path: root/pod/perl51311delta.pod

=encoding utf8

=head1 NAME

perl51311delta - what is new for perl v5.13.11

=head1 DESCRIPTION

This document describes differences between the 5.13.10 release and
the 5.13.11 release.

If you are upgrading from an earlier release such as 5.13.9, first read
L<perl5139delta>, which describes differences between 5.13.9 and
5.13.10.

=head1 Security

=head2 User-defined regular expression properties

Perl no longer allows a tainted regular expression to invoke a user-defined
property via C<\p{...}> syntax. It simply dies instead [perl #82616].

=head1 Incompatible Changes

=head2 local($_) will strip all magic from $_

local() on scalar variables will give them a new value, but keep all
their magic intact.  This has proven to be problematic for the default
scalar variable $_, where L<perlsub> recommends that any subroutine
that assigns to $_ should localize it first.  This would throw an
exception if $_ is aliased to a read-only variable, and could have
various unintentional side-effects in general.

Therefore, as an exception to the general rule, local($_) will not
only assign a new value to $_, but also remove all existing magic from
it as well.

=head2 Passing references to warn()

An earlier Perl 5.13.x release changed C<warn($ref)> to leave the reference
unchanged, allowing C<$SIG{__WARN__}> handlers to access the original
reference. But this stopped warnings that were references from having the
file and line number appended even when there was no C<$SIG{__WARN__}>
handler in place.

Now C<warn> checks for the presence of such a handler and, if there is
none, proceeds to stringify the reference and append the file and line
number. This allows simple uses of C<warn> for debugging to continue to
work as they did before.

=head2 fork() emulation will not wait for signalled children

On Windows parent processes would not terminate until all forked
childred had terminated first.  However, C<kill('KILL', ...)> is
inherently unstable on pseudo-processes, and C<kill('TERM', ...)>
might not get delivered if the child if blocked in a system call.

To avoid the deadlock and still provide a safe mechanism to terminate
the hosting process, Perl will now no longer wait for children that
have been sent a SIGTERM signal.  It is up to the parent process to
waitpid() for these children if child clean-up processing must be
allowed to finish. However, it is also the responsibility of the
parent then to avoid the deadlock by making sure the child process
can't be blocked on I/O either.

See L<perlfork> for more information about the fork() emulation on
Windows.

=head2 Perl source code is read in text mode on Windows

Perl scripts used to be read in binary mode on Windows for the benefit
of the ByteLoader module (which is no longer part of core Perl).  This
had the side effect of breaking various operations on the DATA filehandle,
including seek()/tell(), and even simply reading from DATA after file handles
have been flushed by a call to system(), backticks, fork() etc.

The default build options for Windows have been changed to read Perl source
code on Windows in text mode now.  Hopefully ByteLoader will be updated on
CPAN to automatically handle this situation.

=head1 Performance Enhancements

=over 4

=item *

An earlier optimisation to speed up C<my @array = ...> and
C<my %hash = ...> assignments caused a bug and was disabled in Perl 5.12.0.

Now we have found another way to speed up these assignments [perl #82110].

=back

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over 4

=item *

C<attributes> has been upgraded from version 0.13 to 0.14.

=item *

C<base> has been upgraded from version 2.15 to 2.16.

=item *

C<CPAN> has been upgraded from version 1.94_65 to 1.9600.

=item *

C<CPANPLUS> has been upgraded from version 0.9101 to 0.9103

=item *

C<CPANPLUS::Dist::Build> has been upgraded from version 0.52 to 0.54

=item *

C<Cwd> has been downgraded from version 3.37 to 3.36.

An optimisation that recent core changes have rendered unnecessary has been
reverted.

=item *

C<Devel::DProf> has been upgraded from version 20110225.01 to 20110228.00.

=item *

C<Digest::SHA> has been upgraded from version 5.50 to 5.61

New SHA-512/224 and SHA-512/256 transforms ref. NIST Draft FIPS 180-4 (February 2011)

=item *

C<ExtUtils::Command> has been upgraded from version 1.16 to 1.17.

=item *

C<File::Copy> has been downgraded from version 2.22 to 2.21.

An optimisation that recent core changes have rendered unnecessary has been
reverted.

=item *

C<File::Glob> has been upgraded from version 1.11 to 1.12.

=item *

C<GDBM_File> has been upgraded from version 1.13 to 1.14.

=item *

C<Hash::Util> has been upgraded from version 0.10 to 0.11.

