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, $2, ...) are now
83 more consistently unset if the match fails, instead of leaving false
84 data lying around in them.
88 The tr///C and tr///U features have been removed and will not return;
89 the interface was a mistake. Sorry about that. For similar
90 functionality, see pack('U0', ...) and pack('C0', ...).
94 =head1 Core Enhancements
100 C<perl -d:Module=arg,arg,arg> now works (previously one couldn't pass
101 in multiple arguments.)
105 my __PACKAGE__ now works.
109 C<no Module;> now works even if there is no "sub unimport" in the Module.
113 The numerical comparison operators return C<undef> if either operand
114 is a NaN. Previously the behaviour was unspecified.
118 C<pack('U0a*', ...)> can now be used to force a string to UTF8.
122 prototype(\&) is now available.
126 There is now an UNTIE method.
130 =head1 Modules and Pragmata
138 File::Temp allows one to create temporary files and directories in an
139 easy, portable, and secure way.
143 Storable gives persistence to Perl data structures by allowing the
144 storage and retrieval of Perl data to and from files in a fast and
145 compact binary format.
149 =head2 Updated And Improved Modules and Pragmata
155 The following independently supported modules have been updated to
156 newer versions from CPAN: CGI, CPAN, DB_File, File::Spec, Getopt::Long,
157 the podlators bundle, Pod::LaTeX, Pod::Parser, Term::ANSIColor, Test.
161 Bug fixes and minor enhancements have been applied to B::Deparse,
162 Data::Dumper, IO::Poll, IO::Socket::INET, Math::BigFloat,
163 Math::Complex, Math::Trig, re, SelfLoader, Sys::SysLog, Test::Harness,
164 Text::Wrap, UNIVERSAL.
168 The attributes::reftype() now works on tied arguments.
172 AutoLoader can now be disabled with C<no AutoLoader;>,
176 The English module can now be used without the infamous performance
179 use English '-no_performance_hit';
181 (Assuming, of course, that one doesn't need the troublesome variables
182 C<$`>, C<$&>, or C<$'>.) Also, introduce C<@LAST_MATCH_START> and
183 C<@LAST_MATCH_END> English aliases for C<@-> and C<@+>.
187 File::Find now has pre- and post-processing callbacks. It also
188 correctly changes directories when chasing symbolic links. Callbacks
189 (naughtily) exiting with "next;" instead of "return;" now work.
193 File::Glob::glob() renamed to File::Glob::bsd_glob() to avoid
194 prototype mismatch with CORE::glob().
198 IPC::Open3 now allows the use of numeric file descriptors.
202 use lib now works identically to @INC. Removing directories
203 with 'no lib' now works.
207 C<%INC> now localised in a Safe compartment so that use/require work.
211 The Shell module now has an OO interface.
215 =head1 Utility Changes
221 The Emacs perl mode (emacs/cperl-mode.el) has been updated to version 4.31.
225 Perlbug is now much more robust. It also sends the bug report to perl.org,
230 The perlcc utility has been rewritten and its user interface (that is,
231 command line) is much more like that of the UNIX C compiler, cc.
235 The xsubpp utility for extension writers now understands POD
236 documentation embedded in the *.xs files.
240 =head1 New Documentation
246 perl56delta details the changes between the 5.005 release and the
251 perldebtut is a Perl debugging tutorial.
255 perlebcdic contains considerations for running Perl on EBCDIC platforms.
256 Note that unfortunately EBCDIC platforms that used to supported back in
257 Perl 5.005 are still unsupported by Perl 5.7.0; the plan, however, is to
258 bring them back to the fold.
262 perlnewmod tells about writing and submitting a new module.
266 perlposix-bc explains using Perl on the POSIX-BC platform
267 (an EBCDIC mainframe platform).
271 perlretut is a regular expression tutorial.
275 perlrequick is a regular expressions quick-start guide.
