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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
63Previously running C<no re> would only turn off a few things. Now it
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
70and filling in C<$1>, C<$2>, etc... inside of groups:
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
81compiled within its scope, which hopefully will alert you to typos and
82other unintentional behavior that backwards-compatibility issues prevent
83us from doing in normal regular expression compilations. Because the
84behavior of this is subject to change in future Perl releases as we gain
85experience, using this pragma will raise a category
86C<experimental::re_strict> warning.
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
119=head2 Better heuristics on older platforms for determining locale UTF8ness
120
121On platforms that implement neither the C99 standard nor the POSIX 2001
122standard, determining if the current locale is UTF8 or not depends on
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
132Or by using a backslash before a C<foreach> iterator variable, which is
133perhaps the most useful idiom this feature provides:
134
135 foreach \%hash (@array_of_hash_refs) { ... }
136
137This feature is experimental and must be enabled via C<use feature
138'refaliasing'>. It will warn unless the C<experimental::refaliasing>
139warnings category is disabled.
140
141See L<perlref/Assigning to References>
142
143=head2 C<prototype> with no arguments
144
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145C<prototype()> with no arguments now infers C<$_>.
146L<[perl #123514]|https://rt.perl.org/Ticket/Display.html?id=123514>.
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147
148=head2 New "const" subroutine attribute
149
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150The "const" attribute can be applied to an anonymous subroutine. It
151causes the new sub to be executed immediately whenever one is created
152(i.e. when the C<sub> expression is evaluated). Its value is captured
153and used to create a new constant subroutine that is returned. This
154feature is experimental. See L<perlsub/Constant Functions>.
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155
156=head2 C<fileno> now works on directory handles
157
158When the relevant support is available in the operating system, the
159C<fileno> builtin now works on directory handles, yielding the
160underlying file descriptor in the same way as for filehandles. On
161operating systems without such support, C<fileno> on a directory handle
162continues to return the undefined value, as before, but also sets C<$!> to
163indicate that the operation is not supported.
164
165Currently, this uses either a C<dd_fd> member in the OS C<DIR>
4ec8e6f0 166structure, or a C<dirfd(3)> function as specified by POSIX.1-2008.
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167
168=head2 List form of pipe open implemented for Win32
169
170The list form of pipe:
171
172 open my $fh, "-|", "program", @arguments;
173
174is now implemented on Win32. It has the same limitations as C<system
175LIST> on Win32, since the Win32 API doesn't accept program arguments
176as a list.
177
178=head2 C<close> now sets C<$!>
179
180When an I/O error occurs, the fact that there has been an error is recorded
181in the handle. C<close> returns false for such a handle. Previously, the
182value of C<$!> would be untouched by C<close>, so the common convention of
4ec8e6f0 183writing S<C<close $fh or die $!>> did not work reliably. Now the handle
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184records the value of C<$!>, too, and C<close> restores it.
185
186=head2 Assignment to list repetition
187
188C<(...) x ...> can now be used within a list that is assigned to, as long
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189as the left-hand side is a valid lvalue. This allows S<C<(undef,undef,$foo)
190= that_function()>> to be written as S<C<((undef)x2, $foo) = that_function()>>.
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191
192=head2 Infinity and NaN (not-a-number) handling improved
193
194Floating point values are able to hold the special values infinity (also
195-infinity), and NaN (not-a-number). Now we more robustly recognize and
196propagate the value in computations, and on output normalize them to C<Inf> and
197C<NaN>.
198
199See also the L<POSIX> enhancements.
200
201=head2 Floating point parsing has been improved
202
203Parsing and printing of floating point values has been improved.
204
205As a completely new feature, hexadecimal floating point literals
4ec8e6f0 206(like C<0x1.23p-4>) are now supported, and they can be output with
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207C<printf %a>.
208
209=head2 Packing infinity or not-a-number into a character is now fatal
210
211Before, when trying to pack infinity or not-a-number into a
212(signed) character, Perl would warn, and assumed you tried to
213pack C<< 0xFF >>; if you gave it as an argument to C<< chr >>,
214C<< U+FFFD >> was returned.
215
216But now, all such actions (C<< pack >>, C<< chr >>, and C<< print '%c' >>)
217result in a fatal error.
218
219=head2 Experimental C Backtrace API
2e4abf26 220
43831b1f 221Perl now supports (via a C level API) retrieving
eabfc7bc 222the C level backtrace (similar to what symbolic debuggers like gdb do).
fea59588 223
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224The backtrace returns the stack trace of the C call frames,
225with the symbol names (function names), the object names (like "perl"),
226and if it can, also the source code locations (file:line).
227
228The supported platforms are Linux and OS X (some *BSD might work at
229least partly, but they have not yet been tested).
230
231The feature needs to be enabled with C<Configure -Dusecbacktrace>.
232
eabfc7bc 233See L<perlhacktips/"C backtrace"> for more information.
83a5d6b6 234
7f9fef93 235=head1 Security
e455391f 236
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237=head2 Perl is now compiled with -fstack-protector-strong if available
238
239Perl has been compiled with the anti-stack-smashing option
240C<-fstack-protector> since 5.10.1. Now Perl uses the newer variant
241called C<-fstack-protector-strong>, if available.
242
243=head2 The L<Safe> module could allow outside packages to be replaced
244
245Critical bugfix: outside packages could be replaced. L<Safe> has
246been patched to 2.38 to address this.
247
248=head2 Perl is now always compiled with -D_FORTIFY_SOURCE=2 if available
e455391f 249
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250The 'code hardening' option called C<_FORTIFY_SOURCE>, available in
251gcc 4.*, is now always used for compiling Perl, if available.
252
253Note that this isn't necessarily a huge step since in many platforms
254the step had already been taken several years ago: many Linux
255distributions (like Fedora) have been using this option for Perl,
256and OS X has enforced the same for many years.
53902397 257
7f9fef93 258=head1 Incompatible Changes
79a77127 259
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260=head2 Subroutine signatures moved before attributes
261
262The experimental sub signatures feature, as introduced in 5.20, parsed
263signatures after attributes. In this release, the positioning has been
264moved such that signatures occur after the subroutine name (if any) and
265before the attribute list (if any).
266
267=head2 C<&> and C<\&> prototypes accepts only subs
268
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269The C<&> prototype character now accepts only anonymous subs (C<sub
270{...}>), things beginning with C<\&>, or an explicit C<undef>. Formerly
271it erroneously also allowed references to arrays, hashes, and lists.
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272L<[perl #4539]|https://rt.perl.org/Ticket/Display.html?id=4539>.
273L<[perl #123062]|https://rt.perl.org/Ticket/Display.html?id=123062>.
43831b1f 274L<[perl #123062]|https://rt.perl.org/Ticket/Display.html?id=123475>.
eabfc7bc 275
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276In addition, the C<\&> prototype was allowing subroutine calls, whereas
277now it only allows subroutines: C<&foo> is still permitted as an argument,
278while C<&foo()> and C<foo()> no longer are.
a75e6a3a 279L<[perl #77860]|https://rt.perl.org/Ticket/Display.html?id=77860>.
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280
281=head2 C<use encoding> is now lexical
282
283The L<encoding> pragma's effect is now limited to lexical scope. This
284pragma is deprecated, but in the meantime, it could adversely affect
285unrelated modules that are included in the same program.
286
287=head2 List slices returning empty lists
288
289List slices return an empty list now only if the original list was empty
290(or if there are no indices). Formerly, a list slice would return an empty
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291list if all indices fell outside the original list; now it returns a list
292of undef values.
a75e6a3a 293L<[perl #114498]|https://rt.perl.org/Ticket/Display.html?id=114498>.
eabfc7bc 294
01842271 295=head2 C<\N{}> with a sequence of multiple spaces is now a fatal error
eabfc7bc 296
43831b1f 297E.g. C<\N{TOO MANY SPACES}> or C<\N{TRAILING SPACE }>.
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298This has been deprecated since v5.18.
299
300=head2 S<C<use UNIVERSAL '...'>> is now a fatal error
301
302Importing functions from C<UNIVERSAL> has been deprecated since v5.12, and
303is now a fatal error. S<C<"use UNIVERSAL">> without any arguments is still
304allowed.
305
306=head2 In double-quotish C<\cI<X>>, I<X> must now be a printable ASCII character
307
308In prior releases, failure to do this raised a deprecation warning.
309
310=head2 Splitting the tokens C<(?> and C<(*> in regular expressions is
311now a fatal compilation error.
312
313These had been deprecated since v5.18.
314
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315=head2 C<qr/foo/x> now ignores all Unicode pattern white space
316
317The C</x> regular expression modifier allows the pattern to contain
318white space and comments (both of which are ignored) for improved
319readability. Until now, not all the white space characters that Unicode
320designates for this purpose were handled. The additional ones now
321recognized are
322
323 U+0085 NEXT LINE
324 U+200E LEFT-TO-RIGHT MARK
325 U+200F RIGHT-TO-LEFT MARK
326 U+2028 LINE SEPARATOR
327 U+2029 PARAGRAPH SEPARATOR
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328
329The use of these characters with C</x> outside bracketed character
330classes and when not preceded by a backslash has raised a deprecation
43831b1f 331warning since v5.18. Now they will be ignored.
eabfc7bc 332
43831b1f 333=head2 Comment lines within S<C<(?[ ])>> are now ended only by a C<\n>
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334
335S<C<(?[ ])>> is an experimental feature, introduced in v5.18. It operates
43831b1f 336as if C</x> is always enabled. But there was a difference: comment
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337lines (following a C<#> character) were terminated by anything matching
338C<\R> which includes all vertical whitespace, such as form feeds. For
339consistency, this is now changed to match what terminates comment lines
340outside S<C<(?[ ])>>, namely a C<\n> (even if escaped), which is the
341same as what terminates a heredoc string and formats.
342
343=head2 C<(?[...])> operators now follow standard Perl precedence
344
345This experimental feature allows set operations in regular expression patterns.
346Prior to this, the intersection operator had the same precedence as the other
347binary operators. Now it has higher precedence. This could lead to different
348outcomes than existing code expects (though the documentation has always noted
349that this change might happen, recommending fully parenthesizing the
350expressions). See L<perlrecharclass/Extended Bracketed Character Classes>.
351
4ec8e6f0 352=head2 Omitting C<%> and C<@> on hash and array names is no longer permitted
c14a43b7 353
4ec8e6f0 354Really old Perl let you omit the C<@> on array names and the C<%> on hash
eabfc7bc 355names in some spots. This has issued a deprecation warning since Perl
93780ae6 3565.000, and is no longer permitted.
c14a43b7 357
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358=head2 C<"$!"> text is now in English outside C<"use locale"> scope
359
360Previously, the text, unlike almost everything else, always came out
361based on the current underlying locale of the program. (Also affected
362on some systems is C<"$^E>".) For programs that are unprepared to
363handle locale, this can cause garbage text to be displayed. It's better
364to display text that is translatable via some tool than garbage text
365which is much harder to figure out.
366
367=head2 C<"$!"> text will be returned in UTF-8 when appropriate
368
369The stringification of C<$!> and C<$^E> will have the UTF-8 flag set
370when the text is actually non-ASCII UTF-8. This will enable programs
371that are set up to be locale-aware to properly output messages in the
372user's native language. Code that needs to continue the 5.20 and
373earlier behavior can do the stringification within the scopes of both
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374S<C<'use bytes'>> and S<C<'use locale ":messages">>. No other Perl
375operations will
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376be affected by locale; only C<$!> and C<$^E> stringification. The
377'bytes' pragma causes the UTF-8 flag to not be set, just as in previous
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378Perl releases. This resolves
379L<[perl #112208]|https://rt.perl.org/Ticket/Display.html?id=112208>.
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380
381=head2 Support for C<?PATTERN?> without explicit operator has been removed
382
383Starting regular expressions matching only once directly with the
384question mark delimiter is now a syntax error, so that the question mark
385can be available for use in new operators. Write C<m?PATTERN?> instead,
386explicitly using the C<m> operator: the question mark delimiter still
387invokes match-once behaviour.
388
389=head2 C<defined(@array)> and C<defined(%hash)> are now fatal errors
390
391These have been deprecated since v5.6.1 and have raised deprecation
392warnings since v5.16.
393
01842271 394=head2 Using a hash or an array as a reference are now fatal errors
eabfc7bc 395
43831b1f 396For example, C<< %foo->{"bar"} >> now causes a fatal compilation
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397error. These have been deprecated since before v5.8, and have raised
398deprecation warnings since then.
399
400=head2 Changes to the C<*> prototype
401
402The C<*> character in a subroutine's prototype used to allow barewords to take
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403precedence over most, but not all, subroutine names. It was never
404consistent and exhibited buggy behaviour.
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405
406Now it has been changed, so subroutines always take precedence over barewords,
407which brings it into conformity with similarly prototyped built-in functions:
408
409 sub splat(*) { ... }
410 sub foo { ... }
411 splat(foo); # now always splat(foo())
412 splat(bar); # still splat('bar') as before
413 close(foo); # close(foo())
414 close(bar); # close('bar')
c14a43b7 415
7f9fef93 416=head1 Deprecations
47cb8ddb 417
eabfc7bc 418=head2 Setting C<${^ENCODING}> to anything but C<undef>
c14a43b7 419
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420This variable allows Perl scripts to be written in a non-ASCII,
421non-UTF-8 encoding. However, it affects all modules globally, leading
422to wrong answers and segmentation faults. New scripts should be written
423in UTF-8; old scripts should be converted to UTF-8, which is easily done
424with the L<encoding> pragma.
c14a43b7 425
eabfc7bc 426=head2 Use of non-graphic characters in single-character variable names
51c2f40f 427
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428The syntax for single-character variable names is more lenient than
429for longer variable names, allowing the one-character name to be a
430punctuation character or even invisible (a non-graphic). Perl v5.20
431deprecated the ASCII-range controls as such a name. Now, all
432non-graphic characters that formerly were allowed are deprecated.
433The practical effect of this occurs only when not under C<S<"use
434utf8">>, and affects just the C1 controls (code points 0x80 through
4350xFF), NO-BREAK SPACE, and SOFT HYPHEN.
83a5d6b6 436
eabfc7bc 437=head2 Inlining of C<sub () { $var }> with observable side-effects
abec5bed 438
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439In many cases Perl makes S<C<sub () { $var }>> into an inlinable constant
440subroutine, capturing the value of C<$var> at the time the C<sub> expression
eabfc7bc 441is evaluated. This can break the closure behaviour in those cases where
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442C<$var> is subsequently modified, since the subroutine won't return the
443changed value. (Note that this all only applies to anonymous subroutines
444with an empty prototype (C<sub ()>).)
abec5bed 445
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446This usage is now deprecated in those cases where the variable could be
447modified elsewhere. Perl detects those cases and emits a deprecation
448warning. Such code will likely change in the future and stop producing a
449constant.
abec5bed 450
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451If your variable is only modified in the place where it is declared, then
452Perl will continue to make the sub inlinable with no warnings.
c14a43b7 453
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454 sub make_constant {
455 my $var = shift;
456 return sub () { $var }; # fine
457 }
c14a43b7 458
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459 sub make_constant_deprecated {
460 my $var;
461 $var = shift;
462 return sub () { $var }; # deprecated
463 }
c14a43b7 464
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465 sub make_constant_deprecated2 {
466 my $var = shift;
467 log_that_value($var); # could modify $var
468 return sub () { $var }; # deprecated
469 }
c14a43b7 470
4ec8e6f0 471In the second example above, detecting that C<$var> is assigned to only once
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472is too hard to detect. That it happens in a spot other than the C<my>
473declaration is enough for Perl to find it suspicious.
