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 lstat(FILEHANDLE) now gives a warning because the operation makes no sense.
79 In future releases this may become a fatal error.
83 The long deprecated uppercase aliases for the string comparison
84 operators (EQ, NE, LT, LE, GE, GT) have now been removed.
88 The regular expression captured submatches ($1, $2, ...) are now
89 more consistently unset if the match fails, instead of leaving false
90 data lying around in them.
94 The tr///C and tr///U features have been removed and will not return;
95 the interface was a mistake. Sorry about that. For similar
96 functionality, see pack('U0', ...) and pack('C0', ...).
100 =head1 Core Enhancements
106 C<perl -d:Module=arg,arg,arg> now works (previously one couldn't pass
107 in multiple arguments.)
111 my __PACKAGE__ now works.
115 C<no Module;> now works even if there is no "sub unimport" in the Module.
119 The numerical comparison operators return C<undef> if either operand
120 is a NaN. Previously the behaviour was unspecified.
124 C<pack('U0a*', ...)> can now be used to force a string to UTF8.
128 prototype(\&) is now available.
132 There is now an UNTIE method.
136 =head1 Modules and Pragmata
144 File::Temp allows one to create temporary files and directories in an
145 easy, portable, and secure way.
149 Storable gives persistence to Perl data structures by allowing the
150 storage and retrieval of Perl data to and from files in a fast and
151 compact binary format.
155 =head2 Updated And Improved Modules and Pragmata
161 The following independently supported modules have been updated to
162 newer versions from CPAN: CGI, CPAN, DB_File, File::Spec, Getopt::Long,
163 the podlators bundle, Pod::LaTeX, Pod::Parser, Term::ANSIColor, Test.
167 Bug fixes and minor enhancements have been applied to B::Deparse,
168 Data::Dumper, IO::Poll, IO::Socket::INET, Math::BigFloat,
169 Math::Complex, Math::Trig, Net::protoent, the re pragma, SelfLoader,
170 Sys::SysLog, Test::Harness, Text::Wrap, UNIVERSAL, and the warnings
175 The attributes::reftype() now works on tied arguments.
179 AutoLoader can now be disabled with C<no AutoLoader;>,
183 The English module can now be used without the infamous performance
186 use English '-no_performance_hit';
188 (Assuming, of course, that one doesn't need the troublesome variables
189 C<$`>, C<$&>, or C<$'>.) Also, introduced C<@LAST_MATCH_START> and
190 C<@LAST_MATCH_END> English aliases for C<@-> and C<@+>.
194 File::Find now has pre- and post-processing callbacks. It also
195 correctly changes directories when chasing symbolic links. Callbacks
196 (naughtily) exiting with "next;" instead of "return;" now work.
200 File::Glob::glob() renamed to File::Glob::bsd_glob() to avoid
201 prototype mismatch with CORE::glob().
205 IPC::Open3 now allows the use of numeric file descriptors.
209 use lib now works identically to @INC. Removing directories
210 with 'no lib' now works.
214 C<%INC> now localised in a Safe compartment so that use/require work.
218 The Shell module now has an OO interface.
224 =head1 Utility Changes
230 The Emacs perl mode (emacs/cperl-mode.el) has been updated to version
235 Perlbug is now much more robust. It also sends the bug report to
236 perl.org, not perl.com.
240 The perlcc utility has been rewritten and its user interface (that is,
241 command line) is much more like that of the UNIX C compiler, cc.
245 The xsubpp utility for extension writers now understands POD
246 documentation embedded in the *.xs files.
250 =head1 New Documentation
256 perl56delta details the changes between the 5.005 release and the
261 perldebtut is a Perl debugging tutorial.
265 perlebcdic contains considerations for running Perl on EBCDIC platforms.
266 Note that unfortunately EBCDIC platforms that used to supported back in
267 Perl 5.005 are still unsupported by Perl 5.7.0; the plan, however, is to
268 bring them back to the fold.
272 perlnewmod tells about writing and submitting a new module.
276 perlposix-bc explains using Perl on the POSIX-BC platform
277 (an EBCDIC mainframe platform).
281 perlretut is a regular expression tutorial.
285 perlrequick is a regular expressions quick-start guide.
286 Yes, much quicker than perlretut.
290 perlutil explains the command line utilities packaged with the Perl
295 =head1 Performance Enhancements
301 map() that changes the size of the list should now work faster.
