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1=encoding utf8
2
3=head1 NAME
4
4026b091 5perldelta - what is new for perl v5.28.0
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7=head1 DESCRIPTION
8
9This document describes differences between the 5.26.0 release and the 5.28.0
10release.
11
12If you are upgrading from an earlier release such as 5.24.0, first read
7edbd7f0 13L<perl5260delta>, which describes differences between 5.24.0 and 5.26.0.
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14
15=head1 Core Enhancements
16
17=head2 Unicode 10.0 is supported
18
19A list of changes is at
20L<http://www.unicode.org/versions/Unicode10.0.0>.
21
604776f7 22=head2 L<C<delete>|perlfunc/delete EXPR> on key/value hash slices
4026b091 23
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24L<C<delete>|perlfunc/delete EXPR> can now be used on
25L<keyE<sol>value hash slices|perldata/KeyE<sol>Value Hash Slices>,
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26returning the keys along with the deleted values.
27L<[perl #131328]|https://rt.perl.org/Ticket/Display.html?id=131328>
28
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29=head2 Experimentally, there are now alphabetic synonyms for some regular expression assertions
30
31If you find it difficult to remember how to write certain of the pattern
32assertions, there are now alphabetic synonyms.
33
34 CURRENT NEW SYNONYMS
35 ------ ------------
36 (?=...) (*pla:...) or (*positive_lookahead:...)
37 (?!...) (*nla:...) or (*negative_lookahead:...)
38 (?<=...) (*plb:...) or (*positive_lookbehind:...)
39 (?<!...) (*nlb:...) or (*negative_lookbehind:...)
40 (?>...) (*atomic:...)
41
42These are considered experimental, so using any of these will raise
43(unless turned off) a warning in the C<experimental::alpha_assertions>
44category.
45
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46=head2 Mixed Unicode scripts are now detectable
47
48A mixture of scripts, such as Cyrillic and Latin, in a string is often
49the sign of a spoofing attack. A new regular expression construct
50now allows for easy detection of these. For example, you can say
51
52 qr/(*script_run: \d+ \b )/x
53
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54And the digits matched will all be from the same set of 10. You won't
55get a look-alike digit from a different script that has a different
56value than what it appears to be.
57
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58Or:
59
60 qr/(*sr: \b \w+ \b )/x
61
62makes sure that all the characters come from the same script.
63
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64You can also combine script runs with C<(?E<gt>...)> (or
65C<*atomic:...)>).
66
67Instead of writing:
68
69 (*sr:(?<...))
70
71you can now run:
72
73 (*asr:...)
74 # or
75 (*atomic_script_run:...)
76
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77This is considered experimental, so using it will raise (unless turned
78off) a warning in the C<experimental::script_run> category.
4026b091 79
75a718b3 80See L<perlre/Script Runs>.
4026b091 81
8af2daae 82=head2 In-place editing with C<perl -i> is now safer
4026b091 83
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84Previously in-place editing (C<perl -i>) would delete or rename the
85input file as soon as you started working on a new file.
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86
87Without backups this would result in loss of data if there was an
88error, such as a full disk, when writing to the output file.
89
90This has changed so that the input file isn't replaced until the
91output file has been completely written and successfully closed.
92
93This works by creating a work file in the same directory, which is
94renamed over the input file once the output file is complete.
95
96Incompatibilities:
97
98=over
99
100=item *
101
102Since this renaming needs to only happen once, if you create a thread
103or child process, that renaming will only happen in the original
104thread or process.
105
106=item *
107
108If you change directories while processing a file, and your operating
109system doesn't provide the C<unlinkat()>, C<renameat()> and C<fchmodat()>
110functions, the final rename step may fail.
111
112=back
113
114L<[perl #127663]|https://rt.perl.org/Public/Bug/Display.html?id=127663>
115
116=head2 Initialisation of aggregate state variables
117
118A persistent lexical array or hash variable can now be initialized,
119by an expression such as C<state @a = qw(x y z)>. Initialization of a
120list of persistent lexical variables is still not possible.
121
122=head2 Full-size inode numbers
123
124On platforms where inode numbers are of a type larger than perl's native
125integer numerical types, L<stat|perlfunc/stat> will preserve the full
126content of large inode numbers by returning them in the form of strings of
127decimal digits. Exact comparison of inode numbers can thus be achieved by
128comparing with C<eq> rather than C<==>. Comparison with C<==>, and other
129numerical operations (which are usually meaningless on inode numbers),
130work as well as they did before, which is to say they fall back to
131floating point, and ultimately operate on a fairly useless rounded inode
132number if the real inode number is too big for the floating point format.
133
75a718b3 134=head2 The C<sprintf> C<%j> format size modifier is now available with pre-C99 compilers
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135
136The actual size used depends on the platform, so remains unportable.
137
138=head2 Close-on-exec flag set atomically
139
140When opening a file descriptor, perl now generally opens it with its
141close-on-exec flag already set, on platforms that support doing so.
142This improves thread safety, because it means that an C<exec> initiated
143by one thread can no longer cause a file descriptor in the process
144of being opened by another thread to be accidentally passed to the
145executed program.
146
147Additionally, perl now sets the close-on-exec flag more reliably, whether
148it does so atomically or not. Most file descriptors were getting the
149flag set, but some were being missed.
150
151=head2 String- and number-specific bitwise ops are no longer experimental
152
153The new string-specific (C<&. |. ^. ~.>) and number-specific (C<& | ^ ~>)
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154bitwise operators introduced in Perl 5.22 that are available within the
155scope of C<use feature 'bitwise'> are no longer experimental.
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156Because the number-specific ops are spelled the same way as the existing
157operators that choose their behaviour based on their operands, these
158operators must still be enabled via the "bitwise" feature, in either of
159these two ways:
160
161 use feature "bitwise";
162
163 use v5.28; # "bitwise" now included
164
165They are also now enabled by the B<-E> command-line switch.
166
167The "bitwise" feature no longer emits a warning. Existing code that
168disables the "experimental::bitwise" warning category that the feature
169previously used will continue to work.
170
171One caveat that module authors ought to be aware of is that the numeric
172operators now pass a fifth TRUE argument to overload methods. Any methods
173that check the number of operands may croak if they do not expect so many.
174XS authors in particular should be aware that this:
175
176 SV *
177 bitop_handler (lobj, robj, swap)
178
179may need to be changed to this:
180
181 SV *
182 bitop_handler (lobj, robj, swap, ...)
94fc6237 183
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184=head2 Locales are now thread-safe on systems that support them
185
186These systems include Windows starting with Visual Studio 2005, and in
187POSIX 2008 systems.
188
94fc6237 189The implication is that you are now free to use locales and change them
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190in a threaded environment. Your changes affect only your thread.
191See L<perllocale/Multi-threaded operation>
192
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193=head2 New read-only predefined variable C<${^SAFE_LOCALES}>
194
195This variable is 1 if the Perl interpreter is operating in an
196environment where it is safe to use and change locales (see
197L<perllocale>.) This variable is true when the perl is
198unthreaded, or compiled in a platform that supports thread-safe locale
199operation (see previous item).
200
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201=head1 Security
202
203=head2 [CVE-2017-12837] Heap buffer overflow in regular expression compiler
204
205Compiling certain regular expression patterns with the case-insensitive
206modifier could cause a heap buffer overflow and crash perl. This has now been
207fixed.
208L<[perl #131582]|https://rt.perl.org/Public/Bug/Display.html?id=131582>
209
210=head2 [CVE-2017-12883] Buffer over-read in regular expression parser
211
212For certain types of syntax error in a regular expression pattern, the error
213message could either contain the contents of a random, possibly large, chunk of
214memory, or could crash perl. This has now been fixed.
215L<[perl #131598]|https://rt.perl.org/Public/Bug/Display.html?id=131598>
216
217=head2 [CVE-2017-12814] C<$ENV{$key}> stack buffer overflow on Windows
218
219A possible stack buffer overflow in the C<%ENV> code on Windows has been fixed
220by removing the buffer completely since it was superfluous anyway.
221L<[perl #131665]|https://rt.perl.org/Public/Bug/Display.html?id=131665>
222
223=head2 Default Hash Function Change
224
225Perl 5.28.0 retires various older hash functions which are not viewed as
226sufficiently secure for use in Perl. We now support four general purpose
227hash functions, Siphash (2-4 and 1-3 variants), and Zaphod32, and StadtX
228hash. In addition we support SBOX32 (a form of tabular hashing) for hashing
229short strings, in conjunction with any of the other hash functions provided.
230
231By default Perl is configured to support SBOX hashing of strings up to 24
232characters, in conjunction with StadtX hashing on 64 bit builds, and
233Zaphod32 hashing for 32 bit builds.
234
235You may control these settings with the following options to Configure:
236
237 -DPERL_HASH_FUNC_SIPHASH
238 -DPERL_HASH_FUNC_SIPHASH13
239 -DPERL_HASH_FUNC_STADTX
240 -DPERL_HASH_FUNC_ZAPHOD32
241
242To disable SBOX hashing you can use
243
244 -DPERL_HASH_USE_SBOX32_ALSO=0
245
246And to set the maximum length to use SBOX32 hashing on with:
247
248 -DSBOX32_MAX_LEN=16
249
250The maximum length allowed is 256. There probably isn't much point
251in setting it higher than the default.
252
253=head1 Incompatible Changes
254
255=head2 Subroutine attribute and signature order
256
257The experimental subroutine signatures feature has been changed so that
258subroutine attributes must now come before the signature rather than
259after. This is because attributes like C<:lvalue> can affect the
260compilation of code within the signature, for example:
261
262 sub f :lvalue ($a = do { $x = "abc"; return substr($x,0,1)}) { ...}
263
264Note that this the second time they have been flipped:
265
266 sub f :lvalue ($a, $b) { ... }; # 5.20; 5.28 onwards
267 sub f ($a, $b) :lvalue { ... }; # 5.22 - 5.26
268
269=head2 Comma-less variable lists in formats are no longer allowed
270
271Omitting the commas between variables passed to formats is no longer
272allowed. This has been deprecated since Perl 5.000.
273
274=head2 The C<:locked> and C<:unique> attributes have been removed
275
276These have been no-ops and deprecated since Perl 5.12 and 5.10,
277respectively.
278
d778388f 279=head2 C<\N{}> with nothing between the braces is now illegal
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280
281This has been deprecated since Perl 5.24.
282
283=head2 Opening the same symbol as both a file and directory handle is no longer allowed
284
285Using C<open()> and C<opendir()> to associate both a filehandle and a dirhandle
286to the same symbol (glob or scalar) has been deprecated since Perl 5.10.
287
288=head2 Use of bare C<< << >> to mean C<< <<"" >> is no longer allowed
289
290Use of a bare terminator has been deprecated since Perl 5.000.
291
292=head2 Setting $/ to a reference to a non-positive integer no longer allowed
293
294This used to work like setting it to C<undef>, but has been deprecated
295since Perl 5.20.
296
d778388f 297=head2 Unicode code points with values exceeding C<IV_MAX> are now fatal
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298
299This was deprecated since Perl 5.24.
300
d778388f 301=head2 The C<B::OP::terse> method has been removed
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302
303Use C<B::Concise::b_terse> instead.
304
d778388f 305=head2 Use of inherited AUTOLOAD for non-methods is no longer allowed
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306
307This was deprecated in Perl 5.004.