7f9fef93 474
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475This deprecation warning happens only for a simple variable for the body of
476the sub. (A C<BEGIN> block or C<use> statement inside the sub is ignored,
477because it does not become part of the sub's body.) For more complex
4ec8e6f0 478cases, such as S<C<sub () { do_something() if 0; $var }>> the behaviour has
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479changed such that inlining does not happen if the variable is modifiable
480elsewhere. Such cases should be rare.
c14a43b7 481
eabfc7bc 482=head2 Use of multiple /x regexp modifiers
c14a43b7 483
eabfc7bc 484It is now deprecated to say something like any of the following:
c14a43b7 485
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486 qr/foo/xx;
487 /(?xax:foo)/;
488 use re qw(/amxx);
be39acb2 489
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490That is, now C<x> should only occur once in any string of contiguous
491regular expression pattern modifiers. We do not believe there are any
492occurrences of this in all of CPAN. This is in preparation for a future
493Perl release having C</xx> mean to allow white-space for readability in
494bracketed character classes (those enclosed in square brackets:
495C<[...]>).
c14a43b7 496
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497=head2 Using a NO-BREAK space in a character alias for C<\N{...}> is now
498deprecated
60dcce55 499
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500This non-graphic character is essentially indistinguishable from a
501regular space, and so should not be allowed. See
502L<charnames/CUSTOM ALIASES>.
60dcce55 503
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504=head2 A literal C<"{"> should now be escaped in a pattern
505
506If you want a literal left curly bracket (also called a left brace) in a
507regular expression pattern, you should now escape it by either
508preceding it with a backslash (C<"\{">) or enclosing it within square
509brackets C<"[{]">, or by using C<\Q>; otherwise a deprecation warning
510will be raised. This was first announced as forthcoming in the v5.16
511release; it will allow future extensions to the language to happen.
512
513=head2 Making all warnings fatal is discouraged
514
515The documentation for L<fatal warnings|warnings/Fatal Warnings> notes that
516C<< use warnings FATAL => 'all' >> is discouraged and provides stronger
517language about the risks of fatal warnings in general.
518
519=head1 Performance Enhancements
79a77127 520
7f9fef93 521=over 4
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522
523=item *
524
43831b1f 525If a method or class name is known at compile time, a hash is precomputed
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526to speed up run-time method lookup. Also, compound method names like
527C<SUPER::new> are parsed at compile time, to save having to parse them at
528run time.
9749148e 529
eabfc7bc 530=item *
9749148e 531
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532Array and hash lookups (especially nested ones) that use only constants
533or simple variables as keys, are now considerably faster. See
534L</Internal Changes> for more details.
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535
536=item *
537
eabfc7bc
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538C<(...)x1>, C<("constant")x0> and C<($scalar)x0> are now optimised in list
539context. If the right-hand argument is a constant 1, the repetition
540operator disappears. If the right-hand argument is a constant 0, the whole
6a3ea89b 541expression is optimised to the empty list, so long as the left-hand
eabfc7bc 542argument is a simple scalar or constant. C<(foo())x0> is not optimised.
6bb5549b 543
eabfc7bc 544=item *
7f9fef93 545
eabfc7bc
RS
546C<substr> assignment is now optimised into 4-argument C<substr> at the end
547of a subroutine (or as the argument to C<return>). Previously, this
548optimisation only happened in void context.
abec5bed 549
eabfc7bc 550=item *
7f9fef93 551
43831b1f
DM
552Assignment to lexical variables is now more often optimised away. For
553instance, in
eabfc7bc
RS
554C<$lexical = chr $foo>, the C<chr> operator writes directly to the lexical
555variable instead of returning a value that gets copied. This optimisation
556has been extended to C<split>, C<x> and C<vec> on the right-hand side. It
557has also been made to work with state variable initialization.
be39acb2 558
2e4abf26
DG
559=item *
560
43831b1f
DM
561In C<"\L...">, C<"\Q...">, etc., the extra "stringify" op is now optimised
562away, making these just as fast as C<lcfirst>, C<quotemeta>, etc.
2e4abf26 563
eabfc7bc 564=item *
83a5d6b6 565
eabfc7bc
RS
566Assignment to an empty list is now sometimes faster. In particular, it
567never calls C<FETCH> on tied arguments on the right-hand side, whereas it
568used to sometimes.
569
570=item *
83a5d6b6 571
eabfc7bc 572C<length> is up to 20% faster for non-magical/non-tied scalars containing a
4ec8e6f0 573string if it is a non-utf8 string or if is in scope of C<use bytes>.
338906ce 574
eabfc7bc 575=item *
5de148ee 576
43831b1f
DM
577On most perl builds with 64 bit integers, non-magical/non-tied scalars
578that contain only a floating point value now use between 8 and 32 less bytes
579of memory, depending on OS.
5de148ee 580
eabfc7bc 581=item *
5de148ee 582
eabfc7bc
RS
583In C<@array = split>, the assignment can be optimized away with C<split>
584writing directly to the array. This optimisation was happening only for
43831b1f
DM
585package arrays other than C<@_>, and only sometimes. Now this
586optimisation happens almost all the time.
5de148ee 587
eabfc7bc 588=item *
7f9fef93 589
43831b1f
DM
590C<join> is now subject to constant folding. So for example
591C<join "-", "a", "b"> is converted at compile-time to C<"a-b">.
592Moreover, C<join> with a scalar or constant for the separator and a
593single-item list to join is simplified to a stringification. The
594separator doesn't even get evaluated.
5de148ee 595
eabfc7bc 596=item *
47cb8ddb 597
eabfc7bc 598C<qq(@array)> is implemented using two ops: a stringify op and a join op.
4ec8e6f0 599If the C<qq> contains nothing but a single array, the stringification is
eabfc7bc 600optimized away.
47cb8ddb
SH
601
602=item *
603
4ec8e6f0
KW
604S<C<our $var>> and S<C<our($s,@a,%h)>> in void context are no longer evaluated at
605run time. Even a whole sequence of S<C<our $foo;>> statements will simply be
eabfc7bc 606skipped over. The same applies to C<state> variables.
47cb8ddb 607
eabfc7bc 608=item *
47cb8ddb 609
eabfc7bc
RS
610Many internal functions have been refactored to improve performance and reduce
611their memory footprints.
eabfc7bc
RS
612L<[perl #121436]|https://rt.perl.org/Ticket/Display.html?id=121436>
613L<[perl #121906]|https://rt.perl.org/Ticket/Display.html?id=121906>
614L<[perl #121969]|https://rt.perl.org/Ticket/Display.html?id=121969>
47cb8ddb 615
eabfc7bc 616=item *
47cb8ddb 617
eabfc7bc 618C<-T> and C<-B> filetests will return sooner when an empty file is detected.
a75e6a3a 619L<[perl #121489]|https://rt.perl.org/Ticket/Display.html?id=121489>
47cb8ddb 620
eabfc7bc 621=item *
5de148ee 622
01842271 623Hash lookups where the key is a constant are faster.
be39acb2
SH
624
625=item *
626
eabfc7bc
RS
627Subroutines with an empty prototype and bodies containing just C<undef> are now
628eligible for inlining.
629L<[perl #122728]|https://rt.perl.org/Ticket/Display.html?id=122728>
be39acb2 630
eabfc7bc 631=item *
be39acb2 632
43831b1f
DM
633Subroutines in packages no longer need to be stored in typeglobs:
634declaring a subroutine will now put a simple sub reference directly in the
635stash if possible, saving memory. The typeglob still notionally exists,
636so accessing it will cause the stash entry to be upgraded to a typeglob
637(i.e. this is just an internal implementation detail).
638This optimization does not currently apply to XSUBs or exported
639subroutines, and method calls will undo it, since they cache things in
640typeglobs.
eabfc7bc 641L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
7f9fef93 642
eabfc7bc 643=item *
be39acb2 644
eabfc7bc
RS
645The functions C<utf8::native_to_unicode()> and C<utf8::unicode_to_native()>
646(see L<utf8>) are now optimized out on ASCII platforms. There is now not even
647a minimal performance hit in writing code portable between ASCII and EBCDIC
648platforms.
be39acb2
SH
649
650=item *
651
eabfc7bc 652Win32 Perl uses 8 KB less of per-process memory than before for every perl
43831b1f 653process, because some data is now memory mapped from disk and shared
eabfc7bc 654between perl processes from the same perl binary.
be39acb2
SH
655
656=back
657
eabfc7bc 658=head1 Modules and Pragmata
83a5d6b6 659
eabfc7bc
RS
660XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
661go here. If Module::CoreList is updated, generate an initial draft of the
662following sections using F<Porting/corelist-perldelta.pl>. A paragraph summary
663for important changes should then be added by hand. In an ideal world,
664dual-life modules would have a F<Changes> file that could be cribbed.
83a5d6b6 665
eabfc7bc 666[ Within each section, list entries as a =item entry ]
338906ce 667
eabfc7bc 668=head2 New Modules and Pragmata
cd7bac54 669
b5d4d3b9 670=over 4
83b69bfd
DD
671
672=item *
673
7f9fef93 674XXX
13adb056 675
b5d4d3b9 676=back
391823f2 677
eabfc7bc
RS
678=head2 Updated Modules and Pragmata
679
680=over 4
681
682=item *
683
684L<XXX> has been upgraded from version A.xx to B.yy.
6c8457e9 685
eabfc7bc 686=back
2bf83140 687
eabfc7bc 688=head2 Removed Modules and Pragmata
041a5927 689
7f9fef93 690=over 4
69e954a5 691
7f9fef93 692=item *
86e0176a 693
7f9fef93 694XXX
69e954a5 695
e5998677 696=back
20b5e916 697
eabfc7bc
RS
698=head1 Documentation
699
700=head2 New Documentation
532ecd00 701
eabfc7bc 702=head3 L<perlunicook>
d76c14eb 703
eabfc7bc
RS
704This document, by Tom Christiansen, provides examples of handling Unicode in
705Perl.
706
707=head2 Changes to Existing Documentation
708
709=head3 L<perlapi>
d547bad0 710
e5998677 711=over 4
d547bad0 712
8a95d307
FC
713=item *
714
eabfc7bc 715Note that C<SvSetSV> doesn't do set magic.
532ecd00 716
eabfc7bc 717=item *
532ecd00 718
eabfc7bc
RS
719C<sv_usepvn_flags> - Fix documentation to mention the use of C<NewX> instead of
720C<malloc>.
532ecd00 721
eabfc7bc 722L<[perl #121869]|https://rt.perl.org/Ticket/Display.html?id=121869>
532ecd00 723
eabfc7bc 724=item *
532ecd00 725
eabfc7bc 726Clarify where C<NUL> may be embedded or is required to terminate a string.
532ecd00 727
eabfc7bc 728=item *
532ecd00 729
eabfc7bc 730Previously missing documentation due to formatting errors are now included.
532ecd00 731
eabfc7bc 732=item *
532ecd00 733
eabfc7bc 734Entries are now organized into groups rather than by file where they are found.
532ecd00 735
eabfc7bc 736=item *
532ecd00 737
eabfc7bc
RS
738Alphabetical sorting of entries is now handled by the POD generator to make
739entries easier to find when scanning.
740
741=back
338906ce 742
eabfc7bc 743=head3 L<perldata>
338906ce 744
e5998677 745=over 4
338906ce 746
eabfc7bc 747=item *
2f304be9 748
eabfc7bc
RS
749The syntax of single-character variable names has been brought
750up-to-date and more fully explained.
9749148e 751
7f9fef93 752=back
9749148e 753
eabfc7bc 754=head3 L<perlebcdic>
47cb8ddb 755
7f9fef93 756=over 4
47cb8ddb 757
eabfc7bc 758=item *
47cb8ddb 759
eabfc7bc
RS
760This document has been significantly updated in the light of recent
761improvements to EBCDIC support.
47cb8ddb 762
7f9fef93 763=back
47cb8ddb 764
eabfc7bc 765=head3 L<perlfunc>
be39acb2 766
eabfc7bc 767=over 4
be39acb2 768
eabfc7bc 769=item *
be39acb2 770
eabfc7bc 771Mention that C<study()> is currently a no-op.
be39acb2
SH
772
773=item *
774
eabfc7bc
RS
775Calling C<delete> or C<exists> on array values is now described as "strongly
776discouraged" rather than "deprecated".
be39acb2 777
eabfc7bc 778=item *
7f9fef93 779
eabfc7bc 780Improve documentation of C<< our >>.
be39acb2 781
eabfc7bc 782=item *
be39acb2 783
eabfc7bc
RS
784C<-l> now notes that it will return false if symlinks aren't supported by the
785file system.
be39acb2 786
eabfc7bc 787L<[perl #121523]|https://rt.perl.org/Ticket/Display.html?id=121523>
be39acb2
SH
788
789=item *
790
eabfc7bc
RS
791Note that C<exec LIST> and C<system LIST> may fall back to the shell on
792Win32. Only C<exec PROGRAM LIST> and C<system PROGRAM LIST> indirect object
793syntax will reliably avoid using the shell.
794
795This has also been noted in L<perlport>.
796
797L<[perl #122046]|https://rt.perl.org/Ticket/Display.html?id=122046>
be39acb2 798
7f9fef93 799=back
be39acb2 800
eabfc7bc
RS
801=head3 L<perlguts>
802
803=over 4
804
805=item *
806
807The OOK example has been updated to account for COW changes and a change in the
808storage of the offset.
809
810=item *
be39acb2 811
eabfc7bc 812Details on C level symbols and libperl.t added.
be39acb2 813
ce93e38b
KW
814=item *
815
816Information on Unicode handling has been added
817
818=item *
819
820Information on EBCDIC handling has been added
821
eabfc7bc
RS
822=back
823
824=head3 L<perlhacktips>
7f9fef93
SH
825
826=over 4
be39acb2
SH
827
828=item *
829
eabfc7bc
RS
830Documentation has been added illustrating the perils of assuming the contents
831of static memory pointed to by the return values of Perl wrappers for C library
832functions doesn't change.
833
834=item *
835
836Recommended replacements for tmpfile, atoi, strtol, and strtoul added.
837
838=item *
839
840Updated documentation for the C<test.valgrind> C<make> target.
841
842L<[perl #121431]|https://rt.perl.org/Ticket/Display.html?id=121431>
be39acb2 843
a9c3e753 844=back
ea13b07e 845
eabfc7bc 846=head3 L<perlmodstyle>
0d42058e 847
7f9fef93
SH
848=over 4
849
850=item *
2a7a05b4 851
eabfc7bc
RS
852Instead of pointing to the module list, we are now pointing to
853L<PrePAN|http://prepan.org/>.
2a7a05b4 854
7f9fef93
SH
855=back
856
eabfc7bc
RS
857=head3 L<perlpolicy>
858
859=over 4
860
861=item *
862
863We now have a code of conduct for the I<< p5p >> mailing list, as documented
864in L<< perlpolicy/STANDARDS OF CONDUCT >>.
2a7a05b4 865
eabfc7bc
RS
866=item *
867
868The conditions for marking an experimental feature as non-experimental are now
869set out.
870
871=back
872
873=head3 L<perlport>
874
875=over 4
876
877=item *
878
879Out-of-date VMS-specific information has been fixed/simplified.
880
ce93e38b
KW
881=item *
882
883Notes about EBCDIC have been added.
884
eabfc7bc
RS
885=back
886
887=head3 L<perlre>
888
889=over 4
890
891=item *
892
893The C</x> modifier has been clarified to note that comments cannot be continued
894onto the next line by escaping them.
895
896=back
897
898=head3 L<perlrebackslash>
899
900=over 4
901
902=item *
903
904Added documentation of C<\b{sb}>, C<\b{wb}>, C<\b{gcb}>, and C<\b{g}>.
