3 perldelta - what is new for perl v5.9.0
7 This document describes differences between the 5.8.0 release and
10 =head1 Incompatible Changes
12 =head2 Hash Randomisation
14 Mainly due to security reasons, the "random ordering" of hashes
15 has been made even more random. Previously while the order of hash
16 elements from keys(), values(), and each() was essentially random,
17 it was still repeatable. Now, however, the order varies between
18 different runs of Perl.
20 B<Perl has never guaranteed any ordering of the hash keys>, and the
21 ordering has already changed several times during the lifetime of
22 Perl 5. Also, the ordering of hash keys has always been, and
23 continues to be, affected by the insertion order.
25 The added randomness may affect applications.
27 One possible scenario is when output of an application has included
28 hash data. For example, if you have used the Data::Dumper module to
29 dump data into different files, and then compared the files to see
30 whether the data has changed, now you will have false positives since
31 the order in which hashes are dumped will vary. In general the cure
32 is to sort the keys (or the values); in particular for Data::Dumper to
33 use the C<Sortkeys> option. If some particular order is really
34 important, use tied hashes: for example the Tie::IxHash module
35 which by default preserves the order in which the hash elements
38 More subtle problem is reliance on the order of "global destruction".
39 That is what happens at the end of execution: Perl destroys all data
40 structures, including user data. If your destructors (the DESTROY
41 subroutines) have assumed any particular ordering to the global
42 destruction, there might be problems ahead. For example, in a
43 destructor of one object you cannot assume that objects of any other
44 class are still available, unless you hold a reference to them.
45 If the environment variable PERL_DESTRUCT_LEVEL is set to a non-zero
46 value, or if Perl is exiting a spawned thread, it will also destruct
47 the ordinary references and the symbol tables that are no longer in use.
48 You can't call a class method or an ordinary function on a class that
49 has been collected that way.
51 The hash randomisation is certain to reveal hidden assumptions about
52 some particular ordering of hash elements, and outright bugs: it
53 revealed a few bugs in the Perl core and core modules.
55 To disable the hash randomisation in runtime, set the environment
56 variable PERL_HASH_SEED to 0 (zero) before running Perl (for more
57 information see L<perlrun/PERL_HASH_SEED>), or to disable the feature
58 completely in compile time, compile with C<-DNO_HASH_SEED> (see F<INSTALL>).
60 See L<perlsec/"Algorithmic Complexity Attacks"> for the original
61 rationale behind this change.
63 =head2 UTF-8 On Filehandles No Longer Activated By Locale
65 In Perl 5.8.0 all filehandles, including the standard filehandles,
66 were implicitly set to be in Unicode UTF-8 if the locale settings
67 indicated the use of UTF-8. This feature caused too many problems,
68 so the feature was turned off and redesigned: see L</"Core Enhancements">.
70 =head2 Single-number v-strings are no longer v-strings before "=>"
72 The version strings or v-strings (see L<perldata/"Version Strings">)
73 feature introduced in Perl 5.6.0 has been a source of some confusion--
74 especially when the user did not want to use it, but Perl thought it
75 knew better. Especially troublesome has been the feature that before
76 a "=>" a version string (a "v" followed by digits) has been interpreted
77 as a v-string instead of a string literal. In other words:
81 has meant since Perl 5.6.0
85 (at least in platforms of ASCII progeny) Perl 5.8.1 restored the
86 more natural interpretation
90 The multi-number v-strings like v65.66 and 65.66.67 still continue to
91 be v-strings in Perl 5.8.
93 =head2 (Win32) The -C Switch Has Been Repurposed
95 The -C switch has changed in an incompatible way. The old semantics
96 of this switch only made sense in Win32 and only in the "use utf8"
97 universe in 5.6.x releases, and do not make sense for the Unicode
98 implementation in 5.8.0. Since this switch could not have been used
99 by anyone, it has been repurposed. The behavior that this switch
100 enabled in 5.6.x releases may be supported in a transparent,
101 data-dependent fashion in a future release.