308
75a718b3 309=head2 Use of strings with code points over 0xFF is not allowed for bitwise string operators
4026b091 310
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311Code points over C<0xFF> do not make sense for bitwise operators and such
312an operation will now croak, except for a few remaining cases. See
313L<perldeprecation>.
4026b091 314
94fc6237 315This was deprecated in Perl 5.24.
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316
317=head2 Setting C<${^ENCODING}> to a defined value is now illegal
318
319This has been deprecated since Perl 5.22 and a no-op since Perl 5.26.
320
321=head2 Backslash no longer escapes colon in PATH for the C<-S> switch
322
323Previously the C<-S> switch incorrectly treated backslash ("\") as an
324escape for colon when traversing the C<PATH> environment variable.
ec30d9c4 325L<[perl #129183]|https://rt.perl.org/Ticket/Display.html?id=129183>
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326
327=head2 the -DH (DEBUG_H) misfeature has been removed
328
329On a perl built with debugging support, the C<H> flag to the C<-D>
330debugging option has been removed. This was supposed to dump hash values,
331but has been broken for many years.
332
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333=head2 Yada-yada is now strictly a statement
334
335By the time of its initial stable release in Perl 5.12, the C<...>
336(yada-yada) operator was explicitly intended to serve as a statement,
337not an expression. However, the original implementation was confused
338on this point, leading to inconsistent parsing. The operator was
339accidentally accepted in a few situations where it did not serve as a
340complete statement, such as
341
342 ... . "foo";
343 ... if $a < $b;
344
345The parsing has now been made consistent, permitting yada-yada only as
346a statement. Affected code can use C<do{...}> to put a yada-yada into
347an arbitrary expression context.
348
349=head2 Sort algorithm can no longer be specified
350
351Since Perl 5.8, the L<sort> pragma has had subpragmata C<_mergesort>,
352C<_quicksort>, and C<_qsort> that can be used to specify which algorithm
353perl should use to implement the L<sort|perlfunc/sort> builtin.
354This was always considered a dubious feature that might not last,
355hence the underscore spellings, and they were documented as not being
356portable beyond Perl 5.8. These subpragmata have now been deleted,
357and any attempt to use them is an error. The L<sort> pragma otherwise
358remains, and the algorithm-neutral C<stable> subpragma can be used to
359control sorting behaviour.
ec30d9c4 360L<[perl #119635]|https://rt.perl.org/Ticket/Display.html?id=119635>
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361
362=head2 Over-radix digits in floating point literals
363
364Octal and binary floating point literals used to permit any hexadecimal
365digit to appear after the radix point. The digits are now restricted
366to those appropriate for the radix, as digits before the radix point
367always were.
368
369=head2 Return type of C<unpackstring()>
370
371The return types of the C API functions C<unpackstring()> and
372C<unpack_str()> have changed from C<I32> to C<SSize_t>, in order to
373accommodate datasets of more than two billion items.
374
375=head1 Deprecations
376
d778388f 377=head2 Use of L<C<vec>|perlfunc/vec EXPR,OFFSET,BITS> on strings with code points above 0xFF is deprecated
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379Such strings are represented internally in UTF-8, and C<vec> is a
380bit-oriented operation that will likely give unexpected results on those
381strings.
4026b091 382
94fc6237 383=head2 Some uses of unescaped C<"{"> in regexes are no longer fatal
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384
385Perl 5.26.0 fatalized some uses of an unescaped left brace, but an
386exception was made at the last minute, specifically crafted to be a
94fc6237 387minimal change to allow GNU Autoconf to work. That tool is heavily
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388depended upon, and continues to use the deprecated usage. Its use of an
389unescaped left brace is one where we have no intention of repurposing
390C<"{"> to be something other than itself.
391
392That exception is now generalized to include various other such cases
393where the C<"{"> will not be repurposed.
394
395Note that these uses continue to raise a deprecation message.
396
0ba4cd08 397=head2 Use of unescaped C<"{"> immediately after a C<"("> in regular expression patterns is deprecated
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398
399Using unescaped left braces is officially deprecated everywhere, but it
400is not enforced in contexts where their use does not interfere with
401expected extensions to the language. A deprecation is added in this
402release when the brace appears immediately after an opening parenthesis.
403Before this, even if the brace was part of a legal quantifier, it was
404not interpreted as such, but as the literal characters, unlike other
405quantifiers that follow a C<"("> which are considered errors. Now,
406their use will raise a deprecation message, unless turned off.
407
408=head2 Assignment to C<$[> will be fatal in Perl 5.30
409
410Assigning a non-zero value to L<C<$[>|perlvar/$[> has been deprecated
411since Perl 5.12, but was never given a deadline for removal. This has
412now been scheduled for Perl 5.30.
413
414=head2 hostname() won't accept arguments in Perl 5.32
415
416Passing arguments to C<Sys::Hostname::hostname()> was already deprecated,
417but didn't have a removal date. This has now been scheduled for Perl
ec30d9c4 4185.32. L<[perl #124349]|https://rt.perl.org/Ticket/Display.html?id=124349>
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419
420=head2 Module removals
421
422The following modules will be removed from the core distribution in a
423future release, and will at that time need to be installed from CPAN.
424Distributions on CPAN which require these modules will need to list them as
425prerequisites.
426
427The core versions of these modules will now issue C<"deprecated">-category
428warnings to alert you to this fact. To silence these deprecation warnings,
429install the modules in question from CPAN.
430
431Note that these are (with rare exceptions) fine modules that you are encouraged
432to continue to use. Their disinclusion from core primarily hinges on their
433necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
434not usually on concerns over their design.
435
436=over
437
438=item B::Debug
439
440=item L<Locale::Codes> and its associated Country, Currency and Language modules
441
442=back
443
444=head1 Performance Enhancements
445
446=over 4
447
448=item *
449
450The start up overhead for creating regular expression patterns with
451Unicode properties (C<\p{...}>) has been greatly reduced in most cases.
452
453=item *
454
455Many string concatenation expressions are now considerably faster, due
456to the introduction internally of a C<multiconcat> opcode which combines
457multiple concatenations, and optionally a C<=> or C<.=>, into a single
458action. For example, apart from retrieving C<$s>, C<$a> and C<$b>, this
459whole expression is now handled as a single op:
460
461 $s .= "a=$a b=$b\n"
462
463As a special case, if the LHS of an assignment is a lexical variable or
464C<my $s>, the op itself handles retrieving the lexical variable, which
465is faster.
466
467In general, the more the expression includes a mix of constant strings and
468variable expressions, the longer the expression, and the more it mixes
469together non-utf8 and utf8 strings, the more marked the performance
470improvement. For example on a C<x86_64> system, this code has been
471benchmarked running four times faster:
472
473 my $s;
474 my $a = "ab\x{100}cde";
475 my $b = "fghij";
476 my $c = "\x{101}klmn";
477
478 for my $i (1..10_000_000) {
479 $s = "\x{100}wxyz";
480 $s .= "foo=$a bar=$b baz=$c";
481 }
482
483In addition, C<sprintf> expressions which have a constant format
484containing only C<%s> and C<%%> format elements, and which have a fixed
485number of arguments, are now also optimised into a C<multiconcat> op.
486
487=item *
488
489The C<ref()> builtin is now much faster in boolean context, since it no
490longer bothers to construct a temporary string like C<Foo=ARRAY(0x134af48)>.
491
492=item *
493
494C<keys()> in void and scalar contexts is now more efficient.
495
496=item *
497
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498The common idiom of comparing the result of index() with -1 is now
499specifically optimised, e.g.
500
501 if (index(...) != -1) { ... }
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502
503=item *
504
505C<for()> loops and similar constructs are now more efficient in most cases.
506
507=item *
508
509L<File::Glob> has been modified to remove unnecessary backtracking and
510recursion, thanks to Russ Cox. See L<https://research.swtch.com/glob>
511for more details.
512
513=item *
514
94fc6237 515The XS-level C<SvTRUE()> API function is now more efficient.
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516
517=item *
518
519Various integer-returning ops are now more efficient in scalar/boolean context.
520
521=item *
522
523Slightly improved performance when parsing stash names.
524L<[perl #129990]|https://rt.perl.org/Public/Bug/Display.html?id=129990>
525
526=item *
527
528Calls to C<require> for an already loaded module are now slightly faster.
529L<[perl #132171]|https://rt.perl.org/Public/Bug/Display.html?id=132171>
530
531=item *
532
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533The performance of pattern matching C<[[:ascii:]]> and C<[[:^ascii:]]>
534has been improved significantly except on EBCDIC platforms.
535
536=item *
537
538Various optimizations have been applied to matching regular expression
539patterns, so under the right circumstances, significant performance
540gains may be noticed. But in an application with many varied patterns,
541little overall improvement likely will be seen.
542
543=item *
544
545Other optimizations have been applied to UTF-8 handling, but these are
546not typically a major factor in most applications.
547
548=back
549
550=head1 Modules and Pragmata
551
552Key highlights in this release across several modules:
553
554=head2 Removal of use vars
555
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556The usage of C<use vars> has been discouraged since the introduction of
557C<our> in Perl 5.6.0. Where possible the usage of this pragma has now been
558removed from the Perl source code.
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559
560This had a slight effect (for the better) on the output of WARNING_BITS in
561L<B::Deparse>.
562
563=head2 Use of DynaLoader changed to XSLoader in many modules
564
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565XSLoader is more modern, and most modules already require perl 5.6 or
566greater, so no functionality is lost by switching. In some cases, we have
567also made changes to the local implementation that may not be reflected in
568the version on CPAN due to a desire to maintain more backwards
569compatibility.
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570
571=head2 Updated Modules and Pragmata
572
573=over 4
574
575=item *
576
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577L<Archive::Tar> has been upgraded from version 2.24 to 2.30.
578
579This update also handled CVE-2018-12015: directory traversal
580vulnerability.
581L<[cpan #125523]|https://rt.cpan.org/Ticket/Display.html?id=125523>
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582
583=item *
584
585L<arybase> has been upgraded from version 0.12 to 0.15.
586
587=item *
588
0423cb17 589L<Attribute::Handlers> has been upgraded from version 0.99 to 1.01.
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590
591=item *
592
0423cb17 593L<attributes> has been upgraded from version 0.29 to 0.33.
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594
595=item *
596
597L<B> has been upgraded from version 1.68 to 1.74.
598
599=item *
600
0423cb17 601L<B::Concise> has been upgraded from version 0.999 to 1.003.
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602
603=item *
604
605L<B::Debug> has been upgraded from version 1.24 to 1.26.
606
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607NOTE: L<B::Debug> is deprecated and may be removed from a future version
608of Perl.
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609
610=item *
611
612L<B::Deparse> has been upgraded from version 1.40 to 1.48.
613
614It includes many bug fixes, and in particular, it now deparses variable
615attributes correctly:
616
617 my $x :foo; # used to deparse as
618 # 'attributes'->import('main', \$x, 'foo'), my $x;
619
620=item *
621
622L<base> has been upgraded from version 2.25 to 2.27.
623
624=item *
625
626L<bignum> has been upgraded from version 0.47 to 0.49.
627
628=item *
629
630L<blib> has been upgraded from version 1.06 to 1.07.
631
632=item *
633
634L<bytes> has been upgraded from version 1.05 to 1.06.
635
636=item *
637
638L<Carp> has been upgraded from version 1.42 to 1.50.
639
640If a package on the call stack contains a constant named C<ISA>, Carp no
641longer throws a "Not a GLOB reference" error.