905
906=back
907
908=head3 L<perlrecharclass>
909
910=over 4
911
912=item *
913
914Clarifications have been added to L<perlrecharclass/Character Ranges>
915to the effect that Perl guarantees that C<[A-Z]>, C<[a-z]>, C<[0-9]> and
916any subranges thereof in regular expression bracketed character classes
917are guaranteed to match exactly what a naive English speaker would
918expect them to match, even on platforms (such as EBCDIC) where special
919handling is required to accomplish this.
920
921=item *
922
923The documentation of Bracketed Character Classes has been expanded to cover the
924improvements in C<qr/[\N{named sequence}]/> (see under L</Selected Bug Fixes>).
925
926=back
927
928=head3 L<perlsec>
929
930=over 4
931
932=item *
933
934Comments added on algorithmic complexity and tied hashes.
935
936=back
937
938=head3 L<perlsyn>
939
940=over 4
941
942=item *
943
944An ambiguity in the documentation of the C<...> statement has been corrected.
945L<[perl #122661]|https://rt.perl.org/Ticket/Display.html?id=122661>
946
947=item *
948
949The empty conditional in C<< for >> and C<< while >> is now documented
950in L<< perlsyn >>.
951
952=back
953
954=head3 L<perlunicode>
955
956=over 4
957
958=item *
959
ce93e38b
KW
960This has had extensive revisions to bring it up-to-date with current
961Unicode support and to make it more readable.
eabfc7bc
RS
962
963=back
964
965=head3 L<perluniintro>
966
967=over 4
968
969=item *
970
971Advice for how to make sure your strings and regular expression patterns are
ce93e38b 972interpreted as Unicode has been updated.
eabfc7bc
RS
973
974=back
975
976=head3 L<perlvar>
977
978=over 4
979
980=item *
981
982Further clarify version number representations and usage.
983
984=back
985
986=head3 L<perlvms>
987
988=over 4
989
990=item *
991
992Out-of-date and/or incorrect material has been removed.
993
994=item *
995
996Updated documentation on environment and shell interaction in VMS.
997
998=back
999
1000=head3 L<perlxs>
1001
1002=over 4
1003
1004=item *
1005
1006Added a discussion of locale issues in XS code.
1007
1008=back
1009
1010=head1 Diagnostics
1011
1012The following additions or changes have been made to diagnostic output,
1013including warnings and fatal error messages. For the complete list of
1014diagnostic messages, see L<perldiag>.
1015
1016=head2 New Diagnostics
1017
1018=head3 New Errors
1019
1020=over 4
1021
1022=item *
1023
1024L<Bad symbol for scalar|perldiag/"Bad symbol for scalar">
1025
1026(P) An internal request asked to add a scalar entry to something that
1027wasn't a symbol table entry.
1028
1029=item *
1030
1031L<Can't use a hash as a reference|perldiag/"Can't use a hash as a reference">
1032
1033(F) You tried to use a hash as a reference, as in
1034C<< %foo->{"bar"} >> or C<< %$ref->{"hello"} >>. Versions of perl E<lt>= 5.6.1
1035used to allow this syntax, but shouldn't have.
1036
1037=item *
1038
1039L<Can't use an array as a reference|perldiag/"Can't use an array as a reference">
1040
1041(F) You tried to use an array as a reference, as in
1042C<< @foo->[23] >> or C<< @$ref->[99] >>. Versions of perl E<lt>= 5.6.1 used to
1043allow this syntax, but shouldn't have.
1044
1045=item *
1046
1047L<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()?)">
1048
4ec8e6f0 1049(F) C<defined()> is not useful on arrays because it
eabfc7bc 1050checks for an undefined I<scalar> value. If you want to see if the
4ec8e6f0 1051array is empty, just use S<C<if (@array) { # not empty }>> for example.
eabfc7bc
RS
1052
1053=item *
1054
1055L<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()?)">
1056
1057(F) C<defined()> is not usually right on hashes.
1058
4ec8e6f0 1059Although S<C<defined %hash>> is false on a plain not-yet-used hash, it
eabfc7bc 1060becomes true in several non-obvious circumstances, including iterators,
4ec8e6f0
KW
1061weak references, stash names, even remaining true after S<C<undef %hash>>.
1062These things make S<C<defined %hash>> fairly useless in practice, so it now
eabfc7bc
RS
1063generates a fatal error.
1064
1065If a check for non-empty is what you wanted then just put it in boolean
1066context (see L<perldata/Scalar values>):
1067
1068 if (%hash) {
1069 # not empty
1070 }
1071
4ec8e6f0 1072If you had S<C<defined %Foo::Bar::QUUX>> to check whether such a package
eabfc7bc
RS
1073variable exists then that's never really been reliable, and isn't
1074a good way to enquire about the features of a package, or whether
1075it's loaded, etc.
1076
1077=item *
1078
1079L<Cannot chr %f|perldiag/"Cannot chr %f">
1080
c21a1c59
RS
1081(F) You passed an invalid number (like an infinity or not-a-number) to
1082C<chr>.
1083
eabfc7bc
RS
1084=item *
1085
1086L<Cannot compress %f in pack|perldiag/"Cannot compress %f in pack">
1087
c21a1c59
RS
1088(F) You tried converting an infinity or not-a-number to an unsigned
1089character, which makes no sense.
1090
eabfc7bc
RS
1091=item *
1092
1093L<Cannot pack %f with '%c'|perldiag/"Cannot pack %f with '%c'">
1094
c21a1c59
RS
1095(F) You tried converting an infinity or not-a-number to a character,
1096which makes no sense.
1097
eabfc7bc
RS
1098=item *
1099
1100L<Cannot print %f with '%c'|perldiag/"Cannot printf %f with '%c'">
1101
4ec8e6f0
KW
1102(F) You tried printing an infinity or not-a-number as a character (C<%c>),
1103which makes no sense. Maybe you meant C<'%s'>, or just stringifying it?
c21a1c59 1104
eabfc7bc
RS
1105=item *
1106
1107L<charnames alias definitions may not contain a sequence of multiple spaces|perldiag/"charnames alias definitions may not contain a sequence of multiple spaces">
1108
1109(F) You defined a character name which had multiple space
1110characters in a row. Change them to single spaces. Usually these
1111names are defined in the C<:alias> import argument to C<use charnames>, but
1112they could be defined by a translator installed into C<$^H{charnames}>.
1113See L<charnames/CUSTOM ALIASES>.
1114
1115=item *
1116
1117L<charnames alias definitions may not contain trailing white-space|perldiag/"charnames alias definitions may not contain trailing white-space">
1118
1119(F) You defined a character name which ended in a space
1120character. Remove the trailing space(s). Usually these names are
1121defined in the C<:alias> import argument to C<use charnames>, but they
1122could be defined by a translator installed into C<$^H{charnames}>.
1123See L<charnames/CUSTOM ALIASES>.
1124
1125=item *
1126
1127L<:const is not permitted on named subroutines|perldiag/":const is not permitted on named subroutines">
1128
1129(F) The "const" attribute causes an anonymous subroutine to be run and
1130its value captured at the time that it is cloned. Names subroutines are
1131not cloned like this, so the attribute does not make sense on them.
1132
1133=item *
1134
1135L<Hexadecimal float: internal error|perldiag/"Hexadecimal float: internal error">
1136
1137(F) Something went horribly bad in hexadecimal float handling.
1138
1139=item *
1140
1141L<Hexadecimal float: unsupported long double format|perldiag/"Hexadecimal float: unsupported long double format">
1142
1143(F) You have configured Perl to use long doubles but
1144the internals of the long double format are unknown,
1145therefore the hexadecimal float output is impossible.
1146
1147=item *
1148
1149L<Illegal suidscript|perldiag/"Illegal suidscript">
1150
1151(F) The script run under suidperl was somehow illegal.
1152
1153=item *
1154
1155L<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/">
1156
1157(F) The two-character sequence C<"(?"> in
1158this context in a regular expression pattern should be an
1159indivisible token, with nothing intervening between the C<"(">
1160and the C<"?">, but you separated them.
1161
1162=item *
1163
1164L<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/">
1165
1166(F) The two-character sequence C<"(*"> in
1167this context in a regular expression pattern should be an
1168indivisible token, with nothing intervening between the C<"(">
1169and the C<"*">, but you separated them.
1170
1171=item *
1172
1173L<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/">
1174
1175(F) The pattern looks like a {min,max} quantifier, but the min or max could not
1176be parsed as a valid number - either it has leading zeroes, or it represents
1177too big a number to cope with. The S<<-- HERE> shows where in the regular
1178expression the problem was discovered. See L<perlre>.
1179
1180=back
1181
1182=head3 New Warnings
1183
1184=over 4
1185
1186=item *
1187
43831b1f
DM
1188L<\C is deprecated in regex|perldiag/"\C is deprecated in regex; marked by <-- HERE in m/%s/">
1189
1190(D deprecated) The C<< /\C/ >> character class was deprecated in v5.20, and
1191now emits a warning. It is intended that it will become an error in v5.24.
1192This character class matches a single byte even if it appears within a
1193multi-byte character, breaks encapsulation, and can corrupt utf8
1194strings.
1195
1196=item *
1197
eabfc7bc
RS
1198L<'%s' is an unknown bound type in regex|perldiag/"'%s' is an unknown bound type in regex; marked by <-- HERE in m/%s/">
1199
1200You used C<\b{...}> or C<\B{...}> and the C<...> is not known to
1201Perl. The current valid ones are given in
1202L<perlrebackslash/\b{}, \b, \B{}, \B>.
1203
1204=item *
1205
1206L<"%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>>
1207
1208(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1209
1210You specified a character that has the given plainer way of writing it,
1211and which is also portable to platforms running with different character
1212sets.
1213
1214=item *
1215
1216L<Argument "%s" treated as 0 in increment (++)|perldiag/"Argument "%s" treated
1217as 0 in increment (++)">
1218
1219(W numeric) The indicated string was fed as an argument to the C<++> operator
1220which expects either a number or a string matching C</^[a-zA-Z]*[0-9]*\z/>.
1221See L<perlop/Auto-increment and Auto-decrement> for details.
1222
1223=item *
1224
1225L<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/">
1226
1227(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1228
1229In a bracketed character class in a regular expression pattern, you
1230had a range which has exactly one end of it specified using C<\N{}>, and
1231the other end is specified using a non-portable mechanism. Perl treats
1232the range as a Unicode range, that is, all the characters in it are
1233considered to be the Unicode characters, and which may be different code
1234points on some platforms Perl runs on. For example, C<[\N{U+06}-\x08]>
1235is treated as if you had instead said C<[\N{U+06}-\N{U+08}]>, that is it
1236matches the characters whose code points in Unicode are 6, 7, and 8.
1237But that C<\x08> might indicate that you meant something different, so
1238the warning gets raised.
1239
1240=item *
1241
eabfc7bc
RS
1242L<:const is experimental|perldiag/":const is experimental">
1243
1244(S experimental::const_attr) The "const" attribute is experimental.
1245If you want to use the feature, disable the warning with C<no warnings
1246'experimental::const_attr'>, but know that in doing so you are taking
1247the risk that your code may break in a future Perl version.
1248
1249=item *
1250
1251L<gmtime(%f) failed|perldiag/"gmtime(%f) failed">
1252
1253(W overflow) You called C<gmtime> with a number that it could not handle:
1254too large, too small, or NaN. The returned value is C<undef>.
1255
1256=item *
1257
1258L<Hexadecimal float: exponent overflow|perldiag/"Hexadecimal float: exponent overflow">
1259
1260(W overflow) The hexadecimal floating point has larger exponent
1261than the floating point supports.
1262
1263=item *
1264
1265L<Hexadecimal float: exponent underflow|perldiag/"Hexadecimal float: exponent underflow">
1266
1267(W overflow) The hexadecimal floating point has smaller exponent
1268than the floating point supports.
1269
1270=item *
1271
1272L<Hexadecimal float: mantissa overflow|perldiag/"Hexadecimal float: mantissa overflow">
1273
1274(W overflow) The hexadecimal floating point literal had more bits in
1275the mantissa (the part between the 0x and the exponent, also known as
1276the fraction or the significand) than the floating point supports.
1277
1278=item *
1279
1280L<Hexadecimal float: precision loss|perldiag/"Hexadecimal float: precision loss">
1281
1282(W overflow) The hexadecimal floating point had internally more
1283digits than could be output. This can be caused by unsupported
1284long double formats, or by 64-bit integers not being available
1285(needed to retrieve the digits under some configurations).
1286
eabfc7bc
RS
1287=item *
1288
1289L<localtime(%f) failed|perldiag/"localtime(%f) failed">
1290
1291(W overflow) You called C<localtime> with a number that it could not handle:
1292too large, too small, or NaN. The returned value is C<undef>.
1293
1294=item *
1295
1296L<Negative repeat count does nothing|perldiag/"Negative repeat count does nothing">
1297
1298(W numeric) You tried to execute the
1299L<C<x>|perlop/Multiplicative Operators> repetition operator fewer than 0
1300times, which doesn't make sense.
1301
1302=item *
1303
1304L<NO-BREAK SPACE in a charnames alias definition is deprecated|perldiag/"NO-BREAK SPACE in a charnames alias definition is deprecated">
1305
1306(D deprecated) You defined a character name which contained a no-break
1307space character. Change it to a regular space. Usually these names are
1308defined in the C<:alias> import argument to C<use charnames>, but they
1309could be defined by a translator installed into C<$^H{charnames}>. See
1310L<charnames/CUSTOM ALIASES>.
1311
1312=item *
1313
1314L<Non-finite repeat count does nothing|perldiag/"Non-finite repeat count does nothing">
1315
1316(W numeric) You tried to execute the
1317L<C<x>|perlop/Multiplicative Operators> repetition operator C<Inf> (or
1318C<-Inf>) or C<NaN> times, which doesn't make sense.
1319
1320=item *
1321
1322L<PerlIO layer ':win32' is experimental|perldiag/"PerlIO layer ':win32' is experimental">
1323
1324(S experimental::win32_perlio) The C<:win32> PerlIO layer is
1325experimental. If you want to take the risk of using this layer,
1326simply disable this warning:
1327
1328 no warnings "experimental::win32_perlio";
1329
1330=item *
1331
1332L<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>">
1333
1334(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1335
1336Stricter rules help to find typos and other errors. Perhaps you didn't
1337even intend a range here, if the C<"-"> was meant to be some other
1338character, or should have been escaped (like C<"\-">). If you did
1339intend a range, the one that was used is not portable between ASCII and
1340EBCDIC platforms, and doesn't have an obvious meaning to a casual
1341reader.
1342
1343 [3-7] # OK; Obvious and portable
1344 [d-g] # OK; Obvious and portable
1345 [A-Y] # OK; Obvious and portable
1346 [A-z] # WRONG; Not portable; not clear what is meant
1347 [a-Z] # WRONG; Not portable; not clear what is meant
1348 [%-.] # WRONG; Not portable; not clear what is meant
1349 [\x41-Z] # WRONG; Not portable; not obvious to non-geek
1350
1351(You can force portability by specifying a Unicode range, which means that
1352the endpoints are specified by
1353L<C<\N{...}>|perlrecharclass/Character Ranges>, but the meaning may
1354still not be obvious.)
1355The stricter rules require that ranges that start or stop with an ASCII
93780ae6 1356character that is not a control have all their endpoints be a literal
eabfc7bc
RS
1357character, and not some escape sequence (like C<"\x41">), and the ranges
1358must be all digits, or all uppercase letters, or all lowercase letters.
1359
1360=item *
1361
1362L<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/">
1363
1364(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1365
1366Stricter rules help to find typos and other errors. You included a
1367range, and at least one of the end points is a decimal digit. Under the
1368stricter rules, when this happens, both end points should be digits in
1369the same group of 10 consecutive digits.