305 sort() has been changed to use mergesort internally as opposed to the
306 earlier quicksort. For very small lists this may result in slightly
307 slower sorting times, but in general the speedup should be at least
308 20%. Additional bonuses are that the worst case behaviour of sort()
309 is now better (in computer science terms it now runs in time O(N log N),
310 as opposed to quicksort's Theta(N**2) worst-case run time behaviour),
311 and that sort() is now stable (meaning that elements with identical
312 keys will stay ordered as they were before the sort).
316 =head1 Installation and Configuration Improvements
318 =head2 Generic Improvements
324 INSTALL now explains how you can configure Perl to use 64-bit
325 integers even on non-64-bit platforms.
329 Policy.sh policy change: if you are reusing a Policy.sh file
330 (see INSTALL) and you use Configure -Dprefix=/foo/bar and in the old
331 Policy $prefix eq $siteprefix and $prefix eq $vendorprefix, all of
332 them will now be changed to the new prefix, /foo/bar. (Previously
333 only $prefix changed.) If you do not like this new behaviour,
334 specify prefix, siteprefix, and vendorprefix explicitly.
338 A new optional location for Perl libraries, otherlibdirs, is available.
339 It can be used for example for vendor add-ons without disturbing Perl's
340 own library directories.
344 In many platforms the vendor-supplied 'cc' is too stripped-down to
345 build Perl (basically, 'cc' doesn't do ANSI C). If this seems
346 to be the case and 'cc' does not seem to be the GNU C compiler
347 'gcc', an automatic attempt is made to find and use 'gcc' instead.
351 gcc needs to closely track the operating system release to avoid
352 build problems. If Configure finds that gcc was built for a different
353 operating system release than is running, it now gives a clearly visible
354 warning that there may be trouble ahead.
358 If binary compatibility with the 5.005 release is not wanted, Configure
359 no longer suggests including the 5.005 modules in @INC.
363 Configure C<-S> can now run non-interactively.
367 configure.gnu now works with options with whitespace in them.
371 installperl now outputs everything to STDERR.
375 $Config{byteorder} is now computed dynamically (this is more robust
376 with "fat binaries" where an executable image contains binaries for
377 more than one binary platform.)
381 Configure no longer included the DBM libraries (dbm, gdbm, db, ndbm)
382 when building the Perl binary. The only exception to this is SunOS 4.x,
387 =head1 Selected Bug Fixes
393 Several debugger fixes: exit code now reflects the script exit code,
394 condition C<"0"> now treated correctly, the C<d> command now checks
395 line number, the C<$.> no longer gets corrupted, all debugger output now
396 goes correctly to the socket if RemotePort is set.
400 C<*foo{FORMAT}> now works.
404 Lexical warnings now propagating correctly between scopes.
408 Line renumbering with eval and C<#line> now works.
412 Fixed numerous memory leaks, especially in eval "".
416 Modulus of unsigned numbers now works (4063328477 % 65535 used to
417 return 27406, instead of 27047).
421 Some "not a number" warnings introduced in 5.6.0 eliminated to be
422 more compatible with 5.005. Infinity is now recognised as a number.
426 our() variables will not cause "will not stay shared" warnings.
430 pack "Z" now correctly terminates the string with "\0".
434 Fix password routines which in some shadow password platforms
435 (e.g. HP-UX) caused getpwent() to return every other entry.
439 printf() no longer resets the numeric locale to "C".
443 C<q(a\\b)> now parses correctly as C<'a\\b'>.
447 Printing quads (64-bit integers) with printf/sprintf now works
448 without the q L ll prefixes (assuming you are on a quad-capable platform).
452 Regular expressions on references and overloaded scalars now work.
456 scalar() now forces scalar context even when used in void context.
460 sort() arguments are now compiled in the right wantarray context
461 (they were accidentally using the context of the sort() itself).
465 Changed the POSIX character class C<[[:space:]]> to include the (very
466 rare) vertical tab character. Added a new POSIX-ish character class
467 C<[[:blank:]]> which stands for horizontal whitespace (currently,
468 the space and the tab).
472 $AUTOLOAD, sort(), lock(), and spawning subprocesses
473 in multiple threads simultaneously are now thread-safe.
477 Allow read-only string on left hand side of non-modifying tr///.
481 Several Unicode fixes (but still not perfect).
487 BOMs (byte order marks) in the beginning of Perl files
488 (scripts, modules) should now be transparently skipped.