642
643L<Carp>, when generating stack traces, now attempts to work around
644longstanding bugs resulting from Perl's non-reference-counted stack.
ec30d9c4 645L<[perl #52610]|https://rt.perl.org/Ticket/Display.html?id=52610>
4026b091
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646
647Carp has been modified to avoid assuming that objects cannot be
648overloaded without the L<overload> module loaded (this can happen with
649objects created by XS modules). Previously, infinite recursion would
ec30d9c4
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650result if an XS-defined overload method itself called Carp.
651L<[perl #132828]|https://rt.perl.org/Ticket/Display.html?id=132828>
4026b091
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652
653Carp now avoids using C<overload::StrVal>, partly because older versions
654of L<overload> (included with perl 5.14 and earlier) load L<Scalar::Util>
655at run time, which will fail if Carp has been invoked after a syntax error.
656
657=item *
658
659L<charnames> has been upgraded from version 1.44 to 1.45.
660
661=item *
662
663L<Compress::Raw::Zlib> has been upgraded from version 2.074 to 2.076.
664
665This addresses a security vulnerability in older versions of the 'zlib' library
666(which is bundled with Compress-Raw-Zlib).
667
668=item *
669
670L<Config::Extensions> has been upgraded from version 0.01 to 0.02.
671
672=item *
673
674L<Config::Perl::V> has been upgraded from version 0.28 to 0.29.
675
676=item *
677
678L<CPAN> has been upgraded from version 2.18 to 2.20.
679
680=item *
681
682L<Data::Dumper> has been upgraded from version 2.167 to 2.170.
683
ec30d9c4
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684Quoting of glob names now obeys the Useqq option
685L<[perl #119831]|https://rt.perl.org/Ticket/Display.html?id=119831>.
686
4026b091 687Attempts to set an option to C<undef> through a combined getter/setter
ec30d9c4
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688method are no longer mistaken for getter calls
689L<[perl #113090]|https://rt.perl.org/Ticket/Display.html?id=113090>.
4026b091
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690
691=item *
692
693L<Devel::Peek> has been upgraded from version 1.26 to 1.27.
694
695=item *
696
697L<Devel::PPPort> has been upgraded from version 3.35 to 3.40.
698
699L<Devel::PPPort> has moved from cpan-first to perl-first maintenance
700
701Primary responsibility for the code in Devel::PPPort has moved into core perl.
702In a practical sense there should be no change except that hopefully it will
703stay more up to date with changes made to symbols in perl, rather than needing
704to be updated after the fact.
705
706=item *
707
708L<Digest::SHA> has been upgraded from version 5.96 to 6.01.
709
710=item *
711
712L<DirHandle> has been upgraded from version 1.04 to 1.05.
713
714=item *
715
716L<DynaLoader> has been upgraded from version 1.42 to 1.45.
717
718Its documentation now shows the use of C<__PACKAGE__> and direct object
ec30d9c4
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719syntax
720L<[perl #132247]|https://rt.perl.org/Ticket/Display.html?id=132247>.
4026b091
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721
722=item *
723
724L<Encode> has been upgraded from version 2.88 to 2.97.
725
726=item *
727
728L<encoding> has been upgraded from version 2.19 to 2.22.
729
730=item *
731
732L<Errno> has been upgraded from version 1.28 to 1.29.
733
734=item *
735
736L<experimental> has been upgraded from version 0.016 to 0.019.
737
738=item *
739
740L<Exporter> has been upgraded from version 5.72 to 5.73.
741
742=item *
743
744L<ExtUtils::CBuilder> has been upgraded from version 0.280225 to 0.280230.
745
746=item *
747
748L<ExtUtils::Constant> has been upgraded from version 0.23 to 0.25.
749
750=item *
751
752L<ExtUtils::Embed> has been upgraded from version 1.34 to 1.35.
753
754=item *
755
756L<ExtUtils::Install> has been upgraded from version 2.04 to 2.14.
757
758=item *
759
760L<ExtUtils::MakeMaker> has been upgraded from version 7.24 to 7.34.
761
762=item *
763
764L<ExtUtils::Miniperl> has been upgraded from version 1.06 to 1.08.
765
766=item *
767
768L<ExtUtils::ParseXS> has been upgraded from version 3.34 to 3.39.
769
770=item *
771
772L<ExtUtils::Typemaps> has been upgraded from version 3.34 to 3.38.
773
774=item *
775
776L<ExtUtils::XSSymSet> has been upgraded from version 1.3 to 1.4.
777
778=item *
779
780L<feature> has been upgraded from version 1.47 to 1.52.
781
782=item *
783
784L<fields> has been upgraded from version 2.23 to 2.24.
785
786=item *
787
788L<File::Copy> has been upgraded from version 2.32 to 2.33.
789
94fc6237
DM
790It will now use the sub-second precision variant of utime() supplied by
791L<Time::HiRes> where available.
fbd5718f 792L<[perl #132401]|https://rt.perl.org/Ticket/Display.html?id=132401>.
4026b091
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793
794=item *
795
796L<File::Fetch> has been upgraded from version 0.52 to 0.56.
797
798=item *
799
800L<File::Glob> has been upgraded from version 1.28 to 1.31.
801
802=item *
803
804L<File::Path> has been upgraded from version 2.12_01 to 2.15.
805
806=item *
807
808L<File::Spec> and L<Cwd> have been upgraded from version 3.67 to 3.74.
809
810=item *
811
812L<File::stat> has been upgraded from version 1.07 to 1.08.
813
814=item *
815
816L<FileCache> has been upgraded from version 1.09 to 1.10.
817
818=item *
819
820L<Filter::Simple> has been upgraded from version 0.93 to 0.95.
821
822=item *
823
824L<Filter::Util::Call> has been upgraded from version 1.55 to 1.58.
825
826=item *
827
828L<GDBM_File> has been upgraded from version 1.15 to 1.17.
829
830Its documentation now explains that C<each> and C<delete> don't mix in
ec30d9c4
AC
831hashes tied to this module
832L<[perl #117449]|https://rt.perl.org/Ticket/Display.html?id=117449>.
4026b091
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833
834It will now retry opening with an acceptable block size if asking gdbm
ec30d9c4
AC
835to default the block size failed
836L<[perl #119623]|https://rt.perl.org/Ticket/Display.html?id=119623>.
4026b091
S
837
838=item *
839
840L<Getopt::Long> has been upgraded from version 2.49 to 2.5.
841
842=item *
843
844L<Hash::Util::FieldHash> has been upgraded from version 1.19 to 1.20.
845
846=item *
847
848L<I18N::Langinfo> has been upgraded from version 0.13 to 0.17.
849
850This module is now available on all platforms, emulating the system
4026b091
S
851L<nl_langinfo(3)> on systems that lack it. Some caveats apply, as
852L<detailed in its documentation|I18N::Langinfo>, the most severe being
853that, except for MS Windows, the C<CODESET> item is not implemented on
854those systems, always returning C<"">.
855
856It now sets the UTF-8 flag in its returned scalar if the string contains
ec30d9c4
AC
857legal non-ASCII UTF-8, and the locale is UTF-8
858L<[perl #127288]|https://rt.perl.org/Ticket/Display.html?id=127288>.
4026b091
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859
860This update also fixes a bug in which the underlying locale was ignored
861for the C<RADIXCHAR> (always was returned as a dot) and the C<THOUSEP>
862(always empty). Now the locale-appropriate values are returned.
863
864=item *
865
866L<I18N::LangTags> has been upgraded from version 0.42 to 0.43.
867
868=item *
869
870L<if> has been upgraded from version 0.0606 to 0.0608.
871
872=item *
873
874L<IO> has been upgraded from version 1.38 to 1.39.
875
876=item *
877
878L<IO::Socket::IP> has been upgraded from version 0.38 to 0.39.
879
880=item *
881
882L<IPC::Cmd> has been upgraded from version 0.96 to 1.00.
883
884=item *
885
886L<JSON::PP> has been upgraded from version 2.27400_02 to 2.97001.
887
888=item *
889
94fc6237 890The C<libnet> distribution has been upgraded from version 3.10 to 3.11.
4026b091
S
891
892=item *
893
894L<List::Util> has been upgraded from version 1.46_02 to 1.49.
895
896=item *
897
898L<Locale::Codes> has been upgraded from version 3.42 to 3.56.
899
900B<NOTE>: L<Locale::Codes> scheduled to be removed from core in Perl 5.30.
901
902=item *
903
904L<Locale::Maketext> has been upgraded from version 1.28 to 1.29.
905
906=item *
907
908L<Math::BigInt> has been upgraded from version 1.999806 to 1.999811.
909
910=item *
911
912L<Math::BigInt::FastCalc> has been upgraded from version 0.5005 to 0.5006.
913
914=item *
915
916L<Math::BigRat> has been upgraded from version 0.2611 to 0.2613.
917
918=item *
919
6e7bf791 920L<Module::CoreList> has been upgraded from version 5.20170530 to 5.20180619.
4026b091
S
921
922=item *
923
924L<mro> has been upgraded from version 1.20 to 1.22.
925
926=item *
927
928L<Net::Ping> has been upgraded from version 2.55 to 2.62.
929
930=item *
931
932L<NEXT> has been upgraded from version 0.67 to 0.67_01.
933
934=item *
935
936L<ODBM_File> has been upgraded from version 1.14 to 1.15.
937
938=item *
939
940L<Opcode> has been upgraded from version 1.39 to 1.43.
941
942=item *
943
944L<overload> has been upgraded from version 1.28 to 1.30.
945
946=item *
947
948L<PerlIO::encoding> has been upgraded from version 0.25 to 0.26.
949
950=item *
951
952L<PerlIO::scalar> has been upgraded from version 0.26 to 0.29.
953
954=item *
955
956L<PerlIO::via> has been upgraded from version 0.16 to 0.17.
957
958=item *
959
960L<Pod::Functions> has been upgraded from version 1.11 to 1.13.
961
962=item *
963
964L<Pod::Html> has been upgraded from version 1.2202 to 1.24.
965
966A title for the HTML document will now be automatically generated by
967default from a "NAME" section in the POD document, as it used to be
968before the module was rewritten to use L<Pod::Simple::XHTML> to do the
ec30d9c4
AC
969core of its job
970L<[perl #110520]|https://rt.perl.org/Ticket/Display.html?id=110520>.
4026b091
S
971
972=item *
973
974L<Pod::Perldoc> has been upgraded from version 3.28 to 3.2801.
975
976=item *
977
94fc6237 978The C<podlators> distribution has been upgraded from version 4.09 to 4.10.
4026b091
S
979
980Man page references and function names now follow the Linux man page
981formatting standards, instead of the Solaris standard.
982
983=item *
984
985L<POSIX> has been upgraded from version 1.76 to 1.84.
986
987Some more cautions were added about using locale-specific functions in
988threaded applications.
989
990=item *
991
992L<re> has been upgraded from version 0.34 to 0.36.
993
994=item *
995
996L<Scalar::Util> has been upgraded from version 1.46_02 to 1.50.
997
998=item *
999
1000L<SelfLoader> has been upgraded from version 1.23 to 1.25.
1001
1002=item *
1003
1004L<Socket> has been upgraded from version 2.020_03 to 2.027.
1005
1006=item *
1007
1008L<sort> has been upgraded from version 2.02 to 2.04.
1009
1010=item *
1011
1012L<Storable> has been upgraded from version 2.62 to 3.08.
1013
1014=item *
1015
1016L<Sub::Util> has been upgraded from version 1.48 to 1.49.
1017
1018=item *
1019
1020L<subs> has been upgraded from version 1.02 to 1.03.
