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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
89=head2 C<qr/foo/x> now ignores any Unicode pattern white space
90
91The C</x> regular expression modifier allows the pattern to contain
92white space and comments, both of which are ignored, for improved
93readability. Until now, not all the white space characters that Unicode
94designates for this purpose were handled. The additional ones now
95recognized are
96U+0085 NEXT LINE,
97U+200E LEFT-TO-RIGHT MARK,
98U+200F RIGHT-TO-LEFT MARK,
99U+2028 LINE SEPARATOR,
100and
101U+2029 PARAGRAPH SEPARATOR.
102
ce93e38b 103=head2 Unicode 7.0 (with correction) is now supported
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104
105For details on what is in this release, see
106L<http://www.unicode.org/versions/Unicode7.0.0/>.
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107The version of Unicode 7.0 that comes with Perl includes
108a correction dealing with glyph shaping in Arabic
109(see L<http://www.unicode.org/errata/#current_errata>).
110
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111
112=head2 S<C<use locale>> can restrict which locale categories are affected
113
114It is now possible to pass a parameter to S<C<use locale>> to specify
115a subset of locale categories to be locale-aware, with the remaining
116ones unaffected. See L<perllocale/The "use locale" pragma> for details.
117
01842271 118=head2 Perl now supports POSIX 2008 locale currency additions
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119
120On platforms that are able to handle POSIX.1-2008, the
121hash returned by
122L<C<POSIX::localeconv()>|perllocale/The localeconv function>
123includes the international currency fields added by that version of the
124POSIX standard. These are
125C<int_n_cs_precedes>,
126C<int_n_sep_by_space>,
127C<int_n_sign_posn>,
128C<int_p_cs_precedes>,
129C<int_p_sep_by_space>,
130and
131C<int_p_sign_posn>.
132
133=head2 Better heuristics on older platforms for determining locale UTF8ness
134
135On platforms that implement neither the C99 standard nor the POSIX 2001
136standard, determining if the current locale is UTF8 or not depends on
137heuristics. These are improved in this release.
138
139=head2 Aliasing via reference
140
141Variables and subroutines can now be aliased by assigning to a reference:
142
143 \$c = \$d;
144 \&x = \&y;
145
146Or by using a backslash before a C<foreach> iterator variable, which is
147perhaps the most useful idiom this feature provides:
148
149 foreach \%hash (@array_of_hash_refs) { ... }
150
151This feature is experimental and must be enabled via C<use feature
152'refaliasing'>. It will warn unless the C<experimental::refaliasing>
153warnings category is disabled.
154
155See L<perlref/Assigning to References>
156
157=head2 C<prototype> with no arguments
158
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159C<prototype()> with no arguments now infers C<$_>.
160L<[perl #123514]|https://rt.perl.org/Ticket/Display.html?id=123514>.
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161
162=head2 New "const" subroutine attribute
163
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164The "const" attribute can be applied to an anonymous subroutine. It
165causes the new sub to be executed immediately whenever one is created
166(i.e. when the C<sub> expression is evaluated). Its value is captured
167and used to create a new constant subroutine that is returned. This
168feature is experimental. See L<perlsub/Constant Functions>.
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169
170=head2 C<fileno> now works on directory handles
171
172When the relevant support is available in the operating system, the
173C<fileno> builtin now works on directory handles, yielding the
174underlying file descriptor in the same way as for filehandles. On
175operating systems without such support, C<fileno> on a directory handle
176continues to return the undefined value, as before, but also sets C<$!> to
177indicate that the operation is not supported.
178
179Currently, this uses either a C<dd_fd> member in the OS C<DIR>
4ec8e6f0 180structure, or a C<dirfd(3)> function as specified by POSIX.1-2008.
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181
182=head2 List form of pipe open implemented for Win32
183
184The list form of pipe:
185
186 open my $fh, "-|", "program", @arguments;
187
188is now implemented on Win32. It has the same limitations as C<system
189LIST> on Win32, since the Win32 API doesn't accept program arguments
190as a list.
191
192=head2 C<close> now sets C<$!>
193
194When an I/O error occurs, the fact that there has been an error is recorded
195in the handle. C<close> returns false for such a handle. Previously, the
196value of C<$!> would be untouched by C<close>, so the common convention of
4ec8e6f0 197writing S<C<close $fh or die $!>> did not work reliably. Now the handle
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198records the value of C<$!>, too, and C<close> restores it.
199
200=head2 Assignment to list repetition
201
202C<(...) x ...> can now be used within a list that is assigned to, as long
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203as the left-hand side is a valid lvalue. This allows S<C<(undef,undef,$foo)
204= that_function()>> to be written as S<C<((undef)x2, $foo) = that_function()>>.
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205
206=head2 Infinity and NaN (not-a-number) handling improved
207
208Floating point values are able to hold the special values infinity (also
209-infinity), and NaN (not-a-number). Now we more robustly recognize and
210propagate the value in computations, and on output normalize them to C<Inf> and
211C<NaN>.
212
213See also the L<POSIX> enhancements.
214
215=head2 Floating point parsing has been improved
216
217Parsing and printing of floating point values has been improved.
218
219As a completely new feature, hexadecimal floating point literals
4ec8e6f0 220(like C<0x1.23p-4>) are now supported, and they can be output with
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221C<printf %a>.
222
223=head2 Packing infinity or not-a-number into a character is now fatal
224
225Before, when trying to pack infinity or not-a-number into a
226(signed) character, Perl would warn, and assumed you tried to
227pack C<< 0xFF >>; if you gave it as an argument to C<< chr >>,
228C<< U+FFFD >> was returned.
229
230But now, all such actions (C<< pack >>, C<< chr >>, and C<< print '%c' >>)
231result in a fatal error.
232
233=head2 Experimental C Backtrace API
2e4abf26 234
19c9b733 235Perl now supports retrieving
eabfc7bc 236the C level backtrace (similar to what symbolic debuggers like gdb do).
fea59588 237
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238The backtrace returns the stack trace of the C call frames,
239with the symbol names (function names), the object names (like "perl"),
240and if it can, also the source code locations (file:line).
241
242The supported platforms are Linux and OS X (some *BSD might work at
243least partly, but they have not yet been tested).
244
245The feature needs to be enabled with C<Configure -Dusecbacktrace>.
246
247Also included is a C API to retrieve backtraces.
248
249See L<perlhacktips/"C backtrace"> for more information.
83a5d6b6 250
7f9fef93 251=head1 Security
e455391f 252
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253=head2 Perl is now compiled with -fstack-protector-strong if available
254
255Perl has been compiled with the anti-stack-smashing option
256C<-fstack-protector> since 5.10.1. Now Perl uses the newer variant
257called C<-fstack-protector-strong>, if available.
258
259=head2 The L<Safe> module could allow outside packages to be replaced
260
261Critical bugfix: outside packages could be replaced. L<Safe> has
262been patched to 2.38 to address this.
263
264=head2 Perl is now always compiled with -D_FORTIFY_SOURCE=2 if available
e455391f 265
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266The 'code hardening' option called C<_FORTIFY_SOURCE>, available in
267gcc 4.*, is now always used for compiling Perl, if available.
268
269Note that this isn't necessarily a huge step since in many platforms
270the step had already been taken several years ago: many Linux
271distributions (like Fedora) have been using this option for Perl,
272and OS X has enforced the same for many years.
53902397 273
7f9fef93 274=head1 Incompatible Changes
79a77127 275
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276=head2 Subroutine signatures moved before attributes
277
278The experimental sub signatures feature, as introduced in 5.20, parsed
279signatures after attributes. In this release, the positioning has been
280moved such that signatures occur after the subroutine name (if any) and
281before the attribute list (if any).
