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, unfortunately,
29 always possible. The suidperl code is being reviewed and if deemed too
30 risky to continue to support it may be completely removed from future
31 releases. In any case, suidperl should only be used by security
32 experts who know exactly what they are doing and why they are using
33 suidperl instead of some other solution such as sudo (see
34 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, $2, ...) are now
83 more consistently unset if the match fails, instead of leaving false
84 data lying around in them.
88 The tr///C and tr///U features have been removed and will not return;
89 the interface was a mistake. Sorry about that. For similar
90 functionality, see pack('U0', ...) and pack('C0', ...).
94 =head1 Core Enhancements
100 C<perl -d:Module=arg,arg,arg> now works (previously one couldn't pass
101 in multiple arguments.)
105 my __PACKAGE__ now works.
109 C<no Module;> now works even if there is no "sub unimport" in the Module.
113 The numerical comparison operators return C<undef> if either operand
114 is a NaN. Previously the behaviour was unspecified.
118 C<pack('U0a*', ...)> can now be used to force a string to UTF8.
122 prototype(\&) is now available.
126 =head1 Modules and Pragmata
134 File::Temp allows one to create temporary files and directories in an
135 easy, portable, and secure way.
139 Storable gives persistence to Perl data structures by allowing the
140 storage and retrieval of Perl data to and from files in a fast and
141 compact binary format.
145 =head2 Updated And Improved Modules and Pragmata
151 The following independently supported modules have been updated to
152 newer versions from CPAN: CGI, CPAN, DB_File, File::Spec, Getopt::Long,
153 the podlators bundle, Pod::LaTeX, Pod::Parser, Term::ANSIColor, Test.
157 Bug fixes and minor enhancements have been applied to B::Deparse,
158 Data::Dumper, IO::Poll, IO::Socket::INET, Math::BigFloat, Math::Complex,
159 re, SelfLoader, Sys::SysLog, Test::Harness, Text::Wrap, UNIVERSAL.
163 The attributes::reftype() now works on tied arguments.
167 AutoLoader can now be disabled with C<no AutoLoader;>,
171 The English module can now be used without the infamous performance
174 use English '-no_performance_hit';
176 (Assuming, of course, that one doesn't need the troublesome variables
177 C<$`>, C<$&>, or C<$'>.) Also, introduce C<@LAST_MATCH_START> and
178 C<@LAST_MATCH_END> English aliases for C<@-> and C<@+>.
182 File::Find now has pre- and post-processing callbacks. It also
183 correctly changes directories when chasing symbolic links. Callbacks
184 (naughtily) exiting with "next;" instead of "return;" now work.
188 File::Glob::glob() renamed to File::Glob::bsd_glob() to avoid
189 prototype mismatch with CORE::glob().
193 IPC::Open3 now allows the use of numeric file descriptors.
197 use lib now works identically to @INC. Removing directories
198 with 'no lib' now works.
202 C<%INC> now localised in a Safe compartment so that use/require work.
206 The Shell module now has an OO interface.
210 =head1 Utility Changes
216 The Emacs perl mode (emacs/cperl-mode.el) has been updated to version 4.31.
220 The long-dormant perl bytecompiler has been added to the list of
221 installed utilities since the bytecompiler backend has been improved.
222 The bytecompiler is still very much experimental, though.
226 Perlbug is now much more robust. It also sends the bug report to perl.org,
231 The perlcc utility has been rewritten and its user interface (that is,
232 command line) is much more like that of the UNIX C compiler, cc.
236 The xsubpp utility for extension writers now understands POD
237 documentation embedded in the *.xs files.
241 =head1 New Documentation
247 perl56delta details the changes between the 5.005 release and the
252 perldebtut is a Perl debugging tutorial.
256 perlebcdic contains considerations for running Perl on EBCDIC platforms.
257 Note that unfortunately EBCDIC platforms that used to supported back in
258 Perl 5.005 are still unsupported by Perl 5.7.0; the plan, however, is to
259 bring them back to the fold.
263 perlnewmod tells about writing and submitting a new module.
267 perlposix-bc explains using Perl on the POSIX-BC platform
268 (a mainframe platform).
272 perlretut is a regular expression tutorial.
276 perlrequick is a regular expressions quick-start guide.
277 Yes, much quicker than perlretut.
281 perlutil explains the command line utilities packaged with the Perl
286 =head1 Performance Enhancements
288 map() that changes the size of the list should now work faster.
290 =head1 Installation and Configuration Improvements
292 =head2 Generic Improvements
298 INSTALL now explains how you can configure perl to use 64-bit
299 integers even on non-64-bit platforms.
303 Policy.sh policy change: if you are reusing a Policy.sh file (see
304 INSTALL) and you use Configure -Dprefix=/foo/bar and in the old
305 Policy $prefix eq $siteprefix and $prefix eq $vendorprefix, all of
306 them will now be changed to the new prefix, /foo/bar. (Previously
307 only $prefix changed.) If you do not like this new behaviour,
308 specify prefix, siteprefix, and vendorprefix explicitly.
