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 The very dusty examples in the eg/ directory have been removed.
54 Suggestions for new shiny examples welcome but the main issue is that
55 the examples need to be documented, tested and (most importantly)
60 The obsolete chat2 library that should never have been allowed
61 to escape the laboratory has been decommissioned.
65 The unimplemented POSIX regex features [[.cc.]] and [[=c=]] are still
66 recognised but now cause fatal errors. The previous behaviour of
67 ignoring them by default and warning if requested was unacceptable
68 since it, in a way, falsely promised that the features could be used.
72 lstat(FILEHANDLE) now gives a warning because the operation makes no sense.
73 In future releases this may become a fatal error.
77 The long deprecated uppercase aliases for the string comparison
78 operators (EQ, NE, LT, LE, GE, GT) have now been removed.
82 The regular expression captured submatches ($1, $2, ...) are now
83 more consistently unset if the match fails, instead of leaving false
84 data lying around in them.
88 The tr///C and tr///U features have been removed and will not return;
89 the interface was a mistake. Sorry about that. For similar
90 functionality, see pack('U0', ...) and pack('C0', ...).
94 =head1 Core Enhancements
100 C<perl -d:Module=arg,arg,arg> now works (previously one couldn't pass
101 in multiple arguments.)
105 my __PACKAGE__ now works.
109 C<no Module;> now works even if there is no "sub unimport" in the Module.
113 The numerical comparison operators return C<undef> if either operand
114 is a NaN. Previously the behaviour was unspecified.
118 C<pack('U0a*', ...)> can now be used to force a string to UTF8.
122 prototype(\&) is now available.
126 There is now an UNTIE method.
130 =head1 Modules and Pragmata
138 File::Temp allows one to create temporary files and directories in an
139 easy, portable, and secure way.
143 Storable gives persistence to Perl data structures by allowing the
144 storage and retrieval of Perl data to and from files in a fast and
145 compact binary format.
149 =head2 Updated And Improved Modules and Pragmata
155 The following independently supported modules have been updated to
156 newer versions from CPAN: CGI, CPAN, DB_File, File::Spec, Getopt::Long,
157 the podlators bundle, Pod::LaTeX, Pod::Parser, Term::ANSIColor, Test.
161 Bug fixes and minor enhancements have been applied to B::Deparse,
162 Data::Dumper, IO::Poll, IO::Socket::INET, Math::BigFloat,
163 Math::Complex, Math::Trig, Net::protoent, the re pragma, SelfLoader,
164 Sys::SysLog, Test::Harness, Text::Wrap, UNIVERSAL, and the warnings
169 The attributes::reftype() now works on tied arguments.
173 AutoLoader can now be disabled with C<no AutoLoader;>,
177 The English module can now be used without the infamous performance
180 use English '-no_performance_hit';
182 (Assuming, of course, that one doesn't need the troublesome variables
183 C<$`>, C<$&>, or C<$'>.) Also, introduced C<@LAST_MATCH_START> and
184 C<@LAST_MATCH_END> English aliases for C<@-> and C<@+>.
188 File::Find now has pre- and post-processing callbacks. It also
189 correctly changes directories when chasing symbolic links. Callbacks
190 (naughtily) exiting with "next;" instead of "return;" now work.
194 File::Glob::glob() renamed to File::Glob::bsd_glob() to avoid
195 prototype mismatch with CORE::glob().
199 IPC::Open3 now allows the use of numeric file descriptors.
203 use lib now works identically to @INC. Removing directories
204 with 'no lib' now works.
208 C<%INC> now localised in a Safe compartment so that use/require work.
212 The Shell module now has an OO interface.
218 =head1 Utility Changes
224 The Emacs perl mode (emacs/cperl-mode.el) has been updated to version
229 Perlbug is now much more robust. It also sends the bug report to
230 perl.org, not perl.com.
234 The perlcc utility has been rewritten and its user interface (that is,
235 command line) is much more like that of the UNIX C compiler, cc.
239 The xsubpp utility for extension writers now understands POD
240 documentation embedded in the *.xs files.
244 =head1 New Documentation
250 perl56delta details the changes between the 5.005 release and the
255 perldebtut is a Perl debugging tutorial.
259 perlebcdic contains considerations for running Perl on EBCDIC platforms.
260 Note that unfortunately EBCDIC platforms that used to supported back in
261 Perl 5.005 are still unsupported by Perl 5.7.0; the plan, however, is to
262 bring them back to the fold.
266 perlnewmod tells about writing and submitting a new module.