282
283=head2 C<&> and C<\&> prototypes accepts only subs
284
285The C<&> prototype character now accepts only anonymous subs (C<sub {...}>)
286and things beginning with C<\&>. Formerly it erroneously also allowed
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287C<undef> and references to array, hashes, and lists.
288L<[perl #4539]|https://rt.perl.org/Ticket/Display.html?id=4539>.
289L<[perl #123062]|https://rt.perl.org/Ticket/Display.html?id=123062>.
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290
291The C<\&> prototype was allowing subroutine calls, whereas now it only
292allows subroutines. C<&foo> is permitted. C<&foo()> and C<foo()> are not.
a75e6a3a 293L<[perl #77860]|https://rt.perl.org/Ticket/Display.html?id=77860>.
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294
295=head2 C<use encoding> is now lexical
296
297The L<encoding> pragma's effect is now limited to lexical scope. This
298pragma is deprecated, but in the meantime, it could adversely affect
299unrelated modules that are included in the same program.
300
301=head2 List slices returning empty lists
302
303List slices return an empty list now only if the original list was empty
304(or if there are no indices). Formerly, a list slice would return an empty
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305list if all indices fell outside the original list.
306L<[perl #114498]|https://rt.perl.org/Ticket/Display.html?id=114498>.
eabfc7bc 307
01842271 308=head2 C<\N{}> with a sequence of multiple spaces is now a fatal error
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309
310This has been deprecated since v5.18.
311
312=head2 S<C<use UNIVERSAL '...'>> is now a fatal error
313
314Importing functions from C<UNIVERSAL> has been deprecated since v5.12, and
315is now a fatal error. S<C<"use UNIVERSAL">> without any arguments is still
316allowed.
317
318=head2 In double-quotish C<\cI<X>>, I<X> must now be a printable ASCII character
319
320In prior releases, failure to do this raised a deprecation warning.
321
322=head2 Splitting the tokens C<(?> and C<(*> in regular expressions is
323now a fatal compilation error.
324
325These had been deprecated since v5.18.
326
327=head2 5 additional characters are treated as white space under C</x> in
328regex patterns (unless escaped)
329
330The use of these characters with C</x> outside bracketed character
331classes and when not preceded by a backslash has raised a deprecation
332warning since v5.18. Now they will be ignored. See L</"qr/foo/x">
333for the list of the five characters.
334
335=head2 Comment lines within S<C<(?[ ])>> now are ended only by a C<\n>
336
337S<C<(?[ ])>> is an experimental feature, introduced in v5.18. It operates
338as if C</x> is always enabled. But there was a difference, comment
339lines (following a C<#> character) were terminated by anything matching
340C<\R> which includes all vertical whitespace, such as form feeds. For
341consistency, this is now changed to match what terminates comment lines
342outside S<C<(?[ ])>>, namely a C<\n> (even if escaped), which is the
343same as what terminates a heredoc string and formats.
344
345=head2 C<(?[...])> operators now follow standard Perl precedence
346
347This experimental feature allows set operations in regular expression patterns.
348Prior to this, the intersection operator had the same precedence as the other
349binary operators. Now it has higher precedence. This could lead to different
350outcomes than existing code expects (though the documentation has always noted
351that this change might happen, recommending fully parenthesizing the
352expressions). See L<perlrecharclass/Extended Bracketed Character Classes>.
353
4ec8e6f0 354=head2 Omitting C<%> and C<@> on hash and array names is no longer permitted
c14a43b7 355
4ec8e6f0 356Really old Perl let you omit the C<@> on array names and the C<%> on hash
eabfc7bc 357names in some spots. This has issued a deprecation warning since Perl
93780ae6 3585.000, and is no longer permitted.
c14a43b7 359
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360=head2 C<"$!"> text is now in English outside C<"use locale"> scope
361
362Previously, the text, unlike almost everything else, always came out
363based on the current underlying locale of the program. (Also affected
364on some systems is C<"$^E>".) For programs that are unprepared to
365handle locale, this can cause garbage text to be displayed. It's better
366to display text that is translatable via some tool than garbage text
367which is much harder to figure out.
368
369=head2 C<"$!"> text will be returned in UTF-8 when appropriate
370
371The stringification of C<$!> and C<$^E> will have the UTF-8 flag set
372when the text is actually non-ASCII UTF-8. This will enable programs
373that are set up to be locale-aware to properly output messages in the
374user's native language. Code that needs to continue the 5.20 and
375earlier behavior can do the stringification within the scopes of both
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376S<C<'use bytes'>> and S<C<'use locale ":messages">>. No other Perl
377operations will
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378be affected by locale; only C<$!> and C<$^E> stringification. The
379'bytes' pragma causes the UTF-8 flag to not be set, just as in previous
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380Perl releases. This resolves
381L<[perl #112208]|https://rt.perl.org/Ticket/Display.html?id=112208>.
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382
383=head2 Support for C<?PATTERN?> without explicit operator has been removed
384
385Starting regular expressions matching only once directly with the
386question mark delimiter is now a syntax error, so that the question mark
387can be available for use in new operators. Write C<m?PATTERN?> instead,
388explicitly using the C<m> operator: the question mark delimiter still
389invokes match-once behaviour.
390
391=head2 C<defined(@array)> and C<defined(%hash)> are now fatal errors
392
393These have been deprecated since v5.6.1 and have raised deprecation
394warnings since v5.16.
395
01842271 396=head2 Using a hash or an array as a reference are now fatal errors
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397
398For example, C<%foo-E<gt>{"bar"}> now causes a fatal compilation
399error. These have been deprecated since before v5.8, and have raised
400deprecation warnings since then.
401
402=head2 Changes to the C<*> prototype
403
404The C<*> character in a subroutine's prototype used to allow barewords to take
405precedence over most, but not all subroutines. It was never consistent and
406exhibited buggy behaviour.
407
408Now it has been changed, so subroutines always take precedence over barewords,
409which brings it into conformity with similarly prototyped built-in functions:
410
411 sub splat(*) { ... }
412 sub foo { ... }
413 splat(foo); # now always splat(foo())
414 splat(bar); # still splat('bar') as before
415 close(foo); # close(foo())
416 close(bar); # close('bar')
c14a43b7 417
7f9fef93 418=head1 Deprecations
47cb8ddb 419
eabfc7bc 420=head2 Setting C<${^ENCODING}> to anything but C<undef>
c14a43b7 421
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422This variable allows Perl scripts to be written in a non-ASCII,
423non-UTF-8 encoding. However, it affects all modules globally, leading
424to wrong answers and segmentation faults. New scripts should be written
425in UTF-8; old scripts should be converted to UTF-8, which is easily done
426with the L<encoding> pragma.
c14a43b7 427
eabfc7bc 428=head2 C<< /\C/ >> character class
c14a43b7 429
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430This character class, which matches a single byte, even if it appears
431in a multi-byte character has been deprecated. Matching single bytes
432in a multi-byte character breaks encapsulation, and can corrupt utf8
433strings.
51c2f40f 434
eabfc7bc 435=head2 Use of non-graphic characters in single-character variable names
51c2f40f 436
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437The syntax for single-character variable names is more lenient than
438for longer variable names, allowing the one-character name to be a
439punctuation character or even invisible (a non-graphic). Perl v5.20
440deprecated the ASCII-range controls as such a name. Now, all
441non-graphic characters that formerly were allowed are deprecated.
442The practical effect of this occurs only when not under C<S<"use
443utf8">>, and affects just the C1 controls (code points 0x80 through
4440xFF), NO-BREAK SPACE, and SOFT HYPHEN.
