perldelta - Add missing =item directive

[perl5.git] / pod / perl5193delta.pod

=encoding utf8

=head1 NAME

perl5193delta - what is new for perl v5.19.3

=head1 DESCRIPTION

This document describes differences between the 5.19.2 release and the 5.19.3
release.

If you are upgrading from an earlier release such as 5.19.1, first read
L<perl5192delta>, which describes differences between 5.19.1 and 5.19.2.

=head1 Core Enhancements

=head2 B<-F> now implies B<-a> and B<-a> implies B<-n>

Previously B<-F> without B<-a> was a no-op, and B<-a> without B<-n> or B<-p>
was a no-op, with this change, if you supply B<-F> then both B<-a> and B<-n>
are implied and if you supply B<-a> then B<-n> is implied.

You can still use B<-p> for its extra behaviour. [perl #116190]

=head1 Security

=head2 Avoid possible read of free()d memory during parsing

It was possible that free()d memory could be read during parsing in the unusual
circumstance of the Perl program ending with a heredoc and the last line of the
file on disk having no terminating newline character.  This has now been fixed.

=head1 Performance Enhancements

=over 4

=item *

A performance regression introduced in Perl 5.11.2 in non-Unicode
case-insensitive pattern matching has been largely resolved.  In particular,
the disabled optimization is now restored for every ASCII-range character.
[perl #107816]

=back

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over 4

=item *

L<B> has been upgraded from version 1.44 to 1.45.

Calling the C<GV> method on C<B::CV> objects created from a lexical sub would
return nonsense, possibly crashing perl.  C<GV> now returns C<undef> for
lexical subs. [perl #118525]

Added the C<NAME_HEK> method to return the name of a lexical sub.

=item *

L<bignum> has been upgraded from version 0.33 to 0.36.

L<bigrat> wasn't correctly updating an internal variable when C<use>d with a
C<lib> option.

=item *

L<Carp> has been upgraded from 1.30 to 1.31

L<Carp> now handles objects with string overloads.  It also allows objects to
specify how they appear in the stack dump with a C<CARP_TRACE> method, and also
allows the user to specify their own formatter for objects without
C<CARP_TRACE> as well as other references. [perl #92446]

=item *

L<Compress::Raw::Bzip2> has been upgraded from 2.061 to 2.062.

No changes have been made other than the version bump to keep in sync with
other related modules.

=item *

L<Compress::Raw::Zlib> has been upgraded from 2.061 to 2.062.

A minor typo has been fixed in the documentation.

=item *

L<Config::Perl::V> has been upgraded from version 0.18 to 0.19.

The list of build options has been updated.

=item *

L<constant> has been upgraded from version 1.27 to 1.28.

Note that list constants will be inlined and may be read-only in future Perl
versions.

=item *

L<CPAN::Meta> has been upgraded from version 2.131560 to 2.132140.

Some documentation typos have been fixed.

=item *

L<Data::Dumper> has been upgraded from version 2.147 to 2.148.

The compatibility of the XS implementation with the pure perl version under
C<Useqq> has been improved. [perl #118933]

=item *

L<DB> has been upgraded from 1.41 to 1.42.

The Perl debugger no longer crashes with C<PERLDB_OPTS="noTTY frame=2">.

=item *

L<Devel::Peek> has been upgraded from version 1.12 to 1.13.

C<SvREFCNT_inc> and C<SvREFCNT_dec> have been removed and C<SvREFCNT> will now
work on non-scalars. [perl #117793]

C<Dump> now checks its arguments at compile time.  Both arguments are now
evaluated in scalar context, with exceptions for @arrays and %hashes, allowing
aggregates to be dumped directly.  The first argument is evaluated in rvalue
scalar context, allowing rvalue C<pos> and C<substr> to be dumped.

C<fill_mstats> no longer crashes if its argument is not already a string.
[perl #92260]

=item *

L<Devel::PPPort> has been upgraded from version 3.20 to 3.21.

Numerous updates and bug fixes are incorporated.  See the F<Changes> file for
full details.

=item *

L<diagnostics> has been upgraded from version 1.31 to 1.32.

Wrapped links are no longer truncated.

=item *

L<DynaLoader> has been upgraded from version 1.18 to 1.19.

The $dl_dlext variable is now documented.

=item *

L<Encode> has been upgraded from version 2.51 to 2.52.

Encoding "0" with MIME-Headers no longer gets a blank string.

=item *

L<English> has been upgraded from version 1.07 to 1.08.

The documentation of a performance fix has been corrected.

=item *

L<Exporter> has been upgraded from version 5.68 to 5.69.

