extra code in pp_concat, Take 2
[p5sagit/p5-mst-13.2.git] / pod / perl581delta.pod
CommitLineData
b6235c4f 1=head1 NAME
2
38fd2c23 3perl581delta - what is new for perl v5.8.1
b6235c4f 4
5=head1 DESCRIPTION
6
7This document describes differences between the 5.8.0 release and
8the 5.8.1 release.
9
10If you are upgrading from an earlier release such as 5.6.1, first read
11the L<perl58delta>, which describes differences between 5.6.0 and
125.8.0.
13
14In case you are wondering about 5.6.1, it was bug-fix-wise rather
15identical to the development release 5.7.1. Confused? This timeline
16hopefully helps a bit: it lists the new major releases, their maintenance
17releases, and the development releases.
18
19 New Maintenance Development
20
21 5.6.0 2000-Mar-22
22 5.7.0 2000-Sep-02
23 5.6.1 2001-Apr-08
24 5.7.1 2001-Apr-09
25 5.7.2 2001-Jul-13
26 5.7.3 2002-Mar-05
27 5.8.0 2002-Jul-18
28 5.8.1 2003-Sep-25
29
30=head1 Incompatible Changes
31
32=head2 Hash Randomisation
33
34Mainly due to security reasons, the "random ordering" of hashes
35has been made even more random. Previously while the order of hash
36elements from keys(), values(), and each() was essentially random,
37it was still repeatable. Now, however, the order varies between
38different runs of Perl.
39
40B<Perl has never guaranteed any ordering of the hash keys>, and the
41ordering has already changed several times during the lifetime of
42Perl 5. Also, the ordering of hash keys has always been, and
43continues to be, affected by the insertion order.
44
45The added randomness may affect applications.
46
47One possible scenario is when output of an application has included
48hash data. For example, if you have used the Data::Dumper module to
49dump data into different files, and then compared the files to see
50whether the data has changed, now you will have false positives since
51the order in which hashes are dumped will vary. In general the cure
52is to sort the keys (or the values); in particular for Data::Dumper to
53use the C<Sortkeys> option. If some particular order is really
54important, use tied hashes: for example the Tie::IxHash module
55which by default preserves the order in which the hash elements
56were added.
57
58More subtle problem is reliance on the order of "global destruction".
59That is what happens at the end of execution: Perl destroys all data
60structures, including user data. If your destructors (the DESTROY
61subroutines) have assumed any particular ordering to the global
62destruction, there might be problems ahead. For example, in a
63destructor of one object you cannot assume that objects of any other
64class are still available, unless you hold a reference to them.
65If the environment variable PERL_DESTRUCT_LEVEL is set to a non-zero
66value, or if Perl is exiting a spawned thread, it will also destruct
67the ordinary references and the symbol tables that are no longer in use.
68You can't call a class method or an ordinary function on a class that
69has been collected that way.
70
71The hash randomisation is certain to reveal hidden assumptions about
72some particular ordering of hash elements, and outright bugs: it
73revealed a few bugs in the Perl core and core modules.
74
75To disable the hash randomisation in runtime, set the environment
76variable PERL_HASH_SEED to 0 (zero) before running Perl (for more
77information see L<perlrun/PERL_HASH_SEED>), or to disable the feature
78completely in compile time, compile with C<-DNO_HASH_SEED> (see F<INSTALL>).
79
80See L<perlsec/"Algorithmic Complexity Attacks"> for the original
81rationale behind this change.
82
83=head2 UTF-8 On Filehandles No Longer Activated By Locale
84
85In Perl 5.8.0 all filehandles, including the standard filehandles,
86were implicitly set to be in Unicode UTF-8 if the locale settings
87indicated the use of UTF-8. This feature caused too many problems,
88so the feature was turned off and redesigned: see L</"Core Enhancements">.
89
90=head2 Single-number v-strings are no longer v-strings before "=>"
91
92The version strings or v-strings (see L<perldata/"Version Strings">)
93feature introduced in Perl 5.6.0 has been a source of some confusion--
94especially when the user did not want to use it, but Perl thought it
95knew better. Especially troublesome has been the feature that before
96a "=>" a version string (a "v" followed by digits) has been interpreted
97as a v-string instead of a string literal. In other words:
98
99 %h = ( v65 => 42 );
100
101has meant since Perl 5.6.0
102
103 %h = ( 'A' => 42 );
104
105(at least in platforms of ASCII progeny) Perl 5.8.1 restores the
106more natural interpretation
107
108 %h = ( 'v65' => 42 );
109
110The multi-number v-strings like v65.66 and 65.66.67 still continue to
111be v-strings in Perl 5.8.
112
113=head2 (Win32) The -C Switch Has Been Repurposed
114
115The -C switch has changed in an incompatible way. The old semantics
116of this switch only made sense in Win32 and only in the "use utf8"
117universe in 5.6.x releases, and do not make sense for the Unicode
118implementation in 5.8.0. Since this switch could not have been used
119by anyone, it has been repurposed. The behavior that this switch
120enabled in 5.6.x releases may be supported in a transparent,
121data-dependent fashion in a future release.