1370
1371=item *
1372
1373L<Redundant argument in %s|perldiag/Redundant argument in %s>
1374
1375(W redundant) You called a function with more arguments than other
1376arguments you supplied indicated would be needed. Currently only
1377emitted when a printf-type format required fewer arguments than were
1378supplied, but might be used in the future for e.g. L<perlfunc/pack>.
1379
a75e6a3a
SH
1380The warnings category C<< redundant >> is new. See also
1381L<[perl #121025]|https://rt.perl.org/Ticket/Display.html?id=121025>.
eabfc7bc
RS
1382
1383=item *
1384
1385L<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">
1386
1387You are matching a regular expression using locale rules,
1388and a Unicode boundary is being matched, but the locale is not a Unicode
1389one. This doesn't make sense. Perl will continue, assuming a Unicode
1390(UTF-8) locale, but the results could well be wrong except if the locale
1391happens to be ISO-8859-1 (Latin1) where this message is spurious and can
1392be ignored.
1393
1394=item *
1395
1396L<< 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>" >>
1397
1398You used a Unicode boundary (C<\b{...}> or C<\B{...}>) in a
1399portion of a regular expression where the character set modifiers C</a>
1400or C</aa> are in effect. These two modifiers indicate an ASCII
1401interpretation, and this doesn't make sense for a Unicode definition.
1402The generated regular expression will compile so that the boundary uses
1403all of Unicode. No other portion of the regular expression is affected.
1404
1405=item *
1406
1407L<The bitwise feature is experimental|perldiag/"The bitwise feature is experimental">
1408
1409This warning is emitted if you use bitwise
1410operators (C<& | ^ ~ &. |. ^. ~.>) with the "bitwise" feature enabled.
1411Simply suppress the warning if you want to use the feature, but know
1412that in doing so you are taking the risk of using an experimental
1413feature which may change or be removed in a future Perl version:
1414
1415 no warnings "experimental::bitwise";
1416 use feature "bitwise";
1417 $x |.= $y;
1418
1419=item *
1420
1421L<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/">
1422
1423(D deprecated, regexp) You used a literal C<"{"> character in a regular
1424expression pattern. You should change to use C<"\{"> instead, because a future
1425version of Perl (tentatively v5.26) will consider this to be a syntax error. If
1426the pattern delimiters are also braces, any matching right brace
1427(C<"}">) should also be escaped to avoid confusing the parser, for
1428example,
1429
1430 qr{abc\{def\}ghi}
1431
1432=item *
1433
1434L<Use of literal non-graphic characters in variable names is deprecated|perldiag/"Use of literal non-graphic characters in variable names is deprecated">
1435
1436=item *
1437
1438L<Useless use of attribute "const"|perldiag/Useless use of attribute "const">
1439
1440(W misc) The "const" attribute has no effect except
1441on anonymous closure prototypes. You applied it to
1442a subroutine via L<attributes.pm|attributes>. This is only useful
1443inside an attribute handler for an anonymous subroutine.
1444
1445=item *
1446
1447L<E<quot>use re 'strict'E<quot> is experimental|perldiag/"use re 'strict'" is experimental>
1448
1449(S experimental::re_strict) The things that are different when a regular
1450expression pattern is compiled under C<'strict'> are subject to change
1451in future Perl releases in incompatible ways. This means that a pattern
1452that compiles today may not in a future Perl release. This warning is
1453to alert you to that risk.
1454
1455=item *
1456
caa16dbd
TC
1457L<Warning: unable to close filehandle properly: %s|perldiag/"Warning: unable to close filehandle properly: %s">
1458
eabfc7bc
RS
1459L<Warning: unable to close filehandle %s properly: %s|perldiag/"Warning: unable to close filehandle %s properly: %s">
1460
caa16dbd
TC
1461(S io) An error occurred when Perl implicitly closed a filehandle. This
1462usually indicates your file system ran out of disk space.
1463
eabfc7bc
RS
1464=item *
1465
1466L<Wide character (U+%X) in %s|perldiag/"Wide character (U+%X) in %s">
1467
1468(W locale) While in a single-byte locale (I<i.e.>, a non-UTF-8
1469one), a multi-byte character was encountered. Perl considers this
1470character to be the specified Unicode code point. Combining non-UTF8
1471locales and Unicode is dangerous. Almost certainly some characters
1472will have two different representations. For example, in the ISO 8859-7
1473(Greek) locale, the code point 0xC3 represents a Capital Gamma. But so
1474also does 0x393. This will make string comparisons unreliable.
1475
1476You likely need to figure out how this multi-byte character got mixed up
1477with your single-byte locale (or perhaps you thought you had a UTF-8
1478locale, but Perl disagrees).
1479
1480=item *
1481
1482The following two warnings for C<tr///> used to be skipped if the
1483transliteration contained wide characters, but now they occur regardless of
1484whether there are wide characters or not:
1485
1486L<Useless use of E<sol>d modifier in transliteration operator|perldiag/"Useless use of /d modifier in transliteration operator">
1487
1488L<Replacement list is longer than search list|perldiag/Replacement list is longer than search list>
1489
1490=item *
1491
1492A new C<locale> warning category has been created, with the following warning
1493messages currently in it:
1494
1495=over 4
1496
1497=item *
1498
1499L<Locale '%s' may not work well.%s|perldiag/Locale '%s' may not work well.%s>
1500
1501=item *
1502
1503L<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".>
1504
1505=back
1506
1507=back
1508
1509=head2 Changes to Existing Diagnostics
1510
1511=over 4
1512
1513=item *
1514
1515<> should be quotes
1516
1517This warning has been changed to
1518L<< <> at require-statement should be quotes|perldiag/"<> at require-statement should be quotes" >>
1519to make the issue more identifiable.
1520
1521=item *
1522
1523L<Argument "%s" isn't numeric%s|perldiag/"Argument "%s" isn't numeric%s">
1524now adds the following note:
1525
4ec8e6f0 1526 Note that for the Inf and NaN (infinity and not-a-number) the
77c2376a
KW
1527 definition of "numeric" is somewhat unusual: the strings themselves
1528 (like "Inf") are considered numeric, and anything following them is
1529 considered non-numeric.
eabfc7bc
RS
1530
1531=item *
1532
1533L<Global symbol "%s" requires explicit package name|perldiag/"Global symbol "%s" requires explicit package name (did you forget to declare "my %s"?)">
1534
1535This message has had '(did you forget to declare "my %s"?)' appended to it, to
1536make it more helpful to new Perl programmers.
1537L<[perl #121638]|https://rt.perl.org/Ticket/Display.html?id=121638>
1538
1539=item *
1540
1541'"my" variable &foo::bar can't be in a package' has been reworded to say
1542'subroutine' instead of 'variable'.
1543
1544=item *
1545
022a330c 1546L<\N{} in character class restricted to one character in regex; marked by S<<-- HERE> in mE<sol>%sE<sol>|perldiag/"\N{} in inverted character class or as a range end-point is restricted to one character in regex; marked by <-- HERE in m/%s/">
eabfc7bc
RS
1547
1548This message has had 'character class' changed to 'inverted character class or
1549as a range end-point is' to reflect improvements in C<qr/[\N{named sequence}]/>
1550(see under L</Selected Bug Fixes>).
1551
1552=item *
1553
1554L<panic: frexp|perldiag/"panic: frexp: %f">
1555
4ec8e6f0 1556This message has had ': C<%f>' appended to it, to show what the offending floating
eabfc7bc
RS
1557point number is.
1558
1559=item *
1560
1561B<Possible precedence problem on bitwise %c operator> reworded as
1562L<Possible precedence problem on bitwise %s operator|perldiag/"Possible precedence problem on bitwise %s operator">.
1563
1564=item *
1565
1566C<require> with no argument or undef used to warn about a Null filename; now
1567it dies with C<Missing or undefined argument to require>.
1568
1569=item *
1570
1571L<Unsuccessful %s on filename containing newline|perldiag/"Unsuccessful %s on filename containing newline">
1572
1573This warning is now only produced when the newline is at the end of
1574the filename.
1575
1576=item *
1577
4ec8e6f0 1578"Variable C<%s> will not stay shared" has been changed to say "Subroutine"
eabfc7bc
RS
1579when it is actually a lexical sub that will not stay shared.
1580
1581=item *
1582
1583L<Variable length lookbehind not implemented in regex mE<sol>%sE<sol>|perldiag/"Variable length lookbehind not implemented in regex m/%s/">
1584
1585Information about Unicode behaviour has been added.
1586
1587=back
1588
1589=head2 Diagnostic Removals
1590
1591=over
1592
1593=item *
1594
1595"Ambiguous use of -foo resolved as -&foo()"
1596
1597There is actually no ambiguity here, and this impedes the use of negated
1598constants; e.g., C<-Inf>.
1599
1600=item *
1601
1602"Constant is not a FOO reference"
1603
1604Compile-time checking of constant dereferencing (e.g., C<< my_constant->() >>)
1605has been removed, since it was not taking overloading into account.
1606L<[perl #69456]|https://rt.perl.org/Ticket/Display.html?id=69456>
1607L<[perl #122607]|https://rt.perl.org/Ticket/Display.html?id=122607>
1608
1609=back
1610
1611=head1 Utility Changes
1612
1613=head2 F<x2p/>
1614
1615=over 4
1616
1617=item *
1618
1619The F<x2p/> directory has been removed from the Perl core.
1620
1621This removes find2perl, s2p and a2p. They have all been released to CPAN as
1622separate distributions (App::find2perl, App::s2p, App::a2p).
1623
1624=back
1625
1626=head2 L<h2ph>
1627
1628=over 4
1629
1630=item *
1631
1632F<h2ph> now handles hexadecimal constants in the compiler's predefined
a75e6a3a
SH
1633macro definitions, as visible in C<$Config{cppsymbols}>.
1634L<[perl #123784]|https://rt.perl.org/Ticket/Display.html?id=123784>.
eabfc7bc
RS
1635
1636=back
1637
1638=head2 L<encguess>
1639
1640=over 4
1641
1642=item *
1643
f1c9eac6 1644No longer depends on non-core modules.
eabfc7bc
RS
1645
1646=back
1647
1648=head1 Configuration and Compilation
1649
1650=over 4
1651
1652=item *
1653
1654F<Configure> now checks for F<lrintl>, F<lroundl>, F<llrintl>, and F<llroundl>.
1655
1656=item *
1657
a75e6a3a
SH
1658F<Configure> with C<-Dmksymlinks> should now be faster.
1659L<[perl #122002]|https://rt.perl.org/Ticket/Display.html?id=122002>.
eabfc7bc
RS
1660
1661=item *
1662
1663pthreads and lcl will be linked by default if present. This allows XS modules
1664that require threading to work on non-threaded perls. Note that you must still
1665pass C<-Dusethreads> if you want a threaded perl.
1666
1667=item *
1668
1669For long doubles (to get more precision and range for floating point numbers)
1670one can now use the GCC quadmath library which implements the quadruple
f1c9eac6
DM
1671precision floating point numbers on x86 and IA-64 platforms. See
1672F<INSTALL> for details.
eabfc7bc
RS
1673
1674=item *
1675
1676MurmurHash64A and MurmurHash64B can now be configured as the internal hash
1677function.
1678
1679=item *
1680
1681C<make test.valgrind> now supports parallel testing.
1682
1683For example:
1684
1685 TEST_JOBS=9 make test.valgrind
1686
1687See L<perlhacktips/valgrind> for more information.
1688
1689L<[perl #121431]|https://rt.perl.org/Ticket/Display.html?id=121431>
1690
1691=item *
1692
1693The MAD (Misc Attribute Decoration) build option has been removed
1694
1695This was an unmaintained attempt at preserving
1696the Perl parse tree more faithfully so that automatic conversion of
1697Perl 5 to Perl 6 would have been easier.
1698
1699This build-time configuration option had been unmaintained for years,
1700and had probably seriously diverged on both Perl 5 and Perl 6 sides.
1701
1702=item *
1703
1704A new compilation flag, C<< -DPERL_OP_PARENT >> is available. For details,
1705see the discussion below at L<< /Internal Changes >>.
1706
43831b1f
DM
1707=item *
1708
1709Pathtools no longer tries to load XS on miniperl. This speeds up building perl
1710slightly.
1711
1712
eabfc7bc
RS
1713=back
1714
1715=head1 Testing
1716
1717=over 4
1718
1719=item *
1720
1721F<t/porting/re_context.t> has been added to test that L<utf8> and its
1722dependencies only use the subset of the C<$1..$n> capture vars that
4ec8e6f0 1723C<Perl_save_re_context()> is hard-coded to localize, because that function has no
eabfc7bc
RS
1724efficient way of determining at runtime what vars to localize.
1725
1726=item *
1727
1728Tests for performance issues have been added in the file F<t/perf/taint.t>.
1729
1730=item *
1731
1732Some regular expression tests are written in such a way that they will
1733run very slowly if certain optimizations break. These tests have been
1734moved into new files, F<< t/re/speed.t >> and F<< t/re/speed_thr.t >>,
1735and are run with a C<< watchdog() >>.
1736
1737=item *
1738
1739C<< test.pl >> now allows C<< plan skip_all => $reason >>, to make it
1740more compatible with C<< Test::More >>.
1741
1742=item *
1743
1744A new test script, F<op/infnan.t>, has been added to test if Inf and NaN are
1745working correctly. See L</Infinity and NaN (not-a-number) handling improved>.
1746
1747=back
1748
1749=head1 Platform Support
1750
1751=head2 Regained Platforms
1752
1753=over 4
1754
1755=item IRIX and Tru64 platforms are working again.
1756
1757(Some C<make test> failures remain.)
1758
1759=item z/OS running EBCDIC Code Page 1047
1760
1761Core perl now works on this EBCDIC platform. Earlier perls also worked, but,
1762even though support wasn't officially withdrawn, recent perls would not compile
1763and run well. Perl 5.20 would work, but had many bugs which have now been
1764fixed. Many CPAN modules that ship with Perl still fail tests, including
1765Pod::Simple. However the version of Pod::Simple currently on CPAN should work;
1766it was fixed too late to include in Perl 5.22. Work is under way to fix many
1767of the still-broken CPAN modules, which likely will be installed on CPAN when
1768completed, so that you may not have to wait until Perl 5.24 to get a working
1769version.
1770
1771=back
1772
1773=head2 Discontinued Platforms
1774
1775=over 4
1776
1777=item NeXTSTEP/OPENSTEP
1778
f1c9eac6
DM
1779NeXTSTEP was a proprietary operating system bundled with NeXT's
1780workstations in the early to mid 90s; OPENSTEP was an API specification
1781that provided a NeXTSTEP-like environment on a non-NeXTSTEP system. Both
1782are now long dead, so support for building Perl on them has been removed.
eabfc7bc
RS
1783
1784=back
1785
1786=head2 Platform-Specific Notes
1787
1788=over 4
1789
1790=item EBCDIC
1791
1792Special handling is required on EBCDIC platforms to get C<qr/[i-j]/> to
1793match only C<"i"> and C<"j">, since there are 7 characters between the
1794code points for C<"i"> and C<"j">. This special handling had only been
1795invoked when both ends of the range are literals. Now it is also
1796invoked if any of the C<\N{...}> forms for specifying a character by
1797name or Unicode code point is used instead of a literal. See
1798L<perlrecharclass/Character Ranges>.
1799
1800=item HP-UX
1801
1802The archname now distinguishes use64bitint from use64bitall.
1803
1804=item Android
1805
1806Build support has been improved for cross-compiling in general and for
1807Android in particular.
1808
1809=item VMS
1810
1811=over 4
1812
1813=item *
1814
1815When spawning a subprocess without waiting, the return value is now
1816the correct PID.
1817
1818=item *
1819
1820Fix a prototype so linking doesn't fail under the VMS C++ compiler.
