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 August the 20th, 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 gave
21 access to a root shell, resulting in a serious compromise instead of
22 reporting the exploit attempt. If you don't have /bin/mail, or if you
23 have 'safe setuid scripts', or if suidperl is not installed, you
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, $2, ...) are now
83 more consistently unset if the match fails, instead of leaving false
84 data lying around in them.
88 The tr///C and tr///U features have been removed and will not return;
89 the interface was a mistake. Sorry about that. For similar
90 functionality, see pack('U0', ...) and pack('C0', ...).
94 =head1 Core Enhancements
100 C<perl -d:Module=arg,arg,arg> now works (previously one couldn't pass
101 in multiple arguments.)
105 my __PACKAGE__ now works.
109 C<no Module;> now works even if there is no "sub unimport" in the Module.
113 The numerical comparison operators return C<undef> if either operand
114 is a NaN. Previously the behaviour was unspecified.
118 C<pack('U0a*', ...)> can now be used to force a string to UTF8.
122 prototype(\&) is now available.
126 =head1 Modules and Pragmata
134 File::Temp allows one to create temporary files and directories in an
135 easy, portable, and secure way.
139 Storable gives persistence to Perl data structures by allowing the
140 storage and retrieval of Perl data to and from files in a fast and
141 compact binary format.
145 =head2 Updated And Improved Modules and Pragmata
151 The following independently supported modules have been updated to
152 newer versions from CPAN: CGI, CPAN, DB_File, File::Spec, Getopt::Long,
153 the podlators bundle, Pod::LaTeX, Pod::Parser, Term::ANSIColor, Test.
157 Bug fixes and minor enhancements have been applied to B::Deparse,
158 Data::Dumper, IO::Poll, IO::Socket::INET, Math::BigFloat,
159 Math::Complex, Math::Trig, re, SelfLoader, Sys::SysLog, Test::Harness,
160 Text::Wrap, UNIVERSAL.
164 The attributes::reftype() now works on tied arguments.
168 AutoLoader can now be disabled with C<no AutoLoader;>,
172 The English module can now be used without the infamous performance
175 use English '-no_performance_hit';
177 (Assuming, of course, that one doesn't need the troublesome variables
178 C<$`>, C<$&>, or C<$'>.) Also, introduce C<@LAST_MATCH_START> and
179 C<@LAST_MATCH_END> English aliases for C<@-> and C<@+>.
183 File::Find now has pre- and post-processing callbacks. It also
184 correctly changes directories when chasing symbolic links. Callbacks
185 (naughtily) exiting with "next;" instead of "return;" now work.
189 File::Glob::glob() renamed to File::Glob::bsd_glob() to avoid
190 prototype mismatch with CORE::glob().
194 IPC::Open3 now allows the use of numeric file descriptors.
198 use lib now works identically to @INC. Removing directories
199 with 'no lib' now works.
203 C<%INC> now localised in a Safe compartment so that use/require work.
207 The Shell module now has an OO interface.
211 =head1 Utility Changes
217 The Emacs perl mode (emacs/cperl-mode.el) has been updated to version 4.31.
221 Perlbug is now much more robust. It also sends the bug report to perl.org,
226 The perlcc utility has been rewritten and its user interface (that is,
227 command line) is much more like that of the UNIX C compiler, cc.
231 The xsubpp utility for extension writers now understands POD
232 documentation embedded in the *.xs files.
236 =head1 New Documentation
242 perl56delta details the changes between the 5.005 release and the
247 perldebtut is a Perl debugging tutorial.
251 perlebcdic contains considerations for running Perl on EBCDIC platforms.
252 Note that unfortunately EBCDIC platforms that used to supported back in
253 Perl 5.005 are still unsupported by Perl 5.7.0; the plan, however, is to
254 bring them back to the fold.
258 perlnewmod tells about writing and submitting a new module.
262 perlposix-bc explains using Perl on the POSIX-BC platform
263 (an EBCDIC mainframe platform).
267 perlretut is a regular expression tutorial.
271 perlrequick is a regular expressions quick-start guide.
272 Yes, much quicker than perlretut.
276 perlutil explains the command line utilities packaged with the Perl
281 =head1 Performance Enhancements
287 map() that changes the size of the list should now work faster.
291 =head1 Installation and Configuration Improvements
293 =head2 Generic Improvements
299 INSTALL now explains how you can configure perl to use 64-bit
300 integers even on non-64-bit platforms.
304 Policy.sh policy change: if you are reusing a Policy.sh file (see
305 INSTALL) and you use Configure -Dprefix=/foo/bar and in the old
306 Policy $prefix eq $siteprefix and $prefix eq $vendorprefix, all of
307 them will now be changed to the new prefix, /foo/bar. (Previously
308 only $prefix changed.) If you do not like this new behaviour,
309 specify prefix, siteprefix, and vendorprefix explicitly.
313 A new optional location for Perl libraries, otherlibdirs, is available.
314 It can be used for example for vendor add-ons without disturbing Perl's
315 own library directories.
