extra code in pp_concat, Take 2
[p5sagit/p5-mst-13.2.git] / pod / perl590delta.pod
CommitLineData
d4432bb5 1=head1 NAME
cc0fca54 2
55e8fca7 3perldelta - what is new for perl v5.9.0
cc0fca54 4
5=head1 DESCRIPTION
6
55e8fca7 7This document describes differences between the 5.8.0 release and
8the 5.9.0 release.
f39f21d8 9
55e8fca7 10=head1 Incompatible Changes
87880fe6 11
1ea9f2df 12=head2 Hash Randomisation
13
14Mainly due to security reasons, the "random ordering" of hashes
15has been made even more random. Previously while the order of hash
16elements from keys(), values(), and each() was essentially random,
17it was still repeatable. Now, however, the order varies between
18different runs of Perl.
19
20B<Perl has never guaranteed any ordering of the hash keys>, and the
21ordering has already changed several times during the lifetime of
22Perl 5. Also, the ordering of hash keys has always been, and
23continues to be, affected by the insertion order.
24
25The added randomness may affect applications.
26
27One possible scenario is when output of an application has included
28hash data. For example, if you have used the Data::Dumper module to
29dump data into different files, and then compared the files to see
30whether the data has changed, now you will have false positives since
31the order in which hashes are dumped will vary. In general the cure
32is to sort the keys (or the values); in particular for Data::Dumper to
33use the C<Sortkeys> option. If some particular order is really
34important, use tied hashes: for example the Tie::IxHash module
35which by default preserves the order in which the hash elements
36were added.
37
38More subtle problem is reliance on the order of "global destruction".
39That is what happens at the end of execution: Perl destroys all data
40structures, including user data. If your destructors (the DESTROY
41subroutines) have assumed any particular ordering to the global
42destruction, there might be problems ahead. For example, in a
43destructor of one object you cannot assume that objects of any other
44class are still available, unless you hold a reference to them.
45If the environment variable PERL_DESTRUCT_LEVEL is set to a non-zero
46value, or if Perl is exiting a spawned thread, it will also destruct
47the ordinary references and the symbol tables that are no longer in use.
48You can't call a class method or an ordinary function on a class that
49has been collected that way.
50
51The hash randomisation is certain to reveal hidden assumptions about
52some particular ordering of hash elements, and outright bugs: it
53revealed a few bugs in the Perl core and core modules.
54
55To disable the hash randomisation in runtime, set the environment
56variable PERL_HASH_SEED to 0 (zero) before running Perl (for more
57information see L<perlrun/PERL_HASH_SEED>), or to disable the feature
58completely in compile time, compile with C<-DNO_HASH_SEED> (see F<INSTALL>).
59
60See L<perlsec/"Algorithmic Complexity Attacks"> for the original
61rationale behind this change.
62
63=head2 UTF-8 On Filehandles No Longer Activated By Locale
64
65In Perl 5.8.0 all filehandles, including the standard filehandles,
66were implicitly set to be in Unicode UTF-8 if the locale settings
67indicated the use of UTF-8. This feature caused too many problems,
68so the feature was turned off and redesigned: see L</"Core Enhancements">.
69
70=head2 Single-number v-strings are no longer v-strings before "=>"
71
72The version strings or v-strings (see L<perldata/"Version Strings">)
73feature introduced in Perl 5.6.0 has been a source of some confusion--
74especially when the user did not want to use it, but Perl thought it
75knew better. Especially troublesome has been the feature that before
76a "=>" a version string (a "v" followed by digits) has been interpreted
77as a v-string instead of a string literal. In other words:
78
79 %h = ( v65 => 42 );
80
81has meant since Perl 5.6.0
82
83 %h = ( 'A' => 42 );
84
85(at least in platforms of ASCII progeny) Perl 5.8.1 restored the
86more natural interpretation
87
88 %h = ( 'v65' => 42 );
89
90The multi-number v-strings like v65.66 and 65.66.67 still continue to
91be v-strings in Perl 5.8.
92
93=head2 (Win32) The -C Switch Has Been Repurposed
94
95The -C switch has changed in an incompatible way. The old semantics
96of this switch only made sense in Win32 and only in the "use utf8"
97universe in 5.6.x releases, and do not make sense for the Unicode
98implementation in 5.8.0. Since this switch could not have been used
99by anyone, it has been repurposed. The behavior that this switch
100enabled in 5.6.x releases may be supported in a transparent,
101data-dependent fashion in a future release.
102
103For the new life of this switch, see L<"UTF-8 no longer default under
104UTF-8 locales">, and L<perlrun/-C>.
