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 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 The printf and sprintf now support parameter reordering using the
135 C<%\d+\$> and C<*\d+\$> syntaxes.
139 prototype(\&) is now available.
143 There is now an UNTIE method.
147 =head1 Modules and Pragmata
155 File::Temp allows one to create temporary files and directories in an
156 easy, portable, and secure way.
160 Storable gives persistence to Perl data structures by allowing the
161 storage and retrieval of Perl data to and from files in a fast and
162 compact binary format.
166 =head2 Updated And Improved Modules and Pragmata
172 The following independently supported modules have been updated to
173 newer versions from CPAN: CGI, CPAN, DB_File, File::Spec, Getopt::Long,
174 the podlators bundle, Pod::LaTeX, Pod::Parser, Term::ANSIColor, Test.
178 Bug fixes and minor enhancements have been applied to B::Deparse,
179 Data::Dumper, IO::Poll, IO::Socket::INET, Math::BigFloat,
180 Math::Complex, Math::Trig, Net::protoent, the re pragma, SelfLoader,
181 Sys::SysLog, Test::Harness, Text::Wrap, UNIVERSAL, and the warnings
186 The attributes::reftype() now works on tied arguments.
190 AutoLoader can now be disabled with C<no AutoLoader;>,
194 The English module can now be used without the infamous performance
197 use English '-no_performance_hit';
199 (Assuming, of course, that one doesn't need the troublesome variables
200 C<$`>, C<$&>, or C<$'>.) Also, introduced C<@LAST_MATCH_START> and
201 C<@LAST_MATCH_END> English aliases for C<@-> and C<@+>.
205 File::Find now has pre- and post-processing callbacks. It also
206 correctly changes directories when chasing symbolic links. Callbacks
207 (naughtily) exiting with "next;" instead of "return;" now work.
211 File::Glob::glob() renamed to File::Glob::bsd_glob() to avoid
212 prototype mismatch with CORE::glob().
216 IPC::Open3 now allows the use of numeric file descriptors.
220 use lib now works identically to @INC. Removing directories
221 with 'no lib' now works.
225 C<%INC> now localised in a Safe compartment so that use/require work.
229 The Shell module now has an OO interface.
235 =head1 Utility Changes
241 The Emacs perl mode (emacs/cperl-mode.el) has been updated to version
246 Perlbug is now much more robust. It also sends the bug report to
247 perl.org, not perl.com.
251 The perlcc utility has been rewritten and its user interface (that is,
252 command line) is much more like that of the UNIX C compiler, cc.
256 The xsubpp utility for extension writers now understands POD
257 documentation embedded in the *.xs files.
261 =head1 New Documentation
267 perl56delta details the changes between the 5.005 release and the
272 perldebtut is a Perl debugging tutorial.
276 perlebcdic contains considerations for running Perl on EBCDIC platforms.
277 Note that unfortunately EBCDIC platforms that used to supported back in
278 Perl 5.005 are still unsupported by Perl 5.7.0; the plan, however, is to
279 bring them back to the fold.
283 perlnewmod tells about writing and submitting a new module.
287 perlposix-bc explains using Perl on the POSIX-BC platform
288 (an EBCDIC mainframe platform).
292 perlretut is a regular expression tutorial.
296 perlrequick is a regular expressions quick-start guide.
297 Yes, much quicker than perlretut.
301 perlutil explains the command line utilities packaged with the Perl
306 =head1 Performance Enhancements
312 map() that changes the size of the list should now work faster.
316 sort() has been changed to use mergesort internally as opposed to the
317 earlier quicksort. For very small lists this may result in slightly
318 slower sorting times, but in general the speedup should be at least
319 20%. Additional bonuses are that the worst case behaviour of sort()
320 is now better (in computer science terms it now runs in time O(N log N),
321 as opposed to quicksort's Theta(N**2) worst-case run time behaviour),
322 and that sort() is now stable (meaning that elements with identical
323 keys will stay ordered as they were before the sort).
327 =head1 Installation and Configuration Improvements
329 =head2 Generic Improvements
335 INSTALL now explains how you can configure Perl to use 64-bit
336 integers even on non-64-bit platforms.