L<Exporter> would ignore custom $SIG{__WARN__} handlers in C<Exporter::Heavy>.
[perl #39739]

=item *

L<ExtUtils::MakeMaker> has been upgraded from 6.68 to 6.72.

The C<dist> target now reports the file created, an infinite loop in
C<clean_subdirs> has been fixed, an invisible interactive question is now
avoided when rebuilding Makefile, issues with F</cygdrive> on Cygwin have been
resolved, C<LD> and C<OPTIMIZE> are now used in recursive F<Makefile.PL>
invocations, C<VERSION> and C<VERSION_FROM> now handle v-strings correctly, and
control characters are now stripped from C<ABSTRACT>.

=item *

L<File::Spec> has been upgraded from 3.41 to 3.44.

The module is now partly implemented in XS, for performance.

=item *

L<Getopt::Std> has been upgraded from version 1.09 to 1.10.

Clarified documentation of what happens when a switch is expecting an argument
but fails to be provided with one.

=item *

The IO-Compress module collection has been upgraded from 2.061 to 2.062.

Some documentation typos have been fixed.

=item *

L<IPC::Cmd> has been upgraded from version 0.82 to 0.84.

C<run_forked> has various fixes/improvements, L<Socket> is only used where
needed and a regression introduced in 0.78 has been fixed.

=item *

L<IPC::Open3> has been upgraded from version 1.14 to 1.15.

C<open3> would leak a zombie process if the child process I/O redirection or
C<exec> failed. [perl #114722]

=item *

L<IPC::SysV> has been upgraded from version 2.03 to 2.04.

$EXPORT_TAGS{all} has been added and a couple of typos have been fixed.

=item *

The libnet module collection has been upgraded from version 1.22 to 1.23.

Numerous bug fixes and documentation improvements have been made.  See the
F<Changes> file for full details.

=item *

L<List::Util> has been upgraded from version 1.27 to 1.31.

L<List::Util> now includes C<pairgrep>, C<pairmap>, C<pairs>, C<pairkeys>,
C<pairvalues> and C<pairfirst> functions that operate on even-sized lists of
pairs.

=item *

L<Module::Build> has been upgraded from 0.4005 to 0.4007.

The test suite has been significantly sped up, Unicode man page support has
been enhanced and hash argument parsing in subclasses has been fixed.

=item *

L<Module::CoreList> has been upgraded from 2.92 to 2.97.

The list of Perl versions covered has been updated.

=item *

L<mro> has been upgraded from version 1.12 to 1.13.

A minor typo has been fixed in the documentation.

=item *

L<parent> has been upgraded from version 0.225 to 0.226.

Internal changes only have been made to the test suite.

=item *

L<PerlIO> has been upgraded from version 1.07 to 1.08.

Although not a security vulnerability, it was possible to inject code via
C<PerlIO-E<gt>import()>.  This has now been fixed. [perl #119287]

=item *

L<Pod::Functions> has been upgraded from version 1.07 to 1.08.

Internal changes only have been made to the test suite.

=item *

L<Socket> has been upgraded from version 2.010 to 2.011.

Handle FreeBSD (or other platforms) returning shorter AF_UNIX sockaddr
structures due to embedded sun_len. [cpan #86613]

=item *

L<Storable> has been upgraded from version 2.45 to 2.46.

Avoid creating temporary objects for STORABLE_attach when they aren't required.
[perl #118907]

=item *

L<Time::HiRes> has been upgraded from version 1.9725 to 1.9726.

An C<lstat> function is now provided and various bugs have been fixed.  See the
F<Changes> file for full details.

=item *

L<Time::Piece> has been upgraded from version 1.21 to 1.22.

A minor documentation encoding problem has been fixed.

=item *

L<utf8> has been upgraded from version 1.12 to 1.13.

A minor clarification has been made in the documentation.

=item *

L<version> has been upgraded from version 0.9902 to 0.9903.

Various installation, testing and documentation changes have been made.

=back

=head1 Documentation

=head2 Changes to Existing Documentation

=head3 L<perlfunc>

=over 4

=item *

The documentation of C<ref> has been updated to recommend the use of
C<blessed>, C<isa> and C<reftype> when dealing with references to blessed
objects.

=back

=head3 L<perlguts>

=over 4

=item *

The explanation of the use of the C<SVs_PADMY> and C<SVs_PADTMP> flags in
determining whether an SV lives on a scratchpad has been clarified.

=back

=head3 L<perlopentut>

=over 4

=item *

The C<open> tutorial has been completely rewritten by Tom Christiansen, and now
focuses on covering only the basics, rather than providing a comprehensive
reference to all things openable.  This rewrite came as the result of a
vigorous discussion on perl5-porters kicked off by a set of improvements
written by Alexander Hartmaier to the existing L<perlopentut>.  A "more than
you ever wanted to know about C<open>" document may follow in subsequent
versions of perl.