1821
1822=item *
1823
1824C<finite>, C<finitel>, and C<isfinite> detection has been added to
1825C<configure.com>, environment handling has had some minor changes, and
1826a fix for legacy feature checking status.
1827
1828=back
1829
1830=item Win32
1831
1832=over 4
1833
1834=item *
1835
1836F<miniperl.exe> is now built with C<-fno-strict-aliasing>, allowing 64-bit
1837builds to complete on GCC 4.8.
1838L<[perl #123976]|https://rt.perl.org/Ticket/Display.html?id=123976>
1839
1840=item *
1841
17fcdc49
TC
1842C<nmake minitest> now works on Win32. Due to dependency issues you
1843need to build C<nmake test-prep> first, and a small number of the
1844tests fail.
1845L<[perl #123394]|https://rt.perl.org/Ticket/Display.html?id=123394>
1846
1847=item *
1848
eabfc7bc
RS
1849Perl can now be built in C++ mode on Windows by setting the makefile macro
1850C<USE_CPLUSPLUS> to the value "define".
1851
1852=item *
1853
18f4cc8e
TC
1854List form of pipe open has been implemented for Win32. Note: unlike
1855C< system LIST >> this does not fall back to the shell.
1856L<[perl #121159]|https://rt.perl.org/Ticket/Display.html?id=121159>
eabfc7bc
RS
1857
1858=item *
1859
eabfc7bc
RS
1860New C<DebugSymbols> and C<DebugFull> configuration options added to
1861Windows makefiles.
1862
1863=item *
1864
1865L<B> now compiles again on Windows.
1866
1867=item *
1868
f1c9eac6
DM
1869Previously compiling XS modules (including CPAN ones) using Visual C++ for
1870Win64 resulted in around a dozen warnings per file from hv_func.h. These
1871warnings have been silenced.
eabfc7bc
RS
1872
1873=item *
1874
1875Support for building without PerlIO has been removed from the Windows
1876makefiles. Non-PerlIO builds were all but deprecated in Perl 5.18.0 and are
1877already not supported by F<Configure> on POSIX systems.
1878
1879=item *
1880
1881Between 2 and 6 ms and 7 I/O calls have been saved per attempt to open a perl
1882module for each path in C<@INC>.
1883
1884=item *
1885
1886Intel C builds are now always built with C99 mode on.
1887
1888=item *
1889
1890C<%I64d> is now being used instead of C<%lld> for MinGW.
1891
1892=item *
1893
1894In the experimental C<:win32> layer, a crash in C<open> was fixed. Also
1895opening C</dev/null>, which works the Win32 Perl's normal C<:unix> layer, was
1896implemented for C<:win32>.
1897L<[perl #122224]|https://rt.perl.org/Ticket/Display.html?id=122224>
1898
1899=item *
1900
1901A new makefile option, C<USE_LONG_DOUBLE>, has been added to the Windows
1902dmake makefile for gcc builds only. Set this to "define" if you want perl to
1903use long doubles to give more accuracy and range for floating point numbers.
1904
1905=back
1906
1907=item OpenBSD
1908
1909On OpenBSD, Perl will now default to using the system C<malloc> due to the
1910security features it provides. Perl's own malloc wrapper has been in use
1911since v5.14 due to performance reasons, but the OpenBSD project believes
1912the tradeoff is worth it and would prefer that users who need the speed
1913specifically ask for it.
1914
1915L<[perl #122000]|https://rt.perl.org/Ticket/Display.html?id=122000>.
1916
1917=item Solaris
1918
1919=over 4
1920
1921=item *
1922
1923We now look for the Sun Studio compiler in both F</opt/solstudio*> and
1924F</opt/solarisstudio*>.
1925
1926=item *
1927
1928Builds on Solaris 10 with C<-Dusedtrace> would fail early since make
1929didn't follow implied dependencies to build C<perldtrace.h>. Added an
1930explicit dependency to C<depend>.
1931L<[perl #120120]|https://rt.perl.org/Ticket/Display.html?id=120120>
1932
1933=item *
1934
1935C<c99> options have been cleaned up, hints look for C<solstudio>
1936as well as C<SUNWspro>, and support for native C<setenv> has been added.
1937
1938=back
1939
1940=back
1941
1942=head1 Internal Changes
1943
1944=over 4
1945
1946=item *
1947
bad0181b
DM
1948Experimental support has been added to allow ops in the optree to locate
1949their parent, if any. This is enabled by the non-default build option
1950C<-DPERL_OP_PARENT>. It is envisaged that this will eventually become
1951enabled by default, so XS code which directly accesses the C<op_silbing>
1952field of ops should be updated to be future-proofed.
eabfc7bc
RS
1953
1954On C<PERL_OP_PARENT> builds, the C<op_sibling> field has been renamed
bad0181b
DM
1955C<op_sibparent> and a new flag, C<op_moresib>, added. On the last op in a
1956sibling chain, C<op_moresib> is false and C<op_sibparent> points to the
1957parent (if any) rather than to being C<NULL>.
1958
1959To make existing code work transparently whether using C<-DPERL_OP_PARENT>
1960or not, a number of new macros and functions have been added that should
1961be used, rather than directly manipulating C<op_sibling>.
1962
1963For the case of just reading C<op_sibling> to determine the next sibling,
1964two new macros have been added. A simple scan through a sibling chain
1965like this:
1966
1967 for (; kid->op_sibling; kid = kid->op_sibling) { ... }
1968
1969should now be written as:
1970
1971 for (; OpHAS_SIBLING(kid); kid = OpSIBLING(kid)) { ... }
1972
1973For altering optrees, A general-purpose function C<op_sibling_splice()>
1974has been added, which allows for manipulation of a chain of sibling ops.
1975By analogy with the Perl function C<splice()>, it allows you to cut out
1976zero or more ops from a sibling chain and replace them with zero or more
1977new ops. It transparently handles all the updating of sibling, parent,
1978op_last pointers etc.
1979
1980If you need to manipulate ops at a lower level, then three new macros,
1981C<OpMORESIB_set>, C<OpLASTSIB_set> and C<OpMAYBESIB_set> are intended to
1982be a low-level portable way to set C<op_sibling> / C<op_sibparent> while
1983also updating C<op_moresib>. The first sets the sibling pointer to a new
1984sibling, the second makes the op the last sibling, and the third
1985conditionally does the first or second action. Note that unlike
1986C<op_sibling_splice()> these macros won't maintain consistency in the
1987parent at the same time (e.g. by updating C<op_first> and C<op_last> where
1988appropriate).
1989
1990A C-level C<Perl_op_parent()> function and a perl-level C<B::OP::parent()>
1991method have been added. The C function only exists under
1992C<-DPERL_OP_PARENT> builds (using it is build-time error on vanilla
1993perls). C<B::OP::parent()> exists always, but on a vanilla build it
1994always returns C<NULL>. Under C<-DPERL_OP_PARENT>, they return the parent
1995of the current op, if any. The variable C<$B::OP::does_parent> allows you
1996to determine whether C<B> supports retrieving an op's parent.
1997
19c9b733 1998XXX C<-DPERL_OP_PARENT> was introduced in 5.21.2, but the interface was
bad0181b
DM
1999changed considerably in 5.21.11. If you updated your code before the
20005.21.11 changes, it may require further revision. The main changes after
20015.21.2 were:
eabfc7bc 2002
bad0181b 2003=over 4
eabfc7bc
RS
2004
2005=item *
2006
bad0181b
DM
2007The C<OP_SIBLING> and C<OP_HAS_SIBLING> macros have been renamed
2008C<OpSIBLING> and C<OpHAS_SIBLING> for consistency with other
2009op-manipulating macros.
eabfc7bc
RS
2010
2011=item *
2012
bad0181b
DM
2013The C<op_lastsib> field has been renamed C<op_moresib>, and its meaning
2014inverted.
eabfc7bc
RS
2015
2016=item *
2017
bad0181b
DM
2018The macro C<OpSIBLING_set> has been removed, and has been superseded by
2019C<OpMORESIB_set> et al.
eabfc7bc
RS
2020
2021=item *
2022
bad0181b
DM
2023The C<op_sibling_splice()> function now accepts a null C<parent> argument
2024where the splicing doesn't affect the first or last ops in the sibling
2025chain
eabfc7bc
RS
2026
2027=back
2028
2029=item *
2030
2031Macros have been created to allow XS code to better manipulate the POSIX locale
2032category C<LC_NUMERIC>. See L<perlapi/Locale-related functions and macros>.
2033
2034=item *
2035
2036The previous C<atoi> et al replacement function, C<grok_atou>, has now been
2037superseded by C<grok_atoUV>. See L<perlclib> for details.
2038
2039=item *
2040
4ec8e6f0 2041Added C<Perl_sv_get_backrefs()> to determine if an SV is a weak-referent.
eabfc7bc
RS
2042
2043Function either returns an SV * of type AV, which contains the set of
2044weakreferences which reference the passed in SV, or a simple RV * which
2045is the only weakref to this item.
2046
2047=item *
2048
f1c9eac6
DM
2049The C<screaminstr> perl function has been removed. Although marked as
2050public API, it was undocumented and had no usage in CPAN modules. Calling
2051it has been fatal since 5.17.0.
eabfc7bc
RS
2052
2053=item *
2054
2055C<newDEFSVOP>, C<block_start>, C<block_end> and C<intro_my> have been added
2056to the API.
2057
2058=item *
2059
2060The internal C<convert> function in F<op.c> has been renamed
2061C<op_convert_list> and added to the API.
2062
2063=item *
2064
2065C<sv_magic> no longer forbids "ext" magic on read-only values. After all,
2066perl can't know whether the custom magic will modify the SV or not.
a75e6a3a 2067L<[perl #123103]|https://rt.perl.org/Ticket/Display.html?id=123103>.
eabfc7bc
RS
2068
2069=item *
2070
19c9b733 2071Accessing L<perlapi/CvPADLIST> in an XSUB is now forbidden.
4488fd23
KW
2072C<CvPADLIST> has been reused for a different internal purpose for XSUBs. Guard all
2073C<CvPADLIST> expressions with C<CvISXSUB()> if your code doesn't already block
eabfc7bc
RS
2074XSUB CV*s from going through optree CV* expecting code.
2075
2076=item *
2077
2078SVs of type SVt_NV are now bodyless when a build configure and platform allow
2079it, specifically C<sizeof(NV) <= sizeof(IV)>. The bodyless trick is the same one
2080as for IVs since 5.9.2, but for NVs, unlike IVs, is not guaranteed on all
2081platforms and build configurations.
2082
2083=item *
2084
2085The C<$DB::single>, C<$DB::signal> and C<$DB::trace> now have set and
2086get magic that stores their values as IVs and those IVs are used when
2087testing their values in C<pp_dbstate>. This prevents perl from
f1c9eac6 2088recursing infinitely if an overloaded object is assigned to any of those
a75e6a3a
SH
2089variables.
2090L<[perl #122445]|https://rt.perl.org/Ticket/Display.html?id=122445>.
eabfc7bc
RS
2091
2092=item *
2093
f1c9eac6 2094C<Perl_tmps_grow> which is marked as public API but is undocumented, has been
eabfc7bc
RS
2095removed from public API. If you use C<EXTEND_MORTAL> macro in your XS code to
2096preextend the mortal stack, you are unaffected by this change.
2097
2098=item *
2099
19c9b733 2100XXX C<cv_name>, which was introduced in 5.21.4, has been changed incompatibly.
eabfc7bc
RS
2101It now has a flags field that allows the caller to specify whether the name
2102should be fully qualified. See L<perlapi/cv_name>.
2103
2104=item *
2105
2106Internally Perl no longer uses the C<SVs_PADMY> flag. C<SvPADMY()> now
2107returns a true value for anything not marked PADTMP. C<SVs_PADMY> is now
2108defined as 0.
2109
2110=item *
2111
2112The macros SETsv and SETsvUN have been removed. They were no longer used
2113in the core since commit 6f1401dc2a, and have not been found present on
2114CPAN.
2115
2116=item *
2117
2118The C<< SvFAKE >> bit (unused on HVs) got informally reserved by
2119David Mitchell for future work on vtables.
2120
2121=item *
2122
2123The C<sv_catpvn_flags> function accepts C<SV_CATBYTES> and C<SV_CATUTF8>
2124flags, which specify whether the appended string is bytes or utf8,
2125respectively.
2126
2127=item *
2128
f1c9eac6 2129A new opcode class, C<< METHOP >>, has been introduced. It holds
eabfc7bc
RS
2130class/method related info needed at runtime to improve performance
2131of class/object method calls.
2132
2133C<< OP_METHOD >> and C<< OP_METHOD_NAMED >> are moved from being
2134C<< UNOP/SVOP >> to being C<< METHOP >>.
2135
2136=item *
2137
2138C<save_re_context> no longer does anything and has been moved to F<mathoms.c>.
2139
2140=item *
2141
2142C<cv_name> is a new API function that can be passed a CV or GV. It returns an
2143SV containing the name of the subroutine for use in diagnostics.
2144L<[perl #116735]|https://rt.perl.org/Ticket/Display.html?id=116735>
2145L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
2146
2147=item *
2148
2149C<cv_set_call_checker_flags> is a new API function that works like
2150C<cv_set_call_checker>, except that it allows the caller to specify whether the
2151call checker requires a full GV for reporting the subroutine's name, or whether
2152it could be passed a CV instead. Whatever value is passed will be acceptable
2153to C<cv_name>. C<cv_set_call_checker> guarantees there will be a GV, but it
2154may have to create one on the fly, which is inefficient.
2155L<[perl #116735]|https://rt.perl.org/Ticket/Display.html?id=116735>
2156
2157=item *
2158
2159C<CvGV> (which is not part of the API) is now a more complex macro, which may
2160call a function and reify a GV. For those cases where is has been used as a
2161boolean, C<CvHASGV> has been added, which will return true for CVs that
2162notionally have GVs, but without reifying the GV. C<CvGV> also returns a GV
2163now for lexical subs.
2164L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
2165
2166=item *
2167
2168Added L<perlapi/sync_locale>. Changing the program's locale should be avoided
2169by XS code. Nevertheless, certain non-Perl libraries called from XS, such as
2170C<Gtk> do so. When this happens, Perl needs to be told that the locale has
2171changed. Use this function to do so, before returning to Perl.
2172
2173=item *
2174
2175The defines and labels for the flags in the C<op_private> field of OPs are now
2176auto-generated from data in F<regen/op_private>. The noticeable effect of this
2177is that some of the flag output of C<Concise> might differ slightly, and the
2178flag output of C<perl -Dx> may differ considerably (they both use the same set
2179of labels now). Also in debugging builds, there is a new assert in
2180C<op_free()> that checks that the op doesn't have any unrecognized flags set in
2181C<op_private>.
2182
2183=item *
2184
eabfc7bc
RS
2185The deprecated variable C<PL_sv_objcount> has been removed.
2186
2187=item *
2188
2189Perl now tries to keep the locale category C<LC_NUMERIC> set to "C"
2190except around operations that need it to be set to the program's
2191underlying locale. This protects the many XS modules that cannot cope
2192with the decimal radix character not being a dot. Prior to this
2193release, Perl initialized this category to "C", but a call to
2194C<POSIX::setlocale()> would change it. Now such a call will change the
2195underlying locale of the C<LC_NUMERIC> category for the program, but the
ce93e38b
KW
2196locale exposed to XS code will remain "C". There are new macros
2197to manipulate the LC_NUMERIC locale, including
2198C<STORE_LC_NUMERIC_SET_TO_NEEDED> and
2199C<STORE_LC_NUMERIC_FORCE_TO_UNDERLYING>.