340 Policy.sh policy change: if you are reusing a Policy.sh file
341 (see INSTALL) and you use Configure -Dprefix=/foo/bar and in the old
342 Policy $prefix eq $siteprefix and $prefix eq $vendorprefix, all of
343 them will now be changed to the new prefix, /foo/bar. (Previously
344 only $prefix changed.) If you do not like this new behaviour,
345 specify prefix, siteprefix, and vendorprefix explicitly.
349 A new optional location for Perl libraries, otherlibdirs, is available.
350 It can be used for example for vendor add-ons without disturbing Perl's
351 own library directories.
355 In many platforms the vendor-supplied 'cc' is too stripped-down to
356 build Perl (basically, 'cc' doesn't do ANSI C). If this seems
357 to be the case and 'cc' does not seem to be the GNU C compiler
358 'gcc', an automatic attempt is made to find and use 'gcc' instead.
362 gcc needs to closely track the operating system release to avoid
363 build problems. If Configure finds that gcc was built for a different
364 operating system release than is running, it now gives a clearly visible
365 warning that there may be trouble ahead.
369 If binary compatibility with the 5.005 release is not wanted, Configure
370 no longer suggests including the 5.005 modules in @INC.
374 Configure C<-S> can now run non-interactively.
378 configure.gnu now works with options with whitespace in them.
382 installperl now outputs everything to STDERR.
386 $Config{byteorder} is now computed dynamically (this is more robust
387 with "fat binaries" where an executable image contains binaries for
388 more than one binary platform.)
392 Configure no longer included the DBM libraries (dbm, gdbm, db, ndbm)
393 when building the Perl binary. The only exception to this is SunOS 4.x,
398 =head1 Selected Bug Fixes
404 Several debugger fixes: exit code now reflects the script exit code,
405 condition C<"0"> now treated correctly, the C<d> command now checks
406 line number, the C<$.> no longer gets corrupted, all debugger output now
407 goes correctly to the socket if RemotePort is set.
411 C<*foo{FORMAT}> now works.
415 Lexical warnings now propagating correctly between scopes.
419 Line renumbering with eval and C<#line> now works.
423 Fixed numerous memory leaks, especially in eval "".
427 Modulus of unsigned numbers now works (4063328477 % 65535 used to
428 return 27406, instead of 27047).
432 Some "not a number" warnings introduced in 5.6.0 eliminated to be
433 more compatible with 5.005. Infinity is now recognised as a number.
437 our() variables will not cause "will not stay shared" warnings.
441 pack "Z" now correctly terminates the string with "\0".
445 Fix password routines which in some shadow password platforms
446 (e.g. HP-UX) caused getpwent() to return every other entry.
450 printf() no longer resets the numeric locale to "C".
454 C<q(a\\b)> now parses correctly as C<'a\\b'>.
458 Printing quads (64-bit integers) with printf/sprintf now works
459 without the q L ll prefixes (assuming you are on a quad-capable platform).
463 Regular expressions on references and overloaded scalars now work.
467 scalar() now forces scalar context even when used in void context.
471 sort() arguments are now compiled in the right wantarray context
472 (they were accidentally using the context of the sort() itself).
476 Changed the POSIX character class C<[[:space:]]> to include the (very
477 rare) vertical tab character. Added a new POSIX-ish character class
478 C<[[:blank:]]> which stands for horizontal whitespace (currently,
479 the space and the tab).
483 $AUTOLOAD, sort(), lock(), and spawning subprocesses
484 in multiple threads simultaneously are now thread-safe.
488 Allow read-only string on left hand side of non-modifying tr///.
492 Several Unicode fixes (but still not perfect).
498 BOMs (byte order marks) in the beginning of Perl files
499 (scripts, modules) should now be transparently skipped.
500 UTF-16 (UCS-2)encoded Perl files should now be read correctly.
504 The character tables have been updated to Unicode 3.0.1.
508 chr() for values greater than 127 now create utf8 when under use
513 Comparing with utf8 data does not magically upgrade non-utf8 data into
518 C<IsAlnum>, C<IsAlpha>, and C<IsWord> now match titlecase.
522 Concatenation with the C<.> operator or via variable interpolation,
523 C<eq>, C<substr>, C<reverse>, C<quotemeta>, the C<x> operator,
524 substitution with C<s///>, single-quoted UTF8, should now work--in
529 The C<tr///> operator now works I<slightly> better but is still rather
530 broken. Note that the C<tr///CU> functionality has been removed (but
531 see pack('U0', ...)).