103 For the new life of this switch, see L<"UTF-8 no longer default under
104 UTF-8 locales">, and L<perlrun/-C>.
106 =head2 (Win32) The /d Switch Of cmd.exe
108 Since version 5.8.1, perl uses the /d switch when running the cmd.exe shell
109 internally for system(), backticks, and when opening pipes to external
110 programs. The extra switch disables the execution of AutoRun commands
111 from the registry, which is generally considered undesirable when
112 running external programs. If you wish to retain compatibility with
113 the older behavior, set PERL5SHELL in your environment to C<cmd /x/c>.
115 =head2 The C<$*> variable has been removed
117 C<$*>, which was deprecated in favor of the C</s> and C</m> regexp
118 modifiers, has been removed.
120 =head1 Core Enhancements
124 Perl 5.9.0 has experimental support for assertions. Note that hhe user
125 interface is not fully stabilized yet, and it may change until the 5.10.0
126 release. A new command-line switch, B<-A>, is used to activate
127 assertions, which are declared with the C<assertions> pragma. See
130 =head2 Defined-or operators
132 A new operator C<//> (defined-or) has been implemented.
133 The following statement:
137 is merely equivalent to
145 can be used instead of
147 $c = $d unless defined $c;
149 This operator has the same precedence and associativity as C<||>.
150 It has a low-precedence counterpart, C<err>, which has the same precedence
151 and associativity as C<or>. Special care has been taken to ensure that
152 those operators Do What You Mean while not breaking old code, but some
153 edge cases involving the empty regular expression may now parse
154 differently. See L<perlop> for details.
156 =head2 UTF-8 no longer default under UTF-8 locales
158 In Perl 5.8.0 many Unicode features were introduced. One of them
159 was found to be of more nuisance than benefit: the automagic
160 (and silent) "UTF-8-ification" of filehandles, including the
161 standard filehandles, if the user's locale settings indicated
164 For example, if you had C<en_US.UTF-8> as your locale, your STDIN and
165 STDOUT were automatically "UTF-8", in other words an implicit
166 binmode(..., ":utf8") was made. This meant that trying to print, say,
167 chr(0xff), ended up printing the bytes 0xc3 0xbf. Hardly what
168 you had in mind unless you were aware of this feature of Perl 5.8.0.
169 The problem is that the vast majority of people weren't: for example
170 in RedHat releases 8 and 9 the B<default> locale setting is UTF-8, so
171 all RedHat users got UTF-8 filehandles, whether they wanted it or not.
172 The 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
174 tr///. (Bugs that have been fixed in 5.8.1)
176 Therefore a decision was made to backtrack the feature and change it
177 from implicit silent default to explicit conscious option. The new
178 Perl command line option C<-C> and its counterpart environment
179 variable PERL_UNICODE can now be used to control how Perl and Unicode
180 interact at interfaces like I/O and for example the command line
181 arguments. See L<perlrun/-C> and L<perlrun/PERL_UNICODE> for more
184 =head2 Unsafe signals again available
186 In Perl 5.8.0 the so-called "safe signals" were introduced. This
187 means that Perl no longer handles signals immediately but instead
188 "between opcodes", when it is safe to do so. The earlier immediate
189 handling easily could corrupt the internal state of Perl, resulting
190 in mysterious crashes.
192 However, the new safer model has its problems too. Because now an
193 opcode, a basic unit of Perl execution, is never interrupted but
194 instead let to run to completion, certain operations that can take a
195 long time now really do take a long time. For example, certain
196 network operations have their own blocking and timeout mechanisms, and
197 being able to interrupt them immediately would be nice.
199 Therefore 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
201 PERL_SIGNALS to C<unsafe>, and the old immediate (and unsafe)
202 signal handling behaviour returns. See L<perlrun/PERL_SIGNALS>
203 and L<perlipc/"Deferred Signals (Safe Signals)">.