1021
1022=item *
1023
1024L<Sys::Hostname> has been upgraded from version 1.20 to 1.22.
1025
1026=item *
1027
1028L<Term::ReadLine> has been upgraded from version 1.16 to 1.17.
1029
1030=item *
1031
1032L<Test> has been upgraded from version 1.30 to 1.31.
1033
1034=item *
1035
1036L<Test::Harness> has been upgraded from version 3.38 to 3.42.
1037
1038=item *
1039
1040L<Test::Simple> has been upgraded from version 1.302073 to 1.302133.
1041
1042=item *
1043
1044L<threads> has been upgraded from version 2.15 to 2.22.
1045
1046The documentation now better describes the problems that arise when
1047returning values from threads, and no longer warns about creating threads
ec30d9c4
AC
1048in C<BEGIN> blocks.
1049L<[perl #96538]|https://rt.perl.org/Ticket/Display.html?id=96538>
4026b091
S
1050
1051=item *
1052
1053L<threads::shared> has been upgraded from version 1.56 to 1.58.
1054
1055=item *
1056
1057L<Tie::Array> has been upgraded from version 1.06 to 1.07.
1058
1059=item *
1060
1061L<Tie::StdHandle> has been upgraded from version 4.4 to 4.5.
1062
1063=item *
1064
1065L<Time::gmtime> has been upgraded from version 1.03 to 1.04.
1066
1067=item *
1068
1069L<Time::HiRes> has been upgraded from version 1.9741 to 1.9759.
1070
1071=item *
1072
1073L<Time::localtime> has been upgraded from version 1.02 to 1.03.
1074
1075=item *
1076
1077L<Time::Piece> has been upgraded from version 1.31 to 1.3204.
1078
1079=item *
1080
1081L<Unicode::Collate> has been upgraded from version 1.19 to 1.25.
1082
1083=item *
1084
1085L<Unicode::Normalize> has been upgraded from version 1.25 to 1.26.
1086
1087=item *
1088
1089L<Unicode::UCD> has been upgraded from version 0.68 to 0.70.
1090
1091The function C<num> now accepts an optional parameter to help in
1092diagnosing error returns.
1093
1094=item *
1095
1096L<User::grent> has been upgraded from version 1.01 to 1.02.
1097
1098=item *
1099
1100L<User::pwent> has been upgraded from version 1.00 to 1.01.
1101
1102=item *
1103
1104L<utf8> has been upgraded from version 1.19 to 1.21.
1105
1106=item *
1107
1108L<vars> has been upgraded from version 1.03 to 1.04.
1109
1110=item *
1111
1112L<version> has been upgraded from version 0.9917 to 0.9923.
1113
1114=item *
1115
1116L<VMS::DCLsym> has been upgraded from version 1.08 to 1.09.
1117
1118=item *
1119
1120L<VMS::Stdio> has been upgraded from version 2.41 to 2.44.
1121
1122=item *
1123
1124L<warnings> has been upgraded from version 1.37 to 1.42.
1125
1126It now includes new functions with names ending in C<_at_level>, allowing
ec30d9c4
AC
1127callers to specify the exact call frame.
1128L<[perl #132468]|https://rt.perl.org/Ticket/Display.html?id=132468>
4026b091
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1129
1130=item *
1131
1132L<XS::Typemap> has been upgraded from version 0.15 to 0.16.
1133
1134=item *
1135
1136L<XSLoader> has been upgraded from version 0.27 to 0.30.
1137
1138Its documentation now shows the use of C<__PACKAGE__>, and direct object
ec30d9c4
AC
1139syntax for example C<DynaLoader> usage
1140L<[perl #132247]|https://rt.perl.org/Ticket/Display.html?id=132247>.
4026b091
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1141
1142Platforms that use C<mod2fname> to edit the names of loadable
1143libraries now look for bootstrap (.bs) files under the correct,
1144non-edited name.
1145
1146=back
1147
1148=head2 Removed Modules and Pragmata
1149
1150=over 4
1151
1152=item *
1153
1154The C<VMS::stdio> compatibility shim has been removed.
1155
1156=back
1157
1158=head1 Documentation
1159
1160=head2 Changes to Existing Documentation
1161
1162We have attempted to update the documentation to reflect the changes
1163listed in this document. If you find any we have missed, send email
1164to L<perlbug@perl.org|mailto:perlbug@perl.org>.
1165
1166Additionally, the following selected changes have been made:
1167
1168=head3 L<perlapi>
1169
1170=over 4
1171
1172=item *
1173
1174The API functions C<perl_parse()>, C<perl_run()>, and C<perl_destruct()>
1175are now documented comprehensively, where previously the only
1176documentation was a reference to the L<perlembed> tutorial.
1177
1178=item *
1179
1180The documentation of C<newGIVENOP()> has been belatedly updated to
1181account for the removal of lexical C<$_>.
1182
1183=item *
1184
1185The API functions C<newCONSTSUB()> and C<newCONSTSUB_flags()> are
1186documented much more comprehensively than before.
1187
1188=back
1189
1190=head3 L<perldata>
1191
1192=over 4
1193
1194=item *
1195
1196The section "Truth and Falsehood" in L<perlsyn> has been moved into
1197L<perldata>.
1198
1199=back
1200
1201=head3 L<perldebguts>
1202
1203=over 4
1204
1205=item *
1206
1207The description of the conditions under which C<DB::sub()> will be called
ec30d9c4
AC
1208has been clarified.
1209L<[perl #131672]|https://rt.perl.org/Ticket/Display.html?id=131672>
4026b091
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1210
1211=back
1212
1213=head3 L<perldiag>
1214
1215=over 4
1216
eefffb17 1217=item * L<perldiag/Variable length lookbehind not implemented in regex mE<sol>%sE<sol>>
4026b091
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1218
1219This now gives more ideas as to workarounds to the issue that was
1220introduced in Perl 5.18 (but not documented explicitly in its perldelta)
1221for the fact that some Unicode C</i> rules cause a few sequences such as
1222
1223 (?<!st)
1224
1225to be considered variable length, and hence disallowed.
1226
1227=item * "Use of state $_ is experimental" in L<perldiag>
1228
1229This entry has been removed, as the experimental support of this construct was
1230removed in perl 5.24.0.
1231
1232=item *
1233
1234The diagnostic C<Initialization of state variables in list context
1235currently forbidden> has changed to C<Initialization of state variables
1236in list currently forbidden>, because list-context initialization of
1237single aggregate state variables is now permitted.
1238
1239=back
1240
1241=head3 L<perlembed>
1242
1243=over 4
1244
1245=item *
1246
1247The examples in L<perlembed> have been made more portable in the way
1248they exit, and the example that gets an exit code from the embedded Perl
1249interpreter now gets it from the right place. The examples that pass
1250a constructed argv to Perl now show the mandatory null C<argv[argc]>.
1251
1252=item *
1253
1254An example in L<perlembed> used the string value of C<ERRSV> as a
1255format string when calling croak(). If that string contains format
1256codes such as C<%s> this could crash the program.
1257
1258This has been changed to a call to croak_sv().
1259
1260An alternative could have been to supply a trivial format string:
1261
1262 croak("%s", SvPV_nolen(ERRSV));
1263
1264or as a special case for C<ERRSV> simply:
1265
1266 croak(NULL);
1267
1268=back
1269
1270=head3 L<perlfunc>
1271
1272=over 4
1273
1274=item *
1275
1276There is now a note that warnings generated by built-in functions are
ec30d9c4
AC
1277documented in L<perldiag> and L<warnings>.
1278L<[perl #116080]|https://rt.perl.org/Ticket/Display.html?id=116080>
4026b091
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1279
1280=item *
1281
1282The documentation for the C<exists> operator no longer says that
1283autovivification behaviour "may be fixed in a future release".
1284We've determined that we're not going to change the default behaviour.
ec30d9c4 1285L<[perl #127712]|https://rt.perl.org/Ticket/Display.html?id=127712>
4026b091
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1286
1287=item *
1288
1289A couple of small details in the documentation for the C<bless> operator
ec30d9c4
AC
1290have been clarified.
1291L<[perl #124428]|https://rt.perl.org/Ticket/Display.html?id=124428>
4026b091
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1292
1293=item *
1294
1295The description of C<@INC> hooks in the documentation for C<require>
1296has been corrected to say that filter subroutines receive a useless
ec30d9c4
AC
1297first argument.
1298L<[perl #115754]|https://rt.perl.org/Ticket/Display.html?id=115754>
4026b091
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1299
1300=item *
1301
1302The documentation of C<ref> has been rewritten for clarity.
1303
1304=item *
1305
1306The documentation of C<use> now explains what syntactically qualifies
1307as a version number for its module version checking feature.
1308
1309=item *
1310
1311The documentation of C<warn> has been updated to reflect that since Perl
13125.14 it has treated complex exception objects in a manner equivalent
ec30d9c4
AC
1313to C<die>.
1314L<[perl #121372]|https://rt.perl.org/Ticket/Display.html?id=121372>
4026b091
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1315
1316=item *
1317
1318The documentation of C<die> and C<warn> has been revised for clarity.
1319
1320=item *
1321
94fc6237 1322The documentation of C<each> has been improved, with a slightly more
4026b091 1323explicit description of the sharing of iterator state, and with
ec30d9c4
AC
1324caveats regarding the fragility of while-each loops.
1325L<[perl #132644]|https://rt.perl.org/Ticket/Display.html?id=132644>
4026b091
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1326
1327=item *
1328
94fc6237 1329Clarification to C<require> was added to explain the differences between
4026b091 1330
94fc6237
DM
1331 require Foo::Bar;
1332 require "Foo/Bar.pm";
4026b091
S
1333
1334=back
1335
1336=head3 L<perlgit>
1337
1338=over 4
1339
1340=item *
1341
1342The precise rules for identifying C<smoke-me> branches are now stated.
1343
1344=back
1345
1346=head3 L<perlguts>
1347
1348=over 4
1349
1350=item *
1351
1352The section on reference counting in L<perlguts> has been heavily revised,
1353to describe references in the way a programmer needs to think about them
1354rather than in terms of the physical data structures.
1355
1356=item *
1357
1358Improve documentation related to UTF-8 multibytes.
1359
1360=back
1361
1362=head3 L<perlintern>
1363
1364=over 4
1365
1366=item *
1367
1368The internal functions C<newXS_len_flags()> and C<newATTRSUB_x()> are
1369now documented.
1370
1371=back
1372
1373=head3 L<perlobj>
1374
1375=over 4
1376
1377=item *
1378
1379The documentation about C<DESTROY> methods has been corrected, updated,
1380and revised, especially in regard to how they interact with exceptions.
ec30d9c4 1381L<[perl #122753]|https://rt.perl.org/Ticket/Display.html?id=122753>
4026b091
S
1382
1383=back
1384
1385=head3 L<perlop>
1386
1387=over 4
1388
1389=item *
1390
ec30d9c4
AC
1391The description of the C<x> operator in L<perlop> has been clarified.
1392L<[perl #132460]|https://rt.perl.org/Ticket/Display.html?id=132460>
4026b091
S
1393
1394=item *
1395
94fc6237
DM
1396L<perlop> has been updated to note that C<qw>'s whitespace rules differ
1397from that of C<split>'s in that only ASCII whitespace is used.
4026b091
S
1398
1399=item *
1400
1401The general explanation of operator precedence and associativity has
ec30d9c4
AC
1402been corrected and clarified.