535 vec() now tries to work with characters <= 255 when possible, but it leaves
536 higher character values in place. In that case, if vec() was used to modify
537 the string, it is no longer considered to be utf8-encoded.
541 Zero entries were missing from the Unicode classes like C<IsDigit>.
547 UNIVERSAL::isa no longer caches methods incorrectly. (This broke
548 the Tk extension with 5.6.0.)
552 =head2 Platform Specific Changes and Fixes
560 Perl now works on post-4.0 BSD/OSes.
566 Setting C<$0> now works (as much as possible; see perlvar for details).
572 Numerous updates; currently synchronised with Cygwin 1.1.4.
578 EPOC update after Perl 5.6.0. See README.epoc.
584 Perl now works on post-3.0 FreeBSDs.
590 README.hpux updated; C<Configure -Duse64bitall> now almost works.
596 Numerous compilation flag and hint enhancements; accidental mixing
597 of 32-bit and 64-bit libraries (a doomed attempt) made much harder.
603 Long doubles should now work (see INSTALL).
609 Compilation of the standard Perl distribution in MacOS Classic should
610 now work if you have the Metrowerks development environment and
611 the missing Mac-specific toolkit bits. Contact the macperl mailing
618 MPE/iX update after Perl 5.6.0. See README.mpeix.
624 Perl now works on NetBSD/sparc.
630 Now works with usethreads (see INSTALL).
636 64-bitness using the Sun Workshop compiler now works.
640 Tru64 (aka Digital UNIX, aka DEC OSF/1)
642 The operating system version letter now recorded in $Config{osvers}.
643 Allow compiling with gcc (previously explicitly forbidden). Compiling
644 with gcc still not recommended because buggy code results, even with
651 Fixed various alignment problems that lead into core dumps either
652 during build or later; no longer dies on math errors at runtime;
653 now using full quad integers (64 bits), previously was using
654 only 46 bit integers for speed.
660 chdir() now works better despite a CRT bug; now works with MULTIPLICITY
661 (see INSTALL); now works with Perl's malloc.
671 accept() no longer leaks memory.
675 Better chdir() return value for a non-existent directory.
679 New %ENV entries now propagate to subprocesses.
683 $ENV{LIB} now used to search for libs under Visual C.
687 A failed (pseudo)fork now returns undef and sets errno to EAGAIN.
691 Allow REG_EXPAND_SZ keys in the registry.
695 Can now send() from all threads, not just the first one.
699 Fake signal handling reenabled, bugs and all.
703 Less stack reserved per thread so that more threads can run
704 concurrently. (Still 16M per thread.)
708 C<File::Spec->tmpdir()> now prefers C:/temp over /tmp
709 (works better when perl is running as service).
713 Better UNC path handling under ithreads.
717 wait() and waitpid() now work much better.
721 winsock handle leak fixed.
725 =head1 New or Changed Diagnostics
727 All regular expression compilation error messages are now hopefully
728 easier to understand both because the error message now comes before
729 the failed regex and because the point of failure is now clearly
732 The various "opened only for", "on closed", "never opened" warnings
733 drop the C<main::> prefix for filehandles in the C<main> package,
734 for example C<STDIN> instead of <main::STDIN>.
736 The "Unrecognized escape" warning has been extended to include C<\8>,
737 C<\9>, and C<\_>. There is no need to escape any of the C<\w> characters.
739 =head1 Changed Internals
745 perlapi.pod (a companion to perlguts) now attempts to document the
750 You can now build a really minimal perl called microperl.
751 Building microperl does not require even running Configure;
752 C<make -f Makefile.micro> should be enough. Beware: microperl makes
753 many assumptions, some of which may be too bold; the resulting
754 executable may crash or otherwise misbehave in wondrous ways.