205 In completely unrelated news, you can now use safe signals with
206 POSIX::SigAction. See L<POSIX/POSIX::SigAction>.
208 =head2 Tied Arrays with Negative Array Indices
210 Formerly, the indices passed to C<FETCH>, C<STORE>, C<EXISTS>, and
211 C<DELETE> methods in tied array class were always non-negative. If
212 the actual argument was negative, Perl would call FETCHSIZE implicitly
213 and add the result to the index before passing the result to the tied
214 array method. This behaviour is now optional. If the tied array class
215 contains a package variable named C<$NEGATIVE_INDICES> which is set to
216 a true value, negative values will be passed to C<FETCH>, C<STORE>,
217 C<EXISTS>, and C<DELETE> unchanged.
219 =head2 Tied hashes in scalar context
221 As of perl 5.8.2, tied hashes did not return anything useful in scalar
222 context, for example when used as boolean tests:
224 if (%tied_hash) { ... }
226 The old nonsensical behaviour was always to return false,
227 regardless of whether the hash is empty or has elements.
229 There is now an interface for the implementors of tied hashes to implement
230 the behaviour of a hash in scalar context, via the SCALAR method (see
231 L<perltie>). Without a SCALAR method, perl will try to guess whether
232 the hash is empty, by testing if it's inside an iteration (in this case
233 it can't be empty) or by calling FIRSTKEY.
243 now do localise variables, given that the $x is a valid variable name.
245 =head2 Unicode Character Database 4.0.0
247 The copy of the Unicode Character Database included in Perl 5.8 has
248 been updated to 4.0.0 from 3.2.0. This means for example that the
249 Unicode character properties are as in Unicode 4.0.0.
251 =head2 Miscellaneous Enhancements
253 C<unpack()> now defaults to unpacking the C<$_>.
255 C<map> in void context is no longer expensive. C<map> is now context
256 aware, and will not construct a list if called in void context.
258 If a socket gets closed by the server while printing to it, the client
259 now gets a SIGPIPE. While this new feature was not planned, it fell
260 naturally out of PerlIO changes, and is to be considered an accidental
263 PerlIO::get_layers(FH) returns the names of the PerlIO layers
264 active on a filehandle.
266 PerlIO::via layers can now have an optional UTF8 method to
267 indicate whether the layer wants to "auto-:utf8" the stream.
269 utf8::is_utf8() has been added as a quick way to test whether
270 a scalar is encoded internally in UTF-8 (Unicode).
272 =head1 Modules and Pragmata
274 =head2 Updated Modules And Pragmata
276 The following modules and pragmata have been updated since Perl 5.8.0:
284 In much better shape than it used to be. Still far from perfect, but
293 An optional feature, C<:hireswallclock>, now allows for high
294 resolution wall clock times (uses Time::HiRes).
302 Now has bytes::substr.
308 One can now have custom character name aliases.
312 There is now a simple command line frontend to the CPAN.pm
313 module called F<cpan>.
317 A new option, Pair, allows choosing the separator between hash keys
328 Significant updates on the encoding pragma functionality
329 (tr/// and the DATA filehandle, formats).
331 If a filehandle has been marked as to have an encoding, unmappable
332 characters are detected already during input, not later (when the
333 corrupted data is being used).
335 The ISO 8859-6 conversion table has been corrected (the 0x30..0x39
336 erroneously mapped to U+0660..U+0669, instead of U+0030..U+0039). The
337 GSM 03.38 conversion did not handle escape sequences correctly. The
338 UTF-7 encoding has been added (making Encode feature-complete with
347 A lot of bugs have been fixed since v1.60, the version included in Perl
348 v5.8.0. Especially noteworthy are the bug in Calc that caused div and mod to
349 fail for some large values, and the fixes to the handling of bad inputs.
351 Some new features were added, e.g. the broot() method, you can now pass
352 parameters to config() to change some settings at runtime, and it is now
353 possible to trap the creation of NaN and infinity.
355 As usual, some optimizations took place and made the math overall a tad
356 faster. In some cases, quite a lot faster, actually. Especially alternative
357 libraries like Math::BigInt::GMP benefit from this. In addition, a lot of the
358 quite clunky routines like fsqrt() and flog() are now much much faster.
364 Diamond inheritance now works.
370 Reading from non-string scalars (like the special variables, see
371 L<perlvar>) now works.
381 Complete rewrite. As a side-effect, no longer refuses to startup when
386 New utilities: refaddr, isvstring, looks_like_number, set_prototype.
390 Can now store code references (via B::Deparse, so not foolproof).
394 Earlier versions of the strict pragma did not check the parameters
395 implicitly passed to its "import" (use) and "unimport" (no) routine.
