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, \9, and \_ now give an optional
79 warning ("Unrecognized escape passed through"). There is no need
80 to \-escape any C<\w> character.
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, $2, ...) are now
95 more consistently unset if the match fails, instead of leaving false
96 data lying around in them.
100 The tr///C and tr///U features have been removed and will not return;
101 the interface was a mistake. Sorry about that. For similar
102 functionality, see pack('U0', ...) and pack('C0', ...).
106 =head1 Core Enhancements
112 C<perl -d:Module=arg,arg,arg> now works (previously one couldn't pass
113 in multiple arguments.)
117 my __PACKAGE__ now works.
121 C<no Module;> now works even if there is no "sub unimport" in the Module.
125 The numerical comparison operators return C<undef> if either operand
126 is a NaN. Previously the behaviour was unspecified.
130 C<pack('U0a*', ...)> can now be used to force a string to UTF8.
134 prototype(\&) is now available.
138 There is now an UNTIE method.
142 =head1 Modules and Pragmata
150 File::Temp allows one to create temporary files and directories in an
151 easy, portable, and secure way.
155 Storable gives persistence to Perl data structures by allowing the
156 storage and retrieval of Perl data to and from files in a fast and
157 compact binary format.
161 =head2 Updated And Improved Modules and Pragmata
167 The following independently supported modules have been updated to
168 newer versions from CPAN: CGI, CPAN, DB_File, File::Spec, Getopt::Long,
169 the podlators bundle, Pod::LaTeX, Pod::Parser, Term::ANSIColor, Test.
173 Bug fixes and minor enhancements have been applied to B::Deparse,
174 Data::Dumper, IO::Poll, IO::Socket::INET, Math::BigFloat,
175 Math::Complex, Math::Trig, Net::protoent, the re pragma, SelfLoader,
176 Sys::SysLog, Test::Harness, Text::Wrap, UNIVERSAL, and the warnings
181 The attributes::reftype() now works on tied arguments.
185 AutoLoader can now be disabled with C<no AutoLoader;>,
189 The English module can now be used without the infamous performance
192 use English '-no_performance_hit';
194 (Assuming, of course, that one doesn't need the troublesome variables
195 C<$`>, C<$&>, or C<$'>.) Also, introduced C<@LAST_MATCH_START> and
196 C<@LAST_MATCH_END> English aliases for C<@-> and C<@+>.
200 File::Find now has pre- and post-processing callbacks. It also
201 correctly changes directories when chasing symbolic links. Callbacks
202 (naughtily) exiting with "next;" instead of "return;" now work.
206 File::Glob::glob() renamed to File::Glob::bsd_glob() to avoid
207 prototype mismatch with CORE::glob().
211 IPC::Open3 now allows the use of numeric file descriptors.
215 use lib now works identically to @INC. Removing directories
216 with 'no lib' now works.
220 C<%INC> now localised in a Safe compartment so that use/require work.
224 The Shell module now has an OO interface.
230 =head1 Utility Changes
236 The Emacs perl mode (emacs/cperl-mode.el) has been updated to version
241 Perlbug is now much more robust. It also sends the bug report to
242 perl.org, not perl.com.
246 The perlcc utility has been rewritten and its user interface (that is,
247 command line) is much more like that of the UNIX C compiler, cc.
251 The xsubpp utility for extension writers now understands POD
252 documentation embedded in the *.xs files.
256 =head1 New Documentation
262 perl56delta details the changes between the 5.005 release and the
267 perldebtut is a Perl debugging tutorial.
271 perlebcdic contains considerations for running Perl on EBCDIC platforms.
272 Note that unfortunately EBCDIC platforms that used to supported back in
273 Perl 5.005 are still unsupported by Perl 5.7.0; the plan, however, is to
274 bring them back to the fold.
278 perlnewmod tells about writing and submitting a new module.
282 perlposix-bc explains using Perl on the POSIX-BC platform
283 (an EBCDIC mainframe platform).
287 perlretut is a regular expression tutorial.
291 perlrequick is a regular expressions quick-start guide.
292 Yes, much quicker than perlretut.
296 perlutil explains the command line utilities packaged with the Perl
301 =head1 Performance Enhancements
307 map() that changes the size of the list should now work faster.