1403L<[perl #127391]|https://rt.perl.org/Ticket/Display.html?id=127391>
4026b091
S
1404
1405=item *
1406
1407The documentation for the C<\> referencing operator now explains the
ec30d9c4
AC
1408unusual context that it supplies to its operand.
1409L<[perl #131061]|https://rt.perl.org/Ticket/Display.html?id=131061>
4026b091 1410
4026b091
S
1411=back
1412
1413=head3 L<perlrequick>
1414
1415=over 4
1416
1417=item *
1418
1419Clarifications on metacharacters and character classes
1420
1421=back
1422
1423=head3 L<perlretut>
1424
1425=over 4
1426
1427=item *
1428
1429Clarify metacharacters.
1430
1431=back
1432
1433=head3 L<perlrun>
1434
1435=over 4
1436
1437=item *
1438
94fc6237 1439Clarify the differences between B<< -M >> and B<< -m >>.
ec30d9c4 1440L<[perl #131518]|https://rt.perl.org/Ticket/Display.html?id=131518>
4026b091
S
1441
1442=back
1443
1444=head3 L<perlsec>
1445
1446=over 4
1447
1448=item *
1449
1450The documentation about set-id scripts has been updated and revised.
ec30d9c4 1451L<[perl #74142]|https://rt.perl.org/Ticket/Display.html?id=74142>
4026b091
S
1452
1453=item *
1454
1455A section about using C<sudo> to run Perl scripts has been added.
1456
1457=back
1458
1459=head3 L<perlsyn>
1460
1461=over 4
1462
1463=item *
1464
1465The section "Truth and Falsehood" in L<perlsyn> has been removed from
1466that document, where it didn't belong, and merged into the existing
1467paragraph on the same topic in L<perldata>.
1468
1469=item *
1470
1471The means to disambiguate between code blocks and hash constructors,
1472already documented in L<perlref>, are now documented in L<perlsyn> too.
ec30d9c4 1473L<[perl #130958]|https://rt.perl.org/Ticket/Display.html?id=130958>
4026b091 1474
4026b091
S
1475=back
1476
1477=head3 L<perluniprops>
1478
1479=over 4
1480
1481=item *
1482
1483L<perluniprops> has been updated to note that C<\p{Word}> now includes
1484code points matching the C<\p{Join_Control}> property. The change to
1485the property was made in Perl 5.18, but not documented until now. There
1486are currently only two code points that match this property U+200C (ZERO
1487WIDTH NON-JOINER) and U+200D (ZERO WIDTH JOINER).
1488
1489=item *
1490
1491For each binary table or property, the documentation now includes which
1492characters in the range C<\x00-\xFF> it matches, as well as a list of
1493the first few ranges of code points matched above that.
1494
1495=back
1496
1497=head3 L<perlvar>
1498
1499=over 4
1500
1501=item *
1502
1503The entry for C<$+> in perlvar has been expanded upon to describe handling of
1504multiply-named capturing groups.
1505
1506=back
1507
0423cb17
S
1508=head3 L<perlfunc>, L<perlop>, L<perlsyn>
1509
1510=over 4
1511
1512=item *
1513
94fc6237
DM
1514In various places, improve the documentation of the special cases
1515in the condition expression of a while loop, such as implicit C<defined>
1516and assignment to C<$_>.
ec30d9c4 1517L<[perl #132644]|https://rt.perl.org/Ticket/Display.html?id=132644>
0423cb17
S
1518
1519=back
1520
4026b091
S
1521=head1 Diagnostics
1522
1523The following additions or changes have been made to diagnostic output,
1524including warnings and fatal error messages. For the complete list of
1525diagnostic messages, see L<perldiag>.
1526
1527=head2 New Diagnostics
1528
1529=head3 New Errors
1530
1531=over 4
1532
1533=item *
1534
1535L<Can't "goto" into a "given" block|perldiag/"Can't E<quot>gotoE<quot> into a E<quot>givenE<quot> block">
1536
1537(F) A "goto" statement was executed to jump into the middle of a C<given>
1538block. You can't get there from here. See L<perlfunc/goto>.
1539
1540=item *
1541
1542L<Can't "goto" into a binary or list expression|perldiag/"Can't E<quot>gotoE<quot> into a binary or list expression">
1543
1544Use of C<goto> to jump into the parameter of a binary or list operator has
ec30d9c4
AC
1545been prohibited, to prevent crashes and stack corruption.
1546L<[perl #130936]|https://rt.perl.org/Ticket/Display.html?id=130936>
4026b091
S
1547
1548You may only enter the I<first> argument of an operator that takes a fixed
1549number of arguments, since this is a case that will not cause stack
ec30d9c4
AC
1550corruption.
1551L<[perl #132854]|https://rt.perl.org/Ticket/Display.html?id=132854>
4026b091
S
1552
1553=back
1554
1555=head3 New Warnings
1556
1557=over 4
1558
1559=item *
1560
1561L<Old package separator used in string|perldiag/"Old package separator used in string">
1562
1563(W syntax) You used the old package separator, "'", in a variable
1564named inside a double-quoted string; e.g., C<"In $name's house">. This
1565is equivalent to C<"In $name::s house">. If you meant the former, put
1566a backslash before the apostrophe (C<"In $name\'s house">).
1567
1568=item *
1569
1570L<perldiag/Locale '%s' contains (at least) the following characters which
1571have unexpected meanings: %s The Perl program will use the expected
1572meanings>
1573
1574=back
1575
1576=head2 Changes to Existing Diagnostics
1577
1578=over 4
1579
1580=item *
1581
1582A false-positive warning that was issued when using a
1583numerically-quantified sub-pattern in a recursive regex has been
1584silenced. L<[perl #131868]|https://rt.perl.org/Public/Bug/Display.html?id=131868>
1585
1586=item *
1587
1588The warning about useless use of a concatenation operator in void context
1589is now generated for expressions with multiple concatenations, such as
ec30d9c4
AC
1590C<$a.$b.$c>, which used to mistakenly not warn.
1591L<[perl #6997]|https://rt.perl.org/Ticket/Display.html?id=6997>
4026b091
S
1592
1593=item *
1594
1595Warnings that a variable or subroutine "masks earlier declaration in same
1596...", or that an C<our> variable has been redeclared, have been moved to a
1597new warnings category "shadow". Previously they were in category "misc".
1598
1599=item *
1600
1601The deprecation warning from C<Sys::Hostname::hostname()> saying that
1602it doesn't accept arguments now states the Perl version in which the
ec30d9c4
AC
1603warning will be upgraded to an error.
1604L<[perl #124349]|https://rt.perl.org/Ticket/Display.html?id=124349>
4026b091
S
1605
1606=item *
1607
1608The L<perldiag> entry for the error regarding a set-id script has been
1609expanded to make clear that the error is reporting a specific security
1610vulnerability, and to advise how to fix it.
1611
1612=item *
1613
1614The C<< Unable to flush stdout >> error message was missing a trailing
1615newline. [debian #875361]
1616
1617=back
1618
1619=head1 Utility Changes
1620
1621=head2 L<perlbug>
1622
1623=over 4
1624
1625=item *
1626
1627C<--help> and C<--version> options have been added.
1628
1629=back
89853d76 1630
4026b091 1631=head1 Configuration and Compilation
89853d76 1632
4026b091 1633=over 4
89853d76 1634
4026b091 1635=item * C89 requirement
e4c43fa1 1636
4026b091
S
1637Perl has been documented as requiring a C89 compiler to build since October
16381998. A variety of simplifications have now been made to Perl's internals to
1639rely on the features specified by the C89 standard. We believe that this
1640internal change hasn't altered the set of platforms that Perl builds on, but
1641please report a bug if Perl now has new problems building on your platform.
e4c43fa1 1642
4026b091 1643=item *
e4c43fa1 1644
4026b091
S
1645On GCC, C<-Werror=pointer-arith> is now enabled by default,
1646disallowing arithmetic on void and function pointers.
e4c43fa1 1647
4026b091 1648=item *
e4c43fa1 1649
94fc6237 1650Where an HTML version of the documentation is installed, the HTML
4026b091
S
1651documents now use relative links to refer to each other. Links from
1652the index page of L<perlipc> to the individual section documents are
ec30d9c4
AC
1653now correct.
1654L<[perl #110056]|https://rt.perl.org/Ticket/Display.html?id=110056>
da251d45 1655
4026b091 1656=item *
dad11929 1657
4026b091
S
1658F<lib/unicore/mktables> now correctly canonicalizes the names of the
1659dependencies stored in the files it generates.
dad11929 1660
4026b091
S
1661F<regen/mk_invlists.pl>, unlike the other F<regen/*.pl> scripts, used
1662C<$0> to name itself in the dependencies stored in the files it
1663generates. It now uses a literal so that the path stored in the
1664generated files doesn't depend on how F<regen/mk_invlists.pl> is
1665invoked.
30938b9c 1666
ec30d9c4
AC
1667This lack of canonical names could cause test failures in F<t/porting/regen.t>.
1668L<[perl #132925]|https://rt.perl.org/Ticket/Display.html?id=132925>
30938b9c 1669
4026b091 1670=item * New probes
30938b9c 1671
4026b091 1672=over 2
04f89ea7 1673
4026b091 1674=item HAS_BUILTIN_ADD_OVERFLOW
6201c220 1675
4026b091 1676=item HAS_BUILTIN_MUL_OVERFLOW
472be41b 1677
4026b091 1678=item HAS_BUILTIN_SUB_OVERFLOW
9fca523d 1679
4026b091 1680=item HAS_THREAD_SAFE_NL_LANGINFO_L
da251d45 1681
4026b091 1682=item HAS_LOCALECONV_L
435ebfcb 1683
4026b091 1684=item HAS_MBRLEN
da251d45 1685
4026b091 1686=item HAS_MBRTOWC
da251d45 1687
4026b091 1688=item HAS_MEMRCHR
da251d45 1689
4026b091 1690=item HAS_NANOSLEEP
da251d45 1691
4026b091 1692=item HAS_STRNLEN
435ebfcb 1693
4026b091
S
1694=item HAS_STRTOLD_L
1695
1696=item I_WCHAR
435ebfcb 1697
e4c43fa1 1698=back
dad11929 1699
4026b091 1700=back
dad11929 1701
4026b091 1702=head1 Testing
bdd8ae1c 1703
4026b091 1704=over 4
435ebfcb 1705
4026b091 1706=item *
435ebfcb 1707
4026b091
S
1708Testing of the XS-APItest directory is now done in parallel, where
1709applicable.
dad11929 1710
b17b3b97 1711=item *
435ebfcb 1712
4026b091 1713Perl now includes a default F<.travis.yml> file for Travis CI testing
ec30d9c4
AC
1714on github mirrors.
1715L<[perl #123981]|https://rt.perl.org/Ticket/Display.html?id=123981>
435ebfcb 1716
4026b091 1717=item *
435ebfcb 1718
94fc6237 1719The watchdog timer count in F<re/pat_psycho.t> can now be overridden.
4026b091
S
1720
1721This test can take a long time to run, so there is a timer to keep
1722this in check (currently, 5 minutes). This commit adds checking
1723the environment variable C<< PERL_TEST_TIME_OUT_FACTOR >>; if set,
1724the time out setting is multiplied by its value.
1725
1726=item *
1727
ec30d9c4
AC
1728F<harness> no longer waits for 30 seconds when running F<t/io/openpid.t>.