319 In many platforms the vendor-supplied 'cc' is too stripped-down to
320 build Perl (basically, 'cc' doesn't do ANSI C). If this seems
321 to be the case and 'cc' does not seem to be the GNU C compiler
322 'gcc', an automatic attempt is made to find and use 'gcc' instead.
326 gcc needs to closely track the operating system release to avoid
327 build problems. If Configure finds that gcc was built for a different
328 operating system release than is running, it now gives a clearly visible
329 warning that there may be trouble ahead.
333 If binary compatibility with the 5.005 release is not wanted, Configure
334 no longer suggests including the 5.005 modules in @INC.
338 Configure C<-S> can now run non-interactively.
342 configure.gnu now works with options with whitespace in them.
346 installperl now outputs everything to STDERR.
350 $Config{byteorder} is now computed dynamically (this is more robust
351 with "fat binaries" where an executable image contains binaries for
352 more than one binary platform.)
356 =head1 Selected Bug Fixes
362 Several debugger fixes: exit code now reflects the script exit code,
363 condition C<"0"> now treated correctly, the C<d> command now checks
364 line number, the C<$.> no longer gets corrupted, all debugger output now
365 goes correctly to the socket if RemotePort is set.
369 C<*foo{FORMAT}> now works.
373 Lexical warnings now propagating correctly between scopes.
377 Line renumbering with eval and C<#line> now works.
381 Fixed numerous memory leaks, especially in eval "".
385 Modulus of unsigned numbers now works (4063328477 % 65535 used to
386 return 27406, instead of 27047).
390 Some "not a number" warnings introduced in 5.6.0 eliminated to be
391 more compatible with 5.005. Infinity is now recognised as a number.
395 our() variables will not cause "will not stay shared" warnings.
399 pack "Z" now correctly terminates the string with "\0".
403 Fix password routines which in some shadow password platforms
404 (e.g. HP-UX) caused getpwent() to return every other entry.
408 printf() no longer resets the numeric locale to "C".
412 C<q(a\\b)> now parses correctly as C<'a\\b'>.
416 Printing quads (64-bit integers) with printf/sprintf now works
417 without the q L ll prefixes (assuming you are on a quad-capable platform).
421 Regular expressions on references and overloaded scalars now work.
425 scalar() now forces scalar context even when used in void context.
429 sort() arguments are now compiled in the right wantarray context
430 (they were accidentally using the context of the sort() itself).
434 Changed the POSIX character class C<[[:space:]]> to include the (very
435 rare) vertical tab character. Added a new POSIX-ish character class
436 C<[[:blank:]]> which stands for horizontal whitespace (currently,
437 the space and the tab).
441 $AUTOLOAD, sort(), lock(), and spawning subprocesses
442 in multiple threads simultaneously are now thread-safe.
446 Allow read-only string on left hand side of non-modifying tr///.
450 Several Unicode fixes (but still not perfect).
456 BOMs (byte order marks) in the beginning of Perl files
457 (scripts, modules) should now be transparently skipped.
458 UTF16 encoded Perl files should now be read correctly.
462 The character tables have been updated to new Unicode 3.0 features.
466 chr() for values greater than 127 now create utf8 when under use
471 Comparing with utf8 data does not magically upgrade non-utf8 data into
476 C<IsAlnum>, C<IsAlpha>, and C<IsWord> now match titlecase.
480 Concatenation with the C<.> operator or via variable interpolation,
481 C<eq>, C<substr>, C<reverse>, C<quotemeta>, the C<x> operator,
482 substitution with C<s///>, single-quoted UTF8, should now work--in
487 The C<tr///> operator now works I<slightly> better but is still rather
488 broken. Note that the C<tr///CU> functionality has been removed (but
489 see pack('U0', ...)).
493 Zero entries were missing from the Unicode classes like C<IsDigit>.
499 UNIVERSAL::isa no longer caches methods incorrectly. (This broke
500 the Tk extension with 5.6.0.)
504 =head2 Platform Specific Changes and Fixes
512 Perl now works on post-4.0 BSD/OSes.
518 Setting C<$0> now works (as much as possible; see perlvar for details).
524 Numerous updates; currently synchronised with Cygwin 1.1.4.
530 EPOC update after Perl 5.6.0. See README.epoc.
536 Perl now works on post-3.0 FreeBSDs.
542 README.hpux updated; C<Configure -Duse64bitall> now almost works.
548 Numerous compilation flag and hint enhancements; accidental mixing
549 of 32-bit and 64-bit libraries (a doomed attempt) made much harder.
555 Long doubles should now work (see INSTALL).
561 Compilation of the standard Perl distribution in MacOS Classic should
562 now work if you have the Metrowerks development environment and
563 the missing Mac-specific toolkit bits. Contact the macperl mailing
570 MPE/iX update after Perl 5.6.0. See README.mpeix.
576 Perl now works on NetBSD/sparc.
582 Now works with usethreads (see INSTALL).
588 64-bitness using the Sun Workshop compiler now works.
