=item *
3100
3101C<qr/@array(?{block})/> no longer dies with "Bizarre copy of ARRAY".
a75e6a3a 3102L<[perl #123344]|https://rt.perl.org/Ticket/Display.html?id=123344>.
eabfc7bc
RS
3103
3104=item *
3105
4ec8e6f0 3106S<C<eval '$variable'>> in nested named subroutines would sometimes look up a
eabfc7bc
RS
3107global variable even with a lexical variable in scope.
3108
3109=item *
3110
3111In perl 5.20.0, C<sort CORE::fake> where 'fake' is anything other than a
33ca8d3c 3112keyword, started chopping off the last 6 characters and treating the result
eabfc7bc 3113as a sort sub name. The previous behaviour of treating "CORE::fake" as a
a75e6a3a
SH
3114sort sub name has been restored.
3115L<[perl #123410]|https://rt.perl.org/Ticket/Display.html?id=123410>.
eabfc7bc
RS
3116
3117=item *
3118
3119Outside of C<use utf8>, a single-character Latin-1 lexical variable is
4ec8e6f0 3120disallowed. The error message for it, "Can't use global C<$foo>...", was
eabfc7bc
RS
3121giving garbage instead of the variable name.
3122
3123=item *
3124
3125C<readline> on a nonexistent handle was causing C<${^LAST_FH}> to produce a
3126reference to an undefined scalar (or fail an assertion). Now
3127C<${^LAST_FH}> ends up undefined.
3128
3129=item *
3130
33ca8d3c 3131C<(...) x ...> in void context now applies scalar context to the left-hand
eabfc7bc 3132argument, instead of the context the current sub was called in.
a75e6a3a 3133L<[perl #123020]|https://rt.perl.org/Ticket/Display.html?id=123020>.
eabfc7bc
RS
3134
3135=back
3136
3137=head1 Known Problems
3138
3139=over 4
3140
3141=item *
3142
65039e73
RS
3143C<pack>-ing a NaN on a perl compiled with Visual C 6 does not behave properly,
3144leading to a test failure in F<t/op/infnan.t>.
3145L<[perl 125203]|https://rt.perl.org/Ticket/Display.html?id=125203>
3146
3147=item *
3148
eabfc7bc
RS
3149A goal is for Perl to be able to be recompiled to work reasonably well on any
3150Unicode version. In Perl 5.22, though, the earliest such version is Unicode
31515.1 (current is 7.0).
3152
3153=item *
3154
3155EBCDIC platforms
3156
3157=over 4
3158
3159=item *
3160
ce93e38b
KW
3161The C<cmp> (and hence C<sort>) operators do not necessarily give the
3162correct results when both operands are UTF-EBCDIC encoded strings and
3163there is a mixture of ASCII and/or control characters, along with other
3164characters.
3165
3166=item *
3167
3168Ranges containing C<\N{...}> in the C<tr///> (and C<y///>)
3169transliteration operators are treated differently than the equivalent
d140c31c 3170ranges in regular expression patterns. They should, but don't, cause
ce93e38b
KW
3171the values in the ranges to all be treated as Unicode code points, and
3172not native ones. (L<perlre/Version 8 Regular Expressions> gives
3173details as to how it should work.)
3174
3175=item *
3176
eabfc7bc
RS
3177Encode and encoding are mostly broken.
3178
3179=item *
3180
0590bd99 3181Many CPAN modules that are shipped with core show failing tests.
eabfc7bc
RS
3182
3183=item *
3184
3185C<pack>/C<unpack> with C<"U0"> format may not work properly.
3186
3187=back
3188
3189=item *
3190
3191The following modules are known to have test failures with this version of
3192Perl. Patches have been submitted, so there will hopefully be new releases
3193soon:
3194
3195=over
3196
3197=item *
3198
3199L<B::Generate> version 1.50
3200
3201=item *
3202
3203L<B::Utils> version 0.25
3204
3205=item *
3206
3207L<Dancer> version 1.3130
3208
3209=item *
3210
3211L<Data::Alias> version 1.18
3212
3213=item *
3214
3215L<Data::Util> version 0.63
3216
3217=item *
3218
ba520a57
RS
3219L<Devel::Spy> version 0.07
3220
3221=item *
3222
2621aeba
RS
3223L<invoker> version 0.34
3224
3225=item *
3226
eabfc7bc
RS
3227L<Lexical::Var> version 0.009
3228
3229=item *
3230
3231L<Mason> version 2.22
3232
3233=item *
3234
6be597e7
RS
3235L<NgxQueue> version 0.02
3236
3237=item *
3238
eabfc7bc
RS
3239L<Padre> version 1.00
3240
3241=item *
3242
3243L<Parse::Keyword> 0.08
3244
3245=back
3246
3247=back
2a7a05b4 3248
30aa8e3f
AC
3249=head1 Obituary
3250
3251Brian McCauley died on May 8, 2015. He was a frequent poster to Usenet, Perl
3252Monks, and other Perl forums, and made several CPAN contributions under the
3253nick NOBULL, including to the Perl FAQ. He attended almost every
3254YAPC::Europe, and indeed, helped organise YAPC::Europe 2006 and the QA
3255Hackathon 2009. His wit and his delight in intricate systems were
3256particularly apparent in his love of board games; many Perl mongers will
3257have fond memories of playing Fluxx and other games with Brian. He will be
3258missed.