311 sort() has been changed to use mergesort internally as opposed to the
312 earlier quicksort. For very small lists this may result in slightly
313 slower sorting times, but in general the speedup should be at least
314 20%. Additional bonuses are that the worst case behaviour of sort()
315 is now better (in computer science terms it now runs in time O(N log N),
316 as opposed to quicksort's Theta(N**2) worst-case run time behaviour),
317 and that sort() is now stable (meaning that elements with identical
318 keys will stay ordered as they were before the sort).
322 =head1 Installation and Configuration Improvements
324 =head2 Generic Improvements
330 INSTALL now explains how you can configure Perl to use 64-bit
331 integers even on non-64-bit platforms.
335 Policy.sh policy change: if you are reusing a Policy.sh file
336 (see INSTALL) and you use Configure -Dprefix=/foo/bar and in the old
337 Policy $prefix eq $siteprefix and $prefix eq $vendorprefix, all of
338 them will now be changed to the new prefix, /foo/bar. (Previously
339 only $prefix changed.) If you do not like this new behaviour,
340 specify prefix, siteprefix, and vendorprefix explicitly.
344 A new optional location for Perl libraries, otherlibdirs, is available.
345 It can be used for example for vendor add-ons without disturbing Perl's
346 own library directories.
350 In many platforms the vendor-supplied 'cc' is too stripped-down to
351 build Perl (basically, 'cc' doesn't do ANSI C). If this seems
352 to be the case and 'cc' does not seem to be the GNU C compiler
353 'gcc', an automatic attempt is made to find and use 'gcc' instead.
357 gcc needs to closely track the operating system release to avoid
358 build problems. If Configure finds that gcc was built for a different
359 operating system release than is running, it now gives a clearly visible
360 warning that there may be trouble ahead.
364 If binary compatibility with the 5.005 release is not wanted, Configure
365 no longer suggests including the 5.005 modules in @INC.
369 Configure C<-S> can now run non-interactively.
373 configure.gnu now works with options with whitespace in them.
377 installperl now outputs everything to STDERR.
381 $Config{byteorder} is now computed dynamically (this is more robust
382 with "fat binaries" where an executable image contains binaries for
383 more than one binary platform.)
387 Configure no longer included the DBM libraries (dbm, gdbm, db, ndbm)
388 when building the Perl binary. The only exception to this is SunOS 4.x,
393 =head1 Selected Bug Fixes
399 Several debugger fixes: exit code now reflects the script exit code,
400 condition C<"0"> now treated correctly, the C<d> command now checks
401 line number, the C<$.> no longer gets corrupted, all debugger output now
402 goes correctly to the socket if RemotePort is set.
406 C<*foo{FORMAT}> now works.
410 Lexical warnings now propagating correctly between scopes.
414 Line renumbering with eval and C<#line> now works.
418 Fixed numerous memory leaks, especially in eval "".
422 Modulus of unsigned numbers now works (4063328477 % 65535 used to
423 return 27406, instead of 27047).
427 Some "not a number" warnings introduced in 5.6.0 eliminated to be
428 more compatible with 5.005. Infinity is now recognised as a number.
432 our() variables will not cause "will not stay shared" warnings.
436 pack "Z" now correctly terminates the string with "\0".
440 Fix password routines which in some shadow password platforms
441 (e.g. HP-UX) caused getpwent() to return every other entry.
445 printf() no longer resets the numeric locale to "C".
449 C<q(a\\b)> now parses correctly as C<'a\\b'>.
453 Printing quads (64-bit integers) with printf/sprintf now works
454 without the q L ll prefixes (assuming you are on a quad-capable platform).
458 Regular expressions on references and overloaded scalars now work.
462 scalar() now forces scalar context even when used in void context.
466 sort() arguments are now compiled in the right wantarray context
467 (they were accidentally using the context of the sort() itself).
471 Changed the POSIX character class C<[[:space:]]> to include the (very
472 rare) vertical tab character. Added a new POSIX-ish character class
473 C<[[:blank:]]> which stands for horizontal whitespace (currently,
474 the space and the tab).
478 $AUTOLOAD, sort(), lock(), and spawning subprocesses
479 in multiple threads simultaneously are now thread-safe.
483 Allow read-only string on left hand side of non-modifying tr///.
487 Several Unicode fixes (but still not perfect).
493 BOMs (byte order marks) in the beginning of Perl files
494 (scripts, modules) should now be transparently skipped.