122
123For the new life of this switch, see L<"UTF-8 no longer default under
124UTF-8 locales">, and L<perlrun/-C>.
125
126=head2 (Win32) The /d Switch Of cmd.exe
127
128Perl 5.8.1 uses the /d switch when running the cmd.exe shell
129internally for system(), backticks, and when opening pipes to external
130programs. The extra switch disables the execution of AutoRun commands
131from the registry, which is generally considered undesirable when
132running external programs. If you wish to retain compatibility with
133the older behavior, set PERL5SHELL in your environment to C<cmd /x/c>.
134
135=head1 Core Enhancements
136
137=head2 UTF-8 no longer default under UTF-8 locales
138
139In Perl 5.8.0 many Unicode features were introduced. One of them
140was found to be of more nuisance than benefit: the automagic
141(and silent) "UTF-8-ification" of filehandles, including the
142standard filehandles, if the user's locale settings indicated
143use of UTF-8.
144
145For example, if you had C<en_US.UTF-8> as your locale, your STDIN and
146STDOUT were automatically "UTF-8", in other words an implicit
147binmode(..., ":utf8") was made. This meant that trying to print, say,
148chr(0xff), ended up printing the bytes 0xc3 0xbf. Hardly what
149you had in mind unless you were aware of this feature of Perl 5.8.0.
150The problem is that the vast majority of people weren't: for example
151in RedHat releases 8 and 9 the B<default> locale setting is UTF-8, so
152all RedHat users got UTF-8 filehandles, whether they wanted it or not.
153The pain was intensified by the Unicode implementation of Perl 5.8.0
154(still) having nasty bugs, especially related to the use of s/// and
155tr///. (Bugs that have been fixed in 5.8.1)
156
157Therefore a decision was made to backtrack the feature and change it
158from implicit silent default to explicit conscious option. The new
159Perl command line option C<-C> and its counterpart environment
160variable PERL_UNICODE can now be used to control how Perl and Unicode
161interact at interfaces like I/O and for example the command line
162arguments. See L<perlrun/-C> and L<perlrun/PERL_UNICODE> for more
163information.
164
165=head2 Unsafe signals again available
166
167In Perl 5.8.0 the so-called "safe signals" were introduced. This
168means that Perl no longer handles signals immediately but instead
169"between opcodes", when it is safe to do so. The earlier immediate
170handling easily could corrupt the internal state of Perl, resulting
171in mysterious crashes.
172
173However, the new safer model has its problems too. Because now an
174opcode, a basic unit of Perl execution, is never interrupted but
175instead let to run to completion, certain operations that can take a
176long time now really do take a long time. For example, certain
177network operations have their own blocking and timeout mechanisms, and
178being able to interrupt them immediately would be nice.
179
180Therefore perl 5.8.1 introduces a "backdoor" to restore the pre-5.8.0
181(pre-5.7.3, really) signal behaviour. Just set the environment variable
182PERL_SIGNALS to C<unsafe>, and the old immediate (and unsafe)
183signal handling behaviour returns. See L<perlrun/PERL_SIGNALS>
184and L<perlipc/"Deferred Signals (Safe Signals)">.
185
186In completely unrelated news, you can now use safe signals with
187POSIX::SigAction. See L<POSIX/POSIX::SigAction>.
188
189=head2 Tied Arrays with Negative Array Indices
190
191Formerly, the indices passed to C<FETCH>, C<STORE>, C<EXISTS>, and
192C<DELETE> methods in tied array class were always non-negative. If
193the actual argument was negative, Perl would call FETCHSIZE implicitly
194and add the result to the index before passing the result to the tied
195array method. This behaviour is now optional. If the tied array class
196contains a package variable named C<$NEGATIVE_INDICES> which is set to
197a true value, negative values will be passed to C<FETCH>, C<STORE>,
198C<EXISTS>, and C<DELETE> unchanged.
199
200=head2 local ${$x}
201
202The syntaxes
203
204 local ${$x}
205 local @{$x}
206 local %{$x}
207
208now do localise variables, given that the $x is a valid variable name.
209
210=head2 Unicode Character Database 4.0.0
211
212The copy of the Unicode Character Database included in Perl 5.8 has
213been updated to 4.0.0 from 3.2.0. This means for example that the
214Unicode character properties are as in Unicode 4.0.0.
215
216=head2 Deprecation Warnings
217
218There is one new feature deprecation. Perl 5.8.0 forgot to add
219some deprecation warnings, these warnings have now been added.
220Finally, a reminder of an impending feature removal.
221
222=head3 (Reminder) Pseudo-hashes are deprecated (really)
223
224Pseudo-hashes were deprecated in Perl 5.8.0 and will be removed in
225Perl 5.10.0, see L<perl58delta> for details. Each attempt to access
226pseudo-hashes will trigger the warning C<Pseudo-hashes are deprecated>.
