3 perldelta - what's new for perl v5.7.0
7 This document describes differences between the 5.6.0 release and
10 =head1 Security Vulnerability Closed
12 A potential security vulnerability in the optional suidperl component
13 of Perl has been identified. suidperl is neither built nor installed
14 by default. As of September the 2nd, 2000, the only known vulnerable
15 platform is Linux, most likely all Linux distributions. CERT and
16 various vendors have been alerted about the vulnerability.
18 The problem was caused by Perl trying to report a suspected security
19 exploit attempt using an external program, /bin/mail. On Linux
20 platforms the /bin/mail program had an undocumented feature which
21 when combined with suidperl gave access to a root shell, resulting in
22 a serious compromise instead of reporting the exploit attempt. If you
23 don't have /bin/mail, or if you have 'safe setuid scripts', or if
24 suidperl is not installed, you are safe.
26 The exploit attempt reporting feature has been completely removed from
27 the Perl 5.7.0 release, so that particular vulnerability isn't there
28 anymore. However, further security vulnerabilities are,
29 unfortunately, always possible. The suidperl code is being reviewed
30 and if deemed too risky to continue to be supported, it may be
31 completely removed from future releases. In any case, suidperl should
32 only be used by security experts who know exactly what they are doing
33 and why they are using suidperl instead of some other solution such as
34 sudo (see http://www.courtesan.com/sudo/).
36 =head1 Incompatible Changes
42 Arrays now always interpolate into double-quoted strings:
43 constructs like "foo@bar" now always assume C<@bar> is an array,
44 whether or not the compiler has seen use of C<@bar>.
48 The semantics of bless(REF, REF) were unclear and until someone proves
49 it to make some sense, it is forbidden.
53 A reference to a reference now stringify as "REF(0x81485ec)" instead
54 of "SCALAR(0x81485ec)" in order to be more consistent with the return
59 The very dusty examples in the eg/ directory have been removed.
60 Suggestions for new shiny examples welcome but the main issue is that
61 the examples need to be documented, tested and (most importantly)
66 The obsolete chat2 library that should never have been allowed
67 to escape the laboratory has been decommissioned.
71 The unimplemented POSIX regex features [[.cc.]] and [[=c=]] are still
72 recognised but now cause fatal errors. The previous behaviour of
73 ignoring them by default and warning if requested was unacceptable
74 since it, in a way, falsely promised that the features could be used.
78 The (bogus) escape sequences \8 and \9 now give an optional warning
79 ("Unrecognized escape passed through"). There is no need to \-escape
84 lstat(FILEHANDLE) now gives a warning because the operation makes no sense.
85 In future releases this may become a fatal error.
89 The long deprecated uppercase aliases for the string comparison
90 operators (EQ, NE, LT, LE, GE, GT) have now been removed.
94 The regular expression captured submatches ($1, $2, ...) are now
95 more consistently unset if the match fails, instead of leaving false
96 data lying around in them.
100 The tr///C and tr///U features have been removed and will not return;
101 the interface was a mistake. Sorry about that. For similar
102 functionality, see pack('U0', ...) and pack('C0', ...).
106 =head1 Core Enhancements
112 Formats now support zero-padded decimal fields.
116 C<perl -d:Module=arg,arg,arg> now works (previously one couldn't pass
117 in multiple arguments.)
121 my __PACKAGE__ now works.
125 C<no Module;> now works even if there is no "sub unimport" in the Module.
129 The numerical comparison operators return C<undef> if either operand
130 is a NaN. Previously the behaviour was unspecified.
134 C<pack('U0a*', ...)> can now be used to force a string to UTF8.
138 The printf and sprintf now support parameter reordering using the
139 C<%\d+\$> and C<*\d+\$> syntaxes.
143 prototype(\&) is now available.
147 There is now an UNTIE method.
151 =head1 Modules and Pragmata
159 File::Temp allows one to create temporary files and directories in an
160 easy, portable, and secure way.
164 Storable gives persistence to Perl data structures by allowing the
165 storage and retrieval of Perl data to and from files in a fast and
166 compact binary format.
