3 perl571delta - what's new for perl v5.7.1
7 This document describes differences between the 5.7.0 release and the
10 (To view the differences between the 5.6.0 release and the 5.7.0
11 release, see L<perl570delta>).
13 =head1 Security Vulnerability Closed
15 (This change was already made in 5.7.0 but bears repeating here.)
17 A potential security vulnerability in the optional suidperl component
18 of Perl was identified in August 2000. suidperl is neither built nor
19 installed by default. As of April 2001 the only known vulnerable
20 platform is Linux, most likely all Linux distributions. CERT and
21 various vendors and distributors have been alerted about the vulnerability.
22 See http://www.cpan.org/src/5.0/sperl-2000-08-05/sperl-2000-08-05.txt
25 The problem was caused by Perl trying to report a suspected security
26 exploit attempt using an external program, /bin/mail. On Linux
27 platforms the /bin/mail program had an undocumented feature which
28 when combined with suidperl gave access to a root shell, resulting in
29 a serious compromise instead of reporting the exploit attempt. If you
30 don't have /bin/mail, or if you have 'safe setuid scripts', or if
31 suidperl is not installed, you are safe.
33 The exploit attempt reporting feature has been completely removed from
34 all the Perl 5.7 releases (and will be gone also from the maintenance
35 release 5.6.1), so that particular vulnerability isn't there anymore.
36 However, further security vulnerabilities are, unfortunately, always
37 possible. The suidperl code is being reviewed and if deemed too risky
38 to continue to be supported, it may be completely removed from future
39 releases. In any case, suidperl should only be used by security
40 experts who know exactly what they are doing and why they are using
41 suidperl instead of some other solution such as sudo (see
42 http://www.courtesan.com/sudo/).
44 =head1 Incompatible Changes
50 Although "you shouldn't do that", it was possible to write code that
51 depends on Perl's hashed key order (Data::Dumper does this). The new
52 algorithm "One-at-a-Time" produces a different hashed key order.
53 More details are in L</"Performance Enhancements">.
57 The list of filenames from glob() (or <...>) is now by default sorted
58 alphabetically to be csh-compliant. (bsd_glob() does still sort platform
59 natively, ASCII or EBCDIC, unless GLOB_ALPHASORT is specified.)
63 =head1 Core Enhancements
69 AUTOLOAD is now lvaluable, meaning that you can add the :lvalue attribute
70 to AUTOLOAD subroutines and you can assign to the AUTOLOAD return value.
74 IO is now by default done via PerlIO rather than system's "stdio".
75 PerlIO allows "layers" to be "pushed" onto a file handle to alter the
76 handle's behaviour. Layers can be specified at open time via 3-arg
79 open($fh,'>:crlf :utf8', $path) || ...
81 or on already opened handles via extended C<binmode>:
83 binmode($fh,':encoding(iso-8859-7)');
85 The built-in layers are: unix (low level read/write), stdio (as in
86 previous Perls), perlio (re-implementation of stdio buffering in a
87 portable manner), crlf (does CRLF <=> "\n" translation as on Win32,
88 but available on any platform). A mmap layer may be available if
89 platform supports it (mostly UNIXes).
91 Layers to be applied by default may be specified via the 'open' pragma.
93 See L</"Installation and Configuration Improvements"> for the effects
94 of PerlIO on your architecture name.
98 File handles can be marked as accepting Perl's internal encoding of Unicode
99 (UTF-8 or UTF-EBCDIC depending on platform) by a pseudo layer ":utf8" :
101 open($fh,">:utf8","Uni.txt");
103 Note for EBCDIC users: the pseudo layer ":utf8" is badly named for you
104 since it's not UTF-8 what you will be getting but instead UTF-EBCDIC.
105 See http://www.unicode.org/unicode/reports/tr16/ for more information.
106 In future release this naming issue may or may not change.
110 File handles can translate character encodings from/to Perl's internal
111 Unicode form on read/write via the ":encoding()" layer.
115 File handles can be opened to "in memory" files held in Perl scalars via:
117 open($fh,'>', \$variable) || ...
121 Anonymous temporary files are available without need to
122 'use FileHandle' or other module via
124 open($fh,"+>", undef) || ...