=back

=head3 L<perlre>

=over 4

=item *

The C</r> modifier (for non-destructive substitution) is now documented. [perl
#119151]

=back

=head3 L<perlsub>

=over 4

=item *

The need to predeclare recursive functions with prototypes in order for the
prototype to be honoured in the recursive call is now documented. [perl #2726]

=back

=head3 L<perlvar>

=over 4

=item *

A new section explaining the performance issues of $`, $& and $', including
workarounds and changes in different versions of Perl, has been added.

=back

=head3 L<perlxs>

=over 4

=item *

Several problems in the C<MY_CXT> example have been fixed.

=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

=head3 New Errors

=over 4

=item *

L<Magical list constants are not supported|perldiag/"Magical list constants are
not supported">

(F) You assigned a magical array to a stash element, and then tried to use the
subroutine from the same slot.  You are asking Perl to do something it cannot
do, details subject to change between Perl versions.

=back

=head3 New Warnings

=over 4

=item *

L<Argument "%s" treated as 0 in increment (++)|perldiag/"Argument "%s" treated
as 0 in increment (++)">

(W numeric) The indicated string was fed as an argument to the C<++> operator
which expects either a number or a string matching C</^[a-zA-Z]*[0-9]*\z/>.
See L<perlop/Auto-increment and Auto-decrement> for details.

=item *

L<Unexpected exit %u|perldiag/"Unexpected exit %u">

(S) exit() was called or the script otherwise finished gracefully when
C<PERL_EXIT_WARN> was set in C<PL_exit_flags>.

=item *

L<Unexpected exit failure %u|perldiag/"Unexpected exit failure %u">

(S) An uncaught die() was called when C<PERL_EXIT_WARN> was set in
C<PL_exit_flags>.

=back

=head1 Testing

=over 4

=item *

The behaviour of C<pos> on very large strings is now tested in the new test
script F<t/bigmem/pos.t>.

=item *

The test script F<t/porting/ss_dup.t> has been created to test that ss_dup()
handles all savestack items.

=item *

The new behaviour of B<-F> and B<-a> (see the L</Core Enhancements> section) is
tested in the new test script F<t/run/switchF2.t>.

=back

=head1 Internal Changes

=over 4

=item *

C<sv_pos_b2u_flags> has been added to the API.  It is similar to C<sv_pos_b2u>,
but supports long strings on 64-bit platforms.

=item *

C<PL_exit_flags> can now be used by perl embedders or other XS code to have
perl C<warn> or C<abort> on an attempted exit. [perl #52000]

=back

=head1 Selected Bug Fixes

=over 4

=item *

Autovivifying a subroutine stub via C<\&$glob> started causing crashes in Perl
5.18.0 if the $glob was merely a copy of a real glob, i.e., a scalar that had
had a glob assigned to it.  This has been fixed. [perl #119051]

=item *

On 64-bit platforms C<pos> can now be set to a value higher than 2**31-1.
[perl #72766]

=item *

Perl used to leak an implementation detail when it came to referencing the
return values of certain operators.  C<for ($a+$b) { warn \$_; warn \$_ }> used
to display two different memory addresses, because the C<\> operator was
copying the variable.  Under threaded builds, it would also happen for
constants (C<for(1) { ... }>).  This has been fixed. [perl #21979, #78194,
#89188, #109746, #114838, #115388]

=item *

The range operator C<..> was returning the same modifiable scalars with each
call, unless it was the only thing in a C<foreach> loop header.  This meant
that changes to values within the list returned would be visible the next time
the operator was executed. [perl #3105]

=item *

Constant folding and subroutine inlining no longer cause operations that would
normally return new modifiable scalars to return read-only values instead.

=item *

Closures of the form C<sub () { $some_variable }> are no longer inlined,
causing changes to the variable to be ignored by callers of the subroutine.
[perl #79908]

=item *

Return values of certain operators such as C<ref> would sometimes be shared
between recursive calls to the same subroutine, causing the inner call to
modify the value returned by C<ref> in the outer call.  This has been fixed.

=item *

C<__PACKAGE__> and constants returning a package name or hash key are now
consistently read-only.  In various previous Perl releases, they have become
mutable under certain circumstances.

=item *

C</$qr/p> was broken in Perl 5.18.0; the C</p> flag was ignored.  This has been
fixed. [perl #118213]

=item *

Starting in Perl 5.18.0, a construct like C</[#](?{})/x> would have its C<#>
incorrectly interpreted as a comment.  The code block would be skipped,
unparsed.  This has been corrected.

