RFC: what are applicable standards for exponent sizes?

[p5sagit/p5-mst-13.2.git] / pod / perl572delta.pod

=head1 NAME

perl571delta - what's new for perl v5.7.2

=head1 DESCRIPTION

This document describes differences between the 5.7.1 release and the
5.7.2 release.  

(To view the differences between the 5.6.0 release and the 5.7.0
release, see L<perl570delta>.  To view the differences between the
5.7.0 release and the 5.7.1 release, see L<perl571delta>.)

=head1 Security Vulnerability Closed

(This change was already made in 5.7.0 but bears repeating here.)

A security vulnerability affecting all Perl versions prior to 5.6.1
was found in August 2000.  The vulnerability does not affect default
installations and as far as is known affects only the Linux platform.

You should upgrade your Perl to 5.6.1 as soon as possible.  Patches
for earlier releases exist but using the patches require full
recompilation from the source code anyway, so 5.6.1 is your best
choice.

See http://www.cpan.org/src/5.0/sperl-2000-08-05/sperl-2000-08-05.txt
for more information.

=head1 Incompatible Changes

=head2 64-bit platforms and malloc

If your pointers are 64 bits wide, the Perl malloc is no more being
used because it simply does not work with 8-byte pointers.  Also,
usually the system malloc on such platforms are much better optimized
for such large memory models than the Perl malloc.

=head2 Future Deprecations

The current user-visible implementation of pseudo-hashes (the weird
use of the first array element) is deprecated starting from Perl 5.8.0
and will be removed in Perl 5.10.0, and the feature will be implemented
differently.  Not only is the current interface rather ugly, but the
current implementation slows down normal array and hash use quite
noticeably. The 'fields' pragma interface will remain available.

The suidperl is also considered to be too much a risk to continue
maintaining and the suidperl code is likely to be removed in a future
release.

=head1 Core Enhancements

In general a lot of fixing has happened in the area of Perl's understanding
of numbers, both integer and floating point.  Since in many systems the
standard number parsing functions like C<strtoul()> and C<atof()> seem
to have bugs, Perl tries to work around their deficiencies.  This results
hopefully in more accurate numbers.

=over 4

=item *

The rules for allowing underscores (underbars) in numeric constants
have been relaxed and simplified: now you can have an underscore
B<between digits>.

=item *

VMS now works under PerlIO.

=item *

GMAGIC (right-hand side magic) could in many cases such as concatenation
of string be invoked too many times.

=item *

The MAGIC constants (e.g. C<'P'>) have been macrofied
(e.g. C<PERL_MAGIC_TIED>) for better source code readability
and maintainability.

=item *

The C<op_clear> and C<op_null> are now exported.

=item *

L<utime> now supports C<utime undef, undef, @files> to change the
times to the current time.

=item *

The Perl parser has been stress tested using both random input and
Markov chain input.

=back

=head1 Modules and Pragmata

=head2 New Modules and Distribution

=over 4

=item *

L<Attribute::Handlers> - Simpler definition of attribute handlers

=item *

L<ExtUtils::Constant> - generate XS code to import C header constants

=item *

L<I18N::LangTags> - functions for dealing with RFC3066-style language tags

=item *

L<libnet> - a collection of perl5 modules related to network programming

=item *

L<List::Util> - selection of general-utility list subroutines

=item *

L<Locale::Maketext> - framework for localization

=item *

L<Memoize> - Make your functions faster by trading space for time

=item *

L<NEXT> - pseudo-class for method redispatch

=item *

L<Scalar::Util> - selection of general-utility scalar subroutines

=item *

L<Time::HiRes> - high resolution ualarm, usleep, and gettimeofday

=item *

L<Time::Piece> - Object Oriented time objects

=back

=head2 Updated And Improved Modules and Pragmata

=over 4

=item *

L<B::Deparse> module has been significantly enhanced.  It now
can deparse almost all of the standard test suite (so that the
tests still succeed).  There is a make target "test.deparse"
for trying this out.