126 That is a literal undef, not an undefined value.
130 The list form of C<open> is now implemented for pipes (at least on UNIX):
132 open($fh,"-|", 'cat', '/etc/motd')
134 creates a pipe, and runs the equivalent of exec('cat', '/etc/motd') in
139 The following builtin functions are now overrideable: chop(), chomp(),
140 each(), keys(), pop(), push(), shift(), splice(), unshift().
144 Formats now support zero-padded decimal fields.
148 Perl now tries internally to use integer values in numeric conversions
149 and basic arithmetics (+ - * /) if the arguments are integers, and
150 tries also to keep the results stored internally as integers.
151 This change leads into often slightly faster and always less lossy
152 arithmetics (previously Perl always preferred floating point numbers
157 The printf() and sprintf() now support parameter reordering using the
158 C<%\d+\$> and C<*\d+\$> syntaxes. For example
160 print "%2\$s %1\$s\n", "foo", "bar";
162 will print "bar foo\n"; This feature helps in writing
163 internationalised software.
167 Unicode in general should be now much more usable. Unicode can be
168 used in hash keys, Unicode in regular expressions should work now,
169 Unicode in tr/// should work now (though tr/// seems to be a
170 particularly tricky to get right, so you have been warned)
174 The Unicode Character Database coming with Perl has been upgraded
175 to Unicode 3.1. For more information, see http://www.unicode.org/,
176 and http://www.unicode.org/unicode/reports/tr27/
178 For developers interested in enhanching Perl's Unicode capabilities:
179 almost all the UCD files are included with the Perl distribution in
180 the lib/unicode subdirectory. The most notable omission, for space
181 considerations, is the Unihan database.
185 The Unicode character classes \p{Blank} and \p{SpacePerl} have been
186 added. "Blank" is like C isblank(), that is, it contains only
187 "horizontal whitespace" (the space character is, the newline isn't),
188 and the "SpacePerl" is the Unicode equivalent of C<\s> (\p{Space}
189 isn't, since that includes the vertical tabulator character, whereas
194 =head2 Modules and Pragmata
202 B::Concise is a new compiler backend for walking the Perl syntax tree,
203 printing concise info about ops. The output is highly customisable,
204 so customisable that B::Terse has been re-implemented in terms of
209 Class::ISA for reporting the search path for a class's ISA tree,
210 from Sean Burke, has been added.
214 Cwd has now a split personality: if possible, an extension is used,
215 (this will hopefully be both faster and more secure and robust) but
216 if not possible, the familiar Perl library implementation is used.
220 Digest, a frontend module for calculating digests (checksums),
221 from Gisle Aas, has been added.
225 Digest::MD5 for calculating MD5 digests (checksums), from Gisle Aas,
228 NOTE: the MD5 backward compatibility module is purposefully not
229 included since its use is discouraged.
233 Encode provides a mechanism to translate between different character
234 encodings. Support for Unicode, ISO-8859-*, ASCII, CP*, KOI8-R, and
235 three variants of EBCDIC are compiled in to the module. Several other
236 encodings (like Japanese, Chinese, and MacIntosh encodings) are
237 included and will be loaded at runtime.
239 Any encoding supported by Encode module is also available to the
240 ":encoding()" layer if PerlIO is used.
244 Filter::Simple is an easy-to-use frontend to Filter::Util::Call,
249 Filter::Util::Call, from Paul Marquess, provides you with the
250 framework to write I<Source Filters> in Perl. For most uses
251 the frontend Filter::Simple is to be preferred.
255 Locale::Constants, Locale::Country, Locale::Currency, and Locale::Language,
256 from Neil Bowers, have been added. They provide the codes for various
257 locale standards, such as "fr" for France, "usd" for US Dollar, and
262 MIME::Base64, from Gisle Aas, allows you to encode data in base64.
266 MIME::QuotedPrint, from Gisle Aas, allows you to encode data in
267 quoted-printable encoding.