3259
7f9fef93 3260=head1 Acknowledgements
2a7a05b4 3261
2cf7809b
RS
3262Perl 5.22.0 represents approximately 12 months of development since Perl 5.20.0
3263and contains approximately 590,000 lines of changes across 2,400 files from 94
3264authors.
3265
3266Excluding auto-generated files, documentation and release tools, there were
3267approximately 370,000 lines of changes to 1,500 .pm, .t, .c and .h files.
3268
3269Perl continues to flourish into its third decade thanks to a vibrant community
3270of users and developers. The following people are known to have contributed the
3271improvements that became Perl 5.22.0:
3272
3273Aaron Crane, Abhijit Menon-Sen, Abigail, Alberto Simões, Alex Solovey, Alex
3274Vandiver, Alexandr Ciornii, Alexandre (Midnite) Jousset, Andreas König,
3275Andreas Voegele, Andrew Fresh, Andy Dougherty, Anthony Heading, Aristotle
3276Pagaltzis, brian d foy, Brian Fraser, Chad Granum, Chris 'BinGOs' Williams,
3277Craig A. Berry, Dagfinn Ilmari Mannsåker, Daniel Dragan, Darin McBride, Dave
3278Rolsky, David Golden, David Mitchell, David Wheeler, Dmitri Tikhonov, Doug
3279Bell, E. Choroba, Ed J, Eric Herman, Father Chrysostomos, George Greer, Glenn
3280D. Golden, Graham Knop, H.Merijn Brand, Herbert Breunung, Hugo van der Sanden,
3281James E Keenan, James McCoy, James Raspass, Jan Dubois, Jarkko Hietaniemi,
3282Jasmine Ngan, Jerry D. Hedden, Jim Cromie, John Goodyear, kafka, Karen
3283Etheridge, Karl Williamson, Kent Fredric, kmx, Lajos Veres, Leon Timmermans,
3284Lukas Mai, Mathieu Arnold, Matthew Horsfall, Max Maischein, Michael Bunk,
3285Nicholas Clark, Niels Thykier, Niko Tyni, Norman Koch, Olivier Mengué, Peter
3286John Acklam, Peter Martini, Petr Písař, Philippe Bruhat (BooK), Pierre
3287Bogossian, Rafael Garcia-Suarez, Randy Stauner, Reini Urban, Ricardo Signes,
3288Rob Hoelz, Rostislav Skudnov, Sawyer X, Shirakata Kentaro, Shlomi Fish,
3289Sisyphus, Slaven Rezic, Smylers, Steffen Müller, Steve Hay, Sullivan Beck,
3290syber, Tadeusz Sośnierz, Thomas Sibley, Todd Rinaldo, Tony Cook, Vincent Pit,
3291Vladimir Marek, Yaroslav Kuzmin, Yves Orton, Ævar Arnfjörð Bjarmason.
3292
3293The list above is almost certainly incomplete as it is automatically generated
3294from version control history. In particular, it does not include the names of
3295the (very much appreciated) contributors who reported issues to the Perl bug
3296tracker.
3297
3298Many of the changes included in this version originated in the CPAN modules
3299included in Perl's core. We're grateful to the entire CPAN community for
3300helping Perl to flourish.
3301
3302For a more complete list of all of Perl's historical contributors, please see
3303the F<AUTHORS> file in the Perl source distribution.
f5b73711 3304
44691e6f
AB
3305=head1 Reporting Bugs
3306
e08634c5
SH
3307If you find what you think is a bug, you might check the articles recently
3308posted to the comp.lang.perl.misc newsgroup and the perl bug database at
e5998677
SH
3309https://rt.perl.org/ . There may also be information at
3310http://www.perl.org/ , the Perl Home Page.
44691e6f 3311
e08634c5
SH
3312If you believe you have an unreported bug, please run the L<perlbug> program
3313included with your release. Be sure to trim your bug down to a tiny but
3314sufficient test case. Your bug report, along with the output of C<perl -V>,
3315will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
44691e6f
AB
3316
3317If the bug you are reporting has security implications, which make it
e08634c5
SH
3318inappropriate to send to a publicly archived mailing list, then please send it
3319to perl5-security-report@perl.org. This points to a closed subscription
3320unarchived mailing list, which includes all the core committers, who will be
3321able to help assess the impact of issues, figure out a resolution, and help
f9001595 3322co-ordinate the release of patches to mitigate or fix the problem across all
e08634c5
SH
3323platforms on which Perl is supported. Please only use this address for
3324security issues in the Perl core, not for modules independently distributed on
3325CPAN.
44691e6f
AB
3326
3327=head1 SEE ALSO
3328
e08634c5
SH
3329The F<Changes> file for an explanation of how to view exhaustive details on
3330what changed.
44691e6f
AB
3331
3332The F<INSTALL> file for how to build Perl.
3333
3334The F<README> file for general stuff.
3335
3336The F<Artistic> and F<Copying> files for copyright information.
3337
3338=cut