perldelta for 3c6ef0a5 / #103260 / #123071

[perl5.git] / pod / perldelta.pod

=encoding utf8

=head1 NAME

[ this is a template for a new perldelta file.  Any text flagged as XXX needs
to be processed before release. ]

perldelta - what is new for perl v5.21.8

=head1 DESCRIPTION

This document describes differences between the 5.21.7 release and the 5.21.8
release.

If you are upgrading from an earlier release such as 5.21.6, first read
L<perl5217delta>, which describes differences between 5.21.6 and 5.21.7.

=head1 Notice

XXX Any important notices here

=head1 Core Enhancements

XXX New core language features go here.  Summarize user-visible core language
enhancements.  Particularly prominent performance optimisations could go
here, but most should go in the L</Performance Enhancements> section.

[ List each enhancement as a =head2 entry ]

=head2 The warnings pragma now supports warnings outside of "all"

Ever since perl v5.6.0 we've had no way of adding new warnings without
retroactively adding them to all existing programs that used C<-w>,
C<-W> or C<use warnings>.

This caused us to not add new useful warnings out of fear that they
might unduly burden users who just wanted to upgrade perl and didn't
want to deal with a bunch of warnings from their existing code.

We now support a way to have our cake and eat it too, and can add new
warnings to the core going forward through other top-level warning
categories. See L<the warnings documentation|warnings/Top-level
warning categories & associated confusion> for details.

=head2 Non-Capturing Regular Expression Flag

Regular expressions now support a C</n> flag that disables capturing
and filling in C<$1>, C<$2>, etc... inside of groups:

  "hello" =~ /(hi|hello)/n; # $1 is not set

This is equivalent to putting C<?:> at the beginning of every capturing group.

See L<perlre/"n"> for more information.

=head1 Security

XXX Any security-related notices go here.  In particular, any security
vulnerabilities closed should be noted here rather than in the
L</Selected Bug Fixes> section.

[ List each security issue as a =head2 entry ]

=head1 Incompatible Changes

XXX For a release on a stable branch, this section aspires to be:

    There are no changes intentionally incompatible with 5.XXX.XXX
    If any exist, they are bugs, and we request that you submit a
    report.  See L</Reporting Bugs> below.

[ List each incompatible change as a =head2 entry ]

=head1 Deprecations

XXX Any deprecated features, syntax, modules etc. should be listed here.

=head2 Module removals

XXX Remove this section if inapplicable.

The following modules will be removed from the core distribution in a
future release, and will at that time need to be installed from CPAN.
Distributions on CPAN which require these modules will need to list them as
prerequisites.

The core versions of these modules will now issue C<"deprecated">-category
warnings to alert you to this fact.  To silence these deprecation warnings,
install the modules in question from CPAN.

Note that these are (with rare exceptions) fine modules that you are encouraged
to continue to use.  Their disinclusion from core primarily hinges on their
necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
not usually on concerns over their design.

=over

=item XXX

XXX Note that deprecated modules should be listed here even if they are listed
as an updated module in the L</Modules and Pragmata> section.

=back

[ List each other deprecation as a =head2 entry ]

=head1 Performance Enhancements

XXX Changes which enhance performance without changing behaviour go here.
There may well be none in a stable release.

[ List each enhancement as a =item entry ]

=over 4

=item *

XXX

=back

=head1 Modules and Pragmata

XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
go here.  If Module::CoreList is updated, generate an initial draft of the
following sections using F<Porting/corelist-perldelta.pl>.  A paragraph summary
for important changes should then be added by hand.  In an ideal world,
dual-life modules would have a F<Changes> file that could be cribbed.

[ Within each section, list entries as a =item entry ]

=head2 New Modules and Pragmata

=over 4

=item *

XXX

=back

=head2 Updated Modules and Pragmata

=over 4

=item *

L<XXX> has been upgraded from version A.xx to B.yy.

=item *

L<attributes> has been upgraded from version 0.24 to 0.25.

Minor internal change only.

=item *

L<B> has been upgraded from version 1.54 to 1.55.

A bug where, after an ithread creation or psuedofork, special/immortal SVs in
the child ithread/psuedoprocess did not have the correct class of
C<B::SPECIAL>, has been fixed.

The C<id> and C<outid> PADLIST methods have been added.

=item *

L<B::Deparse> has been upgraded from version 1.31 to 1.32.

Deparsing C<BEGIN { undef &foo }> with the B<-w> switch enabled started to
emit 'uninitialized' warnings in Perl 5.14.  This has been fixed.

=item *

L<Safe> has been upgraded from version 2.38 to 2.39.

C<reval> was not propagating void context properly.

=back

=head2 Removed Modules and Pragmata

=over 4

=item *

XXX

=back

=head1 Documentation

XXX Changes to files in F<pod/> go here.  Consider grouping entries by
file and be sure to link to the appropriate page, e.g. L<perlfunc>.

=head2 New Documentation

XXX Changes which create B<new> files in F<pod/> go here.

=head3 L<XXX>

XXX Description of the purpose of the new file here

=head2 Changes to Existing Documentation

XXX Changes which significantly change existing files in F<pod/> go here.
However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
section.

=head3 L<XXX>

=over 4

=item *

XXX Description of the change here

=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>.

XXX New or changed warnings emitted by the core's C<C> code go here.  Also
include any changes in L<perldiag> that reconcile it to the C<C> code.