489 UTF-16 (UCS-2)encoded Perl files should now be read correctly.
493 The character tables have been updated to Unicode 3.0.1.
497 chr() for values greater than 127 now create utf8 when under use
502 Comparing with utf8 data does not magically upgrade non-utf8 data into
507 C<IsAlnum>, C<IsAlpha>, and C<IsWord> now match titlecase.
511 Concatenation with the C<.> operator or via variable interpolation,
512 C<eq>, C<substr>, C<reverse>, C<quotemeta>, the C<x> operator,
513 substitution with C<s///>, single-quoted UTF8, should now work--in
518 The C<tr///> operator now works I<slightly> better but is still rather
519 broken. Note that the C<tr///CU> functionality has been removed (but
520 see pack('U0', ...)).
524 vec() now tries to work with characters <= 255 when possible, but it leaves
525 higher character values in place. In that case, if vec() was used to modify
526 the string, it is no longer considered to be utf8-encoded.
530 Zero entries were missing from the Unicode classes like C<IsDigit>.
536 UNIVERSAL::isa no longer caches methods incorrectly. (This broke
537 the Tk extension with 5.6.0.)
541 =head2 Platform Specific Changes and Fixes
549 Perl now works on post-4.0 BSD/OSes.
555 Setting C<$0> now works (as much as possible; see perlvar for details).
561 Numerous updates; currently synchronised with Cygwin 1.1.4.
567 EPOC update after Perl 5.6.0. See README.epoc.
573 Perl now works on post-3.0 FreeBSDs.
579 README.hpux updated; C<Configure -Duse64bitall> now almost works.
585 Numerous compilation flag and hint enhancements; accidental mixing
586 of 32-bit and 64-bit libraries (a doomed attempt) made much harder.
592 Long doubles should now work (see INSTALL).
598 Compilation of the standard Perl distribution in MacOS Classic should
599 now work if you have the Metrowerks development environment and
600 the missing Mac-specific toolkit bits. Contact the macperl mailing
607 MPE/iX update after Perl 5.6.0. See README.mpeix.
613 Perl now works on NetBSD/sparc.
619 Now works with usethreads (see INSTALL).
625 64-bitness using the Sun Workshop compiler now works.
629 Tru64 (aka Digital UNIX, aka DEC OSF/1)
631 The operating system version letter now recorded in $Config{osvers}.
632 Allow compiling with gcc (previously explicitly forbidden). Compiling
633 with gcc still not recommended because buggy code results, even with
640 Fixed various alignment problems that lead into core dumps either
641 during build or later; no longer dies on math errors at runtime;
642 now using full quad integers (64 bits), previously was using
643 only 46 bit integers for speed.
649 chdir() now works better despite a CRT bug; now works with MULTIPLICITY
650 (see INSTALL); now works with Perl's malloc.
660 accept() no longer leaks memory.
664 Better chdir() return value for a non-existent directory.
668 New %ENV entries now propagate to subprocesses.
672 $ENV{LIB} now used to search for libs under Visual C.
676 A failed (pseudo)fork now returns undef and sets errno to EAGAIN.
680 Allow REG_EXPAND_SZ keys in the registry.
684 Can now send() from all threads, not just the first one.
688 Fake signal handling reenabled, bugs and all.
692 Less stack reserved per thread so that more threads can run
693 concurrently. (Still 16M per thread.)
697 C<File::Spec->tmpdir()> now prefers C:/temp over /tmp
698 (works better when perl is running as service).
702 Better UNC path handling under ithreads.
706 wait() and waitpid() now work much better.
710 winsock handle leak fixed.
714 =head1 New or Changed Diagnostics
716 All regular expression compilation error messages are now hopefully
717 easier to understand both because the error message now comes before
718 the failed regex and because the point of failure is now clearly
721 The various "opened only for", "on closed", "never opened" warnings
722 drop the C<main::> prefix for filehandles in the C<main> package,
723 for example C<STDIN> instead of <main::STDIN>.
725 The "Unrecognized escape" warning has been extended to include C<\8>,
726 C<\9>, and C<\_>. There is no need to escape any of the C<\w> characters.
728 =head1 Changed Internals
734 perlapi.pod (a companion to perlguts) now attempts to document the
739 You can now build a really minimal perl called microperl.
740 Building microperl does not require even running Configure;
741 C<make -f Makefile.micro> should be enough. Beware: microperl makes
742 many assumptions, some of which may be too bold; the resulting
743 executable may crash or otherwise misbehave in wondrous ways.