105
106=head2 (Win32) The /d Switch Of cmd.exe
107
108Since version 5.8.1, perl uses the /d switch when running the cmd.exe shell
109internally for system(), backticks, and when opening pipes to external
110programs. The extra switch disables the execution of AutoRun commands
111from the registry, which is generally considered undesirable when
112running external programs. If you wish to retain compatibility with
113the older behavior, set PERL5SHELL in your environment to C<cmd /x/c>.
114
f02c194e 115=head2 The C<$*> variable has been removed
116
117C<$*>, which was deprecated in favor of the C</s> and C</m> regexp
118modifiers, has been removed.
119
55e8fca7 120=head1 Core Enhancements
87880fe6 121
1ea9f2df 122=head2 Assertions
123
fa11829f 124Perl 5.9.0 has experimental support for assertions. Note that the user
1ea9f2df 125interface is not fully stabilized yet, and it may change until the 5.10.0
126release. A new command-line switch, B<-A>, is used to activate
127assertions, which are declared with the C<assertions> pragma. See
128L<assertions>.
129
130=head2 Defined-or operators
131
132A new operator C<//> (defined-or) has been implemented.
133The following statement:
134
135 $a // $b
136
137is merely equivalent to
138
139 defined $a ? $a : $b
140
141and
142
143 $c //= $d;
144
145can be used instead of
146
147 $c = $d unless defined $c;
148
149This operator has the same precedence and associativity as C<||>.
150It has a low-precedence counterpart, C<err>, which has the same precedence
151and associativity as C<or>. Special care has been taken to ensure that
152those operators Do What You Mean while not breaking old code, but some
153edge cases involving the empty regular expression may now parse
154differently. See L<perlop> for details.
155
156=head2 UTF-8 no longer default under UTF-8 locales
157
158In Perl 5.8.0 many Unicode features were introduced. One of them
159was found to be of more nuisance than benefit: the automagic
160(and silent) "UTF-8-ification" of filehandles, including the
161standard filehandles, if the user's locale settings indicated
162use of UTF-8.
163
164For example, if you had C<en_US.UTF-8> as your locale, your STDIN and
165STDOUT were automatically "UTF-8", in other words an implicit
166binmode(..., ":utf8") was made. This meant that trying to print, say,
167chr(0xff), ended up printing the bytes 0xc3 0xbf. Hardly what
168you had in mind unless you were aware of this feature of Perl 5.8.0.
169The problem is that the vast majority of people weren't: for example
170in RedHat releases 8 and 9 the B<default> locale setting is UTF-8, so
171all RedHat users got UTF-8 filehandles, whether they wanted it or not.
172The pain was intensified by the Unicode implementation of Perl 5.8.0
173(still) having nasty bugs, especially related to the use of s/// and
174tr///. (Bugs that have been fixed in 5.8.1)
175
176Therefore a decision was made to backtrack the feature and change it
177from implicit silent default to explicit conscious option. The new
178Perl command line option C<-C> and its counterpart environment
179variable PERL_UNICODE can now be used to control how Perl and Unicode
180interact at interfaces like I/O and for example the command line
181arguments. See L<perlrun/-C> and L<perlrun/PERL_UNICODE> for more
182information.
183
184=head2 Unsafe signals again available
185
186In Perl 5.8.0 the so-called "safe signals" were introduced. This
187means that Perl no longer handles signals immediately but instead
188"between opcodes", when it is safe to do so. The earlier immediate
189handling easily could corrupt the internal state of Perl, resulting
190in mysterious crashes.
191
192However, the new safer model has its problems too. Because now an
193opcode, a basic unit of Perl execution, is never interrupted but
194instead let to run to completion, certain operations that can take a
195long time now really do take a long time. For example, certain
196network operations have their own blocking and timeout mechanisms, and
197being able to interrupt them immediately would be nice.
198
199Therefore perl 5.8.1 introduced a "backdoor" to restore the pre-5.8.0
200(pre-5.7.3, really) signal behaviour. Just set the environment variable
201PERL_SIGNALS to C<unsafe>, and the old immediate (and unsafe)
202signal handling behaviour returns. See L<perlrun/PERL_SIGNALS>
203and L<perlipc/"Deferred Signals (Safe Signals)">.
204
205In completely unrelated news, you can now use safe signals with
206POSIX::SigAction. See L<POSIX/POSIX::SigAction>.
207
13cf4046 208=head2 Tied Arrays with Negative Array Indices
209
210Formerly, the indices passed to C<FETCH>, C<STORE>, C<EXISTS>, and
211C<DELETE> methods in tied array class were always non-negative. If
212the actual argument was negative, Perl would call FETCHSIZE implicitly
213and add the result to the index before passing the result to the tied
1ea9f2df 214array method. This behaviour is now optional. If the tied array class
13cf4046 215contains a package variable named C<$NEGATIVE_INDICES> which is set to
216a true value, negative values will be passed to C<FETCH>, C<STORE>,
217C<EXISTS>, and C<DELETE> unchanged.