396 This caused the false idiom such as:
401 This however (probably) raised the false expectation that the strict
402 refs, vars and subs were being enforced (and that @ISA was somehow
403 "declared"). But the strict refs, vars, and subs are B<not> enforced
404 when using this false idiom.
406 Starting from Perl 5.8.1, the above B<will> cause an error to be
407 raised. This may cause programs which used to execute seemingly
408 correctly without warnings and errors to fail when run under 5.8.1.
413 will now fail with the error:
415 Unknown 'strict' tag(s) '@ISA'
417 The remedy to this problem is to replace this code with the correct idiom:
423 =item Term::ANSIcolor
427 Now much more picky about extra or missing output from test scripts.
437 Use of nanosleep(), if available, allows mixing subsecond sleeps with
442 Several fixes, for example for join() problems and memory
443 leaks. In some platforms (like Linux) that use glibc the minimum memory
444 footprint of one ithread has been reduced by several hundred kilobytes.
446 =item threads::shared
448 Many memory leaks have been fixed.
450 =item Unicode::Collate
452 =item Unicode::Normalize
454 =item Win32::GetFolderPath
456 =item Win32::GetOSVersion
458 Now returns extra information.
462 =head1 Utility Changes
464 The C<h2xs> utility now produces a more modern layout:
465 F<Foo-Bar/lib/Foo/Bar.pm> instead of F<Foo/Bar/Bar.pm>.
466 Also, the boilerplate test is now called F<t/Foo-Bar.t>
469 The Perl debugger (F<lib/perl5db.pl>) has now been extensively
470 documented and bugs found while documenting have been fixed.
472 C<perldoc> has been rewritten from scratch to be more robust and
475 C<perlcc -B> works now at least somewhat better, while C<perlcc -c>
476 is rather more broken. (The Perl compiler suite as a whole continues
479 C<find2perl> now assumes C<-print> as a default action. It needed to be
480 specified explicitly.
482 =head1 New Documentation
484 perl573delta has been added to list the differences between the
485 (now quite obsolete) development releases 5.7.2 and 5.7.3.
487 perl58delta and perl581delta have been added: these are the perldeltas
488 of 5.8.0 and 5.8.1, detailing the differences respectively between
489 5.6.0 and 5.8.0, and between 5.8.0 and 5.8.1.
491 perlartistic has been added: it is the Artistic License in pod format,
492 making it easier for modules to refer to it.
494 perlcheat has been added: it is a Perl cheat sheet.
496 perlgpl has been added: it is the GNU General Public License in pod
497 format, making it easier for modules to refer to it.
499 perlmacosx has been added to tell about the installation and use
502 perlos400 has been added to tell about the installation and use
503 of Perl in OS/400 PASE.
505 perlreref has been added: it is a regular expressions quick reference.
507 =head1 Performance Enhancements
509 =head1 Installation and Configuration Improvements
511 The UNIX standard Perl location, F</usr/bin/perl>, is no longer
512 overwritten by default if it exists. This change was very prudent
513 because so many UNIX vendors already provide a F</usr/bin/perl>,
514 but simultaneously many system utilities may depend on that
515 exact version of Perl, so better not to overwrite it.
517 One can now specify installation directories for site and vendor man
518 and HTML pages, and site and vendor scripts. See F<INSTALL>.
520 One can now specify a destination directory for Perl installation
521 by specifying the DESTDIR variable for C<make install>. (This feature
522 is slightly different from the previous C<Configure -Dinstallprefix=...>.)
525 gcc versions 3.x introduced a new warning that caused a lot of noise
526 during Perl compilation: C<gcc -Ialreadyknowndirectory (warning:
527 changing search order)>. This warning has now been avoided by
528 Configure weeding out such directories before the compilation.
530 One can now build subsets of Perl core modules by using the
531 Configure flags C<-Dnoextensions=...> and C<-Donlyextensions=...>,
534 =head2 Platform-specific enhancements
536 In Cygwin Perl can now be built with threads (C<Configure -Duseithreads>).
537 This works with both Cygwin 1.3.22 and Cygwin 1.5.3.
539 In newer FreeBSD releases Perl 5.8.0 compilation failed because of
540 trying to use F<malloc.h>, which in FreeBSD is just a dummy file, and
541 a fatal error to even try to use. Now F<malloc.h> is not used.