744 For careful hackers only.
748 Added rsignal(), whichsig(), do_join() to the publicised API.
752 Made possible to propagate customised exceptions via croak()ing.
756 Added is_utf8_char(), is_utf8_string(), bytes_to_utf8(), and utf8_to_bytes().
760 Now xsubs can have attributes just like subs.
764 =head1 Known Problems
766 =head2 Unicode Support Still Far From Perfect
768 We're working on it. Stay tuned.
770 =head2 EBCDIC Still A Lost Platform
772 The plan is to bring them back.
774 =head2 Building Extensions Can Fail Because Of Largefiles
776 Certain extensions like mod_perl and BSD::Resource are known to have
777 issues with `largefiles', a change brought by Perl 5.6.0 in which file
778 offsets default to 64 bits wide, where supported. Modules may fail to
779 compile at all or compile and work incorrectly. Currently there is no
780 good solution for the problem, but Configure now provides appropriate
781 non-largefile ccflags, ldflags, libswanted, and libs in the %Config
782 hash (e.g., $Config{ccflags_nolargefiles}) so the extensions that are
783 having problems can try configuring themselves without the
784 largefileness. This is admittedly not a clean solution, and the
785 solution may not even work at all. One potential failure is whether
786 one can (or, if one can, whether it's a good idea) link together at
787 all binaries with different ideas about file offsets, all this is
790 =head2 ftmp-security tests warn 'system possibly insecure'
792 Don't panic. Read INSTALL 'make test' section instead.
794 =head2 Test lib/posix Subtest 9 Fails In LP64-Configured HP-UX
796 If perl is configured with -Duse64bitall, the successful result of the
797 subtest 10 of lib/posix may arrive before the successful result of the
798 subtest 9, which confuses the test harness so much that it thinks the
801 =head2 Long Doubles Still Don't Work In Solaris
803 The experimental long double support is still very much so in Solaris.
804 (Other platforms like Linux and Tru64 are beginning to solidify in
807 =head2 Linux With Sfio Fails op/misc Test 48
811 =head2 Storable tests fail in some platforms
813 If any Storable tests fail the use of Storable is not advisable.
819 Many Storable tests fail on AIX configured with 64 bit integers.
821 So far unidentified problems break Storable in AIX if Perl is
822 configured to use 64 bit integers. AIX in 32-bit mode works and
823 other 64-bit platforms work with Storable.
827 DOS DJGPP may hang when testing Storable.
831 st-06compat fails in UNICOS and UNICOS/mk.
833 This means that you cannot read old (pre-Storable-0.7) Storable images
834 made in other platforms.
838 st-store.t and st-retrieve may fail with Compaq C 6.2 on OpenVMS Alpha 7.2.
840 =head2 Threads Are Still Experimental
842 Multithreading is still an experimental feature. Some platforms
843 emit the following message for lib/thr5005
846 # This is a KNOWN FAILURE, and one of the reasons why threading
847 # is still an experimental feature. It is here to stop people
848 # from deploying threads in production. ;-)
851 and another known thread-related warning is
853 pragma/overload......Unbalanced saves: 3 more saves than restores
854 panic: magic_mutexfree during global destruction.
856 lib/selfloader.......Unbalanced saves: 3 more saves than restores
857 panic: magic_mutexfree during global destruction.
859 lib/st-dclone........Unbalanced saves: 3 more saves than restores
860 panic: magic_mutexfree during global destruction.
863 =head2 The Compiler Suite Is Still Experimental
865 The compiler suite is slowly getting better but is nowhere near
866 working order yet. The backend part that has seen perhaps the most
867 progress is the bytecode compiler.
871 =head1 Reporting Bugs
873 If you find what you think is a bug, you might check the articles
874 recently posted to the comp.lang.perl.misc newsgroup and the perl
875 bug database at http://bugs.perl.org. There may also be
876 information at http://www.perl.com/perl/, the Perl Home Page.
878 If you believe you have an unreported bug, please run the B<perlbug>
879 program included with your release. Be sure to trim your bug down
880 to a tiny but sufficient test case. Your bug report, along with the
881 output of C<perl -V>, will be sent off to perlbug@perl.org to be
882 analysed by the Perl porting team.
886 The F<Changes> file for exhaustive details on what changed.
888 The F<INSTALL> file for how to build Perl.
890 The F<README> file for general stuff.
892 The F<Artistic> and F<Copying> files for copyright information.
896 Written by Jarkko Hietaniemi <F<jhi@iki.fi>>, with many contributions
897 from The Perl Porters and Perl Users submitting feedback and patches.
899 Send omissions or corrections to <F<perlbug@perl.org>>.