269 MIME::QuotedPrint has been enhanced to provide the basic methods
270 necessary to use it with PerlIO::Via as in :
272 use MIME::QuotedPrint;
273 open($fh,">Via(MIME::QuotedPrint)",$path)
277 PerlIO::Scalar provides the IO to "in memory" perl scalars discussed
278 above. It also serves as an example of a loadable layer.
282 PerlIO::Via acts as a PerlIO layer and wraps PerlIO layer
283 functionality provided by a class (typically implemented in
288 Pod::Text::Overstrike, from Joe Smith, has been added.
289 It converts POD data to formatted overstrike text.
293 Switch from Damian Conway has been added. Just by saying
297 you have C<switch> and C<case> available in Perl.
301 Text::Balanced from Damian Conway has been added, for
302 extracting delimited text sequences from strings.
306 Tie::RefHash::Nestable, from Edward Avis, allows storing hash references
307 (unlike the standard Tie::Refhash)
311 XS::Typemap is a test extension that exercises XS typemaps.
312 Nothing gets installed but for extension writers the code is
317 =head2 Updated And Improved Modules and Pragmata
323 B::Deparse should be now more robust (still far from providing a full
324 round trip for any random piece of Perl code).
328 Class::Struct has now compile-time features.
332 Math::BigFloat has undergone much fixing. (The fixed Math::BigFloat
333 module is also available in CPAN for those who can't upgrade their Perl:
334 http://www.cpan.org/authors/id/J/JP/JPEACOCK/)
338 Devel::Peek now has an interface for the Perl memory statistics
339 (this works only if you are using perl's malloc, and if you have
340 compiled with debugging).
344 IO::Socket has now atmark() method, which returns true if the socket
345 is positioned at the out-of-band mark. The method is also exportable
346 as a sockatmark() function.
350 IO::Socket::INET has support for ReusePort option (if your platform
351 supports it). The Reuse option has now an alias, ReuseAddr.
355 Net::Ping has been greatly enhanced.
359 The C<open> pragma allows layers other than ":raw" and ":crlf" when
364 POSIX::sigaction() is now much more flexible and robust.
368 The Test module has been significantly enhanced. Its use is
369 greatly recommended for module writers.
373 The utf8:: name space (as in the pragma) provides various
374 Perl-callable functions to provide low level access to Perl's
375 internal Unicode representation. At the moment only length()
376 has been implemented.
380 The following modules have been upgraded from the versions at CPAN:
381 CPAN, CGI, DB::File, Getopt::Long, Pod::Man, Pod::Text, Storable,
384 =head1 Performance Enhancements
390 Hashes now use Bob Jenkins "One-at-a-Time" hashing key algorithm
391 (http://burtleburtle.net/bob/hash/doobs.html).
392 This algorithm is reasonably fast while producing a much better spread
393 of values. Hash values output from the algorithm on a hash of all
394 3-char printable ASCII keys comes much closer to passing the DIEHARD
395 random number generation tests. According to perlbench, this change
396 has not affected the overall speed of Perl.
400 unshift() should now be noticeably faster.
404 =head1 Utility Changes
410 h2xs now produces template README.
414 s2p has been completely rewritten in Perl. (It is in fact a full
415 implementation of sed in Perl.)
419 xsubpp now supports OUT keyword.
423 =head1 New Documentation
427 Internal replacements for standard C library functions.
428 (Interesting only for extension writers and Perl core hackers.)
432 Internals of PerlIO with layers.
436 Documentation on compiling Perl on AIX has been added. AIX has
437 several different C compilers and getting the right patch level
438 is essential. On install README.aix will be installed as L<perlaix>.
442 Documentation on compiling Perl on the POSIX-BC platform (an EBCDIC
443 mainframe environment) has been added.
445 This was formerly known as README.posix-bc but the name was considered
446 to be too confusing (it has nothing to do with the POSIX module or the
447 POSIX standard). On install README.bs2000 will be installed as L<perlbs2000>.
451 In perl 5.7.1 (and in the 5.6.1) the MacPerl sources have been
452 synchronised with the standard Perl sources. To compile MacPerl
453 some additional steps are required, and this file documents those
454 steps. On install README.macos will be installed as L<perlmacos>.
458 The README.mpeix has been podified, which means that this information
459 about compiling and using Perl on the MPE/iX miniframe platform will
460 be installed as L<perlmpeix>.