543 Perl is now known to build also in Hitachi HI-UXMPP.
545 Perl is now known to build again in LynxOS.
547 Mac OS X now installs with Perl version number embedded in
548 installation directory names for easier upgrading of user-compiled
549 Perl, and the installation directories in general are more standard.
550 In other words, the default installation no longer breaks the
551 Apple-provided Perl. On the other hand, with C<Configure -Dprefix=/usr>
552 you can now really replace the Apple-supplied Perl (B<please be careful>).
554 Mac OS X now builds Perl statically by default. This change was done
555 mainly for faster startup times. The Apple-provided Perl is still
556 dynamically linked and shared, and you can enable the sharedness for
557 your own Perl builds by C<Configure -Duseshrplib>.
559 Perl has been ported to IBM's OS/400 PASE environment. The best way
560 to build a Perl for PASE is to use an AIX host as a cross-compilation
561 environment. See README.os400.
563 Yet another cross-compilation option has been added: now Perl builds
564 on OpenZaurus, an Linux distribution based on Mandrake + Embedix for
565 the Sharp Zaurus PDA. See the Cross/README file.
567 Tru64 when using gcc 3 drops the optimisation for F<toke.c> to C<-O2>
568 because of gigantic memory use with the default C<-O3>.
570 Tru64 can now build Perl with the newer Berkeley DBs.
572 Building Perl on WinCE has been much enhanced, see F<README.ce>
573 and F<README.perlce>.
575 =head1 Selected Bug Fixes
577 =head2 Closures, eval and lexicals
579 There have been many fixes in the area of anonymous subs, lexicals and
580 closures. Although this means that Perl is now more "correct", it is
581 possible that some existing code will break that happens to rely on
582 the faulty behaviour. In practice this is unlikely unless your code
583 contains a very complex nesting of anonymous subs, evals and lexicals.
587 If an input filehandle is marked C<:utf8> and Perl sees illegal UTF-8
588 coming in when doing C<< <FH> >>, if warnings are enabled a warning is
589 immediately given - instead of being silent about it and Perl being
590 unhappy about the broken data later. (The C<:encoding(utf8)> layer
591 also works the same way.)
593 binmode(SOCKET, ":utf8") only worked on the input side, not on the
594 output side of the socket. Now it works both ways.
596 For threaded Perls certain system database functions like getpwent()
597 and getgrent() now grow their result buffer dynamically, instead of
598 failing. This means that at sites with lots of users and groups the
599 functions no longer fail by returning only partial results.
601 Perl 5.8.0 had accidentally broken the capability for users
602 to define their own uppercase<->lowercase Unicode mappings
603 (as advertised by the Camel). This feature has been fixed and
604 is also documented better.
608 $some_unicode .= <FH>;
610 didn't work correctly but instead corrupted the data. This has now
613 Tied methods like FETCH etc. may now safely access tied values, i.e.
614 resulting in a recursive call to FETCH etc. Remember to break the
617 At startup Perl blocks the SIGFPE signal away since there isn't much
618 Perl can do about it. Previously this blocking was in effect also for
619 programs executed from within Perl. Now Perl restores the original
620 SIGFPE handling routine, whatever it was, before running external
623 Linenumbers in Perl scripts may now be greater than 65536, or 2**16.
624 (Perl scripts have always been able to be larger than that, it's just
625 that the linenumber for reported errors and warnings have "wrapped
626 around".) While scripts that large usually indicate a need to rethink
627 your code a bit, such Perl scripts do exist, for example as results
628 from generated code. Now linenumbers can go all the way to
629 4294967296, or 2**32.
631 =head2 Platform-specific fixes
639 Setting $0 works again (with certain limitations that
640 Perl cannot do much about: see L<perlvar/$0>)
650 Setting $0 now works.
660 Configuration now tests for the presence of C<poll()>, and IO::Poll
661 now uses the vendor-supplied function if detected.