83a5d6b6 445
eabfc7bc 446=head2 Inlining of C<sub () { $var }> with observable side-effects
abec5bed 447
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448In many cases Perl makes S<C<sub () { $var }>> into an inlinable constant
449subroutine, capturing the value of C<$var> at the time the C<sub> expression
eabfc7bc 450is evaluated. This can break the closure behaviour in those cases where
4ec8e6f0 451C<$var> is subsequently modified. The subroutine won't return the new value.
abec5bed 452
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453This usage is now deprecated in those cases where the variable could be
454modified elsewhere. Perl detects those cases and emits a deprecation
455warning. Such code will likely change in the future and stop producing a
456constant.
abec5bed 457
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458If your variable is only modified in the place where it is declared, then
459Perl will continue to make the sub inlinable with no warnings.
c14a43b7 460
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461 sub make_constant {
462 my $var = shift;
463 return sub () { $var }; # fine
464 }
c14a43b7 465
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466 sub make_constant_deprecated {
467 my $var;
468 $var = shift;
469 return sub () { $var }; # deprecated
470 }
c14a43b7 471
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472 sub make_constant_deprecated2 {
473 my $var = shift;
474 log_that_value($var); # could modify $var
475 return sub () { $var }; # deprecated
476 }
c14a43b7 477
4ec8e6f0 478In the second example above, detecting that C<$var> is assigned to only once
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479is too hard to detect. That it happens in a spot other than the C<my>
480declaration is enough for Perl to find it suspicious.
7f9fef93 481
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482This deprecation warning happens only for a simple variable for the body of
483the sub. (A C<BEGIN> block or C<use> statement inside the sub is ignored,
484because it does not become part of the sub's body.) For more complex
4ec8e6f0 485cases, such as S<C<sub () { do_something() if 0; $var }>> the behaviour has
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486changed such that inlining does not happen if the variable is modifiable
487elsewhere. Such cases should be rare.
c14a43b7 488
eabfc7bc 489=head2 Use of multiple /x regexp modifiers
c14a43b7 490
eabfc7bc 491It is now deprecated to say something like any of the following:
c14a43b7 492
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493 qr/foo/xx;
494 /(?xax:foo)/;
495 use re qw(/amxx);
be39acb2 496
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497That is, now C<x> should only occur once in any string of contiguous
498regular expression pattern modifiers. We do not believe there are any
499occurrences of this in all of CPAN. This is in preparation for a future
500Perl release having C</xx> mean to allow white-space for readability in
501bracketed character classes (those enclosed in square brackets:
502C<[...]>).
c14a43b7 503
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504=head2 Using a NO-BREAK space in a character alias for C<\N{...}> is now
505deprecated
60dcce55 506
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507This non-graphic character is essentially indistinguishable from a
508regular space, and so should not be allowed. See
509L<charnames/CUSTOM ALIASES>.
60dcce55 510
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511=head2 A literal C<"{"> should now be escaped in a pattern
512
513If you want a literal left curly bracket (also called a left brace) in a
514regular expression pattern, you should now escape it by either
515preceding it with a backslash (C<"\{">) or enclosing it within square
516brackets C<"[{]">, or by using C<\Q>; otherwise a deprecation warning
517will be raised. This was first announced as forthcoming in the v5.16
518release; it will allow future extensions to the language to happen.
519
520=head2 Making all warnings fatal is discouraged
521
522The documentation for L<fatal warnings|warnings/Fatal Warnings> notes that
523C<< use warnings FATAL => 'all' >> is discouraged and provides stronger
524language about the risks of fatal warnings in general.
525
526=head1 Performance Enhancements
79a77127 527
7f9fef93 528=over 4
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529
530=item *
531
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532If method and class names are known at compile time, hashes are precomputed
533to speed up run-time method lookup. Also, compound method names like
534C<SUPER::new> are parsed at compile time, to save having to parse them at
535run time.
9749148e 536
eabfc7bc 537=item *
9749148e 538
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539Array and hash lookups (especially nested ones) that use only constants
540or simple variables as keys, are now considerably faster. See
541L</Internal Changes> for more details.
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542
543=item *
544
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545C<(...)x1>, C<("constant")x0> and C<($scalar)x0> are now optimised in list
546context. If the right-hand argument is a constant 1, the repetition
547operator disappears. If the right-hand argument is a constant 0, the whole
6a3ea89b 548expression is optimised to the empty list, so long as the left-hand
eabfc7bc 549argument is a simple scalar or constant. C<(foo())x0> is not optimised.
6bb5549b 550
eabfc7bc 551=item *
7f9fef93 552
eabfc7bc
RS
553C<substr> assignment is now optimised into 4-argument C<substr> at the end
554of a subroutine (or as the argument to C<return>). Previously, this
555optimisation only happened in void context.
abec5bed 556
eabfc7bc 557=item *
7f9fef93 558
eabfc7bc
RS
559Assignment to lexical variables is often optimised away. For instance, in
560C<$lexical = chr $foo>, the C<chr> operator writes directly to the lexical
561variable instead of returning a value that gets copied. This optimisation
562has been extended to C<split>, C<x> and C<vec> on the right-hand side. It
563has also been made to work with state variable initialization.
be39acb2 564
2e4abf26
DG
565=item *
566
4ec8e6f0 567In "C<\L>...", "C<\Q>...", etc., the extra "stringify" op is now optimised away,
eabfc7bc 568making these just as fast as C<lcfirst>, C<quotemeta>, etc.
2e4abf26 569
eabfc7bc 570=item *
83a5d6b6 571
eabfc7bc
RS
572Assignment to an empty list is now sometimes faster. In particular, it
573never calls C<FETCH> on tied arguments on the right-hand side, whereas it
574used to sometimes.
575
576=item *
83a5d6b6 577
eabfc7bc 578C<length> is up to 20% faster for non-magical/non-tied scalars containing a
4ec8e6f0 579string if it is a non-utf8 string or if is in scope of C<use bytes>.
338906ce 580
eabfc7bc 581=item *
5de148ee 582
eabfc7bc
RS
583Non-magical/non-tied scalars that contain only a floating point value and are
584on most Perl builds with 64 bit integers now use 8-32 less bytes of memory
585depending on OS.
5de148ee 586
eabfc7bc 587=item *
5de148ee 588
eabfc7bc
RS
589In C<@array = split>, the assignment can be optimized away with C<split>
590writing directly to the array. This optimisation was happening only for
4ec8e6f0 591package arrays other than C<@_> and only
eabfc7bc
RS
592sometimes. Now this optimisation happens
593almost all the time.
5de148ee 594
eabfc7bc 595=item *
7f9fef93 596
eabfc7bc
RS
597C<join> is now subject to constant folding. Moreover, C<join> with a
598scalar or constant for the separator and a single-item list to join is
599simplified to a stringification. The separator doesn't even get evaluated.
5de148ee 600
eabfc7bc 601=item *
47cb8ddb 602
eabfc7bc 603C<qq(@array)> is implemented using two ops: a stringify op and a join op.
4ec8e6f0 604If the C<qq> contains nothing but a single array, the stringification is
eabfc7bc 605optimized away.
47cb8ddb
SH
606
607=item *
608
4ec8e6f0
KW
609S<C<our $var>> and S<C<our($s,@a,%h)>> in void context are no longer evaluated at
610run time. Even a whole sequence of S<C<our $foo;>> statements will simply be
eabfc7bc 611skipped over. The same applies to C<state> variables.
47cb8ddb 612
eabfc7bc 613=item *
47cb8ddb 614
eabfc7bc
RS
615Many internal functions have been refactored to improve performance and reduce
616their memory footprints.
eabfc7bc
RS
617L<[perl #121436]|https://rt.perl.org/Ticket/Display.html?id=121436>
618L<[perl #121906]|https://rt.perl.org/Ticket/Display.html?id=121906>
619L<[perl #121969]|https://rt.perl.org/Ticket/Display.html?id=121969>
47cb8ddb 620
eabfc7bc 621=item *
47cb8ddb 622
eabfc7bc 623C<-T> and C<-B> filetests will return sooner when an empty file is detected.
a75e6a3a 624L<[perl #121489]|https://rt.perl.org/Ticket/Display.html?id=121489>
47cb8ddb 625
eabfc7bc 626=item *
5de148ee 627
01842271 628Refactoring of C<< pp_tied >> and C<< pp_ref >> for small improvements.