2200See L<perlapi/Locale-related functions and macros>.
eabfc7bc
RS
2201
2202=item *
2203
2204A new macro L<C<isUTF8_CHAR>|perlapi/isUTF8_CHAR> has been written which
2205efficiently determines if the string given by its parameters begins
2206with a well-formed UTF-8 encoded character.
2207
2208=item *
2209
2210The following private API functions had their context parameter removed,
2211C<Perl_cast_ulong>, C<Perl_cast_i32>, C<Perl_cast_iv>, C<Perl_cast_uv>,
2212C<Perl_cv_const_sv>, C<Perl_mg_find>, C<Perl_mg_findext>, C<Perl_mg_magical>,
2213C<Perl_mini_mktime>, C<Perl_my_dirfd>, C<Perl_sv_backoff>, C<Perl_utf8_hop>.
2214
2215Users of the public API prefix-less calls remain unaffected.
2216
2217=item *
2218
eabfc7bc 2219The PADNAME and PADNAMELIST types are now separate types, and no longer
a75e6a3a
SH
2220simply aliases for SV and AV.
2221L<[perl #123223]|https://rt.perl.org/Ticket/Display.html?id=123223>.
eabfc7bc
RS
2222
2223=item *
2224
2225Pad names are now always UTF8. The C<PadnameUTF8> macro always returns
2226true. Previously, this was effectively the case already, but any support
2227for two different internal representations of pad names has now been
2228removed.
2229
2230=item *
2231
eabfc7bc
RS
2232A new op class, C<UNOP_AUX>, has been added. This is a subclass of
2233C<UNOP> with an C<op_aux> field added, which points to an array of unions
2234of C<UV>, C<SV*> etc. It is intended for where an op needs to store more data
2235than a simple C<op_sv> or whatever. Currently the only op of this type is
2236C<OP_MULTIDEREF> (see below).
2237
2238=item *
2239
2240A new op has been added, C<OP_MULTIDEREF>, which performs one or more
2241nested array and hash lookups where the key is a constant or simple
2242variable. For example the expression C<$a[0]{$k}[$i]>, which previously
2243involved ten C<rv2Xv>, C<Xelem>, C<gvsv> and C<const> ops is now performed
2244by a single C<multideref> op. It can also handle C<local>, C<exists> and
2245C<delete>. A non-simple index expression, such as C<[$i+1]> is still done
77c2376a 2246using C<aelem>/C<helem>, and single-level array lookup with a small constant
eabfc7bc
RS
2247index is still done using C<aelemfast>.
2248
2249=back
2250
2251=head1 Selected Bug Fixes
2252
2253=over 4
2254
2255=item *
2256
2257C<pack("D", $x)> and C<pack("F", $x)> now zero the padding on x86 long double
2258builds. GCC 4.8 and later, under some build options, would either overwrite
2259the zero-initialized padding, or bypass the initialized buffer entirely. This
2260caused F<op/pack.t> to fail.
2261L<[perl #123971]|https://rt.perl.org/Ticket/Display.html?id=123971>
2262
2263=item *
2264
2265Extending an array cloned from a parent thread could result in "Modification of
2266a read-only value attempted" errors when attempting to modify the new elements.
2267L<[perl #124127]|https://rt.perl.org/Ticket/Display.html?id=124127>
2268
2269=item *
2270
2271An assertion failure and subsequent crash with C<< *x=<y> >> has been fixed.
2272L<[perl #123790]|https://rt.perl.org/Ticket/Display.html?id=123790>
2273
2274=item *
2275
19c9b733 2276XXX An optimization for state variable initialization introduced in Perl 5.21.6 has
eabfc7bc
RS
2277been reverted because it was found to exacerbate some other existing buggy
2278behaviour.
2279L<[perl #124160]|https://rt.perl.org/Ticket/Display.html?id=124160>
2280
2281=item *
2282
19c9b733 2283XXX The extension of another optimization to cover more ops in Perl 5.21 has also
eabfc7bc
RS
2284been reverted to its Perl 5.20 state as a temporary fix for regression issues
2285that it caused.
2286L<[perl #123790]|https://rt.perl.org/Ticket/Display.html?id=123790>
2287
2288=item *
2289
eabfc7bc
RS
2290A possible crashing/looping bug has been fixed.
2291L<[perl #124099]|https://rt.perl.org/Ticket/Display.html?id=124099>
2292
2293=item *
2294
2295UTF-8 variable names used in array indexes, unquoted UTF-8 HERE-document
2296terminators and UTF-8 function names all now work correctly.
2297L<[perl #124113]|https://rt.perl.org/Ticket/Display.html?id=124113>
2298
2299=item *
2300
2301Repeated global pattern matches in scalar context on large tainted strings were
2302exponentially slow depending on the current match position in the string.
2303L<[perl #123202]|https://rt.perl.org/Ticket/Display.html?id=123202>
2304
2305=item *
2306
2307Various crashes due to the parser getting confused by syntax errors have been
2308fixed.
2309L<[perl #123801]|https://rt.perl.org/Ticket/Display.html?id=123801>
2310L<[perl #123802]|https://rt.perl.org/Ticket/Display.html?id=123802>
2311L<[perl #123955]|https://rt.perl.org/Ticket/Display.html?id=123955>
2312L<[perl #123995]|https://rt.perl.org/Ticket/Display.html?id=123995>
2313
2314=item *
2315
4ec8e6f0 2316C<split> in the scope of lexical C<$>_ has been fixed not to fail assertions.
eabfc7bc
RS
2317L<[perl #123763]|https://rt.perl.org/Ticket/Display.html?id=123763>
2318
2319=item *
2320
2321C<my $x : attr> syntax inside various list operators no longer fails
2322assertions.
2323L<[perl #123817]|https://rt.perl.org/Ticket/Display.html?id=123817>
2324
2325=item *
2326
4ec8e6f0
KW
2327An C<@> sign in quotes followed by a non-ASCII digit (which is not a valid
2328identifier) would cause the parser to crash, instead of simply trying the C<@> as
eabfc7bc
RS
2329literal. This has been fixed.
2330L<[perl #123963]|https://rt.perl.org/Ticket/Display.html?id=123963>
2331
2332=item *
2333
2334C<*bar::=*foo::=*glob_with_hash> has been crashing since Perl 5.14, but no
2335longer does.
2336L<[perl #123847]|https://rt.perl.org/Ticket/Display.html?id=123847>
2337
2338=item *
2339
2340C<foreach> in scalar context was not pushing an item on to the stack, resulting
4ec8e6f0 2341in bugs. (S<C<print 4, scalar do { foreach(@x){} } + 1>> would print 5.) It has
eabfc7bc
RS
2342been fixed to return C<undef>.
2343L<[perl #124004]|https://rt.perl.org/Ticket/Display.html?id=124004>
2344
2345=item *
2346
eabfc7bc
RS
2347A regression in the behaviour of the C<readline> built-in function, caused by
2348the introduction of the C<< <<>> >> operator, has been fixed.
2349L<[perl #123990]|https://rt.perl.org/Ticket/Display.html?id=123990>
2350
2351=item *
2352
2353Several cases of data used to store environment variable contents in core C
2354code being potentially overwritten before being used have been fixed.
2355L<[perl #123748]|https://rt.perl.org/Ticket/Display.html?id=123748>
2356
2357=item *
2358
a75e6a3a
SH
2359Patterns starting with C</.*/> are now fast again.
2360L<[perl #123743]|https://rt.perl.org/Ticket/Display.html?id=123743>.
eabfc7bc
RS
2361
2362=item *
2363
2364The original visible value of C<$/> is now preserved when it is set to
2365an invalid value. Previously if you set C<$/> to a reference to an
2366array, for example, perl would produce a runtime error and not set
2367C<PL_rs>, but perl code that checked C<$/> would see the array
a75e6a3a
SH
2368reference.
2369L<[perl #123218]|https://rt.perl.org/Ticket/Display.html?id=123218>.
eabfc7bc
RS
2370
2371=item *
2372
2373In a regular expression pattern, a POSIX class, like C<[:ascii:]>, must
93780ae6 2374be inside a bracketed character class, like C<qr/[[:ascii:]]/>. A
eabfc7bc
RS
2375warning is issued when something looking like a POSIX class is not
2376inside a bracketed class. That warning wasn't getting generated when
2377the POSIX class was negated: C<[:^ascii:]>. This is now fixed.
2378
2379=item *
2380
93780ae6 2381Fix a couple of size calculation overflows.
a75e6a3a 2382L<[perl #123554]|https://rt.perl.org/Ticket/Display.html?id=123554>.
eabfc7bc
RS
2383
2384=item *
2385
eabfc7bc 2386Perl 5.14.0 introduced a bug whereby C<eval { LABEL: }> would crash. This
a75e6a3a
SH
2387has been fixed.
2388L<[perl #123652]|https://rt.perl.org/Ticket/Display.html?id=123652>.
eabfc7bc
RS
2389
2390=item *
2391
2392Various crashes due to the parser getting confused by syntax errors have
a75e6a3a
SH
2393been fixed.
2394L<[perl #123617]|https://rt.perl.org/Ticket/Display.html?id=123617>.
2395L<[perl #123737]|https://rt.perl.org/Ticket/Display.html?id=123737>.
2396L<[perl #123753]|https://rt.perl.org/Ticket/Display.html?id=123753>.
2397L<[perl #123677]|https://rt.perl.org/Ticket/Display.html?id=123677>.
eabfc7bc
RS
2398
2399=item *
2400
2401Code like C</$a[/> used to read the next line of input and treat it as
2402though it came immediately after the opening bracket. Some invalid code
2403consequently would parse and run, but some code caused crashes, so this is
a75e6a3a
SH
2404now disallowed.
2405L<[perl #123712]|https://rt.perl.org/Ticket/Display.html?id=123712>.
eabfc7bc
RS
2406
2407=item *
2408
a75e6a3a
SH
2409Fix argument underflow for C<pack>.
2410L<[perl #123874]|https://rt.perl.org/Ticket/Display.html?id=123874>.
eabfc7bc
RS
2411
2412=item *
2413
2414Fix handling of non-strict C<\x{}>. Now C<\x{}> is equivalent to C<\x{0}>
2415instead of faulting.
2416
2417=item *
2418
2419C<stat -t> is now no longer treated as stackable, just like C<-t stat>.
a75e6a3a 2420L<[perl #123816]|https://rt.perl.org/Ticket/Display.html?id=123816>.
eabfc7bc
RS
2421
2422=item *
2423
2424The following no longer causes a SEGV: C<qr{x+(y(?0))*}>.
2425
2426=item *
2427
2428Fixed infinite loop in parsing backrefs in regexp patterns.
2429
2430=item *
2431
2432Several minor bug fixes in behavior of Inf and NaN, including
2433warnings when stringifying Inf-like or NaN-like strings. For example,
2434"NaNcy" doesn't numify to NaN anymore.
2435
2436=item *
2437
a75e6a3a
SH
2438Only stringy classnames are now shared. This fixes some failures in L<autobox>.
2439L<[perl #100819]|https://rt.cpan.org/Ticket/Display.html?id=100819>.
eabfc7bc
RS
2440
2441=item *
2442
2443A bug in regular expression patterns that could lead to segfaults and
2444other crashes has been fixed. This occurred only in patterns compiled
2445with C<"/i">, while taking into account the current POSIX locale (this usually
2446means they have to be compiled within the scope of C<S<"use locale">>),
2447and there must be a string of at least 128 consecutive bytes to match.
a75e6a3a 2448L<[perl #123539]|https://rt.perl.org/Ticket/Display.html?id=123539>.
eabfc7bc
RS
2449
2450=item *
2451
2452C<s///> now works on very long strings instead of dying with 'Substitution
a75e6a3a
SH
2453loop'.
2454L<[perl #103260]|https://rt.perl.org/Ticket/Display.html?id=103260>.
2455L<[perl #123071]|https://rt.perl.org/Ticket/Display.html?id=123071>.
eabfc7bc
RS
2456
2457=item *
2458
a75e6a3a
SH
2459C<gmtime> no longer crashes with not-a-number values.
2460L<[perl #123495]|https://rt.perl.org/Ticket/Display.html?id=123495>.
eabfc7bc
RS
2461
2462=item *
2463
4ec8e6f0 2464C<\()> (reference to an empty list) and C<y///> with lexical C<$_> in scope
eabfc7bc
RS
2465could do a bad write past the end of the stack. They have been fixed
2466to extend the stack first.
2467
2468=item *
2469
2470C<prototype()> with no arguments used to read the previous item on the
2471stack, so C<print "foo", prototype()> would print foo's prototype. It has
4ec8e6f0 2472been fixed to infer C<$_> instead.
a75e6a3a 2473L<[perl #123514]|https://rt.perl.org/Ticket/Display.html?id=123514>.
eabfc7bc
RS
2474
2475=item *
2476
2477Some cases of lexical state subs inside predeclared subs could crash but no
2478longer do.
2479
2480=item *
2481
2482Some cases of nested lexical state subs inside anonymous subs could cause
2483'Bizarre copy' errors or possibly even crash.
2484
2485=item *
2486
2487When trying to emit warnings, perl's default debugger (F<perl5db.pl>) was
2488sometimes giving 'Undefined subroutine &DB::db_warn called' instead. This
a75e6a3a
SH
2489bug, which started to occur in Perl 5.18, has been fixed.
2490L<[perl #123553]|https://rt.perl.org/Ticket/Display.html?id=123553>.
eabfc7bc
RS
2491
2492=item *
2493
2494Certain syntax errors in substitutions, such as C<< s/${E<lt>E<gt>{})// >>, would
2495crash, and had done so since Perl 5.10. (In some cases the crash did not
2496start happening till 5.16.) The crash has, of course, been fixed.
a75e6a3a 2497L<[perl #123542]|https://rt.perl.org/Ticket/Display.html?id=123542>.
eabfc7bc
RS
2498
2499=item *
2500
2501A repeat expression like C<33 x ~3> could cause a large buffer
2502overflow since the new output buffer size was not correctly handled by
2503SvGROW(). An expression like this now properly produces a memory wrap
a75e6a3a
SH
2504panic.
2505L<[perl #123554]|https://rt.perl.org/Ticket/Display.html?id=123554>.
eabfc7bc
RS
2506
2507=item *
2508
2509C<< formline("@...", "a"); >> would crash. The C<FF_CHECKNL> case in
2510pp_formline() didn't set the pointer used to mark the chop position,
2511which led to the C<FF_MORE> case crashing with a segmentation fault.
a75e6a3a
SH
2512This has been fixed.
2513L<[perl #123538]|https://rt.perl.org/Ticket/Display.html?id=123538>.
eabfc7bc
RS
2514
2515=item *
2516
2517A possible buffer overrun and crash when parsing a literal pattern during
a75e6a3a
SH
2518regular expression compilation has been fixed.
2519L<[perl #123604]|https://rt.perl.org/Ticket/Display.html?id=123604>.
eabfc7bc
RS
2520
2521=item *
2522
4ec8e6f0 2523C<fchmod()> and C<futimes()> now set C<$!> when they fail due to being
a75e6a3a
SH
2524passed a closed file handle.
2525L<[perl #122703]|https://rt.perl.org/Ticket/Display.html?id=122703>.
eabfc7bc
RS
2526
2527=item *
2528
eabfc7bc 2529op_free() no longer crashes due to a stack overflow when freeing a
a75e6a3a
SH
2530deeply recursive op tree.
2531L<[perl #108276]|https://rt.perl.org/Ticket/Display.html?id=108276>.
eabfc7bc
RS
2532
2533=item *
2534
2535scalarvoid() would crash due to a stack overflow when processing a
a75e6a3a
SH
2536deeply recursive op tree.
