3 perl590delta - 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 the 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.
227 now do localise variables, given that the $x is a valid variable name.
229 =head2 Unicode Character Database 4.0.0
231 The copy of the Unicode Character Database included in Perl 5.8 has
232 been updated to 4.0.0 from 3.2.0. This means for example that the
233 Unicode character properties are as in Unicode 4.0.0.
235 =head2 Miscellaneous Enhancements
237 C<unpack()> now defaults to unpacking the C<$_>.
239 C<map> in void context is no longer expensive. C<map> is now context
240 aware, and will not construct a list if called in void context.
242 If a socket gets closed by the server while printing to it, the client
243 now gets a SIGPIPE. While this new feature was not planned, it fell
244 naturally out of PerlIO changes, and is to be considered an accidental
247 PerlIO::get_layers(FH) returns the names of the PerlIO layers
248 active on a filehandle.
250 PerlIO::via layers can now have an optional UTF8 method to
251 indicate whether the layer wants to "auto-:utf8" the stream.
253 utf8::is_utf8() has been added as a quick way to test whether
254 a scalar is encoded internally in UTF-8 (Unicode).
256 =head1 Modules and Pragmata
258 =head2 Updated Modules And Pragmata
260 The following modules and pragmata have been updated since Perl 5.8.0:
268 In much better shape than it used to be. Still far from perfect, but
277 An optional feature, C<:hireswallclock>, now allows for high
278 resolution wall clock times (uses Time::HiRes).
286 Now has bytes::substr.
292 One can now have custom character name aliases.
296 There is now a simple command line frontend to the CPAN.pm
297 module called F<cpan>.
301 A new option, Pair, allows choosing the separator between hash keys
312 Significant updates on the encoding pragma functionality
313 (tr/// and the DATA filehandle, formats).
315 If a filehandle has been marked as to have an encoding, unmappable
316 characters are detected already during input, not later (when the
317 corrupted data is being used).
319 The ISO 8859-6 conversion table has been corrected (the 0x30..0x39
320 erroneously mapped to U+0660..U+0669, instead of U+0030..U+0039). The
321 GSM 03.38 conversion did not handle escape sequences correctly. The
322 UTF-7 encoding has been added (making Encode feature-complete with
331 A lot of bugs have been fixed since v1.60, the version included in Perl
332 v5.8.0. Especially noteworthy are the bug in Calc that caused div and mod to
333 fail for some large values, and the fixes to the handling of bad inputs.
335 Some new features were added, e.g. the broot() method, you can now pass
336 parameters to config() to change some settings at runtime, and it is now
337 possible to trap the creation of NaN and infinity.
339 As usual, some optimizations took place and made the math overall a tad
340 faster. In some cases, quite a lot faster, actually. Especially alternative
341 libraries like Math::BigInt::GMP benefit from this. In addition, a lot of the
342 quite clunky routines like fsqrt() and flog() are now much much faster.
348 Diamond inheritance now works.
354 Reading from non-string scalars (like the special variables, see
355 L<perlvar>) now works.
365 Complete rewrite. As a side-effect, no longer refuses to startup when
370 New utilities: refaddr, isvstring, looks_like_number, set_prototype.
374 Can now store code references (via B::Deparse, so not foolproof).
378 Earlier versions of the strict pragma did not check the parameters
379 implicitly passed to its "import" (use) and "unimport" (no) routine.
380 This caused the false idiom such as:
385 This however (probably) raised the false expectation that the strict
386 refs, vars and subs were being enforced (and that @ISA was somehow
387 "declared"). But the strict refs, vars, and subs are B<not> enforced
388 when using this false idiom.
390 Starting from Perl 5.8.1, the above B<will> cause an error to be
391 raised. This may cause programs which used to execute seemingly
392 correctly without warnings and errors to fail when run under 5.8.1.