170 =head2 Updated And Improved Modules and Pragmata
176 The following independently supported modules have been updated to
177 newer versions from CPAN: CGI, CPAN, DB_File, File::Spec, Getopt::Long,
178 the podlators bundle, Pod::LaTeX, Pod::Parser, Term::ANSIColor, Test.
182 Bug fixes and minor enhancements have been applied to B::Deparse,
183 Data::Dumper, IO::Poll, IO::Socket::INET, Math::BigFloat,
184 Math::Complex, Math::Trig, Net::protoent, the re pragma, SelfLoader,
185 Sys::SysLog, Test::Harness, Text::Wrap, UNIVERSAL, and the warnings
190 The attributes::reftype() now works on tied arguments.
194 AutoLoader can now be disabled with C<no AutoLoader;>,
198 The English module can now be used without the infamous performance
201 use English '-no_performance_hit';
203 (Assuming, of course, that one doesn't need the troublesome variables
204 C<$`>, C<$&>, or C<$'>.) Also, introduced C<@LAST_MATCH_START> and
205 C<@LAST_MATCH_END> English aliases for C<@-> and C<@+>.
209 File::Find now has pre- and post-processing callbacks. It also
210 correctly changes directories when chasing symbolic links. Callbacks
211 (naughtily) exiting with "next;" instead of "return;" now work.
215 File::Glob::glob() renamed to File::Glob::bsd_glob() to avoid
216 prototype mismatch with CORE::glob().
220 IPC::Open3 now allows the use of numeric file descriptors.
224 use lib now works identically to @INC. Removing directories
225 with 'no lib' now works.
229 C<%INC> now localised in a Safe compartment so that use/require work.
233 The Shell module now has an OO interface.
239 =head1 Utility Changes
245 The Emacs perl mode (emacs/cperl-mode.el) has been updated to version
250 Perlbug is now much more robust. It also sends the bug report to
251 perl.org, not perl.com.
255 The perlcc utility has been rewritten and its user interface (that is,
256 command line) is much more like that of the UNIX C compiler, cc.
260 The xsubpp utility for extension writers now understands POD
261 documentation embedded in the *.xs files.
265 =head1 New Documentation
271 perl56delta details the changes between the 5.005 release and the
276 perldebtut is a Perl debugging tutorial.
280 perlebcdic contains considerations for running Perl on EBCDIC platforms.
281 Note that unfortunately EBCDIC platforms that used to supported back in
282 Perl 5.005 are still unsupported by Perl 5.7.0; the plan, however, is to
283 bring them back to the fold.
287 perlnewmod tells about writing and submitting a new module.
291 perlposix-bc explains using Perl on the POSIX-BC platform
292 (an EBCDIC mainframe platform).
296 perlretut is a regular expression tutorial.
300 perlrequick is a regular expressions quick-start guide.
301 Yes, much quicker than perlretut.
305 perlutil explains the command line utilities packaged with the Perl
310 =head1 Performance Enhancements
316 map() that changes the size of the list should now work faster.
320 sort() has been changed to use mergesort internally as opposed to the
321 earlier quicksort. For very small lists this may result in slightly
322 slower sorting times, but in general the speedup should be at least
323 20%. Additional bonuses are that the worst case behaviour of sort()
324 is now better (in computer science terms it now runs in time O(N log N),
325 as opposed to quicksort's Theta(N**2) worst-case run time behaviour),
326 and that sort() is now stable (meaning that elements with identical
327 keys will stay ordered as they were before the sort).
331 =head1 Installation and Configuration Improvements
333 =head2 Generic Improvements
339 INSTALL now explains how you can configure Perl to use 64-bit
340 integers even on non-64-bit platforms.
344 Policy.sh policy change: if you are reusing a Policy.sh file
345 (see INSTALL) and you use Configure -Dprefix=/foo/bar and in the old
346 Policy $prefix eq $siteprefix and $prefix eq $vendorprefix, all of
347 them will now be changed to the new prefix, /foo/bar. (Previously
348 only $prefix changed.) If you do not like this new behaviour,
349 specify prefix, siteprefix, and vendorprefix explicitly.