218
1ea9f2df 219=head2 local ${$x}
220
221The syntaxes
222
223 local ${$x}
224 local @{$x}
225 local %{$x}
226
227now do localise variables, given that the $x is a valid variable name.
228
229=head2 Unicode Character Database 4.0.0
230
231The copy of the Unicode Character Database included in Perl 5.8 has
232been updated to 4.0.0 from 3.2.0. This means for example that the
233Unicode character properties are as in Unicode 4.0.0.
234
235=head2 Miscellaneous Enhancements
236
237C<unpack()> now defaults to unpacking the C<$_>.
238
239C<map> in void context is no longer expensive. C<map> is now context
240aware, and will not construct a list if called in void context.
241
242If a socket gets closed by the server while printing to it, the client
243now gets a SIGPIPE. While this new feature was not planned, it fell
244naturally out of PerlIO changes, and is to be considered an accidental
245feature.
246
247PerlIO::get_layers(FH) returns the names of the PerlIO layers
248active on a filehandle.
249
250PerlIO::via layers can now have an optional UTF8 method to
251indicate whether the layer wants to "auto-:utf8" the stream.
252
253utf8::is_utf8() has been added as a quick way to test whether
254a scalar is encoded internally in UTF-8 (Unicode).
255
55e8fca7 256=head1 Modules and Pragmata
87880fe6 257
1ea9f2df 258=head2 Updated Modules And Pragmata
259
260The following modules and pragmata have been updated since Perl 5.8.0:
261
262=over 4
263
264=item base
265
266=item B::Bytecode
267
268In much better shape than it used to be. Still far from perfect, but
269maybe worth a try.
270
271=item B::Concise
272
273=item B::Deparse
274
275=item Benchmark
276
277An optional feature, C<:hireswallclock>, now allows for high
278resolution wall clock times (uses Time::HiRes).
279
280=item ByteLoader
281
282See B::Bytecode.
283
284=item bytes
285
286Now has bytes::substr.
287
288=item CGI
289
290=item charnames
291
292One can now have custom character name aliases.
293
294=item CPAN
295
296There is now a simple command line frontend to the CPAN.pm
297module called F<cpan>.
298
299=item Data::Dumper
300
301A new option, Pair, allows choosing the separator between hash keys
302and values.
303
304=item DB_File
305
306=item Devel::PPPort
307
308=item Digest::MD5
309
310=item Encode
311
312Significant updates on the encoding pragma functionality
313(tr/// and the DATA filehandle, formats).
314
315If a filehandle has been marked as to have an encoding, unmappable
316characters are detected already during input, not later (when the
317corrupted data is being used).
318
319The ISO 8859-6 conversion table has been corrected (the 0x30..0x39
320erroneously mapped to U+0660..U+0669, instead of U+0030..U+0039). The
321GSM 03.38 conversion did not handle escape sequences correctly. The
322UTF-7 encoding has been added (making Encode feature-complete with
323Unicode::String).
324
325=item fields
326
327=item libnet
328
329=item Math::BigInt
330
331A lot of bugs have been fixed since v1.60, the version included in Perl
332v5.8.0. Especially noteworthy are the bug in Calc that caused div and mod to
333fail for some large values, and the fixes to the handling of bad inputs.
334
335Some new features were added, e.g. the broot() method, you can now pass
336parameters to config() to change some settings at runtime, and it is now
337possible to trap the creation of NaN and infinity.
338
339As usual, some optimizations took place and made the math overall a tad
340faster. In some cases, quite a lot faster, actually. Especially alternative
341libraries like Math::BigInt::GMP benefit from this. In addition, a lot of the
342quite clunky routines like fsqrt() and flog() are now much much faster.
343
344=item MIME::Base64
345
346=item NEXT
347
348Diamond inheritance now works.
349
350=item Net::Ping
351
352=item PerlIO::scalar
353
354Reading from non-string scalars (like the special variables, see
355L<perlvar>) now works.
356
357=item podlators
358
359=item Pod::LaTeX
360
361=item PodParsers
362
363=item Pod::Perldoc
364
365Complete rewrite. As a side-effect, no longer refuses to startup when
366run by root.
367
368=item Scalar::Util
369
370New utilities: refaddr, isvstring, looks_like_number, set_prototype.
371
372=item Storable
373
374Can now store code references (via B::Deparse, so not foolproof).
375
376=item strict
377
378Earlier versions of the strict pragma did not check the parameters
379implicitly passed to its "import" (use) and "unimport" (no) routine.