397 will now fail with the error:
399 Unknown 'strict' tag(s) '@ISA'
401 The remedy to this problem is to replace this code with the correct idiom:
407 =item Term::ANSIcolor
411 Now much more picky about extra or missing output from test scripts.
421 Use of nanosleep(), if available, allows mixing subsecond sleeps with
426 Several fixes, for example for join() problems and memory
427 leaks. In some platforms (like Linux) that use glibc the minimum memory
428 footprint of one ithread has been reduced by several hundred kilobytes.
430 =item threads::shared
432 Many memory leaks have been fixed.
434 =item Unicode::Collate
436 =item Unicode::Normalize
438 =item Win32::GetFolderPath
440 =item Win32::GetOSVersion
442 Now returns extra information.
446 =head1 Utility Changes
448 The C<h2xs> utility now produces a more modern layout:
449 F<Foo-Bar/lib/Foo/Bar.pm> instead of F<Foo/Bar/Bar.pm>.
450 Also, the boilerplate test is now called F<t/Foo-Bar.t>
453 The Perl debugger (F<lib/perl5db.pl>) has now been extensively
454 documented and bugs found while documenting have been fixed.
456 C<perldoc> has been rewritten from scratch to be more robust and
459 C<perlcc -B> works now at least somewhat better, while C<perlcc -c>
460 is rather more broken. (The Perl compiler suite as a whole continues
463 =head1 New Documentation
465 perl573delta has been added to list the differences between the
466 (now quite obsolete) development releases 5.7.2 and 5.7.3.
468 perl58delta and perl581delta have been added: these are the perldeltas
469 of 5.8.0 and 5.8.1, detailing the differences respectively between
470 5.6.0 and 5.8.0, and between 5.8.0 and 5.8.1.
472 perlartistic has been added: it is the Artistic License in pod format,
473 making it easier for modules to refer to it.
475 perlcheat has been added: it is a Perl cheat sheet.
477 perlgpl has been added: it is the GNU General Public License in pod
478 format, making it easier for modules to refer to it.
480 perlmacosx has been added to tell about the installation and use
483 perlos400 has been added to tell about the installation and use
484 of Perl in OS/400 PASE.
486 perlreref has been added: it is a regular expressions quick reference.
488 =head1 Installation and Configuration Improvements
490 The Unix standard Perl location, F</usr/bin/perl>, is no longer
491 overwritten by default if it exists. This change was very prudent
492 because so many Unix vendors already provide a F</usr/bin/perl>,
493 but simultaneously many system utilities may depend on that
494 exact version of Perl, so better not to overwrite it.
496 One can now specify installation directories for site and vendor man
497 and HTML pages, and site and vendor scripts. See F<INSTALL>.
499 One can now specify a destination directory for Perl installation
500 by specifying the DESTDIR variable for C<make install>. (This feature
501 is slightly different from the previous C<Configure -Dinstallprefix=...>.)
504 gcc versions 3.x introduced a new warning that caused a lot of noise
505 during Perl compilation: C<gcc -Ialreadyknowndirectory (warning:
506 changing search order)>. This warning has now been avoided by
507 Configure weeding out such directories before the compilation.
509 One can now build subsets of Perl core modules by using the
510 Configure flags C<-Dnoextensions=...> and C<-Donlyextensions=...>,
513 =head2 Platform-specific enhancements
515 In Cygwin Perl can now be built with threads (C<Configure -Duseithreads>).
516 This works with both Cygwin 1.3.22 and Cygwin 1.5.3.
518 In newer FreeBSD releases Perl 5.8.0 compilation failed because of
519 trying to use F<malloc.h>, which in FreeBSD is just a dummy file, and
520 a fatal error to even try to use. Now F<malloc.h> is not used.
522 Perl is now known to build also in Hitachi HI-UXMPP.
524 Perl is now known to build again in LynxOS.
526 Mac OS X now installs with Perl version number embedded in
527 installation directory names for easier upgrading of user-compiled
528 Perl, and the installation directories in general are more standard.
529 In other words, the default installation no longer breaks the
530 Apple-provided Perl. On the other hand, with C<Configure -Dprefix=/usr>
531 you can now really replace the Apple-supplied Perl (B<please be careful>).