312 A new optional location for Perl libraries, otherlibdirs, is available.
313 It can be used for example for vendor add-ons without disturbing Perl's
314 own library directories.
318 In many platforms the vendor-supplied 'cc' is too stripped-down to
319 build Perl (basically, 'cc' doesn't do ANSI C). If this seems
320 to be the case and 'cc' does not seem to be the GNU C compiler
321 'gcc', an automatic attempt is made to find and use 'gcc' instead.
325 gcc needs to closely track the operating system release to avoid
326 build problems. If Configure finds that gcc was built for a different
327 operating system release than is running, it now gives a clearly visible
328 warning that there may be trouble ahead.
332 If binary compatibility with the 5.005 release is not wanted, Configure
333 no longer suggests including the 5.005 modules in @INC.
337 Configure C<-S> can now run non-interactively.
341 configure.gnu now works with options with whitespace in them.
345 installperl now outputs everything to STDERR.
349 $Config{byteorder} is now computed dynamically (this is more robust
350 with "fat binaries" where an executable image contains binaries for
351 more than one binary platform.)
355 =head1 Selected Bug Fixes
361 Several debugger fixes: exit code now reflects the script exit code,
362 condition C<"0"> now treated correctly, the C<d> command now checks
363 line number, the C<$.> no longer gets corrupted, all debugger output now
364 goes correctly to the socket if RemotePort is set.
368 C<*foo{FORMAT}> now works.
372 Lexical warnings now propagating correctly between scopes.
376 Line renumbering with eval and C<#line> now works.
380 Fixed numerous memory leaks, especially in eval "".
384 Modulus of unsigned numbers now works (4063328477 % 65535 used to
385 return 27406, instead of 27047).
389 Some "not a number" warnings introduced in 5.6.0 eliminated to be
390 more compatible with 5.005. Infinity is now recognised as a number.
394 our() variables will not cause "will not stay shared" warnings.
398 pack "Z" now correctly terminates the string with "\0".
402 Fix password routines which in some shadow password platforms
403 (e.g. HP-UX) caused getpwent() to return every other entry.
407 printf() no longer resets the numeric locale to "C".
411 C<q(a\\b)> now parses correctly as C<'a\\b'>.
415 Printing quads (64-bit integers) with printf/sprintf now works
416 without q L ll prefixes (assuming you are on a quad-capable platform).
420 Regular expressions on references and overloaded scalars now work.
424 scalar() now forces scalar context even when used in void context.
428 sort() arguments are now compiled in the right wantarray context
429 (they were accidentally using the context of the sort() itself).
433 Changed the POSIX character class C<[[:space:]]> to include the (very
434 rare) vertical tab character. Added a new POSIX-ish character class
435 C<[[:blank:]]> which stands for horizontal whitespace (currently,
436 the space and the tab).
440 $AUTOLOAD, sort(), lock(), and spawning subprocesses
441 in multiple threads simultaneously are now thread-safe.
445 Allow read-only string on left hand side of non-modifying tr///.
449 Several Unicode fixes (but still not perfect).
455 BOMs (byte order marks) in the beginning of Perl files
456 (scripts, modules) should now be transparently skipped.
457 UTF16 encoded Perl files should now be read correctly.
461 The character tables have been updated to new Unicode 3.0 features.
465 chr() for values greater than 127 now create utf8 when under use
470 Comparing with utf8 data does not magically upgrade non-utf8 data into
475 C<IsAlnum>, C<IsAlpha>, and C<IsWord> now match titlecase.
479 Concatenation with the C<.> operator or via variable interpolation,
480 C<eq>, C<substr>, C<reverse>, C<quotemeta>, the C<x> operator,
481 substitution with C<s///>, single-quoted UTF8, should now work--in
486 The C<tr///> operator now works I<slightly> better but is still rather
487 broken. Note that the C<tr///CU> functionality has been removed (but
488 see pack('U0', ...)).
492 Zero entries were missing from the Unicode classes like C<IsDigit>.
498 UNIVERSAL::isa no longer caches methods incorrectly. (This broke
499 the Tk extension with 5.6.0.)
503 =head2 Platform Specific Changes and Fixes
511 Perl now works on post-4.0 BSD/OSes.
517 Setting C<$0> now works (as much as possible; see perlvar for details).
523 Numerous updates; currently synchronised with Cygwin 1.1.4.
529 EPOC update after Perl 5.6.0. See README.epoc.
535 Perl now works on post-3.0 FreeBSDs.
541 README.hpux updated; C<Configure -Duse64bitall> now almost works.
547 Numerous compilation flag and hint enhancements; accidental mixing
548 of 32-bit and 64-bit libraries (a doomed attempt) made much harder.
554 Long doubles should now work (see INSTALL).
560 Compilation of the standard Perl distribution in MacOS Classic should
561 now work if you have the Metrowerks development environment and
562 the missing Mac-specific toolkit bits. Contact the macperl mailing
569 MPE/iX update after Perl 5.6.0. See README.mpeix.
575 Perl now works on NetBSD/sparc.
581 Now works with usethreads (see INSTALL).
587 64-bitness using the Sun Workshop compiler now works.