5de148ee
SH
629
630=item *
631
f1c9eac6
DM
632Pathtools doesn't try to load XS on miniperl. This speeds up building perl
633slightly.
5de148ee 634
eabfc7bc 635=item *
5de148ee 636
eabfc7bc 637A typo fix reduces the size of the C<< OP >> structure.
be39acb2 638
eabfc7bc
RS
639=item *
640
01842271 641Hash lookups where the key is a constant are faster.
be39acb2
SH
642
643=item *
644
eabfc7bc
RS
645Subroutines with an empty prototype and bodies containing just C<undef> are now
646eligible for inlining.
647L<[perl #122728]|https://rt.perl.org/Ticket/Display.html?id=122728>
be39acb2 648
eabfc7bc 649=item *
be39acb2 650
eabfc7bc
RS
651Subroutines in packages no longer need to carry typeglobs around with them.
652Declaring a subroutine will now put a simple sub reference in the stash if
653possible, saving memory. The typeglobs still notionally exist, so accessing
654them will cause the subroutine reference to be upgraded to a typeglob. This
655optimization does not currently apply to XSUBs or exported subroutines, and
656method calls will undo it, since they cache things in typeglobs.
657L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
7f9fef93 658
eabfc7bc 659=item *
be39acb2 660
eabfc7bc
RS
661The functions C<utf8::native_to_unicode()> and C<utf8::unicode_to_native()>
662(see L<utf8>) are now optimized out on ASCII platforms. There is now not even
663a minimal performance hit in writing code portable between ASCII and EBCDIC
664platforms.
be39acb2
SH
665
666=item *
667
eabfc7bc
RS
668Win32 Perl uses 8 KB less of per-process memory than before for every perl
669process of this version. This data is now memory mapped from disk and shared
670between perl processes from the same perl binary.
be39acb2
SH
671
672=back
673
eabfc7bc 674=head1 Modules and Pragmata
83a5d6b6 675
eabfc7bc
RS
676XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
677go here. If Module::CoreList is updated, generate an initial draft of the
678following sections using F<Porting/corelist-perldelta.pl>. A paragraph summary
679for important changes should then be added by hand. In an ideal world,
680dual-life modules would have a F<Changes> file that could be cribbed.
83a5d6b6 681
eabfc7bc 682[ Within each section, list entries as a =item entry ]
338906ce 683
eabfc7bc 684=head2 New Modules and Pragmata
cd7bac54 685
b5d4d3b9 686=over 4
83b69bfd
DD
687
688=item *
689
7f9fef93 690XXX
13adb056 691
b5d4d3b9 692=back
391823f2 693
eabfc7bc
RS
694=head2 Updated Modules and Pragmata
695
696=over 4
697
698=item *
699
700L<XXX> has been upgraded from version A.xx to B.yy.
6c8457e9 701
eabfc7bc 702=back
2bf83140 703
eabfc7bc 704=head2 Removed Modules and Pragmata
041a5927 705
7f9fef93 706=over 4
69e954a5 707
7f9fef93 708=item *
86e0176a 709
7f9fef93 710XXX
69e954a5 711
e5998677 712=back
20b5e916 713
eabfc7bc
RS
714=head1 Documentation
715
716=head2 New Documentation
532ecd00 717
eabfc7bc 718=head3 L<perlunicook>
d76c14eb 719
eabfc7bc
RS
720This document, by Tom Christiansen, provides examples of handling Unicode in
721Perl.
722
723=head2 Changes to Existing Documentation
724
725=head3 L<perlapi>
d547bad0 726
e5998677 727=over 4
d547bad0 728
8a95d307
FC
729=item *
730
eabfc7bc 731Note that C<SvSetSV> doesn't do set magic.
532ecd00 732
eabfc7bc 733=item *
532ecd00 734
eabfc7bc
RS
735C<sv_usepvn_flags> - Fix documentation to mention the use of C<NewX> instead of
736C<malloc>.
532ecd00 737
eabfc7bc 738L<[perl #121869]|https://rt.perl.org/Ticket/Display.html?id=121869>
532ecd00 739
eabfc7bc 740=item *
532ecd00 741
eabfc7bc 742Clarify where C<NUL> may be embedded or is required to terminate a string.
532ecd00 743
eabfc7bc 744=item *
532ecd00 745
eabfc7bc 746Previously missing documentation due to formatting errors are now included.
532ecd00 747
eabfc7bc 748=item *
532ecd00 749
eabfc7bc 750Entries are now organized into groups rather than by file where they are found.
532ecd00 751
eabfc7bc 752=item *
532ecd00 753
eabfc7bc
RS
754Alphabetical sorting of entries is now handled by the POD generator to make
755entries easier to find when scanning.
756
757=back
338906ce 758
eabfc7bc 759=head3 L<perldata>
338906ce 760
e5998677 761=over 4
338906ce 762
eabfc7bc 763=item *
2f304be9 764
eabfc7bc
RS
765The syntax of single-character variable names has been brought
766up-to-date and more fully explained.
9749148e 767
7f9fef93 768=back
9749148e 769
eabfc7bc 770=head3 L<perlebcdic>
47cb8ddb 771
7f9fef93 772=over 4
47cb8ddb 773
eabfc7bc 774=item *
47cb8ddb 775
eabfc7bc
RS
776This document has been significantly updated in the light of recent
777improvements to EBCDIC support.
47cb8ddb 778
7f9fef93 779=back
47cb8ddb 780
eabfc7bc 781=head3 L<perlfunc>
be39acb2 782
eabfc7bc 783=over 4
be39acb2 784
eabfc7bc 785=item *
be39acb2 786
eabfc7bc 787Mention that C<study()> is currently a no-op.
be39acb2
SH
788
789=item *
790
eabfc7bc
RS
791Calling C<delete> or C<exists> on array values is now described as "strongly
792discouraged" rather than "deprecated".
be39acb2 793
eabfc7bc 794=item *
7f9fef93 795
eabfc7bc 796Improve documentation of C<< our >>.
be39acb2 797
eabfc7bc 798=item *
be39acb2 799
eabfc7bc
RS
800C<-l> now notes that it will return false if symlinks aren't supported by the
801file system.
be39acb2 802
eabfc7bc 803L<[perl #121523]|https://rt.perl.org/Ticket/Display.html?id=121523>
be39acb2
SH
804
805=item *
806
eabfc7bc
RS
807Note that C<exec LIST> and C<system LIST> may fall back to the shell on
808Win32. Only C<exec PROGRAM LIST> and C<system PROGRAM LIST> indirect object
809syntax will reliably avoid using the shell.
810
811This has also been noted in L<perlport>.
812
813L<[perl #122046]|https://rt.perl.org/Ticket/Display.html?id=122046>
be39acb2 814
7f9fef93 815=back
be39acb2 816
eabfc7bc
RS
817=head3 L<perlguts>
818
819=over 4
820
821=item *
822
823The OOK example has been updated to account for COW changes and a change in the
824storage of the offset.
825
826=item *
be39acb2 827
eabfc7bc 828Details on C level symbols and libperl.t added.
be39acb2 829
ce93e38b
KW
830=item *
831
832Information on Unicode handling has been added
833
834=item *
835
836Information on EBCDIC handling has been added
837
eabfc7bc
RS
838=back
839
840=head3 L<perlhacktips>
7f9fef93
SH
841
842=over 4
be39acb2
SH
843
844=item *
845
eabfc7bc
RS
846Documentation has been added illustrating the perils of assuming the contents
847of static memory pointed to by the return values of Perl wrappers for C library
848functions doesn't change.