270 perlposix-bc explains using Perl on the POSIX-BC platform
271 (an EBCDIC mainframe platform).
275 perlretut is a regular expression tutorial.
279 perlrequick is a regular expressions quick-start guide.
280 Yes, much quicker than perlretut.
284 perlutil explains the command line utilities packaged with the Perl
289 =head1 Performance Enhancements
295 map() that changes the size of the list should now work faster.
299 sort() has been changed to use mergesort internally as opposed to the
300 earlier quicksort. For very small lists this may result in slightly
301 slower sorting times, but in general the speedup should be at least
302 20%. Additional bonuses are that the worst case behaviour of sort()
303 is now better (in computer science terms it now runs in time O(N log N),
304 as opposed to quicksort's Theta(N**2) worst-case run time behaviour),
305 and that sort() is now stable (meaning that elements with identical
306 keys will stay ordered as they were before the sort).
310 =head1 Installation and Configuration Improvements
312 =head2 Generic Improvements
318 INSTALL now explains how you can configure perl to use 64-bit
319 integers even on non-64-bit platforms.
323 Policy.sh policy change: if you are reusing a Policy.sh file
324 (see INSTALL) and you use Configure -Dprefix=/foo/bar and in the old
325 Policy $prefix eq $siteprefix and $prefix eq $vendorprefix, all of
326 them will now be changed to the new prefix, /foo/bar. (Previously
327 only $prefix changed.) If you do not like this new behaviour,
328 specify prefix, siteprefix, and vendorprefix explicitly.
332 A new optional location for Perl libraries, otherlibdirs, is available.
333 It can be used for example for vendor add-ons without disturbing Perl's
334 own library directories.
338 In many platforms the vendor-supplied 'cc' is too stripped-down to
339 build Perl (basically, 'cc' doesn't do ANSI C). If this seems
340 to be the case and 'cc' does not seem to be the GNU C compiler
341 'gcc', an automatic attempt is made to find and use 'gcc' instead.
345 gcc needs to closely track the operating system release to avoid
346 build problems. If Configure finds that gcc was built for a different
347 operating system release than is running, it now gives a clearly visible
348 warning that there may be trouble ahead.
352 If binary compatibility with the 5.005 release is not wanted, Configure
353 no longer suggests including the 5.005 modules in @INC.
357 Configure C<-S> can now run non-interactively.
361 configure.gnu now works with options with whitespace in them.
365 installperl now outputs everything to STDERR.
369 $Config{byteorder} is now computed dynamically (this is more robust
370 with "fat binaries" where an executable image contains binaries for
371 more than one binary platform.)
375 =head1 Selected Bug Fixes
381 Several debugger fixes: exit code now reflects the script exit code,
382 condition C<"0"> now treated correctly, the C<d> command now checks
383 line number, the C<$.> no longer gets corrupted, all debugger output now
384 goes correctly to the socket if RemotePort is set.
388 C<*foo{FORMAT}> now works.
392 Lexical warnings now propagating correctly between scopes.
396 Line renumbering with eval and C<#line> now works.
400 Fixed numerous memory leaks, especially in eval "".
404 Modulus of unsigned numbers now works (4063328477 % 65535 used to
405 return 27406, instead of 27047).
409 Some "not a number" warnings introduced in 5.6.0 eliminated to be
410 more compatible with 5.005. Infinity is now recognised as a number.
414 our() variables will not cause "will not stay shared" warnings.
418 pack "Z" now correctly terminates the string with "\0".
422 Fix password routines which in some shadow password platforms
423 (e.g. HP-UX) caused getpwent() to return every other entry.
427 printf() no longer resets the numeric locale to "C".
431 C<q(a\\b)> now parses correctly as C<'a\\b'>.
435 Printing quads (64-bit integers) with printf/sprintf now works
436 without the q L ll prefixes (assuming you are on a quad-capable platform).
440 Regular expressions on references and overloaded scalars now work.
444 scalar() now forces scalar context even when used in void context.
448 sort() arguments are now compiled in the right wantarray context
449 (they were accidentally using the context of the sort() itself).
453 Changed the POSIX character class C<[[:space:]]> to include the (very
454 rare) vertical tab character. Added a new POSIX-ish character class
455 C<[[:blank:]]> which stands for horizontal whitespace (currently,
456 the space and the tab).
460 $AUTOLOAD, sort(), lock(), and spawning subprocesses
461 in multiple threads simultaneously are now thread-safe.