353 A new optional location for Perl libraries, otherlibdirs, is available.
354 It can be used for example for vendor add-ons without disturbing Perl's
355 own library directories.
359 In many platforms the vendor-supplied 'cc' is too stripped-down to
360 build Perl (basically, 'cc' doesn't do ANSI C). If this seems
361 to be the case and 'cc' does not seem to be the GNU C compiler
362 'gcc', an automatic attempt is made to find and use 'gcc' instead.
366 gcc needs to closely track the operating system release to avoid
367 build problems. If Configure finds that gcc was built for a different
368 operating system release than is running, it now gives a clearly visible
369 warning that there may be trouble ahead.
373 If binary compatibility with the 5.005 release is not wanted, Configure
374 no longer suggests including the 5.005 modules in @INC.
378 Configure C<-S> can now run non-interactively.
382 configure.gnu now works with options with whitespace in them.
386 installperl now outputs everything to STDERR.
390 $Config{byteorder} is now computed dynamically (this is more robust
391 with "fat binaries" where an executable image contains binaries for
392 more than one binary platform.)
396 Configure no longer included the DBM libraries (dbm, gdbm, db, ndbm)
397 when building the Perl binary. The only exception to this is SunOS 4.x,
402 =head1 Selected Bug Fixes
408 Several debugger fixes: exit code now reflects the script exit code,
409 condition C<"0"> now treated correctly, the C<d> command now checks
410 line number, the C<$.> no longer gets corrupted, all debugger output now
411 goes correctly to the socket if RemotePort is set.
415 C<*foo{FORMAT}> now works.
419 Lexical warnings now propagating correctly between scopes.
423 Line renumbering with eval and C<#line> now works.
427 Fixed numerous memory leaks, especially in eval "".
431 Modulus of unsigned numbers now works (4063328477 % 65535 used to
432 return 27406, instead of 27047).
436 Some "not a number" warnings introduced in 5.6.0 eliminated to be
437 more compatible with 5.005. Infinity is now recognised as a number.
441 our() variables will not cause "will not stay shared" warnings.
445 pack "Z" now correctly terminates the string with "\0".
449 Fix password routines which in some shadow password platforms
450 (e.g. HP-UX) caused getpwent() to return every other entry.
454 printf() no longer resets the numeric locale to "C".
458 C<q(a\\b)> now parses correctly as C<'a\\b'>.
462 Printing quads (64-bit integers) with printf/sprintf now works
463 without the q L ll prefixes (assuming you are on a quad-capable platform).
467 Regular expressions on references and overloaded scalars now work.
471 scalar() now forces scalar context even when used in void context.
475 sort() arguments are now compiled in the right wantarray context
476 (they were accidentally using the context of the sort() itself).
480 Changed the POSIX character class C<[[:space:]]> to include the (very
481 rare) vertical tab character. Added a new POSIX-ish character class
482 C<[[:blank:]]> which stands for horizontal whitespace (currently,
483 the space and the tab).
487 $AUTOLOAD, sort(), lock(), and spawning subprocesses
488 in multiple threads simultaneously are now thread-safe.
492 Allow read-only string on left hand side of non-modifying tr///.
496 Several Unicode fixes (but still not perfect).
502 BOMs (byte order marks) in the beginning of Perl files
503 (scripts, modules) should now be transparently skipped.
504 UTF-16 (UCS-2)encoded Perl files should now be read correctly.
508 The character tables have been updated to Unicode 3.0.1.
512 chr() for values greater than 127 now create utf8 when under use
517 Comparing with utf8 data does not magically upgrade non-utf8 data into
522 C<IsAlnum>, C<IsAlpha>, and C<IsWord> now match titlecase.
526 Concatenation with the C<.> operator or via variable interpolation,
527 C<eq>, C<substr>, C<reverse>, C<quotemeta>, the C<x> operator,
528 substitution with C<s///>, single-quoted UTF8, should now work--in
533 The C<tr///> operator now works I<slightly> better but is still rather
534 broken. Note that the C<tr///CU> functionality has been removed (but
535 see pack('U0', ...)).
539 vec() now tries to work with characters <= 255 when possible, but it leaves
540 higher character values in place. In that case, if vec() was used to modify
541 the string, it is no longer considered to be utf8-encoded.