=item *

L<Class::Struct> now assigns the array/hash element if the accessor
is called with an array/hash element as the B<sole> argument.

=item *

L<Cwd> extension is now (even) faster.

=item *

L<DB_File> extension has been updated to version 1.77.

=item *

L<Fcntl>, L<Socket>, and L<Sys::Syslog> have been rewritten to use the
new-style constant dispatch section (see L<ExtUtils::Constant>).

=item *

L<File::Find> is now (again) reentrant.  It also has been made
more portable.

=item *

L<File::Glob> now supports C<GLOB_LIMIT> constant to limit the
size of the returned list of filenames.

=item *

L<vars> now supports declaring qualified variables.

=back

=head1 Utility Changes

=over 4

=item *

The F<emacs/e2ctags.pl> is now much faster.

=item *

L<h2xs> uses the new L<ExtUtils::Constant> module which will affect
newly created extensions that define constants.  Since the new code is
more correct (if you have two constants where the first one is a
prefix of the second one, the first constant B<never> gets defined),
less lossy (it uses integers for integer constant, as opposed to the
old code that used floating point numbers even for integer constants),
and slightly faster, you might want to consider regenerating your
extension code (the new scheme makes regenerating easy).

=item *

L<libnetcfg> has been added to configure the libnet.

=item *

The F<Pod::Html> (and thusly L<pod2html>) now allows specifying
a cache directory.

=back

=head1 New Documentation

=over 4

=item *

L<Locale::Maketext::TPJ13> is an article about software localization,
originally published in The Perl Journal #13, republished here with
kind permission.

=item *

More README.$PLATFORM files have been converted into pod, which also
means that they also be installed as perl$PLATFORM documentation
files.  The new files are L<perlapollo>, L<perlbeos>, L<perldgux>,
L<perlhurd>, L<perlmint>, L<perlnetware>, L<perlplan9>, L<perlqnx>,
and L<perltru64>.

=item *

The F<Todo> and F<Todo-5.6> files have been merged into L<perltodo>.

=item *

Use of the F<gprof> tool to profile Perl has been documented in
L<perlhack>.  There is a make target "perl.gprof" for generating a
gprofiled Perl executable.

=back

=head1 Installation and Configuration Improvements

=head2 New Or Improved Platforms

=over 4

=item *

AIX should now work better with gcc.  Also longdouble support in AIX
should be better now.  See L<perlaix>.

=item *

AtheOS (http://www.atheos.cx/) is a new platform.

=item *

DG/UX platform now supports the 5.005-style threads.  See L<perldgux>.

=item *

Several MacOS (Classic) portability patches have been applied.  We
hope to get a fully working port by 5.8.0.  (The remaining problems
relate to the changed IO model of Perl.)  See L<perlmacos>.

=item *

MacOS X (or Darwin) should now be able to build Perl even on HFS+
filesystems.  (The case-insensitivity confused the Perl build process.)

=item *

NetWare from Novell is now supported.  See L<perlnetware>.

=item *

The Amdahl UTS UNIX mainframe platform is now supported.

=back

=head2 Generic Improvements

=over 4

=item *

The C code has been made much more C<gcc -Wall> clean.  Some warning
messages still remain, though, so if you are compiling with gcc you
will see some warnings about dubious practices.  The warnings are
being worked on.

=item *

In AFS installations one can configure the root of the AFS to be
somewhere else than the default F</afs> by using the Configure
parameter C<-Dafsroot=/some/where/else>.

=item *

The version of Berkeley DB used when the Perl (and, presumably, the
DB_File extension) was built is now available as
C<@Config{qw(db_version_major db_version_minor db_version_patch)}>
from Perl and as C<DB_VERSION_MAJOR_CFG DB_VERSION_MINOR_CFG
DB_VERSION_PATCH_CFG> from C.