=head2 New Diagnostics

XXX Newly added diagnostic messages go under here, separated into New Errors
and New Warnings

=head3 New Errors

=over 4

=item *

XXX L<message|perldiag/"message">

=back

=head3 New Warnings

=over 4

=item *

XXX L<message|perldiag/"message">

=item *

L<Wide character (U+%X) in %s|perldiag/"Wide character (U+%X) in %s">

=back

=head2 Changes to Existing Diagnostics

XXX Changes (i.e. rewording) of diagnostic messages go here

=over 4

=item *

XXX Describe change here

The message
L<Locale '%s' may not work well.%s|perldiag/"Locale '%s' may not work well.%s">
is no longer raised unless the problemtatic locale is actually used in
the Perl program.  Previously it was raised if it merely was the
underlying locale.  All Perl programs have an underlying locale at all
times, but something like a C<S<use locale>> is needed for that locale
to actually have some effect.  This message will not be raised when
the underlying locale is hidden.

=back

=head1 Utility Changes

XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
Most of these are built within the directory F<utils>.

[ List utility changes as a =head2 entry for each utility and =item
entries for each change
Use L<XXX> with program names to get proper documentation linking. ]

=head2 L<XXX>

=over 4

=item *

XXX

=back

=head1 Configuration and Compilation

XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
go here.  Any other changes to the Perl build process should be listed here.
However, any platform-specific changes should be listed in the
L</Platform Support> section, instead.

[ List changes as a =item entry ].

=over 4

=item *

XXX

=back

=head1 Testing

XXX Any significant changes to the testing of a freshly built perl should be
listed here.  Changes which create B<new> files in F<t/> go here as do any
large changes to the testing harness (e.g. when parallel testing was added).
Changes to existing files in F<t/> aren't worth summarizing, although the bugs
that they represent may be covered elsewhere.

[ List each test improvement as a =item entry ]

=over 4

=item *

XXX

=back

=head1 Platform Support

XXX Any changes to platform support should be listed in the sections below.

[ Within the sections, list each platform as a =item entry with specific
changes as paragraphs below it. ]

=head2 New Platforms

XXX List any platforms that this version of perl compiles on, that previous
versions did not.  These will either be enabled by new files in the F<hints/>
directories, or new subdirectories and F<README> files at the top level of the
source tree.

=over 4

=item XXX-some-platform

XXX

=back

=head2 Discontinued Platforms

XXX List any platforms that this version of perl no longer compiles on.

=over 4

=item XXX-some-platform

XXX

=back

=head2 Platform-Specific Notes

XXX List any changes for specific platforms.  This could include configuration
and compilation changes or changes in portability/compatibility.  However,
changes within modules for platforms should generally be listed in the
L</Modules and Pragmata> section.

=over 4

=item Win32

=over 4

=item *

Previously, on Visual C++ for Win64 built Perls only, when compiling every Perl
XS module (including CPAN ones) and Perl aware .c file with a 64 bit Visual C++,
would uncondtionally have around a dozen warnings from hv_func.h.  These
warnings have been silenced.  GCC all bitness and Visual C++ for Win32 were
not affected.

=item *

Support for building without PerlIO has been removed from the Windows
makefiles.  Non-PerlIO builds were all but deprecated in Perl 5.18.0 and are
already not supported by F<Configure> on POSIX systems.

=item *

Between 2 and 6 ms and 7 I/O calls have been saved per attempt to open a perl
module for each path in C<@INC>.

=back

=back

=head1 Internal Changes

XXX Changes which affect the interface available to C<XS> code go here.  Other
significant internal changes for future core maintainers should be noted as
well.

[ List each change as a =item entry ]

=over 4

=item *

Added Perl_sv_get_backrefs() to determine if an SV is a weak-referent.

Function either returns an SV * of type AV, which contains the set of
weakreferences which reference the passed in SV, or a simple RV * which
is the only weakref to this item.

=item *

C<gv_add_by_type> which was added to public API in 5.11.0 but undocumented and
shows no CPAN usage has been removed from public API. Please use public API
C<GvSVn> C<GvIOn> C<GvAVn> and C<GvHVn> for adding elements to a GV.

=item *

C<GvSVn> C<GvIOn> C<GvAVn> and C<GvHVn> have been made rvalues, previously they
were lvalues. If you are assigning a SV to C<GvSVn> C<GvIOn> C<GvAVn> and
C<GvHVn> you are leaking memory. If you want an lvalue, use C<GvSV> C<GvIO>
C<GvAV> and C<GvHV>.

=item *

XXX

=back

=head1 Selected Bug Fixes

XXX Important bug fixes in the core language are summarized here.  Bug fixes in
files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.

[ List each fix as a =item entry ]

=over 4

=item *

A bug in regular expression patterns that could lead to segfaults and
other crashes has been fixed.  This occurred only in patterns compiled
with C<"/i">, while taking into account the current POSIX locale (this usually
means they have to be compiled within the scope of C<S<"use locale">>),
and there must be a string of at least 128 consecutive bytes to match.
[perl #123539]

=item *

C<s///> now works on very long strings instead of dying with 'Substitution
loop'.  [perl #103260] [perl #123071]

=back

=head1 Known Problems

XXX Descriptions of platform agnostic bugs we know we can't fix go here.  Any
tests that had to be C<TODO>ed for the release would be noted here.  Unfixed
platform specific bugs also go here.

[ List each fix as a =item entry ]

=over 4

=item *

XXX

=back

=head1 Errata From Previous Releases

=over 4

=item *

XXX Add anything here that we forgot to add, or were mistaken about, in
the perldelta of a previous release.

=back

=head1 Obituary

XXX If any significant core contributor has died, we've added a short obituary
here.

=head1 Acknowledgements

XXX Generate this with:

  perl Porting/acknowledgements.pl v5.21.7..HEAD

=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
https://rt.perl.org/ .  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