545 Zero entries were missing from the Unicode classes like C<IsDigit>.
551 UNIVERSAL::isa no longer caches methods incorrectly. (This broke
552 the Tk extension with 5.6.0.)
556 =head2 Platform Specific Changes and Fixes
564 Perl now works on post-4.0 BSD/OSes.
570 Setting C<$0> now works (as much as possible; see perlvar for details).
576 Numerous updates; currently synchronised with Cygwin 1.1.4.
582 EPOC update after Perl 5.6.0. See README.epoc.
588 Perl now works on post-3.0 FreeBSDs.
594 README.hpux updated; C<Configure -Duse64bitall> now almost works.
600 Numerous compilation flag and hint enhancements; accidental mixing
601 of 32-bit and 64-bit libraries (a doomed attempt) made much harder.
607 Long doubles should now work (see INSTALL).
613 Compilation of the standard Perl distribution in MacOS Classic should
614 now work if you have the Metrowerks development environment and
615 the missing Mac-specific toolkit bits. Contact the macperl mailing
622 MPE/iX update after Perl 5.6.0. See README.mpeix.
628 Perl now works on NetBSD/sparc.
634 Now works with usethreads (see INSTALL).
640 64-bitness using the Sun Workshop compiler now works.
644 Tru64 (aka Digital UNIX, aka DEC OSF/1)
646 The operating system version letter now recorded in $Config{osvers}.
647 Allow compiling with gcc (previously explicitly forbidden). Compiling
648 with gcc still not recommended because buggy code results, even with
655 Fixed various alignment problems that lead into core dumps either
656 during build or later; no longer dies on math errors at runtime;
657 now using full quad integers (64 bits), previously was using
658 only 46 bit integers for speed.
664 chdir() now works better despite a CRT bug; now works with MULTIPLICITY
665 (see INSTALL); now works with Perl's malloc.
675 accept() no longer leaks memory.
679 Better chdir() return value for a non-existent directory.
683 New %ENV entries now propagate to subprocesses.
687 $ENV{LIB} now used to search for libs under Visual C.
691 A failed (pseudo)fork now returns undef and sets errno to EAGAIN.
695 Allow REG_EXPAND_SZ keys in the registry.
699 Can now send() from all threads, not just the first one.
703 Fake signal handling reenabled, bugs and all.
707 Less stack reserved per thread so that more threads can run
708 concurrently. (Still 16M per thread.)
712 C<File::Spec->tmpdir()> now prefers C:/temp over /tmp
713 (works better when perl is running as service).
717 Better UNC path handling under ithreads.
721 wait() and waitpid() now work much better.
725 winsock handle leak fixed.
729 =head1 New or Changed Diagnostics
731 All regular expression compilation error messages are now hopefully
732 easier to understand both because the error message now comes before
733 the failed regex and because the point of failure is now clearly
736 The various "opened only for", "on closed", "never opened" warnings
737 drop the C<main::> prefix for filehandles in the C<main> package,
738 for example C<STDIN> instead of <main::STDIN>.
740 The "Unrecognized escape" warning has been extended to include C<\8>,
741 C<\9>, and C<\_>. There is no need to escape any of the C<\w> characters.
743 =head1 Changed Internals
749 perlapi.pod (a companion to perlguts) now attempts to document the
754 You can now build a really minimal perl called microperl.
755 Building microperl does not require even running Configure;
756 C<make -f Makefile.micro> should be enough. Beware: microperl makes
757 many assumptions, some of which may be too bold; the resulting
758 executable may crash or otherwise misbehave in wondrous ways.