227If you really want to continue using pseudo-hashes but not to see the
228deprecation warnings, use:
229
230 no warnings 'deprecated';
231
232Or you can continue to use the L<fields> pragma, but please don't
233expect the data structures to be pseudohashes any more.
234
235=head3 (Reminder) 5.005-style threads are deprecated (really)
236
2375.005-style threads (activated by C<use Thread;>) were deprecated in
238Perl 5.8.0 and will be removed after Perl 5.8, see L<perl58delta> for
239details. Each 5.005-style thread creation will trigger the warning
240C<5.005 threads are deprecated>. If you really want to continue
241using the 5.005 threads but not to see the deprecation warnings, use:
242
243 no warnings 'deprecated';
244
245=head3 (Reminder) The $* variable is deprecated (really)
246
247The C<$*> variable controlling multi-line matching has been deprecated
248and will be removed after 5.8. The variable has been deprecated for a
249long time, and a deprecation warning C<Use of $* is deprecated> is given,
250now the variable will just finally be removed. The functionality has
251been supplanted by the C</s> and C</m> modifiers on pattern matching.
252If you really want to continue using the C<$*>-variable but not to see
253the deprecation warnings, use:
254
255 no warnings 'deprecated';
256
257=head2 Miscellaneous Enhancements
258
259C<map> in void context is no longer expensive. C<map> is now context
260aware, and will not construct a list if called in void context.
261
262If a socket gets closed by the server while printing to it, the client
263now gets a SIGPIPE. While this new feature was not planned, it fell
264naturally out of PerlIO changes, and is to be considered an accidental
265feature.
266
267PerlIO::get_layers(FH) returns the names of the PerlIO layers
268active on a filehandle.
269
270PerlIO::via layers can now have an optional UTF8 method to
271indicate whether the layer wants to "auto-:utf8" the stream.
272
273utf8::is_utf8() has been added as a quick way to test whether
274a scalar is encoded internally in UTF-8 (Unicode).
275
276=head1 Modules and Pragmata
277
278=head2 Updated Modules And Pragmata
279
280The following modules and pragmata have been updated since Perl 5.8.0:
281
282=over 4
283
284=item base
285
286=item B::Bytecode
287
288In much better shape than it used to be. Still far from perfect, but
289maybe worth a try.
290
291=item B::Concise
292
293=item B::Deparse
294
295=item Benchmark
296
297An optional feature, C<:hireswallclock>, now allows for high
298resolution wall clock times (uses Time::HiRes).
299
300=item ByteLoader
301
302See B::Bytecode.
303
304=item bytes
305
306Now has bytes::substr.
307
308=item CGI
309
310=item charnames
311
312One can now have custom character name aliases.
313
314=item CPAN
315
316There is now a simple command line frontend to the CPAN.pm
317module called F<cpan>.
318
319=item Data::Dumper
320
321A new option, Pair, allows choosing the separator between hash keys
322and values.
323
324=item DB_File
325
326=item Devel::PPPort
327
328=item Digest::MD5
329
330=item Encode
331
332Significant updates on the encoding pragma functionality
333(tr/// and the DATA filehandle, formats).
334
335If a filehandle has been marked as to have an encoding, unmappable
336characters are detected already during input, not later (when the
337corrupted data is being used).
338
339The ISO 8859-6 conversion table has been corrected (the 0x30..0x39
340erroneously mapped to U+0660..U+0669, instead of U+0030..U+0039). The
341GSM 03.38 conversion did not handle escape sequences correctly. The
342UTF-7 encoding has been added (making Encode feature-complete with
343Unicode::String).
344
345=item fields
346
347=item libnet
348
349=item Math::BigInt
350
351A lot of bugs have been fixed since v1.60, the version included in Perl
352v5.8.0. Especially noteworthy are the bug in Calc that caused div and mod to
353fail for some large values, and the fixes to the handling of bad inputs.
354
355Some new features were added, e.g. the broot() method, you can now pass
356parameters to config() to change some settings at runtime, and it is now
357possible to trap the creation of NaN and infinity.
358
359As usual, some optimizations took place and made the math overall a tad
360faster. In some cases, quite a lot faster, actually. Especially alternative
361libraries like Math::BigInt::GMP benefit from this. In addition, a lot of the
362quite clunky routines like fsqrt() and flog() are now much much faster.
363
364=item MIME::Base64
365
366=item NEXT
367
368Diamond inheritance now works.
369
370=item Net::Ping
371
372=item PerlIO::scalar
373
374Reading from non-string scalars (like the special variables, see
375L<perlvar>) now works.
376
377=item podlators
378
379=item Pod::LaTeX
380
381=item PodParsers
382
383=item Pod::Perldoc
384
385Complete rewrite. As a side-effect, no longer refuses to startup when
386run by root.
387
388=item Scalar::Util
389
390New utilities: refaddr, isvstring, looks_like_number, set_prototype.
391
392=item Storable
393
394Can now store code references (via B::Deparse, so not foolproof).