380This caused the false idiom such as:
381
382 use strict qw(@ISA);
383 @ISA = qw(Foo);
384
385This however (probably) raised the false expectation that the strict
386refs, vars and subs were being enforced (and that @ISA was somehow
387"declared"). But the strict refs, vars, and subs are B<not> enforced
388when using this false idiom.
389
390Starting from Perl 5.8.1, the above B<will> cause an error to be
391raised. This may cause programs which used to execute seemingly
392correctly without warnings and errors to fail when run under 5.8.1.
393This happens because
394
395 use strict qw(@ISA);
396
397will now fail with the error:
398
399 Unknown 'strict' tag(s) '@ISA'
400
401The remedy to this problem is to replace this code with the correct idiom:
402
403 use strict;
404 use vars qw(@ISA);
405 @ISA = qw(Foo);
406
407=item Term::ANSIcolor
408
409=item Test::Harness
410
411Now much more picky about extra or missing output from test scripts.
412
413=item Test::More
414
415=item Test::Simple
416
417=item Text::Balanced
418
419=item Time::HiRes
420
421Use of nanosleep(), if available, allows mixing subsecond sleeps with
422alarms.
423
424=item threads
425
426Several fixes, for example for join() problems and memory
427leaks. In some platforms (like Linux) that use glibc the minimum memory
428footprint of one ithread has been reduced by several hundred kilobytes.
429
430=item threads::shared
431
432Many memory leaks have been fixed.
433
434=item Unicode::Collate
435
436=item Unicode::Normalize
437
438=item Win32::GetFolderPath
439
440=item Win32::GetOSVersion
441
442Now returns extra information.
443
444=back
445
55e8fca7 446=head1 Utility Changes
87880fe6 447
1ea9f2df 448The C<h2xs> utility now produces a more modern layout:
449F<Foo-Bar/lib/Foo/Bar.pm> instead of F<Foo/Bar/Bar.pm>.
450Also, the boilerplate test is now called F<t/Foo-Bar.t>
451instead of F<t/1.t>.
452
453The Perl debugger (F<lib/perl5db.pl>) has now been extensively
454documented and bugs found while documenting have been fixed.
455
456C<perldoc> has been rewritten from scratch to be more robust and
457featureful.
458
459C<perlcc -B> works now at least somewhat better, while C<perlcc -c>
460is rather more broken. (The Perl compiler suite as a whole continues
461to be experimental.)
462
55e8fca7 463=head1 New Documentation
87880fe6 464
1ea9f2df 465perl573delta has been added to list the differences between the
466(now quite obsolete) development releases 5.7.2 and 5.7.3.
467
468perl58delta and perl581delta have been added: these are the perldeltas
469of 5.8.0 and 5.8.1, detailing the differences respectively between
4705.6.0 and 5.8.0, and between 5.8.0 and 5.8.1.
471
472perlartistic has been added: it is the Artistic License in pod format,
473making it easier for modules to refer to it.
474
475perlcheat has been added: it is a Perl cheat sheet.
476
477perlgpl has been added: it is the GNU General Public License in pod
478format, making it easier for modules to refer to it.
479
480perlmacosx has been added to tell about the installation and use
481of Perl in Mac OS X.
482
483perlos400 has been added to tell about the installation and use
484of Perl in OS/400 PASE.
485
486perlreref has been added: it is a regular expressions quick reference.
487
55e8fca7 488=head1 Performance Enhancements
87880fe6 489
55e8fca7 490=head1 Installation and Configuration Improvements
87880fe6 491
1ea9f2df 492The UNIX standard Perl location, F</usr/bin/perl>, is no longer
493overwritten by default if it exists. This change was very prudent
494because so many UNIX vendors already provide a F</usr/bin/perl>,
495but simultaneously many system utilities may depend on that
496exact version of Perl, so better not to overwrite it.
497
498One can now specify installation directories for site and vendor man
499and HTML pages, and site and vendor scripts. See F<INSTALL>.
500
501One can now specify a destination directory for Perl installation
502by specifying the DESTDIR variable for C<make install>. (This feature
503is slightly different from the previous C<Configure -Dinstallprefix=...>.)
504See F<INSTALL>.
505
506gcc versions 3.x introduced a new warning that caused a lot of noise
507during Perl compilation: C<gcc -Ialreadyknowndirectory (warning:
508changing search order)>. This warning has now been avoided by
509Configure weeding out such directories before the compilation.
510
511One can now build subsets of Perl core modules by using the
512Configure flags C<-Dnoextensions=...> and C<-Donlyextensions=...>,
513see F<INSTALL>.