276 Yes, much quicker than perlretut.
280 perlutil explains the command line utilities packaged with the Perl
285 =head1 Performance Enhancements
291 map() that changes the size of the list should now work faster.
295 sort() has been changed to use mergesort internally as opposed to the
296 earlier quicksort. For very small lists this may result in slightly
297 slower sorting times, but in general the speedup should be at least 20%.
298 Additional bonuses are that the worst case behaviour of sort() is now
299 better (in computer science terms it now runs in time O(N log N), as
300 opposed to quicksorts Theta(N**2) worst-case run time behaviour), and
301 that sort() is now stable (meaning that elements with identical keys
302 will stay ordered as they were before the sort).
306 =head1 Installation and Configuration Improvements
308 =head2 Generic Improvements
314 INSTALL now explains how you can configure perl to use 64-bit
315 integers even on non-64-bit platforms.
319 Policy.sh policy change: if you are reusing a Policy.sh file (see
320 INSTALL) and you use Configure -Dprefix=/foo/bar and in the old
321 Policy $prefix eq $siteprefix and $prefix eq $vendorprefix, all of
322 them will now be changed to the new prefix, /foo/bar. (Previously
323 only $prefix changed.) If you do not like this new behaviour,
324 specify prefix, siteprefix, and vendorprefix explicitly.
328 A new optional location for Perl libraries, otherlibdirs, is available.
329 It can be used for example for vendor add-ons without disturbing Perl's
330 own library directories.
334 In many platforms the vendor-supplied 'cc' is too stripped-down to
335 build Perl (basically, 'cc' doesn't do ANSI C). If this seems
336 to be the case and 'cc' does not seem to be the GNU C compiler
337 'gcc', an automatic attempt is made to find and use 'gcc' instead.
341 gcc needs to closely track the operating system release to avoid
342 build problems. If Configure finds that gcc was built for a different
343 operating system release than is running, it now gives a clearly visible
344 warning that there may be trouble ahead.
348 If binary compatibility with the 5.005 release is not wanted, Configure
349 no longer suggests including the 5.005 modules in @INC.
353 Configure C<-S> can now run non-interactively.
357 configure.gnu now works with options with whitespace in them.
361 installperl now outputs everything to STDERR.
365 $Config{byteorder} is now computed dynamically (this is more robust
366 with "fat binaries" where an executable image contains binaries for
367 more than one binary platform.)
371 =head1 Selected Bug Fixes
377 Several debugger fixes: exit code now reflects the script exit code,
378 condition C<"0"> now treated correctly, the C<d> command now checks
379 line number, the C<$.> no longer gets corrupted, all debugger output now
380 goes correctly to the socket if RemotePort is set.
384 C<*foo{FORMAT}> now works.
388 Lexical warnings now propagating correctly between scopes.
392 Line renumbering with eval and C<#line> now works.
396 Fixed numerous memory leaks, especially in eval "".
400 Modulus of unsigned numbers now works (4063328477 % 65535 used to
401 return 27406, instead of 27047).
405 Some "not a number" warnings introduced in 5.6.0 eliminated to be
406 more compatible with 5.005. Infinity is now recognised as a number.
410 our() variables will not cause "will not stay shared" warnings.
414 pack "Z" now correctly terminates the string with "\0".
418 Fix password routines which in some shadow password platforms
419 (e.g. HP-UX) caused getpwent() to return every other entry.
423 printf() no longer resets the numeric locale to "C".
427 C<q(a\\b)> now parses correctly as C<'a\\b'>.
431 Printing quads (64-bit integers) with printf/sprintf now works
432 without the q L ll prefixes (assuming you are on a quad-capable platform).
436 Regular expressions on references and overloaded scalars now work.
440 scalar() now forces scalar context even when used in void context.
444 sort() arguments are now compiled in the right wantarray context
445 (they were accidentally using the context of the sort() itself).