395
396=item strict
397
398Earlier versions of the strict pragma did not check the parameters
399implicitly passed to its "import" (use) and "unimport" (no) routine.
400This caused the false idiom such as:
401
402 use strict qw(@ISA);
403 @ISA = qw(Foo);
404
405This however (probably) raised the false expectation that the strict
406refs, vars and subs were being enforced (and that @ISA was somehow
407"declared"). But the strict refs, vars, and subs are B<not> enforced
408when using this false idiom.
409
410Starting from Perl 5.8.1, the above B<will> cause an error to be
411raised. This may cause programs which used to execute seemingly
412correctly without warnings and errors to fail when run under 5.8.1.
413This happens because
414
415 use strict qw(@ISA);
416
417will now fail with the error:
418
419 Unknown 'strict' tag(s) '@ISA'
420
421The remedy to this problem is to replace this code with the correct idiom:
422
423 use strict;
424 use vars qw(@ISA);
425 @ISA = qw(Foo);
426
427=item Term::ANSIcolor
428
429=item Test::Harness
430
431Now much more picky about extra or missing output from test scripts.
432
433=item Test::More
434
435=item Test::Simple
436
437=item Text::Balanced
438
439=item Time::HiRes
440
441Use of nanosleep(), if available, allows mixing subsecond sleeps with
442alarms.
443
444=item threads
445
446Several fixes, for example for join() problems and memory
447leaks. In some platforms (like Linux) that use glibc the minimum memory
448footprint of one ithread has been reduced by several hundred kilobytes.
449
450=item threads::shared
451
452Many memory leaks have been fixed.
453
454=item Unicode::Collate
455
456=item Unicode::Normalize
457
458=item Win32::GetFolderPath
459
460=item Win32::GetOSVersion
461
462Now returns extra information.
463
464=back
465
466=head1 Utility Changes
467
468The C<h2xs> utility now produces a more modern layout:
469F<Foo-Bar/lib/Foo/Bar.pm> instead of F<Foo/Bar/Bar.pm>.
470Also, the boilerplate test is now called F<t/Foo-Bar.t>
471instead of F<t/1.t>.
472
473The Perl debugger (F<lib/perl5db.pl>) has now been extensively
474documented and bugs found while documenting have been fixed.
475
476C<perldoc> has been rewritten from scratch to be more robust and
477featureful.
478
479C<perlcc -B> works now at least somewhat better, while C<perlcc -c>
480is rather more broken. (The Perl compiler suite as a whole continues
481to be experimental.)
482
483=head1 New Documentation
484
485perl573delta has been added to list the differences between the
486(now quite obsolete) development releases 5.7.2 and 5.7.3.
487
488perl58delta has been added: it is the perldelta of 5.8.0, detailing
489the differences between 5.6.0 and 5.8.0.
490
491perlartistic has been added: it is the Artistic License in pod format,
492making it easier for modules to refer to it.
493
494perlcheat has been added: it is a Perl cheat sheet.
495
496perlgpl has been added: it is the GNU General Public License in pod
497format, making it easier for modules to refer to it.
498
499perlmacosx has been added to tell about the installation and use
500of Perl in Mac OS X.
501
502perlos400 has been added to tell about the installation and use
503of Perl in OS/400 PASE.
504
505perlreref has been added: it is a regular expressions quick reference.
506
507=head1 Installation and Configuration Improvements
508
509The UNIX standard Perl location, F</usr/bin/perl>, is no longer
510overwritten by default if it exists. This change was very prudent
511because so many UNIX vendors already provide a F</usr/bin/perl>,
512but simultaneously many system utilities may depend on that
513exact version of Perl, so better not to overwrite it.
514
515One can now specify installation directories for site and vendor man
516and HTML pages, and site and vendor scripts. See F<INSTALL>.
517
518One can now specify a destination directory for Perl installation
519by specifying the DESTDIR variable for C<make install>. (This feature
520is slightly different from the previous C<Configure -Dinstallprefix=...>.)
521See F<INSTALL>.
522
523gcc versions 3.x introduced a new warning that caused a lot of noise
524during Perl compilation: C<gcc -Ialreadyknowndirectory (warning:
525changing search order)>. This warning has now been avoided by
526Configure weeding out such directories before the compilation.
527
528One can now build subsets of Perl core modules by using the
529Configure flags C<-Dnoextensions=...> and C<-Donlyextensions=...>,
530see F<INSTALL>.
531
532=head2 Platform-specific enhancements
533
534In Cygwin Perl can now be built with threads (C<Configure -Duseithreads>).
535This works with both Cygwin 1.3.22 and Cygwin 1.5.3.
536
537In newer FreeBSD releases Perl 5.8.0 compilation failed because of
538trying to use F<malloc.h>, which in FreeBSD is just a dummy file, and
539a fatal error to even try to use. Now F<malloc.h> is not used.
540
541Perl is now known to build also in Hitachi HI-UXMPP.