1729L<[perl #121028]|https://rt.perl.org/Ticket/Display.html?id=121028>
1730L<[perl #132867]|https://rt.perl.org/Ticket/Display.html?id=132867>
4026b091
S
1731
1732=back
435ebfcb 1733
4026b091 1734=head1 Packaging
bdd8ae1c 1735
4026b091
S
1736For the past few years we have released perl using three different archive
1737formats: bzip (C<.bz2>), LZMA2 (C<.xz>) and gzip (C<.gz>). Since xz compresses
94fc6237
DM
1738better and decompresses faster, and gzip is more compatible and uses less
1739memory, we have dropped the C<.bz2> archive format with this release.
4026b091 1740(If this poses a problem, do let us know; see L</Reporting Bugs>, below.)
4ec06e46 1741
4026b091 1742=head1 Platform Support
da251d45 1743
4026b091 1744=head2 Discontinued Platforms
e4c43fa1
S
1745
1746=over 4
da251d45 1747
4026b091 1748=item PowerUX / Power MAX OS
bdd8ae1c 1749
94fc6237
DM
1750Compiler hints and other support for these apparently long-defunct
1751platforms has been removed.
da251d45 1752
e4c43fa1
S
1753=back
1754
4026b091
S
1755=head2 Platform-Specific Notes
1756
1757=over 4
1758
1759=item CentOS
1760
1761Compilation on CentOS 5 is now fixed.
1762
1763=item Cygwin
1764
1765A build with the quadmath library can now be done on Cygwin.
1766
1767=item Darwin
1768
1769Perl now correctly uses reentrant functions, like C<asctime_r>, on
1770versions of Darwin that have support for them.
1771
1772=item FreeBSD
1773
1774FreeBSD's F<< /usr/share/mk/sys.mk >> specifies C<< -O2 >> for
94fc6237 1775architectures other than ARM and MIPS. By default, perl is now compiled
4026b091
S
1776with the same optimization levels.
1777
1778=item VMS
1779
1780Several fix-ups for F<configure.com>, marking function VMS has
1781(or doesn't have).
1782
94fc6237
DM
1783CRTL features can now be set by embedders before invoking Perl by using
1784the C<decc$feature_set> and C<decc$feature_set_value> functions.
1785Previously any attempt to set features after image initialization were
1786ignored.
4026b091
S
1787
1788=item Windows
435ebfcb 1789
e4c43fa1 1790=over 4
bdd8ae1c 1791
b17b3b97 1792=item *
bdd8ae1c 1793
4026b091
S
1794Support for compiling perl on Windows using Microsoft Visual Studio 2017
1795(containing Visual C++ 14.1) has been added.
1796
1797=item *
bdd8ae1c 1798
4026b091
S
1799Visual C++ compiler version detection has been improved to work on non-English
1800language systems.
e4c43fa1 1801
e18dd902
S
1802=item *
1803
4026b091
S
1804We now set C<$Config{libpth}> correctly for 64-bit builds using Visual C++
1805versions earlier than 14.1.
e18dd902 1806
e4c43fa1
S
1807=back
1808
4026b091
S
1809=back
1810
1811=head1 Internal Changes
bdd8ae1c 1812
e4c43fa1 1813=over 4
435ebfcb
TR
1814
1815=item *
da251d45 1816
4026b091
S
1817A new optimisation phase has been added to the compiler,
1818C<optimize_optree()>, which does a top-down scan of a complete optree
1819just before the peephole optimiser is run. This phase is not currently
1820hookable.
435ebfcb 1821
4026b091 1822=item *
435ebfcb 1823
4026b091
S
1824An C<OP_MULTICONCAT> op has been added. At C<optimize_optree()> time, a
1825chain of C<OP_CONCAT> and C<OP_CONST> ops, together optionally with an
1826C<OP_STRINGIFY> and/or C<OP_SASSIGN>, are combined into a single
1827C<OP_MULTICONCAT> op. The op is of type C<UNOP_AUX>, and the aux array
1828contains the argument count, plus a pointer to a constant string and a set
1829of segment lengths. For example with
cab9f0b0 1830
4026b091 1831 my $x = "foo=$foo, bar=$bar\n";
bdd8ae1c 1832
4026b091
S
1833the constant string would be C<"foo=, bar=\n"> and the segment lengths
1834would be (4,6,1). If the string contains characters such as C<\x80>, whose
1835representation changes under utf8, two sets of strings plus lengths are
1836precomputed and stored.
bdd8ae1c 1837
4026b091 1838=item *
bdd8ae1c 1839
4026b091
S
1840Direct access to L<C<PL_keyword_plugin>|perlapi/PL_keyword_plugin> is not
1841safe in the presence of multithreading. A new
1842L<C<wrap_keyword_plugin>|perlapi/wrap_keyword_plugin> function has been
1843added to allow XS modules to safely define custom keywords even when
1844loaded from a thread, analogous to L<C<PL_check>|perlapi/PL_check> /
1845L<C<wrap_op_checker>|perlapi/wrap_op_checker>.
bdd8ae1c 1846
4026b091 1847=item *
bdd8ae1c 1848
4026b091 1849The C<PL_statbuf> interpreter variable has been removed.
9deb4e0b 1850
4026b091 1851=item *
da251d45 1852
4026b091
S
1853The deprecated function C<to_utf8_case()>, accessible from XS code, has
1854been removed.
bdd8ae1c 1855
4026b091 1856=item *
da251d45 1857
4026b091
S
1858A new function
1859L<C<is_utf8_invariant_string_loc()>|perlapi/is_utf8_invariant_string_loc>
1860has been added that is like
1861L<C<is_utf8_invariant_string()>|perlapi/is_utf8_invariant_string>
1862but takes an extra pointer parameter into which is stored the location
1863of the first variant character, if any are found.
da251d45 1864
4026b091
S
1865=item *
1866
1867A new function, L<C<Perl_langinfo()>|perlapi/Perl_langinfo> has been
1868added. It is an (almost) drop-in replacement for the system
1869C<nl_langinfo(3)>, but works on platforms that lack that; as well as
1870being more thread-safe, and hiding some gotchas with locale handling
1871from the caller. Code that uses this, needn't use L<C<localeconv(3)>>
1872(and be affected by the gotchas) to find the decimal point, thousands
1873separator, or currency symbol. See L<perlapi/Perl_langinfo>.
da251d45
RB
1874
1875=item *
1876
4026b091
S
1877A new API function L<C<sv_rvunweaken()>|perlapi/sv_rvunweaken> has
1878been added to complement L<C<sv_rvweaken()>|perlapi/sv_rvweaken>.
1879The implementation was taken from L<Scalar::Util/unweaken>.
bdd8ae1c 1880
4026b091 1881=item *
bdd8ae1c 1882
4026b091
S
1883A new flag, C<SORTf_UNSTABLE>, has been added. This will allow a
1884future commit to make mergesort unstable when the user specifies ‘no
1885sort stable’, since it has been decided that mergesort should remain
1886stable by default.
435ebfcb 1887
4026b091 1888=item *
435ebfcb 1889
4026b091
S
1890XS modules can now automatically get reentrant versions of system
1891functions on threaded perls.
435ebfcb 1892
94fc6237 1893By adding
da251d45 1894
94fc6237 1895 #define PERL_REENTRANT
da251d45 1896
4026b091
S
1897near the beginning of an C<XS> file, it will be compiled so that
1898whatever reentrant functions perl knows about on that system will
1899automatically and invisibly be used instead of the plain, non-reentrant
1900versions. For example, if you write C<getpwnam()> in your code, on a
75a718b3 1901system that has C<getpwnam_r()> all calls to the former will be translated
4026b091
S
1902invisibly into the latter. This does not happen except on threaded
1903perls, as they aren't needed otherwise. Be aware that which functions
1904have reentrant versions varies from system to system.
4ec06e46 1905
4026b091
S
1906=item *
1907
1908The C<PERL_NO_OP_PARENT> build define is no longer supported, which means
1909that perl is now always built with C<PERL_OP_PARENT> enabled.
1910
1911=item *
1912
94fc6237
DM
1913The format and content of the non-utf8 transliteration table attached to
1914the C<op_pv> field of C<OP_TRANS>/C<OP_TRANSR> ops has changed. It's now a
4026b091
S
1915C<struct OPtrans_map>.
1916
1917=item *
1918
1919A new compiler C<#define>, C<dTHX_DEBUGGING>. has been added. This is
1920useful for XS or C code that only need the thread context because their
1921debugging statements that get compiled only under C<-DDEBUGGING> need
1922one.
1923
1924=item *
1925
1926A new API function L<perlapi/Perl_setlocale> has been added.
1927
1928=item *
1929
1930L<perlapi/sync_locale> has been revised to return a boolean as to
1931whether the system was using the global locale or not.
915366d4 1932
435ebfcb 1933=item *
da251d45 1934
4026b091 1935A new kind of magic scalar, called a "nonelem" scalar, has been introduced.
94fc6237 1936It is stored in an array to denote a non-existent element, whenever such an
4026b091
S
1937element is accessed in a potential lvalue context. It replaces the
1938existing "defelem" (deferred element) magic wherever this is possible,
1939being significantly more efficient. This means that
1940C<some_sub($sparse_array[$nonelem])> no longer has to create a new magic
1941defelem scalar each time, as long as the element is within the array.
1942
1943It partially fixes the rare bug of deferred elements getting out of synch
ec30d9c4
AC
1944with their arrays when the array is shifted or unshifted.
1945L<[perl #132729]|https://rt.perl.org/Ticket/Display.html?id=132729>
915366d4 1946
435ebfcb 1947=back
da251d45 1948
4026b091 1949=head1 Selected Bug Fixes
da251d45
RB
1950
1951=over 4
1952
1953=item *
1954
4026b091 1955List assignment (C<aassign>) could in some rare cases allocate an
94fc6237
DM
1956entry on the mortals stack and leave the entry uninitialized, leading to
1957possible crashes.
2022b8ae 1958L<[perl #131570]|https://rt.perl.org/Ticket/Display.html?id=131570>
da251d45 1959
4026b091 1960=item *
da251d45 1961
4026b091
S
1962Attempting to apply an attribute to an C<our> variable where a
1963function of that name already exists could result in a NULL pointer
2022b8ae
SK
1964being supplied where an SV was expected, crashing perl.
1965L<[perl #131597]|https://rt.perl.org/Ticket/Display.html?id=131597>
bdd8ae1c 1966
4026b091 1967=item *
4ec06e46 1968
4026b091
S
1969C<split ' '> now correctly handles the argument being split when in the
1970scope of the L<< C<unicode_strings>|feature/"The 'unicode_strings' feature"
1971>> feature. Previously, when a string using the single-byte internal
1972representation contained characters that are whitespace by Unicode rules but
1973not by ASCII rules, it treated those characters as part of fields rather
ec30d9c4
AC
1974than as field separators.
1975L<[perl #130907]|https://rt.perl.org/Ticket/Display.html?id=130907>
64b9a139
SH
1976
1977=item *
1978
4026b091
S
1979Several built-in functions previously had bugs that could cause them to
1980write to the internal stack without allocating room for the item being
1981written. In rare situations, this could have led to a crash. These bugs have
1982now been fixed, and if any similar bugs are introduced in future, they will
1983be detected automatically in debugging builds.
a8d9a219 1984
4026b091
S
1985These internal stack usage checks introduced are also done
1986by the C<entersub> operator when calling XSUBs. This means we can
1987report which XSUB failed to allocate enough stack space.