514
515=head2 Platform-specific enhancements
516
517In Cygwin Perl can now be built with threads (C<Configure -Duseithreads>).
518This works with both Cygwin 1.3.22 and Cygwin 1.5.3.
519
520In newer FreeBSD releases Perl 5.8.0 compilation failed because of
521trying to use F<malloc.h>, which in FreeBSD is just a dummy file, and
522a fatal error to even try to use. Now F<malloc.h> is not used.
523
524Perl is now known to build also in Hitachi HI-UXMPP.
525
526Perl is now known to build again in LynxOS.
527
528Mac OS X now installs with Perl version number embedded in
529installation directory names for easier upgrading of user-compiled
530Perl, and the installation directories in general are more standard.
531In other words, the default installation no longer breaks the
532Apple-provided Perl. On the other hand, with C<Configure -Dprefix=/usr>
533you can now really replace the Apple-supplied Perl (B<please be careful>).
534
535Mac OS X now builds Perl statically by default. This change was done
536mainly for faster startup times. The Apple-provided Perl is still
537dynamically linked and shared, and you can enable the sharedness for
538your own Perl builds by C<Configure -Duseshrplib>.
539
540Perl has been ported to IBM's OS/400 PASE environment. The best way
541to build a Perl for PASE is to use an AIX host as a cross-compilation
542environment. See README.os400.
543
544Yet another cross-compilation option has been added: now Perl builds
545on OpenZaurus, an Linux distribution based on Mandrake + Embedix for
546the Sharp Zaurus PDA. See the Cross/README file.
547
548Tru64 when using gcc 3 drops the optimisation for F<toke.c> to C<-O2>
549because of gigantic memory use with the default C<-O3>.
550
551Tru64 can now build Perl with the newer Berkeley DBs.
552
553Building Perl on WinCE has been much enhanced, see F<README.ce>
554and F<README.perlce>.
555
55e8fca7 556=head1 Selected Bug Fixes
87880fe6 557
1ea9f2df 558=head2 Closures, eval and lexicals
559
560There have been many fixes in the area of anonymous subs, lexicals and
561closures. Although this means that Perl is now more "correct", it is
562possible that some existing code will break that happens to rely on
563the faulty behaviour. In practice this is unlikely unless your code
564contains a very complex nesting of anonymous subs, evals and lexicals.
565
566=head2 Generic fixes
567
568If an input filehandle is marked C<:utf8> and Perl sees illegal UTF-8
569coming in when doing C<< <FH> >>, if warnings are enabled a warning is
570immediately given - instead of being silent about it and Perl being
571unhappy about the broken data later. (The C<:encoding(utf8)> layer
572also works the same way.)
573
574binmode(SOCKET, ":utf8") only worked on the input side, not on the
575output side of the socket. Now it works both ways.
576
577For threaded Perls certain system database functions like getpwent()
578and getgrent() now grow their result buffer dynamically, instead of
579failing. This means that at sites with lots of users and groups the
580functions no longer fail by returning only partial results.
581
582Perl 5.8.0 had accidentally broken the capability for users
583to define their own uppercase<->lowercase Unicode mappings
584(as advertised by the Camel). This feature has been fixed and
585is also documented better.
586
587In 5.8.0 this
588
589 $some_unicode .= <FH>;
590
591didn't work correctly but instead corrupted the data. This has now
592been fixed.
593
594Tied methods like FETCH etc. may now safely access tied values, i.e.
595resulting in a recursive call to FETCH etc. Remember to break the
596recursion, though.
597
598At startup Perl blocks the SIGFPE signal away since there isn't much
599Perl can do about it. Previously this blocking was in effect also for
600programs executed from within Perl. Now Perl restores the original
601SIGFPE handling routine, whatever it was, before running external
602programs.
603
604Linenumbers in Perl scripts may now be greater than 65536, or 2**16.
605(Perl scripts have always been able to be larger than that, it's just
606that the linenumber for reported errors and warnings have "wrapped
607around".) While scripts that large usually indicate a need to rethink
608your code a bit, such Perl scripts do exist, for example as results
609from generated code. Now linenumbers can go all the way to
6104294967296, or 2**32.
611
612=head2 Platform-specific fixes
613
614Linux
615
616=over 4
617
618=item *
619
620Setting $0 works again (with certain limitations that
621Perl cannot do much about: see L<perlvar/$0>)
622
623=back
624
625HP-UX
626
627=over 4
628
629=item *
630
631Setting $0 now works.
632
633=back
634
635VMS
636
637=over 4
638
639=item *
640
641Configuration now tests for the presence of C<poll()>, and IO::Poll
642now uses the vendor-supplied function if detected.