759 For careful hackers only.
763 Added rsignal(), whichsig(), do_join() to the publicised API.
767 Made possible to propagate customised exceptions via croak()ing.
771 Added is_utf8_char(), is_utf8_string(), bytes_to_utf8(), and utf8_to_bytes().
775 Now xsubs can have attributes just like subs.
779 =head1 Known Problems
781 =head2 Unicode Support Still Far From Perfect
783 We're working on it. Stay tuned.
785 =head2 EBCDIC Still A Lost Platform
787 The plan is to bring them back.
789 =head2 Building Extensions Can Fail Because Of Largefiles
791 Certain extensions like mod_perl and BSD::Resource are known to have
792 issues with `largefiles', a change brought by Perl 5.6.0 in which file
793 offsets default to 64 bits wide, where supported. Modules may fail to
794 compile at all or compile and work incorrectly. Currently there is no
795 good solution for the problem, but Configure now provides appropriate
796 non-largefile ccflags, ldflags, libswanted, and libs in the %Config
797 hash (e.g., $Config{ccflags_nolargefiles}) so the extensions that are
798 having problems can try configuring themselves without the
799 largefileness. This is admittedly not a clean solution, and the
800 solution may not even work at all. One potential failure is whether
801 one can (or, if one can, whether it's a good idea) link together at
802 all binaries with different ideas about file offsets, all this is
805 =head2 ftmp-security tests warn 'system possibly insecure'
807 Don't panic. Read INSTALL 'make test' section instead.
809 =head2 Test lib/posix Subtest 9 Fails In LP64-Configured HP-UX
811 If perl is configured with -Duse64bitall, the successful result of the
812 subtest 10 of lib/posix may arrive before the successful result of the
813 subtest 9, which confuses the test harness so much that it thinks the
816 =head2 Long Doubles Still Don't Work In Solaris
818 The experimental long double support is still very much so in Solaris.
819 (Other platforms like Linux and Tru64 are beginning to solidify in
822 =head2 Linux With Sfio Fails op/misc Test 48
826 =head2 Storable tests fail in some platforms
828 If any Storable tests fail the use of Storable is not advisable.
834 Many Storable tests fail on AIX configured with 64 bit integers.
836 So far unidentified problems break Storable in AIX if Perl is
837 configured to use 64 bit integers. AIX in 32-bit mode works and
838 other 64-bit platforms work with Storable.
842 DOS DJGPP may hang when testing Storable.
846 st-06compat fails in UNICOS and UNICOS/mk.
848 This means that you cannot read old (pre-Storable-0.7) Storable images
849 made in other platforms.
853 st-store.t and st-retrieve may fail with Compaq C 6.2 on OpenVMS Alpha 7.2.
855 =head2 Threads Are Still Experimental
857 Multithreading is still an experimental feature. Some platforms
858 emit the following message for lib/thr5005
861 # This is a KNOWN FAILURE, and one of the reasons why threading
862 # is still an experimental feature. It is here to stop people
863 # from deploying threads in production. ;-)
866 and another known thread-related warning is
868 pragma/overload......Unbalanced saves: 3 more saves than restores
869 panic: magic_mutexfree during global destruction.
871 lib/selfloader.......Unbalanced saves: 3 more saves than restores
872 panic: magic_mutexfree during global destruction.
874 lib/st-dclone........Unbalanced saves: 3 more saves than restores
875 panic: magic_mutexfree during global destruction.
878 =head2 The Compiler Suite Is Still Experimental
880 The compiler suite is slowly getting better but is nowhere near
881 working order yet. The backend part that has seen perhaps the most
882 progress is the bytecode compiler.
886 =head1 Reporting Bugs
888 If you find what you think is a bug, you might check the articles
889 recently posted to the comp.lang.perl.misc newsgroup and the perl
890 bug database at http://bugs.perl.org. There may also be
891 information at http://www.perl.com/perl/, the Perl Home Page.
893 If you believe you have an unreported bug, please run the B<perlbug>
894 program included with your release. Be sure to trim your bug down
895 to a tiny but sufficient test case. Your bug report, along with the
896 output of C<perl -V>, will be sent off to perlbug@perl.org to be
897 analysed by the Perl porting team.
901 The F<Changes> file for exhaustive details on what changed.
903 The F<INSTALL> file for how to build Perl.
905 The F<README> file for general stuff.
907 The F<Artistic> and F<Copying> files for copyright information.
911 Written by Jarkko Hietaniemi <F<jhi@iki.fi>>, with many contributions
912 from The Perl Porters and Perl Users submitting feedback and patches.
914 Send omissions or corrections to <F<perlbug@perl.org>>.