=item *

The Thread extension is now not built at all under ithreads
(C<Configure -Duseithreads>) because it wouldn't work anyway (the
Thread extension requires being Configured with C<-Duse5005threads>).

=item *

The C<B::Deparse> compiler backend has been so significantly improved
that almost the whole Perl test suite passes after being deparsed.  A
make target has been added to help in further testing: C<make test.deparse>.

=back

=head1 Selected Bug Fixes

=over 5

=item *

The autouse pragma didn't work for Multi::Part::Function::Names.

=item *

The behaviour of non-decimal but numeric string constants such as
"0x23" was platform-dependent: in some platforms that was seen as 35,
in some as 0, in some as a floating point number (don't ask).  This
was caused by Perl using the operating system libraries in a situation
where the result of the string to number conversion is undefined: now
Perl consistently handles such strings as zero in numeric contexts.

=item *

L<dprofpp> -R didn't work.

=item *

PERL5OPT with embedded spaces didn't work.

=item *

L<Sys::Syslog> ignored the C<LOG_AUTH> constant.

=back

=head2 Platform Specific Changes and Fixes

=over 4

=item *

Some versions of glibc have a broken modfl().  This affects builds
with C<-Duselongdouble>.  This version of Perl detects this brokenness
and has a workaround for it.  The glibc release 2.2.2 is known to have
fixed the modfl() bug.

=back

=head1 New or Changed Diagnostics

=over 4

=item *

In the regular expression diagnostics the C<E<lt>E<lt> HERE> marker
introduced in 5.7.0 has been changed to be C<E<lt>-- HERE> since too
many people found the C<E<lt>E<lt>> to be too similar to here-document
starters.

=item *

If you try to L<perlfunc/pack> a number less than 0 or larger than 255
using the C<"C"> format you will get an optional warning.  Similarly
for the C<"c"> format and a number less than -128 or more than 127.

=item *

Certain regex modifiers such as C<(?o)> make sense only if applied to
the entire regex.  You will an optional warning if you try to do otherwise.

=item *

Using arrays or hashes as references (e.g. C<%foo->{bar}> has been
deprecated for a while.  Now you will get an optional warning.

=back

=head1 Changed Internals

=head2 Regex pre-/post-compilation items matched up

The regex compiler now maintains a structure that identifies nodes in
the compiled bytecode with the corresponding syntactic features of the
original regex expression.  The information is attached to the new
C<offsets> member of the C<struct regexp>. See L<perldebguts> for more
complete information.

=head1 New Tests

Several new tests have been added, especially for the F<lib> subsection.

The tests are now reported in a different order than in earlier Perls.
(This happens because the test scripts from under t/lib have been moved
to be closer to the library/extension they are testing.)

=head1 Known Problems

Note that unlike other sections in this document (which describe
changes since 5.7.0) this section is cumulative containing known
problems for all the 5.7 releases.

=head2 AIX vac 5.0.0.0 May Produce Buggy Code For Perl

The AIX C compiler vac version 5.0.0.0 may produce buggy code,
resulting in few random tests failing, but when the failing tests
are run by hand, they succeed.  We suggest upgrading to at least
vac version 5.0.1.0, that has been known to compile Perl correctly.
"lslpp -L|grep vac.C" will tell you the vac version.

=head2 lib/ftmp-security tests warn 'system possibly insecure'

Don't panic.  Read INSTALL 'make test' section instead.

=head2 lib/io_multihomed Fails In LP64-Configured HP-UX

The lib/io_multihomed test may hang in HP-UX if Perl has been
configured to be 64-bit. Because other 64-bit platforms do not hang in
this test, HP-UX is suspect. All other tests pass in 64-bit HP-UX. The
test attempts to create and connect to "multihomed" sockets (sockets
which have multiple IP addresses).

=head2 Test lib/posix Subtest 9 Fails In LP64-Configured HP-UX

If perl is configured with -Duse64bitall, the successful result of the
subtest 10 of lib/posix may arrive before the successful result of the
subtest 9, which confuses the test harness so much that it thinks the
subtest 9 failed.