542
543Perl is now known to build again in LynxOS.
544
545Mac OS X now installs with Perl version number embedded in
546installation directory names for easier upgrading of user-compiled
547Perl, and the installation directories in general are more standard.
548In other words, the default installation no longer breaks the
549Apple-provided Perl. On the other hand, with C<Configure -Dprefix=/usr>
550you can now really replace the Apple-supplied Perl (B<please be careful>).
551
552Mac OS X now builds Perl statically by default. This change was done
553mainly for faster startup times. The Apple-provided Perl is still
554dynamically linked and shared, and you can enable the sharedness for
555your own Perl builds by C<Configure -Duseshrplib>.
556
557Perl has been ported to IBM's OS/400 PASE environment. The best way
558to build a Perl for PASE is to use an AIX host as a cross-compilation
559environment. See README.os400.
560
561Yet another cross-compilation option has been added: now Perl builds
562on OpenZaurus, an Linux distribution based on Mandrake + Embedix for
563the Sharp Zaurus PDA. See the Cross/README file.
564
565Tru64 when using gcc 3 drops the optimisation for F<toke.c> to C<-O2>
566because of gigantic memory use with the default C<-O3>.
567
568Tru64 can now build Perl with the newer Berkeley DBs.
569
570Building Perl on WinCE has been much enhanced, see F<README.ce>
571and F<README.perlce>.
572
573=head1 Selected Bug Fixes
574
575=head2 Closures, eval and lexicals
576
577There have been many fixes in the area of anonymous subs, lexicals and
578closures. Although this means that Perl is now more "correct", it is
579possible that some existing code will break that happens to rely on
580the faulty behaviour. In practice this is unlikely unless your code
581contains a very complex nesting of anonymous subs, evals and lexicals.
582
583=head2 Generic fixes
584
585If an input filehandle is marked C<:utf8> and Perl sees illegal UTF-8
586coming in when doing C<< <FH> >>, if warnings are enabled a warning is
587immediately given - instead of being silent about it and Perl being
588unhappy about the broken data later. (The C<:encoding(utf8)> layer
589also works the same way.)
590
591binmode(SOCKET, ":utf8") only worked on the input side, not on the
592output side of the socket. Now it works both ways.
593
594For threaded Perls certain system database functions like getpwent()
595and getgrent() now grow their result buffer dynamically, instead of
596failing. This means that at sites with lots of users and groups the
597functions no longer fail by returning only partial results.
598
599Perl 5.8.0 had accidentally broken the capability for users
600to define their own uppercase<->lowercase Unicode mappings
601(as advertised by the Camel). This feature has been fixed and
602is also documented better.
603
604In 5.8.0 this
605
606 $some_unicode .= <FH>;
607
608didn't work correctly but instead corrupted the data. This has now
609been fixed.
610
611Tied methods like FETCH etc. may now safely access tied values, i.e.
612resulting in a recursive call to FETCH etc. Remember to break the
613recursion, though.
614
615At startup Perl blocks the SIGFPE signal away since there isn't much
616Perl can do about it. Previously this blocking was in effect also for
617programs executed from within Perl. Now Perl restores the original
618SIGFPE handling routine, whatever it was, before running external
619programs.
620
621Linenumbers in Perl scripts may now be greater than 65536, or 2**16.
622(Perl scripts have always been able to be larger than that, it's just
623that the linenumber for reported errors and warnings have "wrapped
624around".) While scripts that large usually indicate a need to rethink
625your code a bit, such Perl scripts do exist, for example as results
626from generated code. Now linenumbers can go all the way to
6274294967296, or 2**32.
628
629=head2 Platform-specific fixes
630
631Linux
632
633=over 4
634
635=item *
636
637Setting $0 works again (with certain limitations that
638Perl cannot do much about: see L<perlvar/$0>)
639
640=back
641
642HP-UX
643
644=over 4
645
646=item *
647
648Setting $0 now works.
649
650=back
651
652VMS
653
654=over 4
655
656=item *
657
658Configuration now tests for the presence of C<poll()>, and IO::Poll
659now uses the vendor-supplied function if detected.
660
661=item *
662
663A rare access violation at Perl start-up could occur if the Perl image was
664installed with privileges or if there was an identifier with the
665subsystem attribute set in the process's rightslist. Either of these
666circumstances triggered tainting code that contained a pointer bug.
667The faulty pointer arithmetic has been fixed.
668
669=item *
670
671The length limit on values (not keys) in the %ENV hash has been raised
672from 255 bytes to 32640 bytes (except when the PERL_ENV_TABLES setting
673overrides the default use of logical names for %ENV). If it is
674necessary to access these long values from outside Perl, be aware that
675they are implemented using search list logical names that store the
676value in pieces, each 255-byte piece (up to 128 of them) being an
677element in the search list. When doing a lookup in %ENV from within
678Perl, the elements are combined into a single value. The existing
679VMS-specific ability to access individual elements of a search list
680logical name via the $ENV{'foo;N'} syntax (where N is the search list
681index) is unimpaired.