643
644=item *
645
646A rare access violation at Perl start-up could occur if the Perl image was
647installed with privileges or if there was an identifier with the
648subsystem attribute set in the process's rightslist. Either of these
649circumstances triggered tainting code that contained a pointer bug.
650The faulty pointer arithmetic has been fixed.
651
652=item *
653
654The length limit on values (not keys) in the %ENV hash has been raised
655from 255 bytes to 32640 bytes (except when the PERL_ENV_TABLES setting
656overrides the default use of logical names for %ENV). If it is
657necessary to access these long values from outside Perl, be aware that
658they are implemented using search list logical names that store the
659value in pieces, each 255-byte piece (up to 128 of them) being an
660element in the search list. When doing a lookup in %ENV from within
661Perl, the elements are combined into a single value. The existing
662VMS-specific ability to access individual elements of a search list
663logical name via the $ENV{'foo;N'} syntax (where N is the search list
664index) is unimpaired.
665
666=item *
667
668The piping implementation now uses local rather than global DCL
669symbols for inter-process communication.
670
671=item *
672
673File::Find could become confused when navigating to a relative
674directory whose name collided with a logical name. This problem has
675been corrected by adding directory syntax to relative path names, thus
676preventing logical name translation.
677
678=back
679
680Win32
681
682=over 4
683
684=item *
685
686A memory leak in the fork() emulation has been fixed.
687
688=item *
689
690The return value of the ioctl() built-in function was accidentally
691broken in 5.8.0. This has been corrected.
692
693=item *
694
695The internal message loop executed by perl during blocking operations
696sometimes interfered with messages that were external to Perl.
697This often resulted in blocking operations terminating prematurely or
698returning incorrect results, when Perl was executing under environments
699that could generate Windows messages. This has been corrected.
700
701=item *
702
703Pipes and sockets are now automatically in binary mode.
704
705=item *
706
707The four-argument form of select() did not preserve $! (errno) properly
708when there were errors in the underlying call. This is now fixed.
709
710=item *
711
712The "CR CR LF" problem of has been fixed, binmode(FH, ":crlf")
713is now effectively a no-op.
714
715=back
716
55e8fca7 717=head1 New or Changed Diagnostics
f39f21d8 718
1ea9f2df 719All the warnings related to pack() and unpack() were made more
720informative and consistent.
721
722=head2 Changed "A thread exited while %d threads were running"
723
724The old version
725
726 A thread exited while %d other threads were still running
727
728was misleading because the "other" included also the thread giving
729the warning.
730
731=head2 Removed "Attempt to clear a restricted hash"
732
733It is not illegal to clear a restricted hash, so the warning
734was removed.
735
736=head2 New "Illegal declaration of anonymous subroutine"
737
738You must specify the block of code for C<sub>.
739
740=head2 Changed "Invalid range "%s" in transliteration operator"
741
742The old version
743
744 Invalid [] range "%s" in transliteration operator
745
746was simply wrong because there are no "[] ranges" in tr///.
747
748=head2 New "Missing control char name in \c"
749
750Self-explanatory.
751
752=head2 New "Newline in left-justified string for %s"
753
754The padding spaces would appear after the newline, which is
755probably not what you had in mind.
756
757=head2 New "Possible precedence problem on bitwise %c operator"
758
759If you think this
760
761 $x & $y == 0
762
763tests whether the bitwise AND of $x and $y is zero,
764you will like this warning.
765
766=head2 New "read() on %s filehandle %s"
767
768You cannot read() (or sysread()) from a closed or unopened filehandle.
769
770=head2 New "Tied variable freed while still in use"
771
772Something pulled the plug on a live tied variable, Perl plays
773safe by bailing out.
774
775=head2 New "To%s: illegal mapping '%s'"
776
777An illegal user-defined Unicode casemapping was specified.
778
779=head2 New "Use of freed value in iteration"
780
781Something modified the values being iterated over. This is not good.
782
77c8cf41 783=head1 Changed Internals
f39f21d8 784
1ea9f2df 785These news matter to you only if you either write XS code or like to
786know about or hack Perl internals (using Devel::Peek or any of the
787C<B::> modules counts), or like to run Perl with the C<-D> option.
788
789The embedding examples of L<perlembed> have been reviewed to be
790uptodate and consistent: for example, the correct use of
791PERL_SYS_INIT3() and PERL_SYS_TERM().
792
793Extensive reworking of the pad code (the code responsible
794for lexical variables) has been conducted by Dave Mitchell.
795
796Extensive work on the v-strings by John Peacock.
797
798UTF-8 length and position cache: to speed up the handling of Unicode
799(UTF-8) scalars, a cache was introduced. Potential problems exist if
800an extension bypasses the official APIs and directly modifies the PV
801of an SV: the UTF-8 cache does not get cleared as it should.