=item *

Starting in Perl 5.001, a regular expression like C</[#$a]/x> or C</[#]$a/x>
would have its C<#> incorrectly interpreted as a comment, so the variable would
not interpolate.  This has been corrected. [perl #45667]

=item *

On non-threaded builds, setting C<${"_E<lt>filename"}> to a reference or
typeglob no longer causes C<__FILE__> and some error messages to produce a
corrupt string, and no longer prevents C<#line> directives in string evals from
providing the source lines to the debugger.  Threaded builds were unaffected.

=item *

Enabling "used once" warnings no longer causes crashes on stash circularities
created at compile time (C<*Foo::Bar::Foo:: = *Foo::>).

=item *

Undef constants used in hash keys (C<use constant u =E<gt> undef; $h{+u}>) no
longer produce "uninitialized" warnings at compile time.

=item *

Modifying a substitution target inside the substitution replacement no longer
causes crashes.

=item *

The first statement inside a string eval used to use the wrong pragma setting
sometimes during constant folding.  C<eval 'uc chr 0xe0'> would randomly choose
between Unicode, byte, and locale semantics.  This has been fixed.

=item *

The handling of return values of @INC filters (subroutines returned by
subroutines in @INC) has been fixed in various ways.  Previously tied variables
were mishandled, and setting $_ to a reference or typeglob could result in
crashes.

=item *

The C<SvPVbyte> XS function has been fixed to work with tied scalars returning
something other than a string.  It used to return utf8 in those cases where
C<SvPV> would.

=item *

Perl 5.18.0 inadvertently made dereferenced regular expressions
S<(C<${ qr// }>)> false as booleans.  This has been fixed.

=item *

Perl 5.18.0 inadvertently made C<--> and C<++> crash on dereferenced regular
expressions, and stopped C<++> from flattening vstrings.

=item *

C<bless> no longer dies with "Can't bless non-reference value" if its first
argument is a tied reference.

=item *

C<reset> with an argument no longer skips copy-on-write scalars, regular
expressions, typeglob copies, and vstrings.  Also, when encountering those or
read-only values, it no longer skips any array or hash with the same name.

=item *

C<reset> with an argument now skips scalars aliased to typeglobs
(C<for $z (*foo) { reset "z" }>).  Previously it would corrupt memory or crash.

=item *

C<ucfirst> and C<lcfirst> were not respecting the bytes pragma.  This was a
regression from Perl 5.12. [perl #117355]

=item *

The use of C<\G> in regular expressions, where it's not at the start of the
pattern, is now slightly less buggy (although it is still somewhat
problematic).

=item *

Where a regular expression included code blocks (C</(?{...})/>), and where the
use of constant overloading triggered a re-compilation of the code block, the
second compilation didn't see its outer lexical scope.  This was a regression
in Perl 5.18.0.

=item *

Changes to C<UNIVERSAL::DESTROY> now update DESTROY caches in all classes,
instead of causing classes that have already had objects destroyed to continue
using the old sub.  This was a regression in Perl 5.18. [perl #114864]

=item *

All known false-positive occurrences of the deprecation warning "Useless use of
'\'; doesn't escape metacharacter '%c'", added in Perl 5.18.0, have been
removed. [perl #119101]

=back

=head1 Acknowledgements

Perl 5.19.3 represents approximately 4 weeks of development since Perl 5.19.2
and contains approximately 24,000 lines of changes across 710 files from 36
authors.

Perl continues to flourish into its third decade thanks to a vibrant community
of users and developers.  The following people are known to have contributed
the improvements that became Perl 5.19.3:

Alexander Voronov, Andy Dougherty, Aristotle Pagaltzis, Brendan Byrd, Chris
'BinGOs' Williams, Colin Kuskie, Craig A. Berry, Daniel Dragan, Darin McBride,
David Mitchell, Father Chrysostomos, H.Merijn Brand, James E Keenan, John
Gardiner Myers, John Peacock, Karl Williamson, Lukas Mai, Marcus
Holland-Moritz, Nathan Trapuzzano, Neil Bowers, Nicholas Clark, Peter Martini,
Philip Boulain, Ricardo Signes, Sergey Alekseev, Shlomi Fish, Smylers, Steffen
Müller, Steve Hay, Tom Christiansen, Tony Cook, Victor Efimov, Viktor Turskyi,
Vladimir Timofeev, Yves Orton, Zefram.

The list above is almost certainly incomplete as it is automatically generated
from version control history.  In particular, it does not include the names of
the (very much appreciated) contributors who reported issues to the Perl bug
tracker.

Many of the changes included in this version originated in the CPAN modules
included in Perl's core.  We're grateful to the entire CPAN community for
helping Perl to flourish.

For a more complete list of all of Perl's historical contributors, please see
the F<AUTHORS> file in the Perl source distribution.

=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