665 A rare access violation at Perl start-up could occur if the Perl image was
666 installed with privileges or if there was an identifier with the
667 subsystem attribute set in the process's rightslist. Either of these
668 circumstances triggered tainting code that contained a pointer bug.
669 The faulty pointer arithmetic has been fixed.
673 The length limit on values (not keys) in the %ENV hash has been raised
674 from 255 bytes to 32640 bytes (except when the PERL_ENV_TABLES setting
675 overrides the default use of logical names for %ENV). If it is
676 necessary to access these long values from outside Perl, be aware that
677 they are implemented using search list logical names that store the
678 value in pieces, each 255-byte piece (up to 128 of them) being an
679 element in the search list. When doing a lookup in %ENV from within
680 Perl, the elements are combined into a single value. The existing
681 VMS-specific ability to access individual elements of a search list
682 logical name via the $ENV{'foo;N'} syntax (where N is the search list
683 index) is unimpaired.
687 The piping implementation now uses local rather than global DCL
688 symbols for inter-process communication.
692 File::Find could become confused when navigating to a relative
693 directory whose name collided with a logical name. This problem has
694 been corrected by adding directory syntax to relative path names, thus
695 preventing logical name translation.
705 A memory leak in the fork() emulation has been fixed.
709 The return value of the ioctl() built-in function was accidentally
710 broken in 5.8.0. This has been corrected.
714 The internal message loop executed by perl during blocking operations
715 sometimes interfered with messages that were external to Perl.
716 This often resulted in blocking operations terminating prematurely or
717 returning incorrect results, when Perl was executing under environments
718 that could generate Windows messages. This has been corrected.
722 Pipes and sockets are now automatically in binary mode.
726 The four-argument form of select() did not preserve $! (errno) properly
727 when there were errors in the underlying call. This is now fixed.
731 The "CR CR LF" problem of has been fixed, binmode(FH, ":crlf")
732 is now effectively a no-op.
736 =head1 New or Changed Diagnostics
738 All the warnings related to pack() and unpack() were made more
739 informative and consistent.
741 =head2 Changed "A thread exited while %d threads were running"
745 A thread exited while %d other threads were still running
747 was misleading because the "other" included also the thread giving
750 =head2 Removed "Attempt to clear a restricted hash"
752 It is not illegal to clear a restricted hash, so the warning
755 =head2 New "Illegal declaration of anonymous subroutine"
757 You must specify the block of code for C<sub>.
759 =head2 Changed "Invalid range "%s" in transliteration operator"
763 Invalid [] range "%s" in transliteration operator
765 was simply wrong because there are no "[] ranges" in tr///.
767 =head2 New "Missing control char name in \c"
771 =head2 New "Newline in left-justified string for %s"
773 The padding spaces would appear after the newline, which is
774 probably not what you had in mind.
776 =head2 New "Possible precedence problem on bitwise %c operator"
782 tests whether the bitwise AND of $x and $y is zero,
783 you will like this warning.
785 =head2 New "read() on %s filehandle %s"
787 You cannot read() (or sysread()) from a closed or unopened filehandle.
789 =head2 New "Tied variable freed while still in use"
791 Something pulled the plug on a live tied variable, Perl plays
794 =head2 New "To%s: illegal mapping '%s'"
796 An illegal user-defined Unicode casemapping was specified.
798 =head2 New "Use of freed value in iteration"
800 Something modified the values being iterated over. This is not good.
802 =head1 Changed Internals
804 These news matter to you only if you either write XS code or like to
805 know about or hack Perl internals (using Devel::Peek or any of the
806 C<B::> modules counts), or like to run Perl with the C<-D> option.
808 The embedding examples of L<perlembed> have been reviewed to be
809 uptodate and consistent: for example, the correct use of
810 PERL_SYS_INIT3() and PERL_SYS_TERM().
812 Extensive reworking of the pad code (the code responsible
813 for lexical variables) has been conducted by Dave Mitchell.
815 Extensive work on the v-strings by John Peacock.
817 UTF-8 length and position cache: to speed up the handling of Unicode
818 (UTF-8) scalars, a cache was introduced. Potential problems exist if
819 an extension bypasses the official APIs and directly modifies the PV
820 of an SV: the UTF-8 cache does not get cleared as it should.