682
683=item *
684
685The piping implementation now uses local rather than global DCL
686symbols for inter-process communication.
687
688=item *
689
690File::Find could become confused when navigating to a relative
691directory whose name collided with a logical name. This problem has
692been corrected by adding directory syntax to relative path names, thus
693preventing logical name translation.
694
695=back
696
697Win32
698
699=over 4
700
701=item *
702
703A memory leak in the fork() emulation has been fixed.
704
705=item *
706
707The return value of the ioctl() built-in function was accidentally
708broken in 5.8.0. This has been corrected.
709
710=item *
711
712The internal message loop executed by perl during blocking operations
713sometimes interfered with messages that were external to Perl.
714This often resulted in blocking operations terminating prematurely or
715returning incorrect results, when Perl was executing under environments
716that could generate Windows messages. This has been corrected.
717
718=item *
719
720Pipes and sockets are now automatically in binary mode.
721
722=item *
723
724The four-argument form of select() did not preserve $! (errno) properly
725when there were errors in the underlying call. This is now fixed.
726
727=item *
728
729The "CR CR LF" problem of has been fixed, binmode(FH, ":crlf")
730is now effectively a no-op.
731
732=back
733
734=head1 New or Changed Diagnostics
735
736All the warnings related to pack() and unpack() were made more
737informative and consistent.
738
739=head2 Changed "A thread exited while %d threads were running"
740
741The old version
742
743 A thread exited while %d other threads were still running
744
745was misleading because the "other" included also the thread giving
746the warning.
747
748=head2 Removed "Attempt to clear a restricted hash"
749
750It is not illegal to clear a restricted hash, so the warning
751was removed.
752
753=head2 New "Illegal declaration of anonymous subroutine"
754
755You must specify the block of code for C<sub>.
756
757=head2 Changed "Invalid range "%s" in transliteration operator"
758
759The old version
760
761 Invalid [] range "%s" in transliteration operator
762
763was simply wrong because there are no "[] ranges" in tr///.
764
765=head2 New "Missing control char name in \c"
766
767Self-explanatory.
768
769=head2 New "Newline in left-justified string for %s"
770
771The padding spaces would appear after the newline, which is
772probably not what you had in mind.
773
774=head2 New "Possible precedence problem on bitwise %c operator"
775
776If you think this
777
778 $x & $y == 0
779
780tests whether the bitwise AND of $x and $y is zero,
781you will like this warning.
782
783=head2 New "Pseudo-hashes are deprecated"
784
785This warning should have been already in 5.8.0, since they are.
786
787=head2 New "read() on %s filehandle %s"
788
789You cannot read() (or sysread()) from a closed or unopened filehandle.
790
791=head2 New "5.005 threads are deprecated"
792
793This warning should have been already in 5.8.0, since they are.
794
795=head2 New "Tied variable freed while still in use"
796
797Something pulled the plug on a live tied variable, Perl plays
798safe by bailing out.
799
800=head2 New "To%s: illegal mapping '%s'"
801
802An illegal user-defined Unicode casemapping was specified.
803
804=head2 New "Use of freed value in iteration"
805
806Something modified the values being iterated over. This is not good.
807
808=head1 Changed Internals
809
810These news matter to you only if you either write XS code or like to
811know about or hack Perl internals (using Devel::Peek or any of the
812C<B::> modules counts), or like to run Perl with the C<-D> option.
813
814The embedding examples of L<perlembed> have been reviewed to be
815uptodate and consistent: for example, the correct use of
816PERL_SYS_INIT3() and PERL_SYS_TERM().
817
818Extensive reworking of the pad code (the code responsible
819for lexical variables) has been conducted by Dave Mitchell.
820
821Extensive work on the v-strings by John Peacock.
822
823UTF-8 length and position cache: to speed up the handling of Unicode
824(UTF-8) scalars, a cache was introduced. Potential problems exist if
825an extension bypasses the official APIs and directly modifies the PV
826of an SV: the UTF-8 cache does not get cleared as it should.
827
828APIs obsoleted in Perl 5.8.0, like sv_2pv, sv_catpvn, sv_catsv,
829sv_setsv, are again available.
830
831Certain Perl core C APIs like cxinc and regatom are no longer
832available at all to code outside the Perl core of the Perl core
833extensions. This is intentional. They never should have been
834available with the shorter names, and if you application depends on
835them, you should (be ashamed and) contact perl5-porters to discuss
836what are the proper APIs.
837
838Certain Perl core C APIs like C<Perl_list> are no longer available
839without their C<Perl_> prefix. If your XS module stops working
840because some functions cannot be found, in many cases a simple fix is
841to add the C<Perl_> prefix to the function and the thread context
842C<aTHX_> as the first argument of the function call. This is also how
843it should always have been done: letting the Perl_-less forms to leak
844from the core was an accident. For cleaner embedding you can also
845force this for all APIs by defining at compile time the cpp define
846PERL_NO_SHORT_NAMES.