802
803APIs obsoleted in Perl 5.8.0, like sv_2pv, sv_catpvn, sv_catsv,
804sv_setsv, are again available.
805
806Certain Perl core C APIs like cxinc and regatom are no longer
807available at all to code outside the Perl core of the Perl core
808extensions. This is intentional. They never should have been
809available with the shorter names, and if you application depends on
810them, you should (be ashamed and) contact perl5-porters to discuss
811what are the proper APIs.
812
813Certain Perl core C APIs like C<Perl_list> are no longer available
814without their C<Perl_> prefix. If your XS module stops working
815because some functions cannot be found, in many cases a simple fix is
816to add the C<Perl_> prefix to the function and the thread context
817C<aTHX_> as the first argument of the function call. This is also how
818it should always have been done: letting the Perl_-less forms to leak
819from the core was an accident. For cleaner embedding you can also
820force this for all APIs by defining at compile time the cpp define
821PERL_NO_SHORT_NAMES.
822
823Perl_save_bool() has been added.
824
825Regexp objects (those created with C<qr>) now have S-magic rather than
826R-magic. This fixed regexps of the form /...(??{...;$x})/ to no
827longer ignore changes made to $x. The S-magic avoids dropping
828the caching optimization and making (??{...}) constructs obscenely
829slow (and consequently useless). See also L<perlguts/"Magic Variables">.
830Regexp::Copy was affected by this change.
831
832The Perl internal debugging macros DEBUG() and DEB() have been renamed
833to PERL_DEBUG() and PERL_DEB() to avoid namespace conflicts.
834
835C<-DL> removed (the leaktest had been broken and unsupported for years,
836use alternative debugging mallocs or tools like valgrind and Purify).
837
838Verbose modifier C<v> added for C<-DXv> and C<-Dsv>, see L<perlrun>.
839
ebc20e9a 840=head1 New Tests
77c8cf41 841
1ea9f2df 842In Perl 5.8.0 there were about 69000 separate tests in about 700 test files,
843in Perl 5.9.0 there are about 77000 separate tests in about 780 test files.
844The exact numbers depend on the Perl configuration and on the operating
845system platform.
846
f39f21d8 847=head1 Known Problems
848
1ea9f2df 849The hash randomisation mentioned in L</Incompatible Changes> is definitely
850problematic: it will wake dormant bugs and shake out bad assumptions.
851
852Many of the rarer platforms that worked 100% or pretty close to it
853with perl 5.8.0 have been left a little bit untended since their
854maintainers have been otherwise busy lately, and therefore there will
855be more failures on those platforms. Such platforms include Mac OS
856Classic, IBM z/OS (and other EBCDIC platforms), and NetWare. The most
857common Perl platforms (Unix and Unix-like, Microsoft platforms, and
858VMS) have large enough testing and expert population that they are
859doing well.
860
1400179b 861=head2 Tied hashes in scalar context
862
863Tied hashes do not currently return anything useful in scalar context,
864for example when used as boolean tests:
865
866 if (%tied_hash) { ... }
867
868The current nonsensical behaviour is always to return false,
869regardless of whether the hash is empty or has elements.
870
871The root cause is that there is no interface for the implementors of
872tied hashes to implement the behaviour of a hash in scalar context.
873
1ea9f2df 874=head2 Net::Ping 450_service and 510_ping_udp failures
875
876The subtests 9 and 18 of lib/Net/Ping/t/450_service.t, and the
877subtest 2 of lib/Net/Ping/t/510_ping_udp.t might fail if you have
878an unusual networking setup. For example in the latter case the
879test is trying to send a UDP ping to the IP address 127.0.0.1.
880
881=head2 B::C
882
883The C-generating compiler backend B::C (the frontend being
884C<perlcc -c>) is even more broken than it used to be because of
885the extensive lexical variable changes. (The good news is that
886B::Bytecode and ByteLoader are better than they used to be.)
887
51bcf69b 888=head1 Platform Specific Problems
889
1ea9f2df 890=head2 EBCDIC Platforms
891
892IBM z/OS and other EBCDIC platforms continue to be problematic
893regarding Unicode support. Many Unicode tests are skipped when
894they really should be fixed.
895
896=head2 Cygwin 1.5 problems
897
898In Cygwin 1.5 the F<io/tell> and F<op/sysio> tests have failures for
899some yet unknown reason. In 1.5.5 the threads tests stress_cv,
900stress_re, and stress_string are failing unless the environment
901variable PERLIO is set to "perlio" (which makes also the io/tell
902failure go away).