849
850=item *
851
852Recommended replacements for tmpfile, atoi, strtol, and strtoul added.
853
854=item *
855
856Updated documentation for the C<test.valgrind> C<make> target.
857
858L<[perl #121431]|https://rt.perl.org/Ticket/Display.html?id=121431>
be39acb2 859
a9c3e753 860=back
ea13b07e 861
eabfc7bc 862=head3 L<perlmodstyle>
0d42058e 863
7f9fef93
SH
864=over 4
865
866=item *
2a7a05b4 867
eabfc7bc
RS
868Instead of pointing to the module list, we are now pointing to
869L<PrePAN|http://prepan.org/>.
2a7a05b4 870
7f9fef93
SH
871=back
872
eabfc7bc
RS
873=head3 L<perlpolicy>
874
875=over 4
876
877=item *
878
879We now have a code of conduct for the I<< p5p >> mailing list, as documented
880in L<< perlpolicy/STANDARDS OF CONDUCT >>.
2a7a05b4 881
eabfc7bc
RS
882=item *
883
884The conditions for marking an experimental feature as non-experimental are now
885set out.
886
887=back
888
889=head3 L<perlport>
890
891=over 4
892
893=item *
894
895Out-of-date VMS-specific information has been fixed/simplified.
896
ce93e38b
KW
897=item *
898
899Notes about EBCDIC have been added.
900
eabfc7bc
RS
901=back
902
903=head3 L<perlre>
904
905=over 4
906
907=item *
908
909The C</x> modifier has been clarified to note that comments cannot be continued
910onto the next line by escaping them.
911
912=back
913
914=head3 L<perlrebackslash>
915
916=over 4
917
918=item *
919
920Added documentation of C<\b{sb}>, C<\b{wb}>, C<\b{gcb}>, and C<\b{g}>.
921
922=back
923
924=head3 L<perlrecharclass>
925
926=over 4
927
928=item *
929
930Clarifications have been added to L<perlrecharclass/Character Ranges>
931to the effect that Perl guarantees that C<[A-Z]>, C<[a-z]>, C<[0-9]> and
932any subranges thereof in regular expression bracketed character classes
933are guaranteed to match exactly what a naive English speaker would
934expect them to match, even on platforms (such as EBCDIC) where special
935handling is required to accomplish this.
936
937=item *
938
939The documentation of Bracketed Character Classes has been expanded to cover the
940improvements in C<qr/[\N{named sequence}]/> (see under L</Selected Bug Fixes>).
941
942=back
943
944=head3 L<perlsec>
945
946=over 4
947
948=item *
949
950Comments added on algorithmic complexity and tied hashes.
951
952=back
953
954=head3 L<perlsyn>
955
956=over 4
957
958=item *
959
960An ambiguity in the documentation of the C<...> statement has been corrected.
961L<[perl #122661]|https://rt.perl.org/Ticket/Display.html?id=122661>
962
963=item *
964
965The empty conditional in C<< for >> and C<< while >> is now documented
966in L<< perlsyn >>.
967
968=back
969
970=head3 L<perlunicode>
971
972=over 4
973
974=item *
975
ce93e38b
KW
976This has had extensive revisions to bring it up-to-date with current
977Unicode support and to make it more readable.
eabfc7bc
RS
978
979=back
980
981=head3 L<perluniintro>
982
983=over 4
984
985=item *
986
987Advice for how to make sure your strings and regular expression patterns are
ce93e38b 988interpreted as Unicode has been updated.
eabfc7bc
RS
989
990=back
991
992=head3 L<perlvar>
993
994=over 4
995
996=item *
997
998Further clarify version number representations and usage.
999
1000=back
1001
1002=head3 L<perlvms>
1003
1004=over 4
1005
1006=item *
1007
1008Out-of-date and/or incorrect material has been removed.
1009
1010=item *
1011
1012Updated documentation on environment and shell interaction in VMS.
1013
1014=back
1015
1016=head3 L<perlxs>
1017
1018=over 4
1019
1020=item *
1021
1022Added a discussion of locale issues in XS code.
1023
1024=back
1025
1026=head1 Diagnostics
1027
1028The following additions or changes have been made to diagnostic output,
1029including warnings and fatal error messages. For the complete list of
1030diagnostic messages, see L<perldiag>.
1031
1032=head2 New Diagnostics
1033
1034=head3 New Errors
1035
1036=over 4
1037
1038=item *
1039
1040L<Bad symbol for scalar|perldiag/"Bad symbol for scalar">
1041
1042(P) An internal request asked to add a scalar entry to something that
1043wasn't a symbol table entry.
1044
1045=item *
1046
1047L<Can't use a hash as a reference|perldiag/"Can't use a hash as a reference">
1048
1049(F) You tried to use a hash as a reference, as in
1050C<< %foo->{"bar"} >> or C<< %$ref->{"hello"} >>. Versions of perl E<lt>= 5.6.1
1051used to allow this syntax, but shouldn't have.
1052
1053=item *
1054
1055L<Can't use an array as a reference|perldiag/"Can't use an array as a reference">
1056
1057(F) You tried to use an array as a reference, as in
1058C<< @foo->[23] >> or C<< @$ref->[99] >>. Versions of perl E<lt>= 5.6.1 used to
1059allow this syntax, but shouldn't have.
1060
1061=item *
1062
1063L<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()?)">
1064
4ec8e6f0 1065(F) C<defined()> is not useful on arrays because it
eabfc7bc 1066checks for an undefined I<scalar> value. If you want to see if the
4ec8e6f0 1067array is empty, just use S<C<if (@array) { # not empty }>> for example.
eabfc7bc
RS
1068
1069=item *
1070
1071L<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()?)">
1072
1073(F) C<defined()> is not usually right on hashes.
1074
4ec8e6f0 1075Although S<C<defined %hash>> is false on a plain not-yet-used hash, it
eabfc7bc 1076becomes true in several non-obvious circumstances, including iterators,
4ec8e6f0
KW
1077weak references, stash names, even remaining true after S<C<undef %hash>>.
1078These things make S<C<defined %hash>> fairly useless in practice, so it now
eabfc7bc
RS
1079generates a fatal error.
1080
1081If a check for non-empty is what you wanted then just put it in boolean
1082context (see L<perldata/Scalar values>):
1083
1084 if (%hash) {
1085 # not empty
1086 }
1087
4ec8e6f0 1088If you had S<C<defined %Foo::Bar::QUUX>> to check whether such a package
eabfc7bc
RS
1089variable exists then that's never really been reliable, and isn't
1090a good way to enquire about the features of a package, or whether
1091it's loaded, etc.
1092
1093=item *
1094
1095L<Cannot chr %f|perldiag/"Cannot chr %f">
1096
c21a1c59
RS
1097(F) You passed an invalid number (like an infinity or not-a-number) to
1098C<chr>.
1099
eabfc7bc
RS
1100=item *
1101
1102L<Cannot compress %f in pack|perldiag/"Cannot compress %f in pack">
1103
c21a1c59
RS
1104(F) You tried converting an infinity or not-a-number to an unsigned
1105character, which makes no sense.
1106
eabfc7bc
RS
1107=item *
1108
1109L<Cannot pack %f with '%c'|perldiag/"Cannot pack %f with '%c'">
1110
c21a1c59
RS
1111(F) You tried converting an infinity or not-a-number to a character,
1112which makes no sense.
1113
eabfc7bc
RS
1114=item *
1115
1116L<Cannot print %f with '%c'|perldiag/"Cannot printf %f with '%c'">
1117
4ec8e6f0
KW
1118(F) You tried printing an infinity or not-a-number as a character (C<%c>),
1119which makes no sense. Maybe you meant C<'%s'>, or just stringifying it?
c21a1c59 1120
eabfc7bc
RS
1121=item *
1122
1123L<charnames alias definitions may not contain a sequence of multiple spaces|perldiag/"charnames alias definitions may not contain a sequence of multiple spaces">
1124
1125(F) You defined a character name which had multiple space
1126characters in a row. Change them to single spaces. Usually these
1127names are defined in the C<:alias> import argument to C<use charnames>, but
1128they could be defined by a translator installed into C<$^H{charnames}>.