=item *

C<Hash::Util::FieldHash> has been upgraded from version 1.08 to 1.09.

=item *

C<HTTP::Tiny> has been upgraded from version 0.010 to 0.011.

=item *

C<I18N::Langinfo> has been upgraded from version 0.07 to 0.08.

=item *

C<IO> has been upgraded from version 1.25_03 to 1.25_04.

=item *

C<JSON::PP> has been upgraded from version 2.27103 to 2.27105

=item *

C<Locale::Codes> has been upgraded from version 3.15 to 3.16

=item *

C<Math::BigInt> has been upgraded from version 1.992 to 1.994

=item *

C<Math::BigInt::FastCalc> has been upgraded from version 0.24_02 to 0.28

=item *

C<Module::Build> has been upgraded from version 0.37_05 to 0.3800

=item *

C<Module::CoreList> has been upgraded from version 2.45 to 2.46.

=item *

C<mro> has been upgraded from version 1.06 to 1.07.

=item *

C<NDBM_File> has been upgraded from version 1.11 to 1.12.

=item *

C<parent> has been upgraded from version 0.224 to 0.225

=item *

C<Pod::Simple> has been upgraded from version 3.15 to 3.16

=item *

C<Storable> has been upgraded from version 2.26 to 2.27.

=item *

C<Sys::Hostname> has been upgraded from version 1.15 to 1.16.

=item *

C<Test::Harness> has been upgraded from version 3.22 to 3.23

=item *

C<Test::Simple> has been upgraded from version 0.97_01 to 0.98

=item *

C<Tie::Hash::NamedCapture> has been upgraded from version 0.07 to 0.08.

Some of the Perl code has been converted to XS for efficency's sake.

=item *

C<Tie::RefHash> has been upgraded from version 1.38 to 1.39.

=item *

C<Unicode::Collate> has been upgraded from version 0.72 to 0.73

DUCET has been updated for Unicode 6.0.0 as Collate/allkeys.txt and
the default UCA_Version is 22.

=item *

C<Unicode::UCD> has been upgraded from version 0.31 to 0.32.
This includes a number of bug fixes:

=over 4

=item charinfo()

=over 4

=item *

It is now updated to Unicode Version 6 with Corrigendum #8, except,
as with Perl 5.14, the code point at U+1F514 has no name.

=item *

The Hangul syllable code points have the correct names, and their
decompositions are always output without requiring L<Lingua::KO::Hangul::Util>
to be installed.

=item *

The CJK (Chinese-Japanese-Korean) code points U+2A700 - U+2B734
and U+2B740 - 2B81D are now properly handled.

=item *

The numeric values are now output for those CJK code points that have them.

=item *

The names that are output for code points with multiple aliases are now the
corrected ones.

=back

=item charscript()

This now correctly returns "Unknown" instead of C<undef> for the script
of a code point that hasn't been assigned another one.

=item charblock()

This now correctly returns "No_Block" instead of C<undef> for the block
of a code point that hasn't been assigned to another one.

=back

=item *

C<XS::Typemap> has been upgraded from version 0.04 to 0.05.

=back

=head1 Documentation

=head2 Changes to Existing Documentation

=head3 L<perlfunc>

=over 4

=item *

Clarified the order in which to check C<$@> and C<$!> after C<do FILE>.
(RT #80626)

=back

=head1 Diagnostics

The following additions or changes have been made to diagnostic output,
including warnings and fatal error messages.  For the complete list of
diagnostic messages, see L<perldiag>.

=head2 New Diagnostics

=over 4

=item *

Regexp modifier "/%c" may not appear twice

(F syntax) The regular expression pattern had one of the mutually exclusive
modifiers repeated.  Remove all but one of the occurrences.

=item *

Regexp modifiers "/%c" and "/%c" are mutually exclusive

(F syntax) The regular expression pattern had more than one of the mutually
exclusive modifiers.  Retain only the modifier that is supposed to be there.

=item *

Insecure user-defined property %s

(F) Perl detected tainted data when trying to compile a regular
expression that contains a call to a user-defined character property
function, i.e. C<\p{IsFoo}> or C<\p{InFoo}>.
See L<perlunicode/User-Defined Character Properties> and L<perlsec>.

=back

=head1 Testing

Many of the tests have been refactored to use testing libraries more
consistently. In some cases test files were created or deleted:

=over 4

=item *

The tests for C<split /\s/> and Unicode have been moved from
F<t/op/split.t> to the new F<t/op/split_unicode.t>.