=head2 lib/b test 19

The test fails on various platforms (PA64 and IA64 are known), but the
exact cause is still being investigated.

=head2 Linux With Sfio Fails op/misc Test 48

No known fix.

=head2 sigaction test 13 in VMS

The test is known to fail; whether it's because of VMS of because
of faulty test is not known.

=head2 sprintf tests 129 and 130

The op/sprintf tests 129 and 130 are known to fail on some platforms.
Examples include any platform using sfio, and Compaq/Tandem's NonStop-UX.
The failing platforms do not comply with the ANSI C Standard, line
19ff on page 134 of ANSI X3.159 1989 to be exact.  (They produce
something else than "1" and "-1" when formatting 0.6 and -0.6 using
the printf format "%.0f", most often they produce "0" and "-0".)

=head2  Failure of Thread tests

B<Note that support for 5.005-style threading remains experimental.>

The following tests are known to fail due to fundamental problems in
the 5.005 threading implementation. These are not new failures--Perl
5.005_0x has the same bugs, but didn't have these tests.

lib/Memoize/t/correctness.t  23-25
lib/Memoize/t/unmemoize.t    2-5
t/pragma/autouse.t           4
t/lib/thr5005.t              19-20

=head2 Localising a Tied Variable Leaks Memory

    use Tie::Hash;
    tie my %tie_hash => 'Tie::StdHash';

    ...

    local($tie_hash{Foo}) = 1; # leaks

Code like the above is known to leak memory every time the local()
is executed.

=head2 Self-tying of Arrays and Hashes Is Forbidden

Self-tying of arrays and hashes is broken in rather deep and
hard-to-fix ways.  As a stop-gap measure to avoid people from getting
frustrated at the mysterious results (core dumps, most often) it is
for now forbidden (you will get a fatal error even from an attempt).

=head2 Variable Attributes are not Currently Usable for Tieing

This limitation will hopefully be fixed in future.  (Subroutine
attributes work fine for tieing, see L<Attribute::Handlers>).

=head2 Building Extensions Can Fail Because Of Largefiles

Some extensions like mod_perl are known to have issues with
`largefiles', a change brought by Perl 5.6.0 in which file offsets
default to 64 bits wide, where supported.  Modules may fail to compile
at all or compile and work incorrectly.  Currently there is no good
solution for the problem, but Configure now provides appropriate
non-largefile ccflags, ldflags, libswanted, and libs in the %Config
hash (e.g., $Config{ccflags_nolargefiles}) so the extensions that are
having problems can try configuring themselves without the
largefileness.  This is admittedly not a clean solution, and the
solution may not even work at all.  One potential failure is whether
one can (or, if one can, whether it's a good idea) link together at
all binaries with different ideas about file offsets, all this is
platform-dependent.

=head2 The Compiler Suite Is Still Experimental

The compiler suite is slowly getting better but is nowhere near
working order yet.

=head1 Reporting Bugs

If you find what you think is a bug, you might check the articles
recently posted to the comp.lang.perl.misc newsgroup and the perl
bug database at http://bugs.perl.org.  There may also be
information at http://www.perl.com/perl/, the Perl Home Page.

If you believe you have an unreported bug, please run the B<perlbug>
program included with your release.  Be sure to trim your bug down
to a tiny but sufficient test case.  Your bug report, along with the
output of C<perl -V>, will be sent off to perlbug@perl.org to be
analysed by the Perl porting team.

=head1 SEE ALSO

The F<Changes> file for exhaustive details on what changed.

The F<INSTALL> file for how to build Perl.

The F<README> file for general stuff.

The F<Artistic> and F<Copying> files for copyright information.

=head1 HISTORY

Written by Jarkko Hietaniemi <F<jhi@iki.fi>>, with many contributions
from The Perl Porters and Perl Users submitting feedback and patches.

Send omissions or corrections to <F<perlbug@perl.org>>.

=cut