495 UTF-16 (UCS-2)encoded Perl files should now be read correctly.
499 The character tables have been updated to Unicode 3.0.1.
503 chr() for values greater than 127 now create utf8 when under use
508 Comparing with utf8 data does not magically upgrade non-utf8 data into
513 C<IsAlnum>, C<IsAlpha>, and C<IsWord> now match titlecase.
517 Concatenation with the C<.> operator or via variable interpolation,
518 C<eq>, C<substr>, C<reverse>, C<quotemeta>, the C<x> operator,
519 substitution with C<s///>, single-quoted UTF8, should now work--in
524 The C<tr///> operator now works I<slightly> better but is still rather
525 broken. Note that the C<tr///CU> functionality has been removed (but
526 see pack('U0', ...)).
530 vec() now tries to work with characters <= 255 when possible, but it leaves
531 higher character values in place. In that case, if vec() was used to modify
532 the string, it is no longer considered to be utf8-encoded.
536 Zero entries were missing from the Unicode classes like C<IsDigit>.
542 UNIVERSAL::isa no longer caches methods incorrectly. (This broke
543 the Tk extension with 5.6.0.)
547 =head2 Platform Specific Changes and Fixes
555 Perl now works on post-4.0 BSD/OSes.
561 Setting C<$0> now works (as much as possible; see perlvar for details).
567 Numerous updates; currently synchronised with Cygwin 1.1.4.
573 EPOC update after Perl 5.6.0. See README.epoc.
579 Perl now works on post-3.0 FreeBSDs.
585 README.hpux updated; C<Configure -Duse64bitall> now almost works.
591 Numerous compilation flag and hint enhancements; accidental mixing
592 of 32-bit and 64-bit libraries (a doomed attempt) made much harder.
598 Long doubles should now work (see INSTALL).
604 Compilation of the standard Perl distribution in MacOS Classic should
605 now work if you have the Metrowerks development environment and
606 the missing Mac-specific toolkit bits. Contact the macperl mailing
613 MPE/iX update after Perl 5.6.0. See README.mpeix.
619 Perl now works on NetBSD/sparc.
625 Now works with usethreads (see INSTALL).
631 64-bitness using the Sun Workshop compiler now works.
635 Tru64 (aka Digital UNIX, aka DEC OSF/1)
637 The operating system version letter now recorded in $Config{osvers}.
638 Allow compiling with gcc (previously explicitly forbidden). Compiling
639 with gcc still not recommended because buggy code results, even with
646 Fixed various alignment problems that lead into core dumps either
647 during build or later; no longer dies on math errors at runtime;
648 now using full quad integers (64 bits), previously was using
649 only 46 bit integers for speed.
655 chdir() now works better despite a CRT bug; now works with MULTIPLICITY
656 (see INSTALL); now works with Perl's malloc.
666 accept() no longer leaks memory.
670 Better chdir() return value for a non-existent directory.
674 New %ENV entries now propagate to subprocesses.
678 $ENV{LIB} now used to search for libs under Visual C.
682 A failed (pseudo)fork now returns undef and sets errno to EAGAIN.
686 Allow REG_EXPAND_SZ keys in the registry.
690 Can now send() from all threads, not just the first one.
694 Fake signal handling reenabled, bugs and all.
698 Less stack reserved per thread so that more threads can run
699 concurrently. (Still 16M per thread.)
703 C<File::Spec->tmpdir()> now prefers C:/temp over /tmp
704 (works better when perl is running as service).
708 Better UNC path handling under ithreads.
712 wait() and waitpid() now work much better.
716 winsock handle leak fixed.
720 =head1 New or Changed Diagnostics
722 All regular expression compilation error messages are now hopefully
723 easier to understand both because the error message now comes before
724 the failed regex and because the point of failure is now clearly
727 The various "opened only for", "on closed", "never opened" warnings
728 drop the C<main::> prefix for filehandles in the C<main> package,
729 for example C<STDIN> instead of <main::STDIN>.
731 The "Unrecognized escape" warning has been extended to include C<\8>,
732 C<\9>, and C<\_>. There is no need to escape any of the C<\w> characters.
734 =head1 Changed Internals
740 perlapi.pod (a companion to perlguts) now attempts to document the
745 You can now build a really minimal perl called microperl.
746 Building microperl does not require even running Configure;
747 C<make -f Makefile.micro> should be enough. Beware: microperl makes
748 many assumptions, some of which may be too bold; the resulting
749 executable may crash or otherwise misbehave in wondrous ways.