822 APIs obsoleted in Perl 5.8.0, like sv_2pv, sv_catpvn, sv_catsv,
823 sv_setsv, are again available.
825 Certain Perl core C APIs like cxinc and regatom are no longer
826 available at all to code outside the Perl core of the Perl core
827 extensions. This is intentional. They never should have been
828 available with the shorter names, and if you application depends on
829 them, you should (be ashamed and) contact perl5-porters to discuss
830 what are the proper APIs.
832 Certain Perl core C APIs like C<Perl_list> are no longer available
833 without their C<Perl_> prefix. If your XS module stops working
834 because some functions cannot be found, in many cases a simple fix is
835 to add the C<Perl_> prefix to the function and the thread context
836 C<aTHX_> as the first argument of the function call. This is also how
837 it should always have been done: letting the Perl_-less forms to leak
838 from the core was an accident. For cleaner embedding you can also
839 force this for all APIs by defining at compile time the cpp define
842 Perl_save_bool() has been added.
844 Regexp objects (those created with C<qr>) now have S-magic rather than
845 R-magic. This fixed regexps of the form /...(??{...;$x})/ to no
846 longer ignore changes made to $x. The S-magic avoids dropping
847 the caching optimization and making (??{...}) constructs obscenely
848 slow (and consequently useless). See also L<perlguts/"Magic Variables">.
849 Regexp::Copy was affected by this change.
851 The Perl internal debugging macros DEBUG() and DEB() have been renamed
852 to PERL_DEBUG() and PERL_DEB() to avoid namespace conflicts.
854 C<-DL> removed (the leaktest had been broken and unsupported for years,
855 use alternative debugging mallocs or tools like valgrind and Purify).
857 Verbose modifier C<v> added for C<-DXv> and C<-Dsv>, see L<perlrun>.
861 In Perl 5.8.0 there were about 69000 separate tests in about 700 test files,
862 in Perl 5.9.0 there are about 77000 separate tests in about 780 test files.
863 The exact numbers depend on the Perl configuration and on the operating
866 =head1 Known Problems
868 The hash randomisation mentioned in L</Incompatible Changes> is definitely
869 problematic: it will wake dormant bugs and shake out bad assumptions.
871 Many of the rarer platforms that worked 100% or pretty close to it
872 with perl 5.8.0 have been left a little bit untended since their
873 maintainers have been otherwise busy lately, and therefore there will
874 be more failures on those platforms. Such platforms include Mac OS
875 Classic, IBM z/OS (and other EBCDIC platforms), and NetWare. The most
876 common Perl platforms (Unix and Unix-like, Microsoft platforms, and
877 VMS) have large enough testing and expert population that they are
880 =head2 Net::Ping 450_service and 510_ping_udp failures
882 The subtests 9 and 18 of lib/Net/Ping/t/450_service.t, and the
883 subtest 2 of lib/Net/Ping/t/510_ping_udp.t might fail if you have
884 an unusual networking setup. For example in the latter case the
885 test is trying to send a UDP ping to the IP address 127.0.0.1.
889 The C-generating compiler backend B::C (the frontend being
890 C<perlcc -c>) is even more broken than it used to be because of
891 the extensive lexical variable changes. (The good news is that
892 B::Bytecode and ByteLoader are better than they used to be.)
894 =head1 Platform Specific Problems
896 =head2 EBCDIC Platforms
898 IBM z/OS and other EBCDIC platforms continue to be problematic
899 regarding Unicode support. Many Unicode tests are skipped when
900 they really should be fixed.
902 =head2 Cygwin 1.5 problems
904 In Cygwin 1.5 the F<io/tell> and F<op/sysio> tests have failures for
905 some yet unknown reason. In 1.5.5 the threads tests stress_cv,
906 stress_re, and stress_string are failing unless the environment
907 variable PERLIO is set to "perlio" (which makes also the io/tell
910 Perl 5.8.1 does build and work well with Cygwin 1.3: with (uname -a)
911 C<CYGWIN_NT-5.0 ... 1.3.22(0.78/3/2) 2003-03-18 09:20 i686 ...>
912 a 100% "make test" was achieved with C<Configure -des -Duseithreads>.
