=encoding utf8

=head1 NAME

perl5212delta - what is new for perl v5.21.2

=head1 DESCRIPTION

This document describes differences between the 5.21.1 release and the 5.21.2
release.

If you are upgrading from an earlier release such as 5.21.0, first read
L<perl5211delta>, which describes differences between 5.21.0 and 5.21.1.

=head1 Core Enhancements

=head2 Better heuristics on older platforms for determining locale UTF8ness

On platforms that implement neither the C99 standard nor the POSIX 2001
standard, determining if the current locale is UTF8 or not depends on
heuristics.  These are improved in this release.

=head1 Security

=head2 Perl is now always compiled with -D_FORTIFY_SOURCE=2 if available

The 'code hardening' option called C<_FORTIFY_SOURCE>, available in
gcc 4.*, is now always used for compiling Perl, if available.

Note that this isn't necessarily a huge step since in many platforms
the step had already been taken several years ago: many Linux
distributions (like Fedora) have been using this option for Perl,
and OS X has enforced the same for many years.


=head1 Deprecations

=head2 C<< /\C/ >> character class

This character class, which matches a single byte, even if it appears
in a multi-byte character has been deprecated. Matching single bytes
in a multi-byte character breaks encapsulation, and can corrupt utf8
strings.

=head1 Performance Enhancements

=over 4

=item *

Refactoring of C<< pp_tied >> and CC<< pp_ref >> for small improvements.

=item *

Pathtools don't try to load XS on miniperl.

=item *

A typo fix reduces the size of the C<< OP >> structure.

=item *

Hash lookups where the key is a constant is faster.

=back

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over 4

=item *

L<arybase> has been upgraded from version 0.07 to 0.08.

=item *

L<B> has been upgraded from version 1.49 to 1.50.

=item *

L<Devel::Peek> has been upgraded from version 1.17 to 1.18.

=item *

L<experimental> has been upgraded from version 0.007 to 0.008.

=item *

L<ExtUtils::Manifest> has been upgraded from version 1.63 to 1.64.

=item *

L<File::Copy> has been upgraded from version 2.29 to 2.30.

=item *

The PathTools module collection (L<File::Spec> and friends) has been
upgraded from version 3.48 to 3.49.

=item *

L<Filter::Simple> has been upgraded from version 0.91 to 0.92.

=item *

L<Hash::Util> has been upgraded from version 0.17 to 0.18.

=item *

L<IO> has been upgraded from version 1.32 to 1.33.

=item *

L<IO::Socket::IP> has been upgraded from version 0.29 to 0.31.

A better fix for subclassing C<connect()>.
L<[cpan #95983]|https://rt.cpan.org/Ticket/Display.html?id=95983>
L<[cpan #97050]|https://rt.cpan.org/Ticket/Display.html?id=97050>

=item *

L<IPC::Open3> has been upgraded from version 1.16 to 1.17.

=item *

L<Math::BigInt> has been upgraded from version 1.9995 to 1.9996.

Correct handling of subclasses.
L<[cpan #96254]|https://rt.cpan.org/Ticket/Display.html?id=96254>
L<[cpan #96329]|https://rt.cpan.org/Ticket/Display.html?id=96329>

=item *

L<Module::CoreList> has been upgraded from version 5.021001_01 to 5.021002.

=item *

L<Pod::Usage> has been upgraded from version 1.63 to 1.64.

=item *

L<POSIX> has been upgraded from version 1.40 to 1.41.

=item *

L<threads> has been upgraded from version 1.94 to 1.95.

=item *

L<warnings> has been upgraded from version 1.24 to 1.26.

=back

=head1 Documentation

=head2 Changes to Existing Documentation

=head3 L<< perlpolicy >>

=over 4

=item *

We now have a code of conduct for the I<< p5p >> mailing list, as documented
in L<< perlpolicy/STANDARDS OF CONDUCT >>.

=back

=head3 L<< perlfunc >>

=over 4

=item *

Improve documentation of C<< our >>.

=back

=head3 L<< perlsyn >>

=over 4

=item *

The empty conditional in C<< for >> and C<< while >> is now documented
in L<< perlsyn >>.