1988L<[perl #131975]|https://rt.perl.org/Public/Bug/Display.html?id=131975>
e6a2e5ca 1989
4026b091
S
1990=item *
1991
1992Using a symbolic ref with postderef syntax as the key in a hash lookup was
ec30d9c4
AC
1993yielding an assertion failure on debugging builds.
1994L<[perl #131627]|https://rt.perl.org/Ticket/Display.html?id=131627>
e4c43fa1 1995
4026b091 1996=item *
e4c43fa1 1997
4026b091
S
1998Array and hash variables whose names begin with a caret now admit indexing
1999inside their curlies when interpolated into strings, as in C<<
ec30d9c4
AC
2000"${^CAPTURE[0]}" >> to index C<@{^CAPTURE}>.
2001L<[perl #131664]|https://rt.perl.org/Ticket/Display.html?id=131664>
e4c43fa1 2002
4026b091 2003=item *
e4c43fa1 2004
4026b091 2005Fetching the name of a glob that was previously UTF-8 but wasn't any
ec30d9c4
AC
2006longer would return that name flagged as UTF-8.
2007L<[perl #131263]|https://rt.perl.org/Ticket/Display.html?id=131263>
e4c43fa1
S
2008
2009=item *
2010
4026b091
S
2011The perl C<sprintf()> function (via the underlying C function
2012C<Perl_sv_vcatpvfn_flags()>) has been heavily reworked to fix many minor
2013bugs, including the integer wrapping of large width and precision
2014specifiers and potential buffer overruns. It has also been made faster in
2015many cases.
e4c43fa1 2016
4026b091 2017=item *
e4c43fa1 2018
4026b091
S
2019Exiting from an C<eval>, whether normally or via an exception, now always
2020frees temporary values (possibly calling destructors) I<before> setting
2021C<$@>. For example:
e4c43fa1 2022
4026b091
S
2023 sub DESTROY { eval { die "died in DESTROY"; } }
2024 eval { bless []; };
2025 # $@ used to be equal to "died in DESTROY" here; it's now "".
e4c43fa1 2026
4026b091 2027=item *
e4c43fa1 2028
4026b091 2029Fixed a duplicate symbol failure with C<-flto -mieee-fp> builds.
2022b8ae
SK
2030F<pp.c> defined C<_LIB_VERSION> which C<-lieee> already defines.
2031L<[perl #131786]|https://rt.perl.org/Ticket/Display.html?id=131786>
e4c43fa1
S
2032
2033=item *
2034
4026b091 2035The tokenizer no longer consumes the exponent part of a floating
ec30d9c4
AC
2036point number if it's incomplete.
2037L<[perl #131725]|https://rt.perl.org/Ticket/Display.html?id=131725>
e4c43fa1 2038
4026b091 2039=item *
e4c43fa1 2040
4026b091
S
2041On non-threaded builds, for C<m/$null/> where C<$null> is an empty
2042string is no longer treated as if the C</o> flag was present when the
2043previous matching match operator included the C</o> flag. The
2044rewriting used to implement this behavior could confuse the
2022b8ae
SK
2045interpreter. This matches the behaviour of threaded builds.
2046L<[perl #124368]|https://rt.perl.org/Ticket/Display.html?id=124368>
4026b091
S
2047
2048=item *
e4c43fa1 2049
4026b091
S
2050Parsing a C<sub> definition could cause a use after free if the C<sub>
2051keyword was followed by whitespace including newlines (and comments.)
2052L<[perl #131836]|https://rt.perl.org/Public/Bug/Display.html?id=131836>
e4c43fa1 2053
4026b091 2054=item *
e4c43fa1 2055
4026b091 2056The tokenizer now correctly adjusts a parse pointer when skipping
4850dd21 2057whitespace in a C<< ${identifier} >> construct.
4026b091 2058L<[perl #131949]|https://rt.perl.org/Public/Bug/Display.html?id=131949>
e4c43fa1 2059
4026b091 2060=item *
e4c43fa1 2061
4026b091
S
2062Accesses to C<${^LAST_FH}> no longer assert after using any of a
2063variety of I/O operations on a non-glob.
2064L<[perl #128263]|https://rt.perl.org/Public/Bug/Display.html?id=128263>
e4c43fa1 2065
4026b091 2066=item *
e4c43fa1 2067
94fc6237 2068The XS-level C<Copy()>, C<Move()>, C<Zero()> macros and their variants now
4026b091
S
2069assert if the pointers supplied are C<NULL>. ISO C considers
2070supplying NULL pointers to the functions these macros are built upon
2071as undefined behaviour even when their count parameters are zero.
2072Based on these assertions and the original bug report three macro
2073calls were made conditional.
2074L<[perl #131746]|https://rt.perl.org/Public/Bug/Display.html?id=131746>
2075L<[perl #131892]|https://rt.perl.org/Public/Bug/Display.html?id=131892>
e4c43fa1
S
2076
2077=item *
2078
4026b091
S
2079Only the C<=> operator is permitted for defining defaults for
2080parameters in subroutine signatures. Previously other assignment
4850dd21 2081operators, e.g. C<+=>, were also accidentally permitted.
4026b091 2082L<[perl #131777]|https://rt.perl.org/Public/Bug/Display.html?id=131777>
e4c43fa1 2083
4026b091 2084=item *
e4c43fa1 2085
4026b091
S
2086Package names are now always included in C<:prototype> warnings
2087L<[perl #131833]|https://rt.perl.org/Public/Bug/Display.html?id=131833>
e4c43fa1 2088
4026b091 2089=item *
e4c43fa1 2090
4026b091
S
2091The C<je_old_stack_hwm> field, previously only found in the C<jmpenv>
2092structure on debugging builds, has been added to non-debug builds as
2093well. This fixes an issue with some CPAN modules caused by the size of
2094this structure varying between debugging and non-debugging builds.
2095L<[perl #131942]|https://rt.perl.org/Public/Bug/Display.html?id=131942>
e4c43fa1 2096
4026b091 2097=item *
e4c43fa1 2098
4026b091 2099The arguments to the C<ninstr()> macro are now correctly parenthesized.
e4c43fa1 2100
4026b091 2101=item *
e4c43fa1 2102
4026b091
S
2103A NULL pointer dereference in the C<S_regmatch()> function has been
2104fixed.
2105L<[perl #132017]|https://rt.perl.org/Public/Bug/Display.html?id=132017>
e4c43fa1 2106
4026b091 2107=item *
e4c43fa1 2108
4026b091
S
2109Calling L<exec PROGRAM LIST|perlfunc/exec PROGRAM LIST> with an empty C<LIST>
2110has been fixed. This should call C<execvp()> with an empty C<argv> array
2111(containing only the terminating C<NULL> pointer), but was instead just
2112returning false (and not setting L<C<$!>|perlvar/$!>).
2113L<[perl #131730]|https://rt.perl.org/Public/Bug/Display.html?id=131730>
e4c43fa1 2114
4026b091 2115=item *
e4c43fa1 2116
4026b091
S
2117The C<gv_fetchmeth_sv> C function stopped working properly in Perl 5.22 when
2118fetching a constant with a UTF-8 name if that constant subroutine was stored in
2119the stash as a simple scalar reference, rather than a full typeglob. This has
2120been corrected.
e4c43fa1 2121
4026b091 2122=item *
e4c43fa1 2123
4026b091
S
2124Single-letter debugger commands followed by an argument which starts with
2125punctuation (e.g. C<p$^V> and C<x@ARGV>) now work again. They had been
2126wrongly requiring a space between the command and the argument.
2127L<[perl #120174]|https://rt.perl.org/Public/Bug/Display.html?id=120174>
e4c43fa1 2128
4026b091 2129=item *
e4c43fa1 2130
4026b091
S
2131L<splice|perlfunc/splice ARRAY,OFFSET,LENGTH,LIST> now throws an exception
2132("Modification of a read-only value attempted") when modifying a read-only
2133array. Until now it had been silently modifying the array. The new behaviour
2134is consistent with the behaviour of L<push|perlfunc/push ARRAY,LIST> and
2135L<unshift|perlfunc/unshift ARRAY,LIST>.
2136L<[perl #131000]|https://rt.perl.org/Public/Bug/Display.html?id=131000>
e4c43fa1 2137
4026b091 2138=item *
e4c43fa1 2139
4026b091
S
2140C<stat()>, C<lstat()>, and file test operators now fail if given a
2141filename containing a nul character, in the same way that C<open()>
2142already fails.
e4c43fa1 2143
4026b091 2144=item *
e4c43fa1 2145
4026b091
S
2146C<stat()>, C<lstat()>, and file test operators now reliably set C<$!> when
2147failing due to being applied to a closed or otherwise invalid file handle.
e4c43fa1 2148
4026b091 2149=item *
e4c43fa1 2150
4026b091
S
2151File test operators for Unix permission bits that don't exist on a
2152particular platform, such as C<-k> (sticky bit) on Windows, now check that
2153the file being tested exists before returning the blanket false result,
2154and yield the appropriate errors if the argument doesn't refer to a file.
e4c43fa1 2155
4026b091 2156=item *
da251d45 2157
94fc6237
DM
2158Fixed a 'read before buffer' overrun when parsing a range starting with
2159C<\N{}> at the beginning of the character set for the transliteration
ec30d9c4
AC
2160operator.
2161L<[perl #132245]|https://rt.perl.org/Ticket/Display.html?id=132245>
e4c43fa1 2162
4026b091 2163=item *
e4c43fa1 2164
94fc6237 2165Fixed a leaked scalar when parsing an empty C<\N{}> at compile-time.
ec30d9c4 2166L<[perl #132245]|https://rt.perl.org/Ticket/Display.html?id=132245>
e4c43fa1 2167
4026b091 2168=item *
e4c43fa1 2169
4026b091 2170Calling C<do $path> on a directory or block device now yields a meaningful
ec30d9c4
AC
2171error code in C<$!>.
2172L<[perl #125774]|https://rt.perl.org/Ticket/Display.html?id=125774>
e4c43fa1 2173
4026b091
S
2174=item *
2175
2176Regexp substitution using an overloaded replacement value that provides
2177a tainted stringification now correctly taints the resulting string.
ec30d9c4 2178L<[perl #115266]|https://rt.perl.org/Ticket/Display.html?id=115266>
e4c43fa1
S
2179
2180=item *
2181
4026b091
S
2182Lexical sub declarations in C<do> blocks such as C<do { my sub lex; 123 }>
2183could corrupt the stack, erasing items already on the stack in the
ec30d9c4
AC
2184enclosing statement. This has been fixed.
2185L<[perl #132442]|https://rt.perl.org/Ticket/Display.html?id=132442>
e4c43fa1 2186
4026b091
S
2187=item *
2188
2189C<pack> and C<unpack> can now handle repeat counts and lengths that
ec30d9c4
AC
2190exceed two billion.
2191L<[perl #119367]|https://rt.perl.org/Ticket/Display.html?id=119367>
e4c43fa1 2192
4026b091
S
2193=item *
2194
2195Digits past the radix point in octal and binary floating point literals
2196now have the correct weight on platforms where a floating point
2197significand doesn't fit into an integer type.