533 Mac OS X now builds Perl statically by default. This change was done
534 mainly for faster startup times. The Apple-provided Perl is still
535 dynamically linked and shared, and you can enable the sharedness for
536 your own Perl builds by C<Configure -Duseshrplib>.
538 Perl has been ported to IBM's OS/400 PASE environment. The best way
539 to build a Perl for PASE is to use an AIX host as a cross-compilation
540 environment. See README.os400.
542 Yet another cross-compilation option has been added: now Perl builds
543 on OpenZaurus, an Linux distribution based on Mandrake + Embedix for
544 the Sharp Zaurus PDA. See the Cross/README file.
546 Tru64 when using gcc 3 drops the optimisation for F<toke.c> to C<-O2>
547 because of gigantic memory use with the default C<-O3>.
549 Tru64 can now build Perl with the newer Berkeley DBs.
551 Building Perl on WinCE has been much enhanced, see F<README.ce>
552 and F<README.perlce>.
554 =head1 Selected Bug Fixes
556 =head2 Closures, eval and lexicals
558 There have been many fixes in the area of anonymous subs, lexicals and
559 closures. Although this means that Perl is now more "correct", it is
560 possible that some existing code will break that happens to rely on
561 the faulty behaviour. In practice this is unlikely unless your code
562 contains a very complex nesting of anonymous subs, evals and lexicals.
566 If an input filehandle is marked C<:utf8> and Perl sees illegal UTF-8
567 coming in when doing C<< <FH> >>, if warnings are enabled a warning is
568 immediately given - instead of being silent about it and Perl being
569 unhappy about the broken data later. (The C<:encoding(utf8)> layer
570 also works the same way.)
572 binmode(SOCKET, ":utf8") only worked on the input side, not on the
573 output side of the socket. Now it works both ways.
575 For threaded Perls certain system database functions like getpwent()
576 and getgrent() now grow their result buffer dynamically, instead of
577 failing. This means that at sites with lots of users and groups the
578 functions no longer fail by returning only partial results.
580 Perl 5.8.0 had accidentally broken the capability for users
581 to define their own uppercase<->lowercase Unicode mappings
582 (as advertised by the Camel). This feature has been fixed and
583 is also documented better.
587 $some_unicode .= <FH>;
589 didn't work correctly but instead corrupted the data. This has now
592 Tied methods like FETCH etc. may now safely access tied values, i.e.
593 resulting in a recursive call to FETCH etc. Remember to break the
596 At startup Perl blocks the SIGFPE signal away since there isn't much
597 Perl can do about it. Previously this blocking was in effect also for
598 programs executed from within Perl. Now Perl restores the original
599 SIGFPE handling routine, whatever it was, before running external
602 Linenumbers in Perl scripts may now be greater than 65536, or 2**16.
603 (Perl scripts have always been able to be larger than that, it's just
604 that the linenumber for reported errors and warnings have "wrapped
605 around".) While scripts that large usually indicate a need to rethink
606 your code a bit, such Perl scripts do exist, for example as results
607 from generated code. Now linenumbers can go all the way to
608 4294967296, or 2**32.
610 =head2 Platform-specific fixes
618 Setting $0 works again (with certain limitations that
619 Perl cannot do much about: see L<perlvar/$0>)
629 Setting $0 now works.
639 Configuration now tests for the presence of C<poll()>, and IO::Poll
640 now uses the vendor-supplied function if detected.
644 A rare access violation at Perl start-up could occur if the Perl image was
645 installed with privileges or if there was an identifier with the
646 subsystem attribute set in the process's rightslist. Either of these
647 circumstances triggered tainting code that contained a pointer bug.
648 The faulty pointer arithmetic has been fixed.
652 The length limit on values (not keys) in the %ENV hash has been raised
653 from 255 bytes to 32640 bytes (except when the PERL_ENV_TABLES setting
654 overrides the default use of logical names for %ENV). If it is
655 necessary to access these long values from outside Perl, be aware that
656 they are implemented using search list logical names that store the
657 value in pieces, each 255-byte piece (up to 128 of them) being an
658 element in the search list. When doing a lookup in %ENV from within
659 Perl, the elements are combined into a single value. The existing
660 VMS-specific ability to access individual elements of a search list
661 logical name via the $ENV{'foo;N'} syntax (where N is the search list
662 index) is unimpaired.