1129See L<charnames/CUSTOM ALIASES>.
1130
1131=item *
1132
1133L<charnames alias definitions may not contain trailing white-space|perldiag/"charnames alias definitions may not contain trailing white-space">
1134
1135(F) You defined a character name which ended in a space
1136character. Remove the trailing space(s). Usually these names are
1137defined in the C<:alias> import argument to C<use charnames>, but they
1138could be defined by a translator installed into C<$^H{charnames}>.
1139See L<charnames/CUSTOM ALIASES>.
1140
1141=item *
1142
1143L<:const is not permitted on named subroutines|perldiag/":const is not permitted on named subroutines">
1144
1145(F) The "const" attribute causes an anonymous subroutine to be run and
1146its value captured at the time that it is cloned. Names subroutines are
1147not cloned like this, so the attribute does not make sense on them.
1148
1149=item *
1150
1151L<Hexadecimal float: internal error|perldiag/"Hexadecimal float: internal error">
1152
1153(F) Something went horribly bad in hexadecimal float handling.
1154
1155=item *
1156
1157L<Hexadecimal float: unsupported long double format|perldiag/"Hexadecimal float: unsupported long double format">
1158
1159(F) You have configured Perl to use long doubles but
1160the internals of the long double format are unknown,
1161therefore the hexadecimal float output is impossible.
1162
1163=item *
1164
1165L<Illegal suidscript|perldiag/"Illegal suidscript">
1166
1167(F) The script run under suidperl was somehow illegal.
1168
1169=item *
1170
1171L<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/">
1172
1173(F) The two-character sequence C<"(?"> in
1174this context in a regular expression pattern should be an
1175indivisible token, with nothing intervening between the C<"(">
1176and the C<"?">, but you separated them.
1177
1178=item *
1179
1180L<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/">
1181
1182(F) The two-character sequence C<"(*"> in
1183this context in a regular expression pattern should be an
1184indivisible token, with nothing intervening between the C<"(">
1185and the C<"*">, but you separated them.
1186
1187=item *
1188
1189L<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/">
1190
1191(F) The pattern looks like a {min,max} quantifier, but the min or max could not
1192be parsed as a valid number - either it has leading zeroes, or it represents
1193too big a number to cope with. The S<<-- HERE> shows where in the regular
1194expression the problem was discovered. See L<perlre>.
1195
1196=back
1197
1198=head3 New Warnings
1199
1200=over 4
1201
1202=item *
1203
1204L<'%s' is an unknown bound type in regex|perldiag/"'%s' is an unknown bound type in regex; marked by <-- HERE in m/%s/">
1205
1206You used C<\b{...}> or C<\B{...}> and the C<...> is not known to
1207Perl. The current valid ones are given in
1208L<perlrebackslash/\b{}, \b, \B{}, \B>.
1209
1210=item *
1211
1212L<"%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>>
1213
1214(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1215
1216You specified a character that has the given plainer way of writing it,
1217and which is also portable to platforms running with different character
1218sets.
1219
1220=item *
1221
1222L<Argument "%s" treated as 0 in increment (++)|perldiag/"Argument "%s" treated
1223as 0 in increment (++)">
1224
1225(W numeric) The indicated string was fed as an argument to the C<++> operator
1226which expects either a number or a string matching C</^[a-zA-Z]*[0-9]*\z/>.
1227See L<perlop/Auto-increment and Auto-decrement> for details.
1228
1229=item *
1230
1231L<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/">
1232
1233(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1234
1235In a bracketed character class in a regular expression pattern, you
1236had a range which has exactly one end of it specified using C<\N{}>, and
1237the other end is specified using a non-portable mechanism. Perl treats
1238the range as a Unicode range, that is, all the characters in it are
1239considered to be the Unicode characters, and which may be different code
1240points on some platforms Perl runs on. For example, C<[\N{U+06}-\x08]>
1241is treated as if you had instead said C<[\N{U+06}-\N{U+08}]>, that is it
1242matches the characters whose code points in Unicode are 6, 7, and 8.
1243But that C<\x08> might indicate that you meant something different, so
1244the warning gets raised.
1245
1246=item *
1247
eabfc7bc
RS
1248L<:const is experimental|perldiag/":const is experimental">
1249
1250(S experimental::const_attr) The "const" attribute is experimental.
1251If you want to use the feature, disable the warning with C<no warnings
1252'experimental::const_attr'>, but know that in doing so you are taking
1253the risk that your code may break in a future Perl version.
1254
1255=item *
1256
1257L<gmtime(%f) failed|perldiag/"gmtime(%f) failed">
1258
1259(W overflow) You called C<gmtime> with a number that it could not handle:
1260too large, too small, or NaN. The returned value is C<undef>.
1261
1262=item *
1263
1264L<Hexadecimal float: exponent overflow|perldiag/"Hexadecimal float: exponent overflow">
1265
1266(W overflow) The hexadecimal floating point has larger exponent
1267than the floating point supports.
1268
1269=item *
1270
1271L<Hexadecimal float: exponent underflow|perldiag/"Hexadecimal float: exponent underflow">
1272
1273(W overflow) The hexadecimal floating point has smaller exponent
1274than the floating point supports.
1275
1276=item *
1277
1278L<Hexadecimal float: mantissa overflow|perldiag/"Hexadecimal float: mantissa overflow">
1279
1280(W overflow) The hexadecimal floating point literal had more bits in
1281the mantissa (the part between the 0x and the exponent, also known as
1282the fraction or the significand) than the floating point supports.
1283
1284=item *
1285
1286L<Hexadecimal float: precision loss|perldiag/"Hexadecimal float: precision loss">
1287
1288(W overflow) The hexadecimal floating point had internally more
1289digits than could be output. This can be caused by unsupported
1290long double formats, or by 64-bit integers not being available
1291(needed to retrieve the digits under some configurations).
1292
eabfc7bc
RS
1293=item *
1294
1295L<localtime(%f) failed|perldiag/"localtime(%f) failed">
1296
1297(W overflow) You called C<localtime> with a number that it could not handle:
1298too large, too small, or NaN. The returned value is C<undef>.
1299
1300=item *
1301
1302L<Negative repeat count does nothing|perldiag/"Negative repeat count does nothing">
1303
1304(W numeric) You tried to execute the
1305L<C<x>|perlop/Multiplicative Operators> repetition operator fewer than 0
1306times, which doesn't make sense.
1307
1308=item *
1309
1310L<NO-BREAK SPACE in a charnames alias definition is deprecated|perldiag/"NO-BREAK SPACE in a charnames alias definition is deprecated">
1311
1312(D deprecated) You defined a character name which contained a no-break
1313space character. Change it to a regular space. Usually these names are
1314defined in the C<:alias> import argument to C<use charnames>, but they
1315could be defined by a translator installed into C<$^H{charnames}>. See
1316L<charnames/CUSTOM ALIASES>.
1317
1318=item *
1319
1320L<Non-finite repeat count does nothing|perldiag/"Non-finite repeat count does nothing">
1321
1322(W numeric) You tried to execute the
1323L<C<x>|perlop/Multiplicative Operators> repetition operator C<Inf> (or
1324C<-Inf>) or C<NaN> times, which doesn't make sense.