462 =head2 README.solaris
464 README.solaris has been created and Solaris wisdom from elsewhere
465 in the Perl documentation has been collected there. On install
466 README.solaris will be installed as L<perlsolaris>.
470 The README.vos has been podified, which means that this information
471 about compiling and using Perl on the Stratus VOS miniframe platform
472 will be installed as L<perlvos>.
474 =head2 Porting/repository.pod
476 Documentation on how to use the Perl source repository has been added.
478 =head1 Performance Enhancements
480 =head1 Installation and Configuration Improvements
486 Because PerlIO is now the default on most platforms, "-perlio" doesn't
487 get appended to the $Config{archname} (also known as $^O) anymore.
488 Instead, if you explicitly choose not to use perlio (Configure command
489 line option -Uuseperlio), you will get "-stdio" appended.
493 Another change related to the architecture name is that "-64all"
494 (-Duse64bitall, or "maximally 64-bit") is appended only if your pointers
499 APPLLIB_EXP, a less-know configuration-time definition, has been
500 documented. It can be used to prepend site-specific directories
501 to Perl's default search path (@INC), see INSTALL for information.
505 Building Berkeley DB3 for compatibility modes for DB, NDBM, and ODBM
506 has been documented in INSTALL.
510 If you are on IRIX or Tru64 platforms, new profiling/debugging options
511 have been added, see L</perlhack> for more information about pixie and
516 =head2 New Or Improved Platforms
518 For the list of platforms known to support Perl,
519 see L<perlport/"Supported Platforms">.
525 AIX dynamic loading should be now better supported.
529 After a long pause, AmigaOS has been verified to be happy with Perl.
533 EBCDIC platforms (z/OS, also known as OS/390, POSIX-BC, and VM/ESA)
534 have been regained. Many test suite tests still fail and the
535 co-existence of Unicode and EBCDIC isn't quite settled, but the
536 situation is much better than with Perl 5.6. See L<perlos390>,
537 L<perlbs2000> (for POSIX-BC), and L<perlvmesa> for more information.
541 In HP-UX 10.20 Perl threading is now working with the various threading
542 packages available for HP-UX. See L<perlhpux> (or in the source
543 distribution, README.hpux) for more information.
547 MacOS Classic (MacPerl has of course been available since
548 perl 5.004 but now the source code bases of standard Perl
549 and MacPerl have been synchronised)
565 z/OS (formerly known as OS/390, formerly known as MVS OE) has now
566 support for dynamic loading. This is not selected by default,
567 however, you must specify -Dusedl in the arguments of Configure.
571 =head2 Generic Improvements
577 Configure no longer includes the DBM libraries (dbm, gdbm, db, ndbm)
578 when building the Perl binary. The only exception to this is SunOS 4.x,
583 Some new Configure symbols, useful for extension writers:
591 =item d_fcntl_can_lock
593 Whether fcntl() can be used for file locking.
601 For getpagesize(), though you should prefer POSIX::sysconf(_SC_PAGE_SIZE))
609 Whether one needs to use Perl_va_copy() to copy varargs.
619 The number of elements in an array needed to hold all the available signals.
627 Whether one needs to access character data aligned by U32 sized pointers.
637 Removed Configure symbols: the PDP-11 memory model settings: huge,
638 large, medium, models.
642 SOCKS support is now much more robust.
646 If your file system supports symbolic links you can build Perl outside
647 of the source directory by
649 mkdir /tmp/perl/build/directory
650 cd /tmp/perl/build/directory
651 sh /path/to/perl/source/Configure -Dmksymlinks ...
653 This will create in /tmp/perl/build/directory a tree of symbolic links
654 pointing to files in /path/to/perl/source. The original files are left
655 unaffected. After Configure has finished you can just say
659 and Perl will be built and tested, all in /tmp/perl/build/directory.
663 =head1 Selected Bug Fixes
665 Numerous memory leaks have been hunted down. Most importantly anonymous
666 subs used to leak quite a bit.
672 The order of DESTROYS has been made more predictable.
676 mkdir() now ignores trailing slashes in the directory name,
677 as mandated by POSIX.