465 Allow read-only string on left hand side of non-modifying tr///.
469 Several Unicode fixes (but still not perfect).
475 BOMs (byte order marks) in the beginning of Perl files
476 (scripts, modules) should now be transparently skipped.
477 UTF16 encoded Perl files should now be read correctly.
481 The character tables have been updated to Unicode 3.0.1.
485 chr() for values greater than 127 now create utf8 when under use
490 Comparing with utf8 data does not magically upgrade non-utf8 data into
495 C<IsAlnum>, C<IsAlpha>, and C<IsWord> now match titlecase.
499 Concatenation with the C<.> operator or via variable interpolation,
500 C<eq>, C<substr>, C<reverse>, C<quotemeta>, the C<x> operator,
501 substitution with C<s///>, single-quoted UTF8, should now work--in
506 The C<tr///> operator now works I<slightly> better but is still rather
507 broken. Note that the C<tr///CU> functionality has been removed (but
508 see pack('U0', ...)).
512 vec() now refuses to deal with characters >255.
516 Zero entries were missing from the Unicode classes like C<IsDigit>.
522 UNIVERSAL::isa no longer caches methods incorrectly. (This broke
523 the Tk extension with 5.6.0.)
527 =head2 Platform Specific Changes and Fixes
535 Perl now works on post-4.0 BSD/OSes.
541 Setting C<$0> now works (as much as possible; see perlvar for details).
547 Numerous updates; currently synchronised with Cygwin 1.1.4.
553 EPOC update after Perl 5.6.0. See README.epoc.
559 Perl now works on post-3.0 FreeBSDs.
565 README.hpux updated; C<Configure -Duse64bitall> now almost works.
571 Numerous compilation flag and hint enhancements; accidental mixing
572 of 32-bit and 64-bit libraries (a doomed attempt) made much harder.
578 Long doubles should now work (see INSTALL).
584 Compilation of the standard Perl distribution in MacOS Classic should
585 now work if you have the Metrowerks development environment and
586 the missing Mac-specific toolkit bits. Contact the macperl mailing
593 MPE/iX update after Perl 5.6.0. See README.mpeix.
599 Perl now works on NetBSD/sparc.
605 Now works with usethreads (see INSTALL).
611 64-bitness using the Sun Workshop compiler now works.
615 Tru64 (aka Digital UNIX, aka DEC OSF/1)
617 The operating system version letter now recorded in $Config{osvers}.
618 Allow compiling with gcc (previously explicitly forbidden). Compiling
619 with gcc still not recommended because buggy code results, even with
626 Fixed various alignment problems that lead into core dumps either
627 during build or later; no longer dies on math errors at runtime;
628 now using full quad integers (64 bits), previously was using
629 only 46 bit integers for speed.
635 chdir() now works better despite a CRT bug; now works with MULTIPLICITY
636 (see INSTALL); now works with Perl's malloc.
646 accept() no longer leaks memory.
650 Better chdir() return value for a non-existent directory.
654 New %ENV entries now propagate to subprocesses.
658 $ENV{LIB} now used to search for libs under Visual C.
662 A failed (pseudo)fork now returns undef and sets errno to EAGAIN.
666 Allow REG_EXPAND_SZ keys in the registry.
670 Can now send() from all threads, not just the first one.
674 Fake signal handling reenabled, bugs and all.
678 Less stack reserved per thread so that more threads can run
679 concurrently. (still 16M perl thread)
683 C<File::Spec->tmpdir()> now prefers C:/temp over /tmp
684 (works better when perl running as service).
688 Better UNC path handling under ithreads.
692 wait() and waitpid() now work much better.
696 winsock handle leak fixed.
700 =head1 New or Changed Diagnostics
702 All regular expression compilation error messages are now hopefully
703 easier to understand both because the error message now comes before
704 the failed regex and because the point of failure is now clearly
707 The various "opened only for", "on closed", "never opened" warnings
708 drop the C<main::> prefix for filehandles in the C<main> package,
709 for example C<STDIN> instead of <main::STDIN>.
711 The "Unrecognized escape" warning has been extended to include C<\8>,
712 C<\9>, and C<\_>. There is no need to escape any of the C<\w> characters.
714 =head1 Changed Internals
720 perlapi.pod (a companion to perlguts) now attempts to document the
725 You can now build a really minimal perl called microperl.
726 Building microperl does not require even running Configure;
727 C<make -f Makefile.micro> should be enough. Beware: microperl makes
728 many assumptions, some of which may be too bold; the resulting
729 executable may crash or otherwise misbehave in wondrous ways. For
730 careful hackers only.