1325
1326=item *
1327
1328L<PerlIO layer ':win32' is experimental|perldiag/"PerlIO layer ':win32' is experimental">
1329
1330(S experimental::win32_perlio) The C<:win32> PerlIO layer is
1331experimental. If you want to take the risk of using this layer,
1332simply disable this warning:
1333
1334 no warnings "experimental::win32_perlio";
1335
1336=item *
1337
1338L<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>">
1339
1340(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1341
1342Stricter rules help to find typos and other errors. Perhaps you didn't
1343even intend a range here, if the C<"-"> was meant to be some other
1344character, or should have been escaped (like C<"\-">). If you did
1345intend a range, the one that was used is not portable between ASCII and
1346EBCDIC platforms, and doesn't have an obvious meaning to a casual
1347reader.
1348
1349 [3-7] # OK; Obvious and portable
1350 [d-g] # OK; Obvious and portable
1351 [A-Y] # OK; Obvious and portable
1352 [A-z] # WRONG; Not portable; not clear what is meant
1353 [a-Z] # WRONG; Not portable; not clear what is meant
1354 [%-.] # WRONG; Not portable; not clear what is meant
1355 [\x41-Z] # WRONG; Not portable; not obvious to non-geek
1356
1357(You can force portability by specifying a Unicode range, which means that
1358the endpoints are specified by
1359L<C<\N{...}>|perlrecharclass/Character Ranges>, but the meaning may
1360still not be obvious.)
1361The stricter rules require that ranges that start or stop with an ASCII
93780ae6 1362character that is not a control have all their endpoints be a literal
eabfc7bc
RS
1363character, and not some escape sequence (like C<"\x41">), and the ranges
1364must be all digits, or all uppercase letters, or all lowercase letters.
1365
1366=item *
1367
1368L<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/">
1369
1370(W regexp) (only under C<S<use re 'strict'>> or within C<(?[...])>)
1371
1372Stricter rules help to find typos and other errors. You included a
1373range, and at least one of the end points is a decimal digit. Under the
1374stricter rules, when this happens, both end points should be digits in
1375the same group of 10 consecutive digits.
1376
1377=item *
1378
1379L<Redundant argument in %s|perldiag/Redundant argument in %s>
1380
1381(W redundant) You called a function with more arguments than other
1382arguments you supplied indicated would be needed. Currently only
1383emitted when a printf-type format required fewer arguments than were
1384supplied, but might be used in the future for e.g. L<perlfunc/pack>.
1385
a75e6a3a
SH
1386The warnings category C<< redundant >> is new. See also
1387L<[perl #121025]|https://rt.perl.org/Ticket/Display.html?id=121025>.
eabfc7bc
RS
1388
1389=item *
1390
1391L<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">
1392
1393You are matching a regular expression using locale rules,
1394and a Unicode boundary is being matched, but the locale is not a Unicode
1395one. This doesn't make sense. Perl will continue, assuming a Unicode
1396(UTF-8) locale, but the results could well be wrong except if the locale
1397happens to be ISO-8859-1 (Latin1) where this message is spurious and can
1398be ignored.
1399
1400=item *
1401
1402L<< 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>" >>
1403
1404You used a Unicode boundary (C<\b{...}> or C<\B{...}>) in a
1405portion of a regular expression where the character set modifiers C</a>
1406or C</aa> are in effect. These two modifiers indicate an ASCII
1407interpretation, and this doesn't make sense for a Unicode definition.
1408The generated regular expression will compile so that the boundary uses
1409all of Unicode. No other portion of the regular expression is affected.
1410
1411=item *
1412
1413L<The bitwise feature is experimental|perldiag/"The bitwise feature is experimental">
1414
1415This warning is emitted if you use bitwise
1416operators (C<& | ^ ~ &. |. ^. ~.>) with the "bitwise" feature enabled.
1417Simply suppress the warning if you want to use the feature, but know
1418that in doing so you are taking the risk of using an experimental
1419feature which may change or be removed in a future Perl version:
1420
1421 no warnings "experimental::bitwise";
1422 use feature "bitwise";
1423 $x |.= $y;
1424
1425=item *
1426
1427L<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/">
1428
1429(D deprecated, regexp) You used a literal C<"{"> character in a regular
1430expression pattern. You should change to use C<"\{"> instead, because a future
1431version of Perl (tentatively v5.26) will consider this to be a syntax error. If
1432the pattern delimiters are also braces, any matching right brace
1433(C<"}">) should also be escaped to avoid confusing the parser, for
1434example,
1435
1436 qr{abc\{def\}ghi}
1437
1438=item *
1439
1440L<Use of literal non-graphic characters in variable names is deprecated|perldiag/"Use of literal non-graphic characters in variable names is deprecated">
1441
1442=item *
1443
1444L<Useless use of attribute "const"|perldiag/Useless use of attribute "const">
1445
1446(W misc) The "const" attribute has no effect except
1447on anonymous closure prototypes. You applied it to
1448a subroutine via L<attributes.pm|attributes>. This is only useful
1449inside an attribute handler for an anonymous subroutine.
1450
1451=item *
1452
1453L<E<quot>use re 'strict'E<quot> is experimental|perldiag/"use re 'strict'" is experimental>
1454
1455(S experimental::re_strict) The things that are different when a regular
1456expression pattern is compiled under C<'strict'> are subject to change
1457in future Perl releases in incompatible ways. This means that a pattern
1458that compiles today may not in a future Perl release. This warning is
1459to alert you to that risk.
1460
1461=item *
1462
caa16dbd
TC
1463L<Warning: unable to close filehandle properly: %s|perldiag/"Warning: unable to close filehandle properly: %s">
1464
eabfc7bc
RS
1465L<Warning: unable to close filehandle %s properly: %s|perldiag/"Warning: unable to close filehandle %s properly: %s">
1466
caa16dbd
TC
1467(S io) An error occurred when Perl implicitly closed a filehandle. This
1468usually indicates your file system ran out of disk space.
1469
eabfc7bc
RS
1470=item *
1471
1472L<Wide character (U+%X) in %s|perldiag/"Wide character (U+%X) in %s">
1473
1474(W locale) While in a single-byte locale (I<i.e.>, a non-UTF-8
1475one), a multi-byte character was encountered. Perl considers this
1476character to be the specified Unicode code point. Combining non-UTF8
1477locales and Unicode is dangerous. Almost certainly some characters
1478will have two different representations. For example, in the ISO 8859-7
1479(Greek) locale, the code point 0xC3 represents a Capital Gamma. But so
1480also does 0x393. This will make string comparisons unreliable.
1481
1482You likely need to figure out how this multi-byte character got mixed up
1483with your single-byte locale (or perhaps you thought you had a UTF-8
1484locale, but Perl disagrees).
1485
1486=item *
1487
1488The following two warnings for C<tr///> used to be skipped if the
1489transliteration contained wide characters, but now they occur regardless of
1490whether there are wide characters or not:
1491
1492L<Useless use of E<sol>d modifier in transliteration operator|perldiag/"Useless use of /d modifier in transliteration operator">
1493
1494L<Replacement list is longer than search list|perldiag/Replacement list is longer than search list>
1495
1496=item *
1497
1498A new C<locale> warning category has been created, with the following warning
1499messages currently in it:
1500
1501=over 4
1502
1503=item *
1504
1505L<Locale '%s' may not work well.%s|perldiag/Locale '%s' may not work well.%s>
1506
1507=item *
1508
1509L<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".>
1510
1511=back
1512
1513=back
1514
1515=head2 Changes to Existing Diagnostics
1516
1517=over 4
1518
1519=item *
1520
1521<> should be quotes
1522
1523This warning has been changed to
1524L<< <> at require-statement should be quotes|perldiag/"<> at require-statement should be quotes" >>
1525to make the issue more identifiable.