666 The piping implementation now uses local rather than global DCL
667 symbols for inter-process communication.
671 File::Find could become confused when navigating to a relative
672 directory whose name collided with a logical name. This problem has
673 been corrected by adding directory syntax to relative path names, thus
674 preventing logical name translation.
684 A memory leak in the fork() emulation has been fixed.
688 The return value of the ioctl() built-in function was accidentally
689 broken in 5.8.0. This has been corrected.
693 The internal message loop executed by perl during blocking operations
694 sometimes interfered with messages that were external to Perl.
695 This often resulted in blocking operations terminating prematurely or
696 returning incorrect results, when Perl was executing under environments
697 that could generate Windows messages. This has been corrected.
701 Pipes and sockets are now automatically in binary mode.
705 The four-argument form of select() did not preserve $! (errno) properly
706 when there were errors in the underlying call. This is now fixed.
710 The "CR CR LF" problem of has been fixed, binmode(FH, ":crlf")
711 is now effectively a no-op.
715 =head1 New or Changed Diagnostics
717 All the warnings related to pack() and unpack() were made more
718 informative and consistent.
720 =head2 Changed "A thread exited while %d threads were running"
724 A thread exited while %d other threads were still running
726 was misleading because the "other" included also the thread giving
729 =head2 Removed "Attempt to clear a restricted hash"
731 It is not illegal to clear a restricted hash, so the warning
734 =head2 New "Illegal declaration of anonymous subroutine"
736 You must specify the block of code for C<sub>.
738 =head2 Changed "Invalid range "%s" in transliteration operator"
742 Invalid [] range "%s" in transliteration operator
744 was simply wrong because there are no "[] ranges" in tr///.
746 =head2 New "Missing control char name in \c"
750 =head2 New "Newline in left-justified string for %s"
752 The padding spaces would appear after the newline, which is
753 probably not what you had in mind.
755 =head2 New "Possible precedence problem on bitwise %c operator"
761 tests whether the bitwise AND of $x and $y is zero,
762 you will like this warning.
764 =head2 New "read() on %s filehandle %s"
766 You cannot read() (or sysread()) from a closed or unopened filehandle.
768 =head2 New "Tied variable freed while still in use"
770 Something pulled the plug on a live tied variable, Perl plays
773 =head2 New "To%s: illegal mapping '%s'"
775 An illegal user-defined Unicode casemapping was specified.
777 =head2 New "Use of freed value in iteration"
779 Something modified the values being iterated over. This is not good.
781 =head1 Changed Internals
783 These news matter to you only if you either write XS code or like to
784 know about or hack Perl internals (using Devel::Peek or any of the
785 C<B::> modules counts), or like to run Perl with the C<-D> option.
787 The embedding examples of L<perlembed> have been reviewed to be
788 up to date and consistent: for example, the correct use of
789 PERL_SYS_INIT3() and PERL_SYS_TERM().
791 Extensive reworking of the pad code (the code responsible
792 for lexical variables) has been conducted by Dave Mitchell.
794 Extensive work on the v-strings by John Peacock.
796 UTF-8 length and position cache: to speed up the handling of Unicode
797 (UTF-8) scalars, a cache was introduced. Potential problems exist if
798 an extension bypasses the official APIs and directly modifies the PV
799 of an SV: the UTF-8 cache does not get cleared as it should.
801 APIs obsoleted in Perl 5.8.0, like sv_2pv, sv_catpvn, sv_catsv,
802 sv_setsv, are again available.
804 Certain Perl core C APIs like cxinc and regatom are no longer
805 available at all to code outside the Perl core of the Perl core
806 extensions. This is intentional. They never should have been
807 available with the shorter names, and if you application depends on
808 them, you should (be ashamed and) contact perl5-porters to discuss
809 what are the proper APIs.