=back

=head1 Diagnostics

=head2 New Diagnostics

=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<Redundant argument in %s|perldiag/Redundant argument in %s>

(W redundant) You called a function with more arguments than other
arguments you supplied indicated would be needed. Currently only
emitted when a printf-type format required fewer arguments than were
supplied, but might be used in the future for e.g. L<perlfunc/pack>.

The warnings category C<< redundant >> is new. See also [RT #121025]

=back

=head1 Configuration and Compilation

=over 4

=item *

A new compilation flag, C<< -DPERL_OP_PARENT >> is available. For details,
see the discussion below at L<< /Internal Changes >>.

=back

=head1 Testing

=over 4

=item *

C<< test.pl >> now allows C<< plan skip_all => $reason >>, to make it
more compatible with C<< Test::More >>.

=back

=head1 Platform Support

=head2 Platform-Specific Notes

=over 4

=item Solaris

Builds on Solaris 10 with C<-Dusedtrace> would fail early since make
didn't follow implied dependencies to build C<perldtrace.h>.  Added an
explicit dependency to C<depend>.
L<[perl #120120]|https://rt.perl.org/Ticket/Display.html?id=120120>

=back

=head1 Internal Changes

=over 4

=item *

The following private API functions had their context parameter removed,
C<Perl_cast_ulong>,  C<Perl_cast_i32>, C<Perl_cast_iv>,    C<Perl_cast_uv>,
C<Perl_cv_const_sv>, C<Perl_mg_find>,  C<Perl_mg_findext>, C<Perl_mg_magical>,
C<Perl_mini_mktime>, C<Perl_my_dirfd>, C<Perl_sv_backoff>, C<Perl_utf8_hop>.

Users of the public API prefix-less calls remain unaffected.

=item *

Experimental support for ops in the optree to be able to locate their
parent, if any. A general-purpose function, C<< op_sibling_splice() >>
allows for general manipulating an C<< op_sibling >> chain. The last op
in such a chain is now marked with the field C<< op_lastsib >>.

A new build define, C<< -DPERL_OP_PARENT >> has been added; if
given, it forces the core to use C<< op_lastsib >> to detect the
last sibling in a chain, freeing the last C<< op_sibling >> pointer,
which then points back to the parent (instead of being C<< NULL >>).

A C-level C<< op_parent() >> function, and a C<< B >> C<< parent() >> method
have been added; under a default build, they return C<< NULL >>, but when
C<< -DPERL_OP_PARENT >> has been set, they return the parent of the current op.

=back

=head1 Selected Bug Fixes

=over 4

=item *

C<< s///e >> on tainted utf8 strings got C<< pos() >> messed up. This bug,
introduced in 5.20, is now fixed. [RT #122148]

=item *

A non-word boundary in a regular expression (C<< \B >>) did not always
match the end of the string; in particular C<< q{} =~ /\B/ >> did not
match. This bug, introduced in perl 5.14, is now fixed. [RT #122090]

=item *

C<< " P" =~ /(?=.*P)P/ >> should match, but did not. This is now fixed.
[RT #122171].

=back

=head1 Acknowledgements

Perl 5.21.2 represents approximately 4 weeks of development since Perl 5.21.1
and contains approximately 11,000 lines of changes across 220 files from 27
authors.

Excluding auto-generated files, documentation and release tools, there were
approximately 5,700 lines of changes to 140 .pm, .t, .c and .h files.

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 5.21.2:

Aaron Crane, Abhijit Menon-Sen, Abigail, Alexandr Ciornii, brian d foy, Brian
Fraser, Chris 'BinGOs' Williams, Craig A. Berry, Daniel Dragan, David Golden,
David Mitchell, Dmitri Tikhonov, George Greer, H.Merijn Brand, James E Keenan,
Jarkko Hietaniemi, Karen Etheridge, Karl Williamson, Matthew Horsfall, Peter
John Acklam, Peter Martini, Reini Urban, Ricardo Signes, Steve Hay, Tony Cook,
Yves Orton, Ævar Arnfjörð Bjarmason.

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
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