914 =head2 HP-UX: HP cc warnings about sendfile and sendpath
916 With certain HP C compiler releases (e.g. B.11.11.02) you will
917 get many warnings like this (lines wrapped for easier reading):
919 cc: "/usr/include/sys/socket.h", line 504: warning 562:
920 Redeclaration of "sendfile" with a different storage class specifier:
921 "sendfile" will have internal linkage.
922 cc: "/usr/include/sys/socket.h", line 505: warning 562:
923 Redeclaration of "sendpath" with a different storage class specifier:
924 "sendpath" will have internal linkage.
926 The warnings show up both during the build of Perl and during certain
927 lib/ExtUtils tests that invoke the C compiler. The warning, however,
928 is not serious and can be ignored.
930 =head2 IRIX: t/uni/tr_7jis.t falsely failing
932 The test t/uni/tr_7jis.t is known to report failure under 'make test'
933 or the test harness with certain releases of IRIX (at least IRIX 6.5
934 and MIPSpro Compilers Version 7.3.1.1m), but if run manually the test
937 =head2 Mac OS X: no usemymalloc
939 The Perl malloc (C<-Dusemymalloc>) does not work at all in Mac OS X.
940 This is not that serious, though, since the native malloc works just
943 =head2 Tru64: No threaded builds with GNU cc (gcc)
945 In the latest Tru64 releases (e.g. v5.1B or later) gcc cannot be used
946 to compile a threaded Perl (-Duseithreads) because the system
947 C<< <pthread.h> >> file doesn't know about gcc.
949 =head2 Win32: sysopen, sysread, syswrite
951 As of the 5.8.0 release, sysopen()/sysread()/syswrite() do not behave
952 like they used to in 5.6.1 and earlier with respect to "text" mode.
953 These built-ins now always operate in "binary" mode (even if sysopen()
954 was passed the O_TEXT flag, or if binmode() was used on the file
955 handle). Note that this issue should only make a difference for disk
956 files, as sockets and pipes have always been in "binary" mode in the
957 Windows port. As this behavior is currently considered a bug,
958 compatible behavior may be re-introduced in a future release. Until
959 then, the use of sysopen(), sysread() and syswrite() is not supported
960 for "text" mode operations.
964 Here are some things that are planned for perl 5.10.0 :
970 Various Copy-On-Write techniques will be investigated in hopes
975 CPANPLUS, Inline, and Module::Build will become core modules.
979 The ability to write true lexically scoped pragmas will be introduced,
980 perhaps via a C<pragma> pragma.
984 Work will continue on the bytecompiler and byteloader.
988 v-strings as they currently exist are scheduled to be deprecated. The
989 v-less form (1.2.3) will become a "version object" when used with C<use>,
990 C<require>, and C<$VERSION>. $^V will also be a "version object" so the
991 printf("%vd",...) construct will no longer be needed. The v-ful version
992 (v1.2.3) will become obsolete. The equivalence of strings and v-strings (e.g.
993 that currently 5.8.0 is equal to "\5\8\0") will go away. B<There may be no
994 deprecation warning for v-strings>, though: it is quite hard to detect when
995 v-strings are being used safely, and when they are not.
999 =head1 Reporting Bugs
1001 If you find what you think is a bug, you might check the articles
1002 recently posted to the comp.lang.perl.misc newsgroup and the perl
1003 bug database at F<http://bugs.perl.org/>. There may also be
1004 information at F<http://www.perl.com/>, the Perl Home Page.
1006 If you believe you have an unreported bug, please run the B<perlbug>
1007 program included with your release. Be sure to trim your bug down
1008 to a tiny but sufficient test case. Your bug report, along with the
1009 output of C<perl -V>, will be sent off to perlbug@perl.org to be
1010 analysed by the Perl porting team. You can browse and search
1011 the Perl 5 bugs at F<http://bugs.perl.org/>.
1015 The F<Changes> file for exhaustive details on what changed.
1017 The F<INSTALL> file for how to build Perl.
1019 The F<README> file for general stuff.
1021 The F<Artistic> and F<Copying> files for copyright information.