811 Certain Perl core C APIs like C<Perl_list> are no longer available
812 without their C<Perl_> prefix. If your XS module stops working
813 because some functions cannot be found, in many cases a simple fix is
814 to add the C<Perl_> prefix to the function and the thread context
815 C<aTHX_> as the first argument of the function call. This is also how
816 it should always have been done: letting the Perl_-less forms to leak
817 from the core was an accident. For cleaner embedding you can also
818 force this for all APIs by defining at compile time the cpp define
821 Perl_save_bool() has been added.
823 Regexp objects (those created with C<qr>) now have S-magic rather than
824 R-magic. This fixed regexps of the form /...(??{...;$x})/ to no
825 longer ignore changes made to $x. The S-magic avoids dropping
826 the caching optimization and making (??{...}) constructs obscenely
827 slow (and consequently useless). See also L<perlguts/"Magic Variables">.
828 Regexp::Copy was affected by this change.
830 The Perl internal debugging macros DEBUG() and DEB() have been renamed
831 to PERL_DEBUG() and PERL_DEB() to avoid namespace conflicts.
833 C<-DL> removed (the leaktest had been broken and unsupported for years,
834 use alternative debugging mallocs or tools like valgrind and Purify).
836 Verbose modifier C<v> added for C<-DXv> and C<-Dsv>, see L<perlrun>.
840 In Perl 5.8.0 there were about 69000 separate tests in about 700 test files,
841 in Perl 5.9.0 there are about 77000 separate tests in about 780 test files.
842 The exact numbers depend on the Perl configuration and on the operating
845 =head1 Known Problems
847 The hash randomisation mentioned in L</Incompatible Changes> is definitely
848 problematic: it will wake dormant bugs and shake out bad assumptions.
850 Many of the rarer platforms that worked 100% or pretty close to it
851 with perl 5.8.0 have been left a little bit untended since their
852 maintainers have been otherwise busy lately, and therefore there will
853 be more failures on those platforms. Such platforms include Mac OS
854 Classic, IBM z/OS (and other EBCDIC platforms), and NetWare. The most
855 common Perl platforms (Unix and Unix-like, Microsoft platforms, and
856 VMS) have large enough testing and expert population that they are
859 =head2 Tied hashes in scalar context
861 Tied hashes do not currently return anything useful in scalar context,
862 for example when used as boolean tests:
864 if (%tied_hash) { ... }
866 The current nonsensical behaviour is always to return false,
867 regardless of whether the hash is empty or has elements.
869 The root cause is that there is no interface for the implementors of
870 tied hashes to implement the behaviour of a hash in scalar context.
872 =head2 Net::Ping 450_service and 510_ping_udp failures
874 The subtests 9 and 18 of lib/Net/Ping/t/450_service.t, and the
875 subtest 2 of lib/Net/Ping/t/510_ping_udp.t might fail if you have
876 an unusual networking setup. For example in the latter case the
877 test is trying to send a UDP ping to the IP address 127.0.0.1.
881 The C-generating compiler backend B::C (the frontend being
882 C<perlcc -c>) is even more broken than it used to be because of
883 the extensive lexical variable changes. (The good news is that
884 B::Bytecode and ByteLoader are better than they used to be.)
886 =head1 Platform Specific Problems
888 =head2 EBCDIC Platforms
890 IBM z/OS and other EBCDIC platforms continue to be problematic
891 regarding Unicode support. Many Unicode tests are skipped when
892 they really should be fixed.
894 =head2 Cygwin 1.5 problems
896 In Cygwin 1.5 the F<io/tell> and F<op/sysio> tests have failures for
897 some yet unknown reason. In 1.5.5 the threads tests stress_cv,
898 stress_re, and stress_string are failing unless the environment
899 variable PERLIO is set to "perlio" (which makes also the io/tell
902 Perl 5.8.1 does build and work well with Cygwin 1.3: with (uname -a)
903 C<CYGWIN_NT-5.0 ... 1.3.22(0.78/3/2) 2003-03-18 09:20 i686 ...>
904 a 100% "make test" was achieved with C<Configure -des -Duseithreads>.