755 For careful hackers only.
759 Added rsignal(), whichsig(), do_join() to the publicised API.
763 Made possible to propagate customised exceptions via croak()ing.
767 Added is_utf8_char(), is_utf8_string(), bytes_to_utf8(), and utf8_to_bytes().
771 Now xsubs can have attributes just like subs.
775 =head1 Known Problems
777 =head2 Unicode Support Still Far From Perfect
779 We're working on it. Stay tuned.
781 =head2 EBCDIC Still A Lost Platform
783 The plan is to bring them back.
785 =head2 Building Extensions Can Fail Because Of Largefiles
787 Certain extensions like mod_perl and BSD::Resource are known to have
788 issues with `largefiles', a change brought by Perl 5.6.0 in which file
789 offsets default to 64 bits wide, where supported. Modules may fail to
790 compile at all or compile and work incorrectly. Currently there is no
791 good solution for the problem, but Configure now provides appropriate
792 non-largefile ccflags, ldflags, libswanted, and libs in the %Config
793 hash (e.g., $Config{ccflags_nolargefiles}) so the extensions that are
794 having problems can try configuring themselves without the
795 largefileness. This is admittedly not a clean solution, and the
796 solution may not even work at all. One potential failure is whether
797 one can (or, if one can, whether it's a good idea) link together at
798 all binaries with different ideas about file offsets, all this is
801 =head2 ftmp-security tests warn 'system possibly insecure'
803 Don't panic. Read INSTALL 'make test' section instead.
805 =head2 Test lib/posix Subtest 9 Fails In LP64-Configured HP-UX
807 If perl is configured with -Duse64bitall, the successful result of the
808 subtest 10 of lib/posix may arrive before the successful result of the
809 subtest 9, which confuses the test harness so much that it thinks the
812 =head2 Long Doubles Still Don't Work In Solaris
814 The experimental long double support is still very much so in Solaris.
815 (Other platforms like Linux and Tru64 are beginning to solidify in
818 =head2 Linux With Sfio Fails op/misc Test 48
822 =head2 Storable tests fail in some platforms
824 If any Storable tests fail the use of Storable is not advisable.
830 Many Storable tests fail on AIX configured with 64 bit integers.
832 So far unidentified problems break Storable in AIX if Perl is
833 configured to use 64 bit integers. AIX in 32-bit mode works and
834 other 64-bit platforms work with Storable.
838 DOS DJGPP may hang when testing Storable.
842 st-06compat fails in UNICOS and UNICOS/mk.
844 This means that you cannot read old (pre-Storable-0.7) Storable images
845 made in other platforms.
849 st-store.t and st-retrieve may fail with Compaq C 6.2 on OpenVMS Alpha 7.2.
851 =head2 Threads Are Still Experimental
853 Multithreading is still an experimental feature. Some platforms
854 emit the following message for lib/thr5005
857 # This is a KNOWN FAILURE, and one of the reasons why threading
858 # is still an experimental feature. It is here to stop people
859 # from deploying threads in production. ;-)
862 and another known thread-related warning is
864 pragma/overload......Unbalanced saves: 3 more saves than restores
865 panic: magic_mutexfree during global destruction.
867 lib/selfloader.......Unbalanced saves: 3 more saves than restores
868 panic: magic_mutexfree during global destruction.
870 lib/st-dclone........Unbalanced saves: 3 more saves than restores
871 panic: magic_mutexfree during global destruction.
874 =head2 The Compiler Suite Is Still Experimental
876 The compiler suite is slowly getting better but is nowhere near
877 working order yet. The backend part that has seen perhaps the most
878 progress is the bytecode compiler.
882 =head1 Reporting Bugs
884 If you find what you think is a bug, you might check the articles
885 recently posted to the comp.lang.perl.misc newsgroup and the perl
886 bug database at http://bugs.perl.org. There may also be
887 information at http://www.perl.com/perl/, the Perl Home Page.
889 If you believe you have an unreported bug, please run the B<perlbug>
890 program included with your release. Be sure to trim your bug down
891 to a tiny but sufficient test case. Your bug report, along with the
892 output of C<perl -V>, will be sent off to perlbug@perl.org to be
893 analysed by the Perl porting team.
897 The F<Changes> file for exhaustive details on what changed.
899 The F<INSTALL> file for how to build Perl.
901 The F<README> file for general stuff.
903 The F<Artistic> and F<Copying> files for copyright information.
907 Written by Jarkko Hietaniemi <F<jhi@iki.fi>>, with many contributions
908 from The Perl Porters and Perl Users submitting feedback and patches.
910 Send omissions or corrections to <F<perlbug@perl.org>>.