681 Attributes (like :shared) didn't work with our().
685 The PERL5OPT environment variable (for passing command line arguments
686 to Perl) didn't work for more than a single group of options.
690 All but the first argument of the IO syswrite() method are now optional.
694 Tie::ARRAY SPLICE method was broken.
698 vec() now tries to work with characters <= 255 when possible, but it leaves
699 higher character values in place. In that case, if vec() was used to modify
700 the string, it is no longer considered to be utf8-encoded.
704 =head2 Platform Specific Changes and Fixes
710 Linux previously had problems related to sockaddrlen when using
711 accept(), revcfrom() (in Perl: recv()), getpeername(), and getsockname().
715 Previously DYNIX/ptx had problems in its Configure probe for non-blocking I/O.
719 =head1 New or Changed Diagnostics
721 Two new debugging options have been added: if you have compiled your
722 Perl with debugging, you can use the -DT and -DR options to trace
723 tokenising and to add reference counts to displaying variables,
730 If an attempt to use a (non-blessed) reference as an array element
731 is made, a warning is given.
735 C<push @a;> and C<unshift @a;> (with no values to push or unshift)
736 now give a warning. This may be a problem for generated and evaled
741 =head1 Changed Internals
747 Some new APIs: ptr_table_clear(), ptr_table_free(), sv_setref_uv().
748 For the full list of the available APIs see L<perlapi>.
752 dTHR and djSP have been obsoleted; the former removed (because it's
753 a no-op) and the latter replaced with dSP.
757 Perl now uses system malloc instead of Perl malloc in all 64-bit
758 platforms. This change breaks backward compatibility but Perl's
759 malloc has problems with large address spaces and also the speed of
760 vendors' malloc is generally better in large address space machines
761 (Perl's malloc is mostly tuned for space).
765 =head1 Known Problems
769 The test fails in various platforms (PA64 and IA64 are known), but the
770 exact cause is still being investigated.
772 =head2 Localising a Tied Variable Leaks Memory
775 tie my %tie_hash => 'Tie::StdHash';
779 local($tie_hash{Foo}) = 1; # leaks
781 Code like the above is known to leak memory every time the local()
784 =head2 sigaction test 13 in VMS
786 The test is known to fail, whether it's because of VMS of because
787 of faulty test, is not known.
789 =head2 sprintf tests 129 and 130
791 The op/sprintf tests 129 and 130 are known to fail in some platforms.
792 Examples include any platform using sfio, and Tandem's NonStop-UX.
793 The failing platforms do not comply with the ANSI C Standard, line
794 19ff on page 134 of ANSI X3.159 1989 to be exact. (They produce
795 something else than "1" and "-1" when formatting 0.6 and -0.6 using
796 the printf format "%.0f", most often they produce "0" and "-0".)
798 =head2 Self-tying of Arrays and Hashes Is Forbidden
800 Self-tying of arrays and hashes is broken in rather deep and
801 hard-to-fix ways. As a stop-gap measure to avoid people from getting
802 frustrated at the mysterious results (core dumps, most often) it is
803 for now forbidden (you will get a fatal error even from an attempt).
805 =head1 Reporting Bugs
807 If you find what you think is a bug, you might check the articles
808 recently posted to the comp.lang.perl.misc newsgroup and the perl
809 bug database at http://bugs.perl.org. There may also be
810 information at http://www.perl.com/perl/, the Perl Home Page.
812 If you believe you have an unreported bug, please run the B<perlbug>
813 program included with your release. Be sure to trim your bug down
814 to a tiny but sufficient test case. Your bug report, along with the
815 output of C<perl -V>, will be sent off to perlbug@perl.org to be
816 analysed by the Perl porting team.
820 The F<Changes> file for exhaustive details on what changed.
822 The F<INSTALL> file for how to build Perl.
824 The F<README> file for general stuff.
826 The F<Artistic> and F<Copying> files for copyright information.
830 Written by Jarkko Hietaniemi <F<jhi@iki.fi>>, with many contributions
831 from The Perl Porters and Perl Users submitting feedback and patches.
833 Send omissions or corrections to <F<perlbug@perl.org>>.