906 =head2 HP-UX: HP cc warnings about sendfile and sendpath
908 With certain HP C compiler releases (e.g. B.11.11.02) you will
909 get many warnings like this (lines wrapped for easier reading):
911 cc: "/usr/include/sys/socket.h", line 504: warning 562:
912 Redeclaration of "sendfile" with a different storage class specifier:
913 "sendfile" will have internal linkage.
914 cc: "/usr/include/sys/socket.h", line 505: warning 562:
915 Redeclaration of "sendpath" with a different storage class specifier:
916 "sendpath" will have internal linkage.
918 The warnings show up both during the build of Perl and during certain
919 lib/ExtUtils tests that invoke the C compiler. The warning, however,
920 is not serious and can be ignored.
922 =head2 IRIX: t/uni/tr_7jis.t falsely failing
924 The test t/uni/tr_7jis.t is known to report failure under 'make test'
925 or the test harness with certain releases of IRIX (at least IRIX 6.5
926 and MIPSpro Compilers Version 7.3.1.1m), but if run manually the test
929 =head2 Mac OS X: no usemymalloc
931 The Perl malloc (C<-Dusemymalloc>) does not work at all in Mac OS X.
932 This is not that serious, though, since the native malloc works just
935 =head2 Tru64: No threaded builds with GNU cc (gcc)
937 In the latest Tru64 releases (e.g. v5.1B or later) gcc cannot be used
938 to compile a threaded Perl (-Duseithreads) because the system
939 C<< <pthread.h> >> file doesn't know about gcc.
941 =head2 Win32: sysopen, sysread, syswrite
943 As of the 5.8.0 release, sysopen()/sysread()/syswrite() do not behave
944 like they used to in 5.6.1 and earlier with respect to "text" mode.
945 These built-ins now always operate in "binary" mode (even if sysopen()
946 was passed the O_TEXT flag, or if binmode() was used on the file
947 handle). Note that this issue should only make a difference for disk
948 files, as sockets and pipes have always been in "binary" mode in the
949 Windows port. As this behavior is currently considered a bug,
950 compatible behavior may be re-introduced in a future release. Until
951 then, the use of sysopen(), sysread() and syswrite() is not supported
952 for "text" mode operations.
956 Here are some things that are planned for perl 5.10.0 :
962 Various Copy-On-Write techniques will be investigated in hopes
967 CPANPLUS, Inline, and Module::Build will become core modules.
971 The ability to write true lexically scoped pragmas will be introduced,
972 perhaps via a C<pragma> pragma.
976 Work will continue on the bytecompiler and byteloader.
980 v-strings as they currently exist are scheduled to be deprecated. The
981 v-less form (1.2.3) will become a "version object" when used with C<use>,
982 C<require>, and C<$VERSION>. $^V will also be a "version object" so the
983 printf("%vd",...) construct will no longer be needed. The v-ful version
984 (v1.2.3) will become obsolete. The equivalence of strings and v-strings (e.g.
985 that currently 5.8.0 is equal to "\5\8\0") will go away. B<There may be no
986 deprecation warning for v-strings>, though: it is quite hard to detect when
987 v-strings are being used safely, and when they are not.
991 =head1 Reporting Bugs
993 If you find what you think is a bug, you might check the articles
994 recently posted to the comp.lang.perl.misc newsgroup and the perl
995 bug database at F<http://bugs.perl.org/>. There may also be
996 information at F<http://www.perl.com/>, the Perl Home Page.
998 If you believe you have an unreported bug, please run the B<perlbug>
999 program included with your release. Be sure to trim your bug down
1000 to a tiny but sufficient test case. Your bug report, along with the
1001 output of C<perl -V>, will be sent off to perlbug@perl.org to be
1002 analysed by the Perl porting team. You can browse and search
1003 the Perl 5 bugs at F<http://bugs.perl.org/>.
1007 The F<Changes> file for exhaustive details on what changed.
1009 The F<INSTALL> file for how to build Perl.
1011 The F<README> file for general stuff.
1013 The F<Artistic> and F<Copying> files for copyright information.