903
904Perl 5.8.1 does build and work well with Cygwin 1.3: with (uname -a)
905C<CYGWIN_NT-5.0 ... 1.3.22(0.78/3/2) 2003-03-18 09:20 i686 ...>
906a 100% "make test" was achieved with C<Configure -des -Duseithreads>.
907
908=head2 HP-UX: HP cc warnings about sendfile and sendpath
909
910With certain HP C compiler releases (e.g. B.11.11.02) you will
911get many warnings like this (lines wrapped for easier reading):
912
913 cc: "/usr/include/sys/socket.h", line 504: warning 562:
914 Redeclaration of "sendfile" with a different storage class specifier:
915 "sendfile" will have internal linkage.
916 cc: "/usr/include/sys/socket.h", line 505: warning 562:
917 Redeclaration of "sendpath" with a different storage class specifier:
918 "sendpath" will have internal linkage.
919
920The warnings show up both during the build of Perl and during certain
921lib/ExtUtils tests that invoke the C compiler. The warning, however,
922is not serious and can be ignored.
923
924=head2 IRIX: t/uni/tr_7jis.t falsely failing
925
926The test t/uni/tr_7jis.t is known to report failure under 'make test'
927or the test harness with certain releases of IRIX (at least IRIX 6.5
928and MIPSpro Compilers Version 7.3.1.1m), but if run manually the test
929fully passes.
930
931=head2 Mac OS X: no usemymalloc
932
933The Perl malloc (C<-Dusemymalloc>) does not work at all in Mac OS X.
934This is not that serious, though, since the native malloc works just
935fine.
936
937=head2 Tru64: No threaded builds with GNU cc (gcc)
938
939In the latest Tru64 releases (e.g. v5.1B or later) gcc cannot be used
940to compile a threaded Perl (-Duseithreads) because the system
941C<< <pthread.h> >> file doesn't know about gcc.
942
943=head2 Win32: sysopen, sysread, syswrite
944
945As of the 5.8.0 release, sysopen()/sysread()/syswrite() do not behave
946like they used to in 5.6.1 and earlier with respect to "text" mode.
947These built-ins now always operate in "binary" mode (even if sysopen()
948was passed the O_TEXT flag, or if binmode() was used on the file
949handle). Note that this issue should only make a difference for disk
950files, as sockets and pipes have always been in "binary" mode in the
951Windows port. As this behavior is currently considered a bug,
952compatible behavior may be re-introduced in a future release. Until
953then, the use of sysopen(), sysread() and syswrite() is not supported
954for "text" mode operations.
955
956=head1 TODO
957
958Here are some things that are planned for perl 5.10.0 :
959
960=over 4
961
962=item *
963
964Various Copy-On-Write techniques will be investigated in hopes
965of speeding up Perl.
966
967=item *
968
969CPANPLUS, Inline, and Module::Build will become core modules.
970
971=item *
972
973The ability to write true lexically scoped pragmas will be introduced,
974perhaps via a C<pragma> pragma.
975
976=item *
977
978Work will continue on the bytecompiler and byteloader.
979
980=item *
981
982v-strings as they currently exist are scheduled to be deprecated. The
983v-less form (1.2.3) will become a "version object" when used with C<use>,
984C<require>, and C<$VERSION>. $^V will also be a "version object" so the
985printf("%vd",...) construct will no longer be needed. The v-ful version
986(v1.2.3) will become obsolete. The equivalence of strings and v-strings (e.g.
987that currently 5.8.0 is equal to "\5\8\0") will go away. B<There may be no
988deprecation warning for v-strings>, though: it is quite hard to detect when
989v-strings are being used safely, and when they are not.
990
991=back
992
cc0fca54 993=head1 Reporting Bugs
994
d4ad863d 995If you find what you think is a bug, you might check the articles
996recently posted to the comp.lang.perl.misc newsgroup and the perl
f02c194e 997bug database at F<http://bugs.perl.org/>. There may also be
998information at F<http://www.perl.com/>, the Perl Home Page.
cc0fca54 999
1000If you believe you have an unreported bug, please run the B<perlbug>
1001program included with your release. Be sure to trim your bug down
1002to a tiny but sufficient test case. Your bug report, along with the
d4ad863d 1003output of C<perl -V>, will be sent off to perlbug@perl.org to be
1ea9f2df 1004analysed by the Perl porting team. You can browse and search
1005the Perl 5 bugs at F<http://bugs.perl.org/>.
cc0fca54 1006
1007=head1 SEE ALSO
1008
1009The F<Changes> file for exhaustive details on what changed.
1010
1011The F<INSTALL> file for how to build Perl.
1012
1013The F<README> file for general stuff.
1014
1015The F<Artistic> and F<Copying> files for copyright information.
1016
cc0fca54 1017=cut