2537L<[perl #108276]|https://rt.perl.org/Ticket/Display.html?id=108276>.
eabfc7bc
RS
2538
2539=item *
2540
2541In Perl 5.20.0, C<$^N> accidentally had the internal UTF8 flag turned off
2542if accessed from a code block within a regular expression, effectively
a75e6a3a
SH
2543UTF8-encoding the value. This has been fixed.
2544L<[perl #123135]|https://rt.perl.org/Ticket/Display.html?id=123135>.
eabfc7bc
RS
2545
2546=item *
2547
2548A failed C<semctl> call no longer overwrites existing items on the stack,
2549causing C<(semctl(-1,0,0,0))[0]> to give an "uninitialized" warning.
2550
2551=item *
2552
2553C<else{foo()}> with no space before C<foo> is now better at assigning the
a75e6a3a
SH
2554right line number to that statement.
2555L<[perl #122695]|https://rt.perl.org/Ticket/Display.html?id=122695>.
eabfc7bc
RS
2556
2557=item *
2558
2559Sometimes the assignment in C<@array = split> gets optimised and C<split>
2560itself writes directly to the array. This caused a bug, preventing this
2561assignment from being used in lvalue context. So
2562C<(@a=split//,"foo")=bar()> was an error. (This bug probably goes back to
2563Perl 3, when the optimisation was added.) This optimisation, and the bug,
19c9b733 2564started to happen in more cases in XXX 5.21.5. It has now been fixed.
a75e6a3a 2565L<[perl #123057]|https://rt.perl.org/Ticket/Display.html?id=123057>.
eabfc7bc
RS
2566
2567=item *
2568
2569When argument lists that fail the checks installed by subroutine
2570signatures, the resulting error messages now give the file and line number
a75e6a3a
SH
2571of the caller, not of the called subroutine.
2572L<[perl #121374]|https://rt.perl.org/Ticket/Display.html?id=121374>.
eabfc7bc
RS
2573
2574=item *
2575
2576Flip-flop operators (C<..> and C<...> in scalar context) used to maintain
2577a separate state for each recursion level (the number of times the
2578enclosing sub was called recursively), contrary to the documentation. Now
a75e6a3a
SH
2579each closure has one internal state for each flip-flop.
2580L<[perl #122829]|https://rt.perl.org/Ticket/Display.html?id=122829>.
eabfc7bc
RS
2581
2582=item *
2583
2584C<use>, C<no>, statement labels, special blocks (C<BEGIN>) and pod are now
2585permitted as the first thing in a C<map> or C<grep> block, the block after
2586C<print> or C<say> (or other functions) returning a handle, and within
a75e6a3a
SH
2587C<${...}>, C<@{...}>, etc.
2588L<[perl #122782]|https://rt.perl.org/Ticket/Display.html?id=122782>.
eabfc7bc
RS
2589
2590=item *
2591
2592The repetition operator C<x> now propagates lvalue context to its left-hand
2593argument when used in contexts like C<foreach>. That allows
4ec8e6f0 2594S<C<for(($#that_array)x2) { ... }>> to work as expected if the loop modifies
eabfc7bc
RS
2595$_.
2596
2597=item *
2598
2599C<(...) x ...> in scalar context used to corrupt the stack if one operand
2600were an object with "x" overloading, causing erratic behaviour.
a75e6a3a 2601L<[perl #121827]|https://rt.perl.org/Ticket/Display.html?id=121827>.
eabfc7bc
RS
2602
2603=item *
2604
2605Assignment to a lexical scalar is often optimised away (as mentioned under
2606L</Performance Enhancements>). Various bugs related to this optimisation
2607have been fixed. Certain operators on the right-hand side would sometimes
2608fail to assign the value at all or assign the wrong value, or would call
2609STORE twice or not at all on tied variables. The operators affected were
2610C<$foo++>, C<$foo-->, and C<-$foo> under C<use integer>, C<chomp>, C<chr>
2611and C<setpgrp>.
2612
2613=item *
2614
2615List assignments were sometimes buggy if the same scalar ended up on both
2616sides of the assignment due to used of C<tied>, C<values> or C<each>. The
2617result would be the wrong value getting assigned.
2618
2619=item *
2620
2621C<setpgrp($nonzero)> (with one argument) was accidentally changed in 5.16
2622to mean C<setpgrp(0)>. This has been fixed.
2623
2624=item *
2625
2626C<__SUB__> could return the wrong value or even corrupt memory under the
4ec8e6f0 2627debugger (the C<-d> switch) and in subs containing C<eval $string>.
eabfc7bc
RS
2628
2629=item *
2630
4ec8e6f0 2631When S<C<sub () { $var }>> becomes inlinable, it now returns a different
eabfc7bc
RS
2632scalar each time, just as a non-inlinable sub would, though Perl still
2633optimises the copy away in cases where it would make no observable
2634difference.
2635
2636=item *
2637
4ec8e6f0 2638S<C<my sub f () { $var }>> and S<C<sub () : attr { $var }>> are no longer
eabfc7bc
RS
2639eligible for inlining. The former would crash; the latter would just
2640throw the attributes away. An exception is made for the little-known
2641":method" attribute, which does nothing much.
2642
2643=item *
2644
2645Inlining of subs with an empty prototype is now more consistent than
2646before. Previously, a sub with multiple statements, all but the last
2647optimised away, would be inlinable only if it were an anonymous sub
2648containing a string C<eval> or C<state> declaration or closing over an
2649outer lexical variable (or any anonymous sub under the debugger). Now any
2650sub that gets folded to a single constant after statements have been
2651optimised away is eligible for inlining. This applies to things like C<sub
2652() { jabber() if DEBUG; 42 }>.
2653
2654Some subroutines with an explicit C<return> were being made inlinable,
2655contrary to the documentation, Now C<return> always prevents inlining.
2656
2657=item *
2658
2659On some systems, such as VMS, C<crypt> can return a non-ASCII string. If a
2660scalar assigned to had contained a UTF8 string previously, then C<crypt>
2661would not turn off the UTF8 flag, thus corrupting the return value. This
2662would happen with C<$lexical = crypt ...>.
2663
2664=item *
2665
2666C<crypt> no longer calls C<FETCH> twice on a tied first argument.
2667
2668=item *
2669
2670An unterminated here-doc on the last line of a quote-like operator
2671(C<qq[${ <<END }]>, C</(?{ <<END })/>) no longer causes a double free. It
2672started doing so in 5.18.
2673
2674=item *
2675
2676Fixed two assertion failures introduced into C<-DPERL_OP_PARENT>
a75e6a3a
SH
2677builds.
2678L<[perl #108276]|https://rt.perl.org/Ticket/Display.html?id=108276>.
eabfc7bc
RS
2679
2680=item *
2681
4ec8e6f0 2682C<index()> and C<rindex()> no longer crash when used on strings over 2GB in
eabfc7bc
RS
2683size.
2684L<[perl #121562]|https://rt.perl.org/Ticket/Display.html?id=121562>.
2685
2686=item *
2687
2688A small previously intentional memory leak in PERL_SYS_INIT/PERL_SYS_INIT3 on
2689Win32 builds was fixed. This might affect embedders who repeatedly create and
2690destroy perl engines within the same process.
2691
2692=item *
2693
2694C<POSIX::localeconv()> now returns the data for the program's underlying
2695locale even when called from outside the scope of S<C<use locale>>.
2696
2697=item *
2698
2699C<POSIX::localeconv()> now works properly on platforms which don't have
2700C<LC_NUMERIC> and/or C<LC_MONETARY>, or for which Perl has been compiled
2701to disregard either or both of these locale categories. In such
2702circumstances, there are now no entries for the corresponding values in
2703the hash returned by C<localeconv()>.
2704
2705=item *
2706
2707C<POSIX::localeconv()> now marks appropriately the values it returns as
6a3ea89b 2708UTF-8 or not. Previously they were always returned as bytes, even if
eabfc7bc
RS
2709they were supposed to be encoded as UTF-8.
2710
2711=item *
2712
2713On Microsoft Windows, within the scope of C<S<use locale>>, the following
2714POSIX character classes gave results for many locales that did not
2715conform to the POSIX standard:
2716C<[[:alnum:]]>,
2717C<[[:alpha:]]>,
2718C<[[:blank:]]>,
2719C<[[:digit:]]>,
2720C<[[:graph:]]>,
2721C<[[:lower:]]>,
2722C<[[:print:]]>,
2723C<[[:punct:]]>,
2724C<[[:upper:]]>,
2725C<[[:word:]]>,
2726and
2727C<[[:xdigit:]]>.
f1c9eac6 2728This was because the underlying Microsoft implementation does not
eabfc7bc
RS
2729follow the standard. Perl now takes special precautions to correct for
2730this.
2731
2732=item *
2733
2734Many issues have been detected by L<Coverity|http://www.coverity.com/> and
2735fixed.
2736
2737=item *
2738
2739system() and friends should now work properly on more Android builds.
2740
4ec8e6f0 2741Due to an oversight, the value specified through C<-Dtargetsh> to F<Configure>
eabfc7bc 2742would end up being ignored by some of the build process. This caused perls
4ec8e6f0 2743cross-compiled for Android to end up with defective versions of C<system()>,
eabfc7bc
RS
2744exec() and backticks: the commands would end up looking for C</bin/sh>
2745instead of C</system/bin/sh>, and so would fail for the vast majority
2746of devices, leaving C<$!> as C<ENOENT>.
2747
2748=item *
2749
2750C<qr(...\(...\)...)>,
2751C<qr[...\[...\]...]>,
2752and
2753C<qr{...\{...\}...}>
2754now work. Previously it was impossible to escape these three
2755left-characters with a backslash within a regular expression pattern
2756where otherwise they would be considered metacharacters, and the pattern
2757opening delimiter was the character, and the closing delimiter was its
2758mirror character.
2759
2760=item *
2761
2762C<< s///e >> on tainted utf8 strings got C<< pos() >> messed up. This bug,
a75e6a3a
SH
2763introduced in 5.20, is now fixed.
2764L<[perl #122148]|https://rt.perl.org/Ticket/Display.html?id=122148>.
eabfc7bc
RS
2765
2766=item *
2767
2768A non-word boundary in a regular expression (C<< \B >>) did not always
2769match the end of the string; in particular C<< q{} =~ /\B/ >> did not
a75e6a3a
SH
2770match. This bug, introduced in perl 5.14, is now fixed.
2771L<[perl #122090]|https://rt.perl.org/Ticket/Display.html?id=122090>.
eabfc7bc
RS
2772
2773=item *
2774
2775C<< " P" =~ /(?=.*P)P/ >> should match, but did not. This is now fixed.
a75e6a3a 2776L<[perl #122171]|https://rt.perl.org/Ticket/Display.html?id=122171>.
eabfc7bc
RS
2777
2778=item *
2779
2780Failing to compile C<use Foo> in an eval could leave a spurious
2781C<BEGIN> subroutine definition, which would produce a "Subroutine
2782BEGIN redefined" warning on the next use of C<use>, or other C<BEGIN>
a75e6a3a
SH
2783block.
2784L<[perl #122107]|https://rt.perl.org/Ticket/Display.html?id=122107>.
eabfc7bc
RS
2785
2786=item *
2787
2788C<method { BLOCK } ARGS> syntax now correctly parses the arguments if they
a75e6a3a
SH
2789begin with an opening brace.
2790L<[perl #46947]|https://rt.perl.org/Ticket/Display.html?id=46947>.
eabfc7bc
RS
2791
2792=item *
2793
2794External libraries and Perl may have different ideas of what the locale is.
2795This is problematic when parsing version strings if the locale's numeric
2796separator has been changed. Version parsing has been patched to ensure
a75e6a3a
SH
2797it handles the locales correctly.
2798L<[perl #121930]|https://rt.perl.org/Ticket/Display.html?id=121930>.
eabfc7bc
RS
2799
2800=item *
2801
2802A bug has been fixed where zero-length assertions and code blocks inside of a
a75e6a3a
SH
2803regex could cause C<pos> to see an incorrect value.
2804L<[perl #122460]|https://rt.perl.org/Ticket/Display.html?id=122460>.
eabfc7bc
RS
2805
2806=item *
2807
2808Constant dereferencing now works correctly for typeglob constants. Previously
2809the glob was stringified and its name looked up. Now the glob itself is used.
2810L<[perl #69456]|https://rt.perl.org/Ticket/Display.html?id=69456>
2811
2812=item *
2813
4ec8e6f0
KW
2814When parsing a funny character (C<$> C<@> C<%> C<&)> followed by braces,
2815the parser no
eabfc7bc
RS
2816longer tries to guess whether it is a block or a hash constructor (causing a
2817syntax error when it guesses the latter), since it can only be a block.
2818
2819=item *
2820
4ec8e6f0 2821S<C<undef $reference>> now frees the referent immediately, instead of hanging on
eabfc7bc
RS
2822to it until the next statement.
2823L<[perl #122556]|https://rt.perl.org/Ticket/Display.html?id=122556>
2824
2825=item *
2826
2827Various cases where the name of a sub is used (autoload, overloading, error
2828messages) used to crash for lexical subs, but have been fixed.
2829
2830=item *
2831
2832Bareword lookup now tries to avoid vivifying packages if it turns out the
2833bareword is not going to be a subroutine name.
2834
2835=item *
2836
2837Compilation of anonymous constants (e.g., C<sub () { 3 }>) no longer deletes
2838any subroutine named C<__ANON__> in the current package. Not only was
2839C<*__ANON__{CODE}> cleared, but there was a memory leak, too. This bug goes
2840back to Perl 5.8.0.
2841
2842=item *
2843
2844Stub declarations like C<sub f;> and C<sub f ();> no longer wipe out constants
2845of the same name declared by C<use constant>. This bug was introduced in Perl
28465.10.0.
2847
2848=item *
2849
eabfc7bc
RS
2850C<qr/[\N{named sequence}]/> now works properly in many instances. Some names
2851known to C<\N{...}> refer to a sequence of multiple characters, instead of the
2852usual single character. Bracketed character classes generally only match
2853single characters, but now special handling has been added so that they can
2854match named sequences, but not if the class is inverted or the sequence is
2855specified as the beginning or end of a range. In these cases, the only
2856behavior change from before is a slight rewording of the fatal error message
2857given when this class is part of a C<?[...])> construct. When the C<[...]>
2858stands alone, the same non-fatal warning as before is raised, and only the
2859first character in the sequence is used, again just as before.
2860
2861=item *
2862
2863Tainted constants evaluated at compile time no longer cause unrelated
2864statements to become tainted.
2865L<[perl #122669]|https://rt.perl.org/Ticket/Display.html?id=122669>
2866
2867=item *
2868
4ec8e6f0 2869S<C<open $$fh, ...>>, which vivifies a handle with a name like C<"main::_GEN_0">, was
eabfc7bc
RS
2870not giving the handle the right reference count, so a double free could happen.
2871
2872=item *
2873
2874When deciding that a bareword was a method name, the parser would get confused
4ec8e6f0
KW
2875if an C<our> sub with the same name existed, and look up the method in the
2876package of the C<our> sub, instead of the package of the invocant.
eabfc7bc
RS
2877
2878=item *
2879
2880The parser no longer gets confused by C<\U=> within a double-quoted string. It
2881used to produce a syntax error, but now compiles it correctly.
2882L<[perl #80368]|https://rt.perl.org/Ticket/Display.html?id=80368>
2883
2884=item *
2885
2886It has always been the intention for the C<-B> and C<-T> file test operators to
2887treat UTF-8 encoded files as text. (L<perlfunc|perlfunc/-X FILEHANDLE> has
2888been updated to say this.) Previously, it was possible for some files to be
2889considered UTF-8 that actually weren't valid UTF-8. This is now fixed. The
2890operators now work on EBCDIC platforms as well.
2891
2892=item *
2893
2894Under some conditions warning messages raised during regular expression pattern
2895compilation were being output more than once. This has now been fixed.