449 Changed the POSIX character class C<[[:space:]]> to include the (very
450 rare) vertical tab character. Added a new POSIX-ish character class
451 C<[[:blank:]]> which stands for horizontal whitespace (currently,
452 the space and the tab).
456 $AUTOLOAD, sort(), lock(), and spawning subprocesses
457 in multiple threads simultaneously are now thread-safe.
461 Allow read-only string on left hand side of non-modifying tr///.
465 Several Unicode fixes (but still not perfect).
471 BOMs (byte order marks) in the beginning of Perl files
472 (scripts, modules) should now be transparently skipped.
473 UTF16 encoded Perl files should now be read correctly.
477 The character tables have been updated to new Unicode 3.0 features.
481 chr() for values greater than 127 now create utf8 when under use
486 Comparing with utf8 data does not magically upgrade non-utf8 data into
491 C<IsAlnum>, C<IsAlpha>, and C<IsWord> now match titlecase.
495 Concatenation with the C<.> operator or via variable interpolation,
496 C<eq>, C<substr>, C<reverse>, C<quotemeta>, the C<x> operator,
497 substitution with C<s///>, single-quoted UTF8, should now work--in
502 The C<tr///> operator now works I<slightly> better but is still rather
503 broken. Note that the C<tr///CU> functionality has been removed (but
504 see pack('U0', ...)).
508 Zero entries were missing from the Unicode classes like C<IsDigit>.
514 UNIVERSAL::isa no longer caches methods incorrectly. (This broke
515 the Tk extension with 5.6.0.)
519 =head2 Platform Specific Changes and Fixes
527 Perl now works on post-4.0 BSD/OSes.
533 Setting C<$0> now works (as much as possible; see perlvar for details).
539 Numerous updates; currently synchronised with Cygwin 1.1.4.
545 EPOC update after Perl 5.6.0. See README.epoc.
551 Perl now works on post-3.0 FreeBSDs.
557 README.hpux updated; C<Configure -Duse64bitall> now almost works.
563 Numerous compilation flag and hint enhancements; accidental mixing
564 of 32-bit and 64-bit libraries (a doomed attempt) made much harder.
570 Long doubles should now work (see INSTALL).
576 Compilation of the standard Perl distribution in MacOS Classic should
577 now work if you have the Metrowerks development environment and
578 the missing Mac-specific toolkit bits. Contact the macperl mailing
585 MPE/iX update after Perl 5.6.0. See README.mpeix.
591 Perl now works on NetBSD/sparc.
597 Now works with usethreads (see INSTALL).
603 64-bitness using the Sun Workshop compiler now works.
607 Tru64 (aka Digital UNIX, aka DEC OSF/1)
609 The operating system version letter now recorded in $Config{osvers}.
610 Allow compiling with gcc (previously explicitly forbidden). Compiling
611 with gcc still not recommended because buggy code results, even with
618 Fixed various alignment problems that lead into core dumps either
619 during build or later; no longer dies on math errors at runtime;
620 now using full quad integers (64 bits), previously was using
621 only 46 bit integers for speed.
627 chdir() now works better despite a CRT bug; now works with MULTIPLICITY
628 (see INSTALL); now works with Perl's malloc.
638 accept() no longer leaks memory.
642 Better chdir() return value for a non-existent directory.
646 New %ENV entries now propagate to subprocesses.
650 $ENV{LIB} now used to search for libs under Visual C.
654 A failed (pseudo)fork now returns undef and sets errno to EAGAIN.
658 Allow REG_EXPAND_SZ keys in the registry.
662 Can now send() from all threads, not just the first one.
666 Fake signal handling reenabled, bugs and all.
670 Less stack reserved per thread so that more threads can run
671 concurrently. (still 16M perl thread)
675 C<File::Spec->tmpdir()> now prefers C:/temp over /tmp
676 (works better when perl running as service).
680 Better UNC path handling under ithreads.
684 wait() and waitpid() now work much better.
688 winsock handle leak fixed.