435ebfcb 2198
4026b091 2199=item *
bdd8ae1c 2200
94fc6237
DM
2201The canonical truth value no longer has a spurious special meaning as a
2202callable subroutine. It used to be a magic placeholder for a missing
2203C<import> or C<unimport> method, but is now treated like any other string
2204C<1>.
ec30d9c4 2205L<[perl #126042]|https://rt.perl.org/Ticket/Display.html?id=126042>
435ebfcb 2206
4026b091
S
2207=item *
2208
2209C<system> now reduces its arguments to strings in the parent process, so
2210any effects of stringifying them (such as overload methods being called
2211or warnings being emitted) are visible in the way the program expects.
ec30d9c4 2212L<[perl #121105]|https://rt.perl.org/Ticket/Display.html?id=121105>
4026b091
S
2213
2214=item *
2215
2216The C<readpipe()> built-in function now checks at compile time that
2217it has only one parameter expression, and puts it in scalar context,
ec30d9c4
AC
2218thus ensuring that it doesn't corrupt the stack at runtime.
2219L<[perl #4574]|https://rt.perl.org/Ticket/Display.html?id=4574>
4026b091
S
2220
2221=item *
2222
2223C<sort> now performs correct reference counting when aliasing C<$a> and
2224C<$b>, thus avoiding premature destruction and leakage of scalars if they
ec30d9c4
AC
2225are re-aliased during execution of the sort comparator.
2226L<[perl #92264]|https://rt.perl.org/Ticket/Display.html?id=92264>
4026b091
S
2227
2228=item *
2229
2230C<reverse> with no operand, reversing C<$_> by default, is no longer in
ec30d9c4
AC
2231danger of corrupting the stack.
2232L<[perl #132544]|https://rt.perl.org/Ticket/Display.html?id=132544>
4026b091
S
2233
2234=item *
2235
2236C<exec>, C<system>, et al are no longer liable to have their argument
2237lists corrupted by reentrant calls and by magic such as tied scalars.
ec30d9c4 2238L<[perl #129888]|https://rt.perl.org/Ticket/Display.html?id=129888>
4026b091
S
2239
2240=item *
2241
2242Perl's own C<malloc> no longer gets confused by attempts to allocate
ec30d9c4
AC
2243more than a gigabyte on a 64-bit platform.
2244L<[perl #119829]|https://rt.perl.org/Ticket/Display.html?id=119829>
4026b091
S
2245
2246=item *
2247
2248Stacked file test operators in a sort comparator expression no longer
ec30d9c4
AC
2249cause a crash.
2250L<[perl #129347]|https://rt.perl.org/Ticket/Display.html?id=129347>
e4c43fa1
S
2251
2252=item *
2253
4026b091
S
2254An identity C<tr///> transformation on a reference is no longer mistaken
2255for that reference for the purposes of deciding whether it can be
ec30d9c4
AC
2256assigned to.
2257L<[perl #130578]|https://rt.perl.org/Ticket/Display.html?id=130578>
4026b091
S
2258
2259=item *
2260
2261Lengthy hexadecimal, octal, or binary floating point literals no
2262longer cause undefined behaviour when parsing digits that are of such
2263low significance that they can't affect the floating point value.
ec30d9c4 2264L<[perl #131894]|https://rt.perl.org/Ticket/Display.html?id=131894>
4026b091
S
2265
2266=item *
2267
2268C<open $$scalarref...> and similar invocations no longer leak the file
ec30d9c4
AC
2269handle.
2270L<[perl #115814]|https://rt.perl.org/Ticket/Display.html?id=115814>
4026b091
S
2271
2272=item *
2273
2274Some convoluted kinds of regexp no longer cause an arithmetic overflow
ec30d9c4
AC
2275when compiled.
2276L<[perl #131893]|https://rt.perl.org/Ticket/Display.html?id=131893>
4026b091
S
2277
2278=item *
2279
2280The default typemap, by avoiding C<newGVgen>, now no longer leaks when
ec30d9c4
AC
2281XSUBs return file handles (C<PerlIO *> or C<FILE *>).
2282L<[perl #115814]|https://rt.perl.org/Ticket/Display.html?id=115814>
4026b091
S
2283
2284=item *
2285
2286Creating a C<BEGIN> block as an XS subroutine with a prototype no longer
2287crashes because of the early freeing of the subroutine.
2288
2289=item *
2290
2291The C<printf> format specifier C<%.0f> no longer rounds incorrectly
ec30d9c4
AC
2292L<[perl #47602]|https://rt.perl.org/Ticket/Display.html?id=47602>,
2293and now shows the correct sign for a negative zero.
4026b091 2294
4026b091
S
2295=item *
2296
2297Fixed an issue where the error C<< Scalar value @arrayname[0] better
2298written as $arrayname >> would give an error C<< Cannot printf Inf with 'c' >>
ec30d9c4
AC
2299when arrayname starts with C<< Inf >>.
2300L<[perl #132645]|https://rt.perl.org/Ticket/Display.html?id=132645>
4026b091
S
2301
2302=item *
2303
2304The Perl implementation of C<< getcwd() >> in C<< Cwd >> in the PathTools
2305distribution now behaves the same as XS implementation on errors: it
ec30d9c4
AC
2306returns an error, and sets C<< $! >>.
2307L<[perl #132648]|https://rt.perl.org/Ticket/Display.html?id=132648>
4026b091
S
2308
2309=item *
2310
4026b091 2311Vivify array elements when putting them on the stack.
ec30d9c4
AC
2312Fixes L<[perl #8910]|https://rt.perl.org/Ticket/Display.html?id=8910>
2313(reported in April 2002).
4026b091
S
2314
2315=item *
2316
ec30d9c4
AC
2317Fixed parsing of braced subscript after parens. Fixes
2318L<[perl #8045]|https://rt.perl.org/Ticket/Display.html?id=8045>
4026b091
S
2319(reported in December 2001).
2320
2321=item *
2322
2323C<tr/non_utf8/long_non_utf8/c> could give the wrong results when the
2324length of the replacement character list was greater than 0x7fff.
2325
2326=item *
2327
2328C<tr/non_utf8/non_utf8/cd> failed to add the implied
2329C<\x{100}-\x{7fffffff}> to the search character list.
2330
2331=item *
2332
94fc6237
DM
2333Compilation failures within "perl-within-perl" constructs, such as with
2334string interpolation and the right part of C<s///e>, now cause
4026b091
S
2335compilation to abort earlier.
2336
2337Previously compilation could continue in order to report other errors,
2338but the failed sub-parse could leave partly parsed constructs on the
2339parser shift-reduce stack, confusing the parser, leading to perl
ec30d9c4
AC
2340crashes.
2341L<[perl #125351]|https://rt.perl.org/Ticket/Display.html?id=125351>
4026b091
S
2342
2343=item *
2344
2345On threaded perls where the decimal point (radix) character is not a
2346dot, it has been possible for a race to occur between threads when one
94fc6237
DM
2347needs to use the real radix character (such as with C<sprintf>). This has
2348now been fixed by use of a mutex on systems without thread-safe locales,
2349and the problem just doesn't come up on those with thread-safe locales.
4026b091
S
2350
2351=item *
2352
94fc6237
DM
2353Errors while compiling a regex character class could sometime trigger an
2354assertion failure.
ec30d9c4 2355L<[perl #132163]|https://rt.perl.org/Ticket/Display.html?id=132163>
4026b091 2356
e4c43fa1
S
2357=back
2358
e4c43fa1 2359=head1 Acknowledgements
5ef73200 2360
0423cb17 2361Perl 5.28.0 represents approximately 12 months of development since Perl
4026b091 23625.26.0 and contains approximately 730,000 lines of changes across 2,200
e56d2014 2363files from 77 authors.
4026b091
S
2364
2365Excluding auto-generated files, documentation and release tools, there were
2366approximately 580,000 lines of changes to 1,300 .pm, .t, .c and .h files.
2367
2368Perl continues to flourish into its fourth decade thanks to a vibrant
2369community of users and developers. The following people are known to have
2370contributed the improvements that became Perl 5.28.0:
2371
2372Aaron Crane, Abigail, Ævar Arnfjörð Bjarmason, Alberto Simões, Alexandr
2373Savca, Andrew Fresh, Andy Dougherty, Andy Lester, Aristotle Pagaltzis, Ask
2374Bjørn Hansen, Chris 'BinGOs' Williams, Craig A. Berry, Dagfinn Ilmari
2375Mannsåker, Dan Collins, Daniel Dragan, David Cantrell, David Mitchell,
2376Dmitry Ulanov, Dominic Hargreaves, E. Choroba, Eric Herman, Eugen Konkov,
2377Father Chrysostomos, Gene Sullivan, George Hartzell, Graham Knop, Harald
2378Jörg, H.Merijn Brand, Hugo van der Sanden, Jacques Germishuys, James E
2379Keenan, Jarkko Hietaniemi, Jerry D. Hedden, J. Nick Koston, John Lightsey,
2380John Peacock, John P. Linderman, John SJ Anderson, Karen Etheridge, Karl
2381Williamson, Ken Brown, Ken Cotterill, Leon Timmermans, Lukas Mai, Marco
2382Fontani, Marc-Philip Werner, Matthew Horsfall, Neil Bowers, Nicholas Clark,
2383Nicolas R., Niko Tyni, Pali, Paul Marquess, Peter John Acklam, Reini Urban,
2384Renee Baecker, Ricardo Signes, Robin Barker, Sawyer X, Scott Lanning, Sergey
e56d2014
S
2385Aleynikov, Shirakata Kentaro, Shoichi Kaji, Slaven Rezic, Smylers, Steffen
2386Müller, Steve Hay, Sullivan Beck, Thomas Sibley, Todd Rinaldo, Tomasz
2387Konojacki, Tom Hukins, Tom Wyant, Tony Cook, Vitali Peil, Yves Orton,
2388Zefram.
4026b091
S
2389
2390The list above is almost certainly incomplete as it is automatically
2391generated from version control history. In particular, it does not include
2392the names of the (very much appreciated) contributors who reported issues to
2393the Perl bug tracker.
2394
2395Many of the changes included in this version originated in the CPAN modules
2396included in Perl's core. We're grateful to the entire CPAN community for
2397helping Perl to flourish.
2398
2399For a more complete list of all of Perl's historical contributors, please
2400see the F<AUTHORS> file in the Perl source distribution.
f5b73711 2401
44691e6f
AB
2402=head1 Reporting Bugs
2403
b5cbfe35
S
2404If you find what you think is a bug, you might check the perl bug database
2405at L<https://rt.perl.org/> . There may also be information at
2406L<http://www.perl.org/> , the Perl Home Page.
44691e6f 2407
e08634c5
SH
2408If you believe you have an unreported bug, please run the L<perlbug> program
2409included with your release. Be sure to trim your bug down to a tiny but
2410sufficient test case. Your bug report, along with the output of C<perl -V>,
b5cbfe35 2411will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
44691e6f 2412
87c118b9
DM
2413If the bug you are reporting has security implications which make it
2414inappropriate to send to a publicly archived mailing list, then see
c0ea3294
SH
2415L<perlsec/SECURITY VULNERABILITY CONTACT INFORMATION>
2416for details of how to report the issue.
44691e6f 2417
390ae6f9
S
2418=head1 Give Thanks
2419
2420If you wish to thank the Perl 5 Porters for the work we had done in Perl 5,
2421you can do so by running the C<perlthanks> program:
2422
2423 perlthanks
2424
2425This will send an email to the Perl 5 Porters list with your show of thanks.
2426
44691e6f
AB
2427=head1 SEE ALSO
2428
e08634c5
SH
2429The F<Changes> file for an explanation of how to view exhaustive details on
2430what changed.
44691e6f
AB
2431
2432The F<INSTALL> file for how to build Perl.
2433
2434The F<README> file for general stuff.
2435
2436The F<Artistic> and F<Copying> files for copyright information.
2437
2438=cut