734 Added rsignal(), whichsig(), do_join() to the publicised API.
738 Made possible to propagate customised exceptions via croak()ing.
742 Added is_utf8_char(), is_utf8_string(), bytes_to_utf8(), and utf8_to_bytes().
746 Now xsubs can have attributes just like subs.
750 =head1 Known Problems
752 =head2 Unicode Support Still Far From Perfect
754 We're working on it. Stay tuned.
756 =head2 EBCDIC Still A Lost Platform
758 The plan is to bring them back.
760 =head2 Building Extensions Can Fail Because Of Largefiles
762 Certain extensions like mod_perl and BSD::Resource are known to have
763 issues with `largefiles', a change brought by Perl 5.6.0 in which file
764 offsets default to 64 bits wide, where supported. Modules may fail to
765 compile at all or compile and work incorrectly. Currently there is no
766 good solution for the problem, but Configure now provides appropriate
767 non-largefile ccflags, ldflags, libswanted, and libs in the %Config
768 hash (e.g., $Config{ccflags_nolargefiles}) so the extensions that are
769 having problems can try configuring themselves without the
770 largefileness. This is admittedly not a clean solution, and the
771 solution may not even work at all. One potential failure is whether
772 one can (or, if one can, whether it's a good idea) link together at
773 all binaries with different ideas about file offsets, all this is
776 =head2 ftmp-security tests warn 'system possibly insecure'
778 Don't panic. Read INSTALL 'make test' section instead.
780 =head2 Test lib/posix Subtest 9 Fails In LP64-Configured HP-UX
782 If perl is configured with -Duse64bitall, the successful result of the
783 subtest 10 of lib/posix may arrive before the successful result of the
784 subtest 9, which confuses the test harness so much that it thinks the
787 =head2 Long Doubles Still Don't Work In Solaris
789 The experimental long double support is still very much so in Solaris.
790 (Other platforms like Linux and Tru64 are beginning to solidify in
793 =head2 Linux With Sfio Fails op/misc Test 48
797 =head2 Storable tests fail in some platforms
799 If any Storable tests fail the use of Storable is not advisable.
805 Many Storable tests fail on AIX configured with 64 bit integers.
807 So far unidentified problems break Storable in AIX if Perl is
808 configured to use 64 bit integers. AIX in 32-bit mode works and
809 other 64-bit platforms work with Storable.
813 DOS DJGPP may hang when testing Storable.
817 st-06compat fails in UNICOS and UNICOS/mk.
819 This means that you cannot read old (pre-Storable-0.7) Storable images
820 made in other platforms.
824 st-store.t and st-retrieve may fail with Compaq C 6.2 on OpenVMS Alpha 7.2.
826 =head2 Threads Are Still Experimental
828 Multithreading is still an experimental feature. Some platforms
829 emit the following message for lib/thr5005
832 # This is a KNOWN FAILURE, and one of the reasons why threading
833 # is still an experimental feature. It is here to stop people
834 # from deploying threads in production. ;-)
837 and another known warning is
839 pragma/overload......Unbalanced saves: 3 more saves than restores
840 panic: magic_mutexfree during global destruction.
842 lib/selfloader.......Unbalanced saves: 3 more saves than restores
843 panic: magic_mutexfree during global destruction.
845 lib/st-dclone........Unbalanced saves: 3 more saves than restores
846 panic: magic_mutexfree during global destruction.
849 =head2 The Compiler Suite Is Still Experimental
851 The compiler suite is slowly getting better but is nowhere near yet.
852 The backend part that has seen perhaps the most progress is the
857 =head1 Reporting Bugs
859 If you find what you think is a bug, you might check the articles
860 recently posted to the comp.lang.perl.misc newsgroup and the perl
861 bug database at http://bugs.perl.org. There may also be
862 information at http://www.perl.com/perl/, the Perl Home Page.
864 If you believe you have an unreported bug, please run the B<perlbug>
865 program included with your release. Be sure to trim your bug down
866 to a tiny but sufficient test case. Your bug report, along with the
867 output of C<perl -V>, will be sent off to perlbug@perl.org to be
868 analysed by the Perl porting team.
872 The F<Changes> file for exhaustive details on what changed.
874 The F<INSTALL> file for how to build Perl.
876 The F<README> file for general stuff.
878 The F<Artistic> and F<Copying> files for copyright information.
882 Written by Jarkko Hietaniemi <F<jhi@iki.fi>>, with many contributions
883 from The Perl Porters and Perl Users submitting feedback and patches.
885 Send omissions or corrections to <F<perlbug@perl.org>>.