=item *

F<t/re/re.t> has been moved to F<ext/re/t/re_funcs_u.t>.

=item *

The tests for [perl #72922] have been moved from F<t/re/qr.t> to the new
F<t/re/qr-72922.t>.

=item *

F<t/re/reg_unsafe.t> has been deleted and its only test moved to
F<t/re/pat_advanced.t>.

=back

=head1 Selected Bug Fixes

=over 4

=item *

A fix for a bug in C<length(undef)> in 5.13.4 introduced a regression that
meant C<print length undef> did not warn when warnings were enabled. It now
correctly warns [perl #85508].

=item *

The C<(?|...)> regular expression construct no longer crashes if the final
branch has more sets of capturing parentheses than any other branch. This
was fixed in Perl 5.10.1 for the case of a single branch, but that fix did
not take multiple branches into account [perl #84746].

=item *

Accessing an element of a package array with a hard-coded number (as
opposed to an arbitrary expression) would crash if the array did not exist.
Usually the array would be autovivified during compilation, but typeglob
manipulation could remove it, as in these two cases which used to crash:

  *d = *a;  print $d[0];
  undef *d; print $d[0];

=item *

C<#line> directives in string evals were not properly updating the arrays
of lines of code (C<< @{"_<..."} >>) that the debugger (or any debugging or
profiling module) uses. In threaded builds, they were not being updated at
all. In non-threaded builds, the line number was ignored, so any change to
the existing line number would cause the lines to be misnumbered
[perl #79442].

=item *

C<$AUTOLOAD> used to remain tainted forever if it ever became tainted. Now
it is correctly untainted if an autoloaded method is called and the method
name was not tainted.

=item *

A bug has been fixed in the implementation of C<{...}> quantifiers in
regular expressions that prevented the code block in
C</((\w+)(?{ print $2 })){2}/> from seeing the C<$2> sometimes
[perl #84294].

=item *

C<sprintf> now dies when passed a tainted scalar for the format. It did
already die for arbitrary expressions, but not for simple scalars
[perl #82250].

=item *

DESTROY methods of objects implementing ties are no longer able to crash by
accessing the tied variable through a weak reference [perl #86328].

=item *

On Windows, calling kill(9, $child) on a pseudo-process created by the fork()
emulation is inherently unstable.  It can also be responsible for overriding
the parent process exit code with a value of '9' if the parent terminates
right after killing the child.  This condition will now happen a lot less
often than before.

See also L</"fork() emulation will not wait for signalled children"> for a
better way to terminate child processes that avoids deadlocks altogether.

=item *

Ensure that the C<exists &Errno::EFOO> idiom continues to work as documented.

A change post-5.12 caused the documented idiom not to work if Errno was loaded
after the C<exists> code had been compiled, as the compiler implicitly creates
typeglobs in the Errno symbol table when it builds the optree for the C<exists
code>.

=back

=head1 Acknowledgements

Perl 5.13.11 represents approximately one month of development since Perl
5.13.10 and contains approximately 80,000 lines of changes across 549 files from
31 authors and committers:

Alastair Douglas, Arvan, Boris Ratner, brian d foy, Chris 'BinGOs' Williams,
Craig A. Berry, David Golden, David Leadbeater, David Mitchell, Father
Chrysostomos, Florian Ragwitz, Jan Dubois, Karl Williamson, Kevin Ryde, Leon
Brocard, Leon Timmermans, Michael Stevens, Michael Witten, Moritz Lenz, Nicholas
Clark, Paul Johnson, Peter John Acklam, Reini Urban, Robin Barker, Steve Hay,
Sullivan Beck, Tony Cook, Vadim Konovalov, Yves Orton, Zefram and Ævar Arnfjörð
Bjarmason

=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://rt.perl.org/perlbug/ .  There may also be
information at http://www.perl.org/ , the Perl Home Page.

If you believe you have an unreported bug, please run the L<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.

If the bug you are reporting has security implications, which make it
inappropriate to send to a publicly archived mailing list, then please send
it to perl5-security-report@perl.org. This points to a closed subscription
unarchived mailing list, which includes
all the core committers, who will be able
to help assess the impact of issues, figure out a resolution, and help
co-ordinate the release of patches to mitigate or fix the problem across all
platforms on which Perl is supported. Please only use this address for
security issues in the Perl core, not for modules independently
distributed on CPAN.

=head1 SEE ALSO

The F<Changes> file for an explanation of how to view 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.

=cut