2896
2897=item *
2898
2899A regression has been fixed that was introduced in Perl 5.20.0 (fixed in Perl
29005.20.1 as well as here) in which a UTF-8 encoded regular expression pattern
2901that contains a single ASCII lowercase letter does not match its uppercase
2902counterpart.
2903L<[perl #122655]|https://rt.perl.org/Ticket/Display.html?id=122655>
2904
2905=item *
2906
2907Constant folding could incorrectly suppress warnings if lexical warnings (C<use
2908warnings> or C<no warnings>) were not in effect and C<$^W> were false at
2909compile time and true at run time.
2910
2911=item *
2912
2913Loading UTF8 tables during a regular expression match could cause assertion
2914failures under debugging builds if the previous match used the very same
2915regular expression.
2916L<[perl #122747]|https://rt.perl.org/Ticket/Display.html?id=122747>
2917
2918=item *
2919
2920Thread cloning used to work incorrectly for lexical subs, possibly causing
2921crashes or double frees on exit.
2922
2923=item *
2924
2925Since Perl 5.14.0, deleting C<$SomePackage::{__ANON__}> and then undefining an
2926anonymous subroutine could corrupt things internally, resulting in
2927L<Devel::Peek> crashing or L<B.pm|B> giving nonsensical data. This has been
2928fixed.
2929
2930=item *
2931
4ec8e6f0
KW
2932S<C<(caller $n)[3]>> now reports names of lexical subs, instead of treating them
2933as C<"(unknown)">.
eabfc7bc
RS
2934
2935=item *
2936
2937C<sort subname LIST> now supports lexical subs for the comparison routine.
2938
2939=item *
2940
2941Aliasing (e.g., via C<*x = *y>) could confuse list assignments that mention the
2942two names for the same variable on either side, causing wrong values to be
2943assigned.
2944L<[perl #15667]|https://rt.perl.org/Ticket/Display.html?id=15667>
2945
2946=item *
2947
2948Long here-doc terminators could cause a bad read on short lines of input. This
2949has been fixed. It is doubtful that any crash could have occurred. This bug
2950goes back to when here-docs were introduced in Perl 3.000 twenty-five years
2951ago.
2952
2953=item *
2954
2955An optimization in C<split> to treat C<split/^/> like C<split/^/m> had the
2956unfortunate side-effect of also treating C<split/\A/> like C<split/^/m>, which
2957it should not. This has been fixed. (Note, however, that C<split/^x/> does
2958not behave like C<split/^x/m>, which is also considered to be a bug and will be
2959fixed in a future version.)
2960L<[perl #122761]|https://rt.perl.org/Ticket/Display.html?id=122761>
2961
2962=item *
2963
4ec8e6f0 2964The little-known S<C<my Class $var>> syntax (see L<fields> and L<attributes>)
eabfc7bc
RS
2965could get confused in the scope of C<use utf8> if C<Class> were a constant
2966whose value contained Latin-1 characters.
2967
2968=item *
2969
2970Locking and unlocking values via L<Hash::Util> or C<Internals::SvREADONLY>
2971no longer has any effect on values that are read-only to begin.
2972Previously, unlocking such values could result in crashes, hangs or
2973other erratic behaviour.
2974
2975=item *
2976
eabfc7bc
RS
2977The flip-flop operator (C<..> in scalar context) would return the same
2978scalar each time, unless the containing subroutine was called recursively.
a75e6a3a
SH
2979Now it always returns a new scalar.
2980L<[perl #122829]|https://rt.perl.org/Ticket/Display.html?id=122829>.
eabfc7bc
RS
2981
2982=item *
2983
2984Some unterminated C<(?(...)...)> constructs in regular expressions would
2985either crash or give erroneous error messages. C</(?(1)/> is one such
2986example.
2987
2988=item *
2989
4ec8e6f0 2990S<C<pack "w", $tied>> no longer calls FETCH twice.
eabfc7bc
RS
2991
2992=item *
2993
4ec8e6f0
KW
2994List assignments like S<C<($x, $z) = (1, $y)>> now work correctly if C<$x> and
2995C<$y> have been aliased by C<foreach>.
eabfc7bc
RS
2996
2997=item *
2998
2999Some patterns including code blocks with syntax errors, such as
3000C</ (?{(^{})/>, would hang or fail assertions on debugging builds. Now
3001they produce errors.
3002
3003=item *
3004
3005An assertion failure when parsing C<sort> with debugging enabled has been
a75e6a3a
SH
3006fixed.
3007L<[perl #122771]|https://rt.perl.org/Ticket/Display.html?id=122771>.
eabfc7bc
RS
3008
3009=item *
3010
4ec8e6f0 3011S<C<*a = *b; @a = split //, $b[1]>> could do a bad read and produce junk
eabfc7bc
RS
3012results.
3013
3014=item *
3015
4ec8e6f0 3016In S<C<() = @array = split>>, the S<C<() =>> at the beginning no longer confuses
eabfc7bc
RS
3017the optimizer, making it assume a limit of 1.
3018
3019=item *
3020
3021Fatal warnings no longer prevent the output of syntax errors.
a75e6a3a 3022L<[perl #122966]|https://rt.perl.org/Ticket/Display.html?id=122966>.
eabfc7bc
RS
3023
3024=item *
3025
3026Fixed a NaN double to long double conversion error on VMS. For quiet NaNs
3027(and only on Itanium, not Alpha) negative infinity instead of NaN was
3028produced.
3029
3030=item *
3031
3032Fixed the issue that caused C<< make distclean >> to leave files behind
a75e6a3a
SH
3033that shouldn't.
3034L<[perl #122820]|https://rt.perl.org/Ticket/Display.html?id=122820>.
eabfc7bc
RS
3035
3036=item *
3037
a75e6a3a
SH
3038AIX now sets the length in C<< getsockopt >> correctly.
3039L<[perl #120835]|https://rt.perl.org/Ticket/Display.html?id=120835>.
3040L<[cpan #91183]|https://rt.cpan.org/Ticket/Display.html?id=91183>.
3041L<[cpan #85570]|https://rt.cpan.org/Ticket/Display.html?id=85570>.
eabfc7bc
RS
3042
3043=item *
3044
3045During the pattern optimization phase, we no longer recurse into
4ec8e6f0 3046C<GOSUB>/C<GOSTART> when not C<SCF_DO_SUBSTR>. This prevents the optimizer
a75e6a3a
SH
3047to run "forever" and exhaust all memory.
3048L<[perl #122283]|https://rt.perl.org/Ticket/Display.html?id=122283>.
eabfc7bc
RS
3049
3050=item *
3051
3052F<< t/op/crypt.t >> now performs SHA-256 algorithm if the default one
a75e6a3a
SH
3053is disabled.
3054L<[perl #121591]|https://rt.perl.org/Ticket/Display.html?id=121591>.
eabfc7bc
RS
3055
3056=item *
3057
3058Fixed an off-by-one error when setting the size of shared array.
a75e6a3a 3059L<[perl #122950]|https://rt.perl.org/Ticket/Display.html?id=122950>.
eabfc7bc
RS
3060
3061=item *
3062
3063Fixed a bug that could cause perl to execute an infinite loop during
a75e6a3a
SH
3064compilation.
3065L<[perl #122995]|https://rt.perl.org/Ticket/Display.html?id=122995>.
eabfc7bc
RS
3066
3067=item *
3068
3069On Win32, restoring in a child pseudo-process a variable that was
3070C<local()>ed in a parent pseudo-process before the C<fork> happened caused
3071memory corruption and a crash in the child pseudo-process (and therefore OS
a75e6a3a
SH
3072process).
3073L<[perl #40565]|https://rt.perl.org/Ticket/Display.html?id=40565>.
eabfc7bc
RS
3074
3075=item *
3076
3077Calling C<write> on a format with a C<^**> field could produce a panic
4ec8e6f0 3078in C<sv_chop()> if there were insufficient arguments or if the variable
a75e6a3a
SH
3079used to fill the field was empty.
3080L<[perl #123245]|https://rt.perl.org/Ticket/Display.html?id=123245>.
eabfc7bc
RS
3081
3082=item *
3083
3084Non-ASCII lexical sub names (use in error messages) on longer have extra
3085junk on the end.
3086
3087=item *
3088
3089The C<\@> subroutine prototype no longer flattens parenthesized arrays
3090(taking a reference to each element), but takes a reference to the array
a75e6a3a
SH
3091itself.
3092L<[perl #47363]|https://rt.perl.org/Ticket/Display.html?id=47363>.
eabfc7bc
RS
3093
3094=item *
3095
3096A block containing nothing except a C-style C<for> loop could corrupt the
3097stack, causing lists outside the block to lose elements or have elements
3098overwritten. This could happen with C<map { for(...){...} } ...> and with
a75e6a3a
SH
3099lists containing C<do { for(...){...} }>.
3100L<[perl #123286]|https://rt.perl.org/Ticket/Display.html?id=123286>.
eabfc7bc
RS
3101
3102=item *
3103
3104C<scalar()> now propagates lvalue context, so that
4ec8e6f0 3105S<C<for(scalar($#foo)) { ... }>> can modify C<$#foo> through C<$_>.
eabfc7bc
RS
3106
3107=item *
3108
3109C<qr/@array(?{block})/> no longer dies with "Bizarre copy of ARRAY".
a75e6a3a 3110L<[perl #123344]|https://rt.perl.org/Ticket/Display.html?id=123344>.
eabfc7bc
RS
3111
3112=item *
3113
4ec8e6f0 3114S<C<eval '$variable'>> in nested named subroutines would sometimes look up a
eabfc7bc
RS
3115global variable even with a lexical variable in scope.
3116
3117=item *
3118
3119In perl 5.20.0, C<sort CORE::fake> where 'fake' is anything other than a
3120keyword started chopping of the last 6 characters and treating the result
3121as a sort sub name. The previous behaviour of treating "CORE::fake" as a
a75e6a3a
SH
3122sort sub name has been restored.
3123L<[perl #123410]|https://rt.perl.org/Ticket/Display.html?id=123410>.
eabfc7bc
RS
3124
3125=item *
3126
3127Outside of C<use utf8>, a single-character Latin-1 lexical variable is
4ec8e6f0 3128disallowed. The error message for it, "Can't use global C<$foo>...", was
eabfc7bc
RS
3129giving garbage instead of the variable name.
3130
3131=item *
3132
3133C<readline> on a nonexistent handle was causing C<${^LAST_FH}> to produce a
3134reference to an undefined scalar (or fail an assertion). Now
3135C<${^LAST_FH}> ends up undefined.
3136
3137=item *
3138
3139C<(...)x...> in void context now applies scalar context to the left-hand
3140argument, instead of the context the current sub was called in.
a75e6a3a 3141L<[perl #123020]|https://rt.perl.org/Ticket/Display.html?id=123020>.
eabfc7bc
RS
3142
3143=back
3144
3145=head1 Known Problems
3146
3147=over 4
3148
3149=item *
3150
3151A goal is for Perl to be able to be recompiled to work reasonably well on any
3152Unicode version. In Perl 5.22, though, the earliest such version is Unicode
31535.1 (current is 7.0).
3154
3155=item *
3156
3157EBCDIC platforms
3158
3159=over 4
3160
3161=item *
3162
ce93e38b
KW
3163The C<cmp> (and hence C<sort>) operators do not necessarily give the
3164correct results when both operands are UTF-EBCDIC encoded strings and
3165there is a mixture of ASCII and/or control characters, along with other
3166characters.
3167
3168=item *
3169
3170Ranges containing C<\N{...}> in the C<tr///> (and C<y///>)
3171transliteration operators are treated differently than the equivalent
3172ranges in regular expression pattersn. They should, but don't, cause
3173the values in the ranges to all be treated as Unicode code points, and
3174not native ones. (L<perlre/Version 8 Regular Expressions> gives
3175details as to how it should work.)
3176
3177=item *
3178
eabfc7bc
RS
3179Encode and encoding are mostly broken.
3180
3181=item *
3182
0590bd99 3183Many CPAN modules that are shipped with core show failing tests.
eabfc7bc
RS
3184
3185=item *
3186
3187C<pack>/C<unpack> with C<"U0"> format may not work properly.
3188
3189=back
3190
3191=item *
3192
3193The following modules are known to have test failures with this version of
3194Perl. Patches have been submitted, so there will hopefully be new releases
3195soon:
3196
3197=over
3198
3199=item *
3200
3201L<B::Generate> version 1.50
3202
3203=item *
3204
3205L<B::Utils> version 0.25
3206
3207=item *
3208
3209L<Dancer> version 1.3130
3210
3211=item *
3212
3213L<Data::Alias> version 1.18
3214
3215=item *
3216
3217L<Data::Util> version 0.63
3218
3219=item *
3220
ba520a57
RS
3221L<Devel::Spy> version 0.07
3222
3223=item *
3224
2621aeba
RS
3225L<invoker> version 0.34
3226
3227=item *
3228
eabfc7bc
RS
3229L<Lexical::Var> version 0.009
3230
3231=item *
3232
3233L<Mason> version 2.22
3234
3235=item *
3236
6be597e7
RS
3237L<NgxQueue> version 0.02
3238
3239=item *
3240
eabfc7bc
RS
3241L<Padre> version 1.00
3242
3243=item *
3244
3245L<Parse::Keyword> 0.08
3246
3247=back
3248
3249=back
2a7a05b4 3250
30aa8e3f
AC
3251=head1 Obituary
3252
3253Brian McCauley died on May 8, 2015. He was a frequent poster to Usenet, Perl
3254Monks, and other Perl forums, and made several CPAN contributions under the
3255nick NOBULL, including to the Perl FAQ. He attended almost every
3256YAPC::Europe, and indeed, helped organise YAPC::Europe 2006 and the QA
3257Hackathon 2009. His wit and his delight in intricate systems were
3258particularly apparent in his love of board games; many Perl mongers will
3259have fond memories of playing Fluxx and other games with Brian. He will be
3260missed.
3261
7f9fef93 3262=head1 Acknowledgements
2a7a05b4 3263
7f9fef93 3264XXX Generate this with:
2a7a05b4 3265
eabfc7bc 3266 perl Porting/acknowledgements.pl v5.20.0..HEAD
f5b73711 3267
44691e6f
AB
3268=head1 Reporting Bugs
3269
e08634c5
SH
3270If you find what you think is a bug, you might check the articles recently
3271posted to the comp.lang.perl.misc newsgroup and the perl bug database at
e5998677
SH
3272https://rt.perl.org/ . There may also be information at
3273http://www.perl.org/ , the Perl Home Page.
44691e6f 3274
e08634c5
SH
3275If you believe you have an unreported bug, please run the L<perlbug> program
3276included with your release. Be sure to trim your bug down to a tiny but
3277sufficient test case. Your bug report, along with the output of C<perl -V>,
3278will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
44691e6f
AB
3279
3280If the bug you are reporting has security implications, which make it
e08634c5
SH
3281inappropriate to send to a publicly archived mailing list, then please send it
3282to perl5-security-report@perl.org. This points to a closed subscription
3283unarchived mailing list, which includes all the core committers, who will be
3284able to help assess the impact of issues, figure out a resolution, and help
f9001595 3285co-ordinate the release of patches to mitigate or fix the problem across all
e08634c5
SH
3286platforms on which Perl is supported. Please only use this address for
3287security issues in the Perl core, not for modules independently distributed on
3288CPAN.
44691e6f
AB
3289
3290=head1 SEE ALSO
3291
e08634c5
SH
3292The F<Changes> file for an explanation of how to view exhaustive details on
3293what changed.
44691e6f
AB
3294
3295The F<INSTALL> file for how to build Perl.
3296
3297The F<README> file for general stuff.
3298
3299The F<Artistic> and F<Copying> files for copyright information.
3300
3301=cut