692 =head1 New or Changed Diagnostics
694 All regular expression compilation error messages are now hopefully
695 easier to understand both because the error message now comes before
696 the failed regex and because the point of failure is now clearly
699 The various "opened only for", "on closed", "never opened" warnings
700 drop the C<main::> prefix for filehandles in the C<main> package,
701 for example C<STDIN> instead of <main::STDIN>.
703 The "Unrecognized escape" warning has been extended to include C<\8>,
704 C<\9>, and C<\_>. There is no need to escape any of the C<\w> characters.
706 =head1 Changed Internals
712 perlapi.pod (a companion to perlguts) now attempts to document the
717 You can now build a really minimal perl called microperl.
718 Building microperl does not require even running Configure;
719 C<make -f Makefile.micro> should be enough. Beware: microperl makes
720 many assumptions, some of which may be too bold; the resulting
721 executable may crash or otherwise misbehave in wondrous ways. For
722 careful hackers only.
726 Added rsignal(), whichsig(), do_join() to the publicised API.
730 Made possible to propagate customised exceptions via croak()ing.
734 Added is_utf8_char(), is_utf8_string(), bytes_to_utf8(), and utf8_to_bytes().
738 Now xsubs can have attributes just like subs.
742 =head1 Known Problems
744 =head2 Unicode Support Still Far From Perfect
746 We're working on it. Stay tuned.
748 =head2 EBCDIC Still A Lost Platform
750 The plan is to bring them back.
752 =head2 Building Extensions Can Fail Because Of Largefiles
754 Certain extensions like mod_perl and BSD::Resource are known to have
755 issues with `largefiles', a change brought by Perl 5.6.0 in which file
756 offsets default to 64 bits wide, where supported. Modules may fail to
757 compile at all or compile and work incorrectly. Currently there is no
758 good solution for the problem, but Configure now provides appropriate
759 non-largefile ccflags, ldflags, libswanted, and libs in the %Config
760 hash (e.g., $Config{ccflags_nolargefiles}) so the extensions that are
761 having problems can try configuring themselves without the
762 largefileness. This is admittedly not a clean solution, and the
763 solution may not even work at all. One potential failure is whether
764 one can (or, if one can, whether it's a good idea) link together at
765 all binaries with different ideas about file offsets, all this is
768 =head2 ftmp-posix subtest 6 fails in VMS
770 The test exposed a flushing bug in VMS, this failure can be ignored.
772 =head2 Storable tests fail in some platforms
778 Many Storable tests fail on AIX configured with 64 bit integers.
780 So far unidentified problems break Storable in AIX if Perl is
781 configured to use 64 bit integers. AIX in 32-bit mode works and
782 other 64-bit platforms work with Storable.
786 DOS DJGPP may hang when testing Storable.
790 st-06compat fails in UNICOS and UNICOS/mk.
792 This means that you cannot read old (pre-Storable-0.7) Storable images
793 made in other platforms.
797 =head1 Reporting Bugs
799 If you find what you think is a bug, you might check the articles
800 recently posted to the comp.lang.perl.misc newsgroup and the perl
801 bug database at http://bugs.perl.org. There may also be
802 information at http://www.perl.com/perl/, the Perl Home Page.
804 If you believe you have an unreported bug, please run the B<perlbug>
805 program included with your release. Be sure to trim your bug down
806 to a tiny but sufficient test case. Your bug report, along with the
807 output of C<perl -V>, will be sent off to perlbug@perl.org to be
808 analysed by the Perl porting team.
812 The F<Changes> file for exhaustive details on what changed.
814 The F<INSTALL> file for how to build Perl.
816 The F<README> file for general stuff.
818 The F<Artistic> and F<Copying> files for copyright information.
822 Written by Jarkko Hietaniemi <F<jhi@iki.fi>>, with many contributions
823 from The Perl Porters and Perl Users submitting feedback and patches.
825 Send omissions or corrections to <F<perlbug@perl.org>>.