847
848Perl_save_bool() has been added.
849
850Regexp objects (those created with C<qr>) now have S-magic rather than
851R-magic. This fixed regexps of the form /...(??{...;$x})/ to no
852longer ignore changes made to $x. The S-magic avoids dropping
853the caching optimization and making (??{...}) constructs obscenely
854slow (and consequently useless). See also L<perlguts/"Magic Variables">.
855Regexp::Copy was affected by this change.
856
857The Perl internal debugging macros DEBUG() and DEB() have been renamed
858to PERL_DEBUG() and PERL_DEB() to avoid namespace conflicts.
859
860C<-DL> removed (the leaktest had been broken and unsupported for years,
861use alternative debugging mallocs or tools like valgrind and Purify).
862
863Verbose modifier C<v> added for C<-DXv> and C<-Dsv>, see L<perlrun>.
864
865=head1 New Tests
866
867In Perl 5.8.0 there were about 69000 separate tests in about 700 test files,
868in Perl 5.8.1 there are about 77000 separate tests in about 780 test files.
869The exact numbers depend on the Perl configuration and on the operating
870system platform.
871
872=head1 Known Problems
873
874The hash randomisation mentioned in L</Incompatible Changes> is definitely
875problematic: it will wake dormant bugs and shake out bad assumptions.
876
877If you want to use mod_perl 2.x with Perl 5.8.1, you will need
878mod_perl-1.99_10 or higher. Earlier versions of mod_perl 2.x
879do not work with the randomised hashes. (mod_perl 1.x works fine.)
880You will also need Apache::Test 1.04 or higher.
881
882Many of the rarer platforms that worked 100% or pretty close to it
883with perl 5.8.0 have been left a little bit untended since their
884maintainers have been otherwise busy lately, and therefore there will
885be more failures on those platforms. Such platforms include Mac OS
886Classic, IBM z/OS (and other EBCDIC platforms), and NetWare. The most
887common Perl platforms (Unix and Unix-like, Microsoft platforms, and
888VMS) have large enough testing and expert population that they are
889doing well.
890
891=head2 Tied hashes in scalar context
892
893Tied hashes do not currently return anything useful in scalar context,
894for example when used as boolean tests:
895
896 if (%tied_hash) { ... }
897
898The current nonsensical behaviour is always to return false,
899regardless of whether the hash is empty or has elements.
900
901The root cause is that there is no interface for the implementors of
902tied hashes to implement the behaviour of a hash in scalar context.
903
904=head2 Net::Ping 450_service and 510_ping_udp failures
905
906The subtests 9 and 18 of lib/Net/Ping/t/450_service.t, and the
907subtest 2 of lib/Net/Ping/t/510_ping_udp.t might fail if you have
908an unusual networking setup. For example in the latter case the
909test is trying to send a UDP ping to the IP address 127.0.0.1.
910
911=head2 B::C
912
913The C-generating compiler backend B::C (the frontend being
914C<perlcc -c>) is even more broken than it used to be because of
915the extensive lexical variable changes. (The good news is that
916B::Bytecode and ByteLoader are better than they used to be.)
917
918=head1 Platform Specific Problems
919
920=head2 EBCDIC Platforms
921
922IBM z/OS and other EBCDIC platforms continue to be problematic
923regarding Unicode support. Many Unicode tests are skipped when
924they really should be fixed.
925
926=head2 Cygwin 1.5 problems
927
928In Cygwin 1.5 the F<io/tell> and F<op/sysio> tests have failures for
929some yet unknown reason. In 1.5.5 the threads tests stress_cv,
930stress_re, and stress_string are failing unless the environment
931variable PERLIO is set to "perlio" (which makes also the io/tell
932failure go away).
933
934Perl 5.8.1 does build and work well with Cygwin 1.3: with (uname -a)
935C<CYGWIN_NT-5.0 ... 1.3.22(0.78/3/2) 2003-03-18 09:20 i686 ...>
936a 100% "make test" was achieved with C<Configure -des -Duseithreads>.
937
938=head2 HP-UX: HP cc warnings about sendfile and sendpath
939
940With certain HP C compiler releases (e.g. B.11.11.02) you will
941get many warnings like this (lines wrapped for easier reading):
942
943 cc: "/usr/include/sys/socket.h", line 504: warning 562:
944 Redeclaration of "sendfile" with a different storage class specifier:
945 "sendfile" will have internal linkage.
946 cc: "/usr/include/sys/socket.h", line 505: warning 562:
947 Redeclaration of "sendpath" with a different storage class specifier:
948 "sendpath" will have internal linkage.
949
950The warnings show up both during the build of Perl and during certain
951lib/ExtUtils tests that invoke the C compiler. The warning, however,
952is not serious and can be ignored.
953
954=head2 IRIX: t/uni/tr_7jis.t falsely failing
955
956The test t/uni/tr_7jis.t is known to report failure under 'make test'
957or the test harness with certain releases of IRIX (at least IRIX 6.5
958and MIPSpro Compilers Version 7.3.1.1m), but if run manually the test
959fully passes.