1526
1527=item *
1528
1529L<Argument "%s" isn't numeric%s|perldiag/"Argument "%s" isn't numeric%s">
1530now adds the following note:
1531
4ec8e6f0 1532 Note that for the Inf and NaN (infinity and not-a-number) the
77c2376a
KW
1533 definition of "numeric" is somewhat unusual: the strings themselves
1534 (like "Inf") are considered numeric, and anything following them is
1535 considered non-numeric.
eabfc7bc
RS
1536
1537=item *
1538
1539L<Global symbol "%s" requires explicit package name|perldiag/"Global symbol "%s" requires explicit package name (did you forget to declare "my %s"?)">
1540
1541This message has had '(did you forget to declare "my %s"?)' appended to it, to
1542make it more helpful to new Perl programmers.
1543L<[perl #121638]|https://rt.perl.org/Ticket/Display.html?id=121638>
1544
1545=item *
1546
1547'"my" variable &foo::bar can't be in a package' has been reworded to say
1548'subroutine' instead of 'variable'.
1549
1550=item *
1551
022a330c 1552L<\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
1553
1554This message has had 'character class' changed to 'inverted character class or
1555as a range end-point is' to reflect improvements in C<qr/[\N{named sequence}]/>
1556(see under L</Selected Bug Fixes>).
1557
1558=item *
1559
1560L<panic: frexp|perldiag/"panic: frexp: %f">
1561
4ec8e6f0 1562This message has had ': C<%f>' appended to it, to show what the offending floating
eabfc7bc
RS
1563point number is.
1564
1565=item *
1566
1567B<Possible precedence problem on bitwise %c operator> reworded as
1568L<Possible precedence problem on bitwise %s operator|perldiag/"Possible precedence problem on bitwise %s operator">.
1569
1570=item *
1571
1572C<require> with no argument or undef used to warn about a Null filename; now
1573it dies with C<Missing or undefined argument to require>.
1574
1575=item *
1576
1577L<Unsuccessful %s on filename containing newline|perldiag/"Unsuccessful %s on filename containing newline">
1578
1579This warning is now only produced when the newline is at the end of
1580the filename.
1581
1582=item *
1583
4ec8e6f0 1584"Variable C<%s> will not stay shared" has been changed to say "Subroutine"
eabfc7bc
RS
1585when it is actually a lexical sub that will not stay shared.
1586
1587=item *
1588
1589L<Variable length lookbehind not implemented in regex mE<sol>%sE<sol>|perldiag/"Variable length lookbehind not implemented in regex m/%s/">
1590
1591Information about Unicode behaviour has been added.
1592
1593=back
1594
1595=head2 Diagnostic Removals
1596
1597=over
1598
1599=item *
1600
1601"Ambiguous use of -foo resolved as -&foo()"
1602
1603There is actually no ambiguity here, and this impedes the use of negated
1604constants; e.g., C<-Inf>.
1605
1606=item *
1607
1608"Constant is not a FOO reference"
1609
1610Compile-time checking of constant dereferencing (e.g., C<< my_constant->() >>)
1611has been removed, since it was not taking overloading into account.
1612L<[perl #69456]|https://rt.perl.org/Ticket/Display.html?id=69456>
1613L<[perl #122607]|https://rt.perl.org/Ticket/Display.html?id=122607>
1614
1615=back
1616
1617=head1 Utility Changes
1618
1619=head2 F<x2p/>
1620
1621=over 4
1622
1623=item *
1624
1625The F<x2p/> directory has been removed from the Perl core.
1626
1627This removes find2perl, s2p and a2p. They have all been released to CPAN as
1628separate distributions (App::find2perl, App::s2p, App::a2p).
1629
1630=back
1631
1632=head2 L<h2ph>
1633
1634=over 4
1635
1636=item *
1637
1638F<h2ph> now handles hexadecimal constants in the compiler's predefined
a75e6a3a
SH
1639macro definitions, as visible in C<$Config{cppsymbols}>.
1640L<[perl #123784]|https://rt.perl.org/Ticket/Display.html?id=123784>.
eabfc7bc
RS
1641
1642=back
1643
1644=head2 L<encguess>
1645
1646=over 4
1647
1648=item *
1649
f1c9eac6 1650No longer depends on non-core modules.
eabfc7bc
RS
1651
1652=back
1653
1654=head1 Configuration and Compilation
1655
1656=over 4
1657
1658=item *
1659
1660F<Configure> now checks for F<lrintl>, F<lroundl>, F<llrintl>, and F<llroundl>.
1661
1662=item *
1663
a75e6a3a
SH
1664F<Configure> with C<-Dmksymlinks> should now be faster.
1665L<[perl #122002]|https://rt.perl.org/Ticket/Display.html?id=122002>.
eabfc7bc
RS
1666
1667=item *
1668
1669pthreads and lcl will be linked by default if present. This allows XS modules
1670that require threading to work on non-threaded perls. Note that you must still
1671pass C<-Dusethreads> if you want a threaded perl.
1672
1673=item *
1674
1675For long doubles (to get more precision and range for floating point numbers)
1676one can now use the GCC quadmath library which implements the quadruple
f1c9eac6
DM
1677precision floating point numbers on x86 and IA-64 platforms. See
1678F<INSTALL> for details.
eabfc7bc
RS
1679
1680=item *
1681
1682MurmurHash64A and MurmurHash64B can now be configured as the internal hash
1683function.
1684
1685=item *
1686
1687C<make test.valgrind> now supports parallel testing.
1688
1689For example:
1690
1691 TEST_JOBS=9 make test.valgrind
1692
1693See L<perlhacktips/valgrind> for more information.
1694
1695L<[perl #121431]|https://rt.perl.org/Ticket/Display.html?id=121431>
1696
1697=item *
1698
1699The MAD (Misc Attribute Decoration) build option has been removed
1700
1701This was an unmaintained attempt at preserving
1702the Perl parse tree more faithfully so that automatic conversion of
1703Perl 5 to Perl 6 would have been easier.
1704
1705This build-time configuration option had been unmaintained for years,
1706and had probably seriously diverged on both Perl 5 and Perl 6 sides.
1707
1708=item *
1709
1710A new compilation flag, C<< -DPERL_OP_PARENT >> is available. For details,
1711see the discussion below at L<< /Internal Changes >>.
1712
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
7f9fef93 3251=head1 Acknowledgements
2a7a05b4 3252
7f9fef93 3253XXX Generate this with:
2a7a05b4 3254
eabfc7bc 3255 perl Porting/acknowledgements.pl v5.20.0..HEAD
f5b73711 3256
44691e6f
AB
3257=head1 Reporting Bugs
3258
e08634c5
SH
3259If you find what you think is a bug, you might check the articles recently
3260posted to the comp.lang.perl.misc newsgroup and the perl bug database at
e5998677
SH
3261https://rt.perl.org/ . There may also be information at
3262http://www.perl.org/ , the Perl Home Page.
44691e6f 3263
e08634c5
SH
3264If you believe you have an unreported bug, please run the L<perlbug> program
3265included with your release. Be sure to trim your bug down to a tiny but
3266sufficient test case. Your bug report, along with the output of C<perl -V>,
3267will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
44691e6f
AB
3268
3269If the bug you are reporting has security implications, which make it
e08634c5
SH
3270inappropriate to send to a publicly archived mailing list, then please send it
3271to perl5-security-report@perl.org. This points to a closed subscription
3272unarchived mailing list, which includes all the core committers, who will be
3273able to help assess the impact of issues, figure out a resolution, and help
f9001595 3274co-ordinate the release of patches to mitigate or fix the problem across all
e08634c5
SH
3275platforms on which Perl is supported. Please only use this address for
3276security issues in the Perl core, not for modules independently distributed on
3277CPAN.
44691e6f
AB
3278
3279=head1 SEE ALSO
3280
e08634c5
SH
3281The F<Changes> file for an explanation of how to view exhaustive details on
3282what changed.
44691e6f
AB
3283
3284The F<INSTALL> file for how to build Perl.
3285
3286The F<README> file for general stuff.
3287
3288The F<Artistic> and F<Copying> files for copyright information.
3289
3290=cut