591 Tru64 (aka Digital UNIX, aka DEC OSF/1)
593 The operating system version letter now recorded in $Config{osvers}.
594 Allow compiling with gcc (previously explicitly forbidden). Compiling
595 with gcc still not recommended because buggy code results, even with
602 Fixed various alignment problems that lead into core dumps either
603 during build or later; no longer dies on math errors at runtime;
604 now using full quad integers (64 bits), previously was using
605 only 46 bit integers for speed.
611 chdir() now works better despite a CRT bug; now works with MULTIPLICITY
612 (see INSTALL); now works with Perl's malloc.
622 accept() no longer leaks memory.
626 Better chdir() return value for a non-existent directory.
630 New %ENV entries now propagate to subprocesses.
634 $ENV{LIB} now used to search for libs under Visual C.
638 A failed (pseudo)fork now returns undef and sets errno to EAGAIN.
642 Allow REG_EXPAND_SZ keys in the registry.
646 Can now send() from all threads, not just the first one.
650 Fake signal handling reenabled, bugs and all.
654 Less stack reserved per thread so that more threads can run
655 concurrently. (still 16M perl thread)
659 C<File::Spec->tmpdir()> now prefers C:/temp over /tmp
660 (works better when perl running as service).
664 Better UNC path handling under ithreads.
668 wait() and waitpid() now work much better.
672 winsock handle leak fixed.
676 =head1 New or Changed Diagnostics
678 All regular expression compilation error messages are now hopefully
679 easier to understand both because the error message now comes before
680 the failed regex and because the point of failure is now clearly
683 The various "opened only for", "on closed", "never opened" warnings
684 drop the C<main::> prefix for filehandles in the C<main> package,
685 for example C<STDIN> instead of <main::STDIN>.
687 The "Unrecognized escape" warning has been extended to include C<\8>,
688 C<\9>, and C<\_>. There is no need to escape any of the C<\w> characters.
690 =head1 Changed Internals
696 perlapi.pod (a companion to perlguts) now attempts to document the
701 You can now build a really minimal perl called microperl.
702 Building microperl does not require even running Configure;
703 C<make -f Makefile.micro> should be enough. Beware: microperl makes
704 many assumptions, some of which may be too bold; the resulting
705 executable may crash or otherwise misbehave in wondrous ways. For
706 careful hackers only.
710 Added rsignal(), whichsig(), do_join() to the publicised API.
714 Made possible to propagate customised exceptions via croak()ing.
718 Added is_utf8_char(), is_utf8_string(), bytes_to_utf8(), and utf8_to_bytes().
722 Now xsubs can have attributes just like subs.
726 =head1 Known Problems
728 =head2 Unicode Support Still Far From Perfect
730 We're working on it. Stay tuned.
732 =head2 EBCDIC Still A Lost Platform
734 The plan is to bring them back.
736 =head2 Building Extensions Can Fail Because Of Largefiles
738 Certain extensions like mod_perl and BSD::Resource are known to have
739 issues with `largefiles', a change brought by Perl 5.6.0 in which file
740 offsets default to 64 bits wide where supported. Modules may fail to
741 compile at all or compile and work incorrectly. Currently there is no
742 good solution for the problem, but Configure now stores the relevant
743 flags and libraries in the %Config hash so the extensions that are having
744 problems can try configuring themselves without the largefileness.
745 This is admittedly not a clean solution.
749 =item In string, @%s now must be written as \@%s
751 (F) It used to be that Perl would try to guess whether you wanted an
752 array interpolated or a literal @. It did this when the string was
753 first used at runtime. Now strings are parsed at compile time, and
754 ambiguous instances of @ must be disambiguated, either by prepending a
755 backslash to indicate a literal, or by declaring (or using) the array
756 within the program before the string (lexically). (I<Someday it will
757 simply assume that an unbackslashed @ interpolates an array.>)
761 That day has arrived.
763 =head1 Reporting Bugs
765 If you find what you think is a bug, you might check the articles
766 recently posted to the comp.lang.perl.misc newsgroup and the perl
767 bug database at http://bugs.perl.org. There may also be
768 information at http://www.perl.com/perl/, the Perl Home Page.
770 If you believe you have an unreported bug, please run the B<perlbug>
771 program included with your release. Be sure to trim your bug down
772 to a tiny but sufficient test case. Your bug report, along with the
773 output of C<perl -V>, will be sent off to perlbug@perl.org to be
774 analysed by the Perl porting team.
778 The F<Changes> file for exhaustive details on what changed.
780 The F<INSTALL> file for how to build Perl.
782 The F<README> file for general stuff.
784 The F<Artistic> and F<Copying> files for copyright information.
788 Written by Jarkko Hietaniemi <F<jhi@iki.fi>>, with many contributions
789 from The Perl Porters and Perl Users submitting feedback and patches.
791 Send omissions or corrections to <F<perlbug@perl.org>>.