960
961=head2 Mac OS X: no usemymalloc
962
963The Perl malloc (C<-Dusemymalloc>) does not work at all in Mac OS X.
964This is not that serious, though, since the native malloc works just
965fine.
966
967=head2 Tru64: No threaded builds with GNU cc (gcc)
968
969In the latest Tru64 releases (e.g. v5.1B or later) gcc cannot be used
970to compile a threaded Perl (-Duseithreads) because the system
971C<< <pthread.h> >> file doesn't know about gcc.
972
973=head2 Win32: sysopen, sysread, syswrite
974
975As of the 5.8.0 release, sysopen()/sysread()/syswrite() do not behave
976like they used to in 5.6.1 and earlier with respect to "text" mode.
977These built-ins now always operate in "binary" mode (even if sysopen()
978was passed the O_TEXT flag, or if binmode() was used on the file
979handle). Note that this issue should only make a difference for disk
980files, as sockets and pipes have always been in "binary" mode in the
981Windows port. As this behavior is currently considered a bug,
982compatible behavior may be re-introduced in a future release. Until
983then, the use of sysopen(), sysread() and syswrite() is not supported
984for "text" mode operations.
985
986=head1 Future Directions
987
988The following things B<might> happen in future. The first publicly
989available releases having these characteristics will be the developer
990releases Perl 5.9.x, culminating in the Perl 5.10.0 release. These
991are our best guesses at the moment: we reserve the right to rethink.
992
993=over 4
994
995=item *
996
997PerlIO will become The Default. Currently (in Perl 5.8.x) the stdio
998library is still used if Perl thinks it can use certain tricks to
999make stdio go B<really> fast. For future releases our goal is to
1000make PerlIO go even faster.
1001
1002=item *
1003
1004A new feature called I<assertions> will be available. This means that
1005one can have code called assertions sprinkled in the code: usually
1006they are optimised away, but they can be enabled with the C<-A> option.
1007
1008=item *
1009
1010A new operator C<//> (defined-or) will be available. This means that
1011one will be able to say
1012
1013 $a // $b
1014
1015instead of
1016
1017 defined $a ? $a : $b
1018
1019and
1020
1021 $c //= $d;
1022
1023instead of
1024
1025 $c = $d unless defined $c;
1026
1027The operator will have the same precedence and associativity as C<||>.
1028A source code patch against the Perl 5.8.1 sources will be available
1029in CPAN as F<authors/id/H/HM/HMBRAND/dor-5.8.1.diff>.
1030
1031=item *
1032
1033C<unpack()> will default to unpacking the C<$_>.
1034
1035=item *
1036
1037Various Copy-On-Write techniques will be investigated in hopes
1038of speeding up Perl.
1039
1040=item *
1041
1042CPANPLUS, Inline, and Module::Build will become core modules.
1043
1044=item *
1045
1046The ability to write true lexically scoped pragmas will be introduced.
1047
1048=item *
1049
1050Work will continue on the bytecompiler and byteloader.
1051
1052=item *
1053
1054v-strings as they currently exist are scheduled to be deprecated. The
1055v-less form (1.2.3) will become a "version object" when used with C<use>,
1056C<require>, and C<$VERSION>. $^V will also be a "version object" so the
1057printf("%vd",...) construct will no longer be needed. The v-ful version
1058(v1.2.3) will become obsolete. The equivalence of strings and v-strings (e.g.
1059that currently 5.8.0 is equal to "\5\8\0") will go away. B<There may be no
1060deprecation warning for v-strings>, though: it is quite hard to detect when
1061v-strings are being used safely, and when they are not.
1062
1063=item *
1064
10655.005 Threads Will Be Removed
1066
1067=item *
1068
1069The C<$*> Variable Will Be Removed
1070(it was deprecated a long time ago)
1071
1072=item *
1073
1074Pseudohashes Will Be Removed
1075
1076=back
1077
1078=head1 Reporting Bugs
1079
1080If you find what you think is a bug, you might check the articles
1081recently posted to the comp.lang.perl.misc newsgroup and the perl
1082bug database at http://bugs.perl.org/ . There may also be
1083information at http://www.perl.com/ , the Perl Home Page.
1084
1085If you believe you have an unreported bug, please run the B<perlbug>
1086program included with your release. Be sure to trim your bug down
1087to a tiny but sufficient test case. Your bug report, along with the
1088output of C<perl -V>, will be sent off to perlbug@perl.org to be
1089analysed by the Perl porting team. You can browse and search
1090the Perl 5 bugs at http://bugs.perl.org/
1091
1092=head1 SEE ALSO
1093
1094The F<Changes> file for exhaustive details on what changed.
1095
1096The F<INSTALL> file for how to build Perl.
1097
1098The F<README> file for general stuff.
1099
1100The F<Artistic> and F<Copying> files for copyright information.
1101
1102=cut