592 Tru64 (aka Digital UNIX, aka DEC OSF/1)
594 The operating system version letter now recorded in $Config{osvers}.
595 Allow compiling with gcc (previously explicitly forbidden). Compiling
596 with gcc still not recommended because buggy code results, even with
603 Fixed various alignment problems that lead into core dumps either
604 during build or later; no longer dies on math errors at runtime;
605 now using full quad integers (64 bits), previously was using
606 only 46 bit integers for speed.
612 chdir() now works better despite a CRT bug; now works with MULTIPLICITY
613 (see INSTALL); now works with Perl's malloc.
623 accept() no longer leaks memory.
627 Better chdir() return value for a non-existent directory.
631 New %ENV entries now propagate to subprocesses.
635 $ENV{LIB} now used to search for libs under Visual C.
639 A failed (pseudo)fork now returns undef and sets errno to EAGAIN.
643 Allow REG_EXPAND_SZ keys in the registry.
647 Can now send() from all threads, not just the first one.
651 Fake signal handling reenabled, bugs and all.
655 Less stack reserved per thread so that more threads can run
656 concurrently. (still 16M perl thread)
660 C<File::Spec->tmpdir()> now prefers C:/temp over /tmp
661 (works better when perl running as service).
665 Better UNC path handling under ithreads.
669 wait() and waitpid() now work much better.
673 winsock handle leak fixed.
677 =head1 New or Changed Diagnostics
679 All regular expression compilation error messages are now hopefully
680 easier to understand both because the error message now comes before
681 the failed regex and because the point of failure is now clearly
684 The various "opened only for", "on closed", "never opened" warnings
685 drop the C<main::> prefix for filehandles in the C<main> package,
686 for example C<STDIN> instead of <main::STDIN>.
688 The "Unrecognized escape" warning has been extended to include C<\8>,
689 C<\9>, and C<\_>. There is no need to escape any of the C<\w> characters.
691 =head1 Changed Internals
697 perlapi.pod (a companion to perlguts) now attempts to document the
702 You can now build a really minimal perl called microperl.
703 Building microperl does not require even running Configure;
704 C<make -f Makefile.micro> should be enough. Beware: microperl makes
705 many assumptions, some of which may be too bold; the resulting
706 executable may crash or otherwise misbehave in wondrous ways. For
707 careful hackers only.
711 Added rsignal(), whichsig(), do_join() to the publicised API.
715 Made possible to propagate customised exceptions via croak()ing.
719 Added is_utf8_char(), is_utf8_string(), bytes_to_utf8(), and utf8_to_bytes().
723 Now xsubs can have attributes just like subs.
727 =head1 Known Problems
729 =head2 Unicode Support Still Far From Perfect
731 We're working on it. Stay tuned.
733 =head2 EBCDIC Still A Lost Platform
735 The plan is to bring them back.
737 =head2 Building Extensions Can Fail Because Of Largefiles
739 Certain extensions like mod_perl and BSD::Resource are known to have
740 issues with `largefiles', a change brought by Perl 5.6.0 in which file
741 offsets default to 64 bits wide, where supported. Modules may fail to
742 compile at all or compile and work incorrectly. Currently there is no
743 good solution for the problem, but Configure now provides appropriate
744 non-largefile ccflags, ldflags, libswanted, and libs in the %Config
745 hash (e.g., $Config{ccflags_nolargefiles}) so the extensions that are
746 having problems can try configuring themselves without the
747 largefileness. This is admittedly not a clean solution, and the
748 solution may not even work at all. One potential failure is whether
749 one can (or, if one can, whether it's a good idea) link together at
750 all binaries with different ideas about file offsets, all this is
753 =head2 Storable test st-06compat Fails in UNICOS and UNICOS/mk
755 This means that you cannot read old (pre-Storable-0.7) Storable images
756 made in other platforms.
758 =head1 Reporting Bugs
760 If you find what you think is a bug, you might check the articles
761 recently posted to the comp.lang.perl.misc newsgroup and the perl
762 bug database at http://bugs.perl.org. There may also be
763 information at http://www.perl.com/perl/, the Perl Home Page.
765 If you believe you have an unreported bug, please run the B<perlbug>
766 program included with your release. Be sure to trim your bug down
767 to a tiny but sufficient test case. Your bug report, along with the
768 output of C<perl -V>, will be sent off to perlbug@perl.org to be
769 analysed by the Perl porting team.
773 The F<Changes> file for exhaustive details on what changed.
775 The F<INSTALL> file for how to build Perl.
777 The F<README> file for general stuff.
779 The F<Artistic> and F<Copying> files for copyright information.
783 Written by Jarkko Hietaniemi <F<jhi@iki.fi>>, with many contributions
784 from The Perl Porters and Perl Users submitting feedback and patches.
786 Send omissions or corrections to <F<perlbug@perl.org>>.