750 For careful hackers only.
754 Added rsignal(), whichsig(), do_join() to the publicised API.
758 Made possible to propagate customised exceptions via croak()ing.
762 Added is_utf8_char(), is_utf8_string(), bytes_to_utf8(), and utf8_to_bytes().
766 Now xsubs can have attributes just like subs.
770 =head1 Known Problems
772 =head2 Unicode Support Still Far From Perfect
774 We're working on it. Stay tuned.
776 =head2 EBCDIC Still A Lost Platform
778 The plan is to bring them back.
780 =head2 Building Extensions Can Fail Because Of Largefiles
782 Certain extensions like mod_perl and BSD::Resource are known to have
783 issues with `largefiles', a change brought by Perl 5.6.0 in which file
784 offsets default to 64 bits wide, where supported. Modules may fail to
785 compile at all or compile and work incorrectly. Currently there is no
786 good solution for the problem, but Configure now provides appropriate
787 non-largefile ccflags, ldflags, libswanted, and libs in the %Config
788 hash (e.g., $Config{ccflags_nolargefiles}) so the extensions that are
789 having problems can try configuring themselves without the
790 largefileness. This is admittedly not a clean solution, and the
791 solution may not even work at all. One potential failure is whether
792 one can (or, if one can, whether it's a good idea) link together at
793 all binaries with different ideas about file offsets, all this is
796 =head2 ftmp-security tests warn 'system possibly insecure'
798 Don't panic. Read INSTALL 'make test' section instead.
800 =head2 Test lib/posix Subtest 9 Fails In LP64-Configured HP-UX
802 If perl is configured with -Duse64bitall, the successful result of the
803 subtest 10 of lib/posix may arrive before the successful result of the
804 subtest 9, which confuses the test harness so much that it thinks the
807 =head2 Long Doubles Still Don't Work In Solaris
809 The experimental long double support is still very much so in Solaris.
810 (Other platforms like Linux and Tru64 are beginning to solidify in
813 =head2 Linux With Sfio Fails op/misc Test 48
817 =head2 Storable tests fail in some platforms
819 If any Storable tests fail the use of Storable is not advisable.
825 Many Storable tests fail on AIX configured with 64 bit integers.
827 So far unidentified problems break Storable in AIX if Perl is
828 configured to use 64 bit integers. AIX in 32-bit mode works and
829 other 64-bit platforms work with Storable.
833 DOS DJGPP may hang when testing Storable.
837 st-06compat fails in UNICOS and UNICOS/mk.
839 This means that you cannot read old (pre-Storable-0.7) Storable images
840 made in other platforms.
844 st-store.t and st-retrieve may fail with Compaq C 6.2 on OpenVMS Alpha 7.2.
846 =head2 Threads Are Still Experimental
848 Multithreading is still an experimental feature. Some platforms
849 emit the following message for lib/thr5005
852 # This is a KNOWN FAILURE, and one of the reasons why threading
853 # is still an experimental feature. It is here to stop people
854 # from deploying threads in production. ;-)
857 and another known thread-related warning is
859 pragma/overload......Unbalanced saves: 3 more saves than restores
860 panic: magic_mutexfree during global destruction.
862 lib/selfloader.......Unbalanced saves: 3 more saves than restores
863 panic: magic_mutexfree during global destruction.
865 lib/st-dclone........Unbalanced saves: 3 more saves than restores
866 panic: magic_mutexfree during global destruction.
869 =head2 The Compiler Suite Is Still Experimental
871 The compiler suite is slowly getting better but is nowhere near
872 working order yet. The backend part that has seen perhaps the most
873 progress is the bytecode compiler.
877 =head1 Reporting Bugs
879 If you find what you think is a bug, you might check the articles
880 recently posted to the comp.lang.perl.misc newsgroup and the perl
881 bug database at http://bugs.perl.org. There may also be
882 information at http://www.perl.com/perl/, the Perl Home Page.
884 If you believe you have an unreported bug, please run the B<perlbug>
885 program included with your release. Be sure to trim your bug down
886 to a tiny but sufficient test case. Your bug report, along with the
887 output of C<perl -V>, will be sent off to perlbug@perl.org to be
888 analysed by the Perl porting team.
892 The F<Changes> file for exhaustive details on what changed.
894 The F<INSTALL> file for how to build Perl.
896 The F<README> file for general stuff.
898 The F<Artistic> and F<Copying> files for copyright information.
902 Written by Jarkko Hietaniemi <F<jhi@iki.fi>>, with many contributions
903 from The Perl Porters and Perl Users submitting feedback and patches.
905 Send omissions or corrections to <F<perlbug@perl.org>>.