=encoding utf8

=head1 NAME

perldelta - what is new for perl v5.39.2

=head1 DESCRIPTION

This document describes differences between the 5.39.1 release and the 5.39.2
release.

If you are upgrading from an earlier release such as 5.39.0, first read
L<perl5391delta>, which describes differences between 5.39.0 and 5.39.1.

=head1 Core Enhancements

=head2 New C<__CLASS__> Keyword

When using the new C<class> feature, code inside a method, C<ADJUST> block or
field initializer expression is now permitted to use the new C<__CLASS__>
keyword.  This yields a class name, similar to C<__PACKAGE__>, but whereas that
gives the compile-time package that the code appears in, the C<__CLASS__>
keyword is aware of the actual run-time class that the object instance is a
member of.  This makes it useful for method dispatch on that class, especially
during constructors, where access to C<$self> is not permitted.

For more information, see L<perlfunc/__CLASS__>.

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over 4

=item *

L<Compress::Raw::Bzip2> has been upgraded from version 2.205 to 2.206.

=item *

L<Compress::Raw::Zlib> has been upgraded from version 2.205 to 2.206.

=item *

L<Devel::Peek> has been upgraded from version 1.33 to 1.34.

=item *

L<ExtUtils::Miniperl> has been upgraded from version 1.13 to 1.14.

=item *

L<feature> has been upgraded from version 1.83 to 1.84.

=item *

L<File::Spec> has been upgraded from version 3.89 to 3.90.

=item *

L<HTTP::Tiny> has been upgraded from version 0.086 to 0.088.

=item *

L<IO::Compress> has been upgraded from version 2.205 to 2.206.

=item *

L<IO::Socket::IP> has been upgraded from version 0.41_01 to 0.42.

=item *

L<Module::CoreList> has been upgraded from version 5.20230720 to 5.20230820.

=item *

L<NDBM_File> has been upgraded from version 1.16 to 1.17.

=item *

L<Opcode> has been upgraded from version 1.64 to 1.65.

=item *

L<perlfaq> has been upgraded from version 5.20230701 to 5.20230812.

=item *

L<PerlIO::scalar> has been upgraded from version 0.31 to 0.32.

=item *

L<PerlIO::via> has been upgraded from version 0.18 to 0.19.

=item *

L<Pod::Html> has been upgraded from version 1.34 to 1.35.

=item *

L<Pod::Simple> has been upgraded from version 3.43 to 3.45.

=item *

L<POSIX> has been upgraded from version 2.14 to 2.15.

=item *

L<Safe> has been upgraded from version 2.44 to 2.45.

=item *

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

=item *

L<Test::Harness> has been upgraded from version 3.44 to 3.47.

=item *

L<threads> has been upgraded from version 2.37 to 2.38.

=item *

L<warnings> has been upgraded from version 1.66 to 1.67.

=item *

L<XS::APItest> has been upgraded from version 1.32 to 1.33.

=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<Cannot use __CLASS__ outside of a method or field initializer expression|perldiag/"Cannot use __CLASS__ outside of a method or field initializer expression">

(F) A C<__CLASS__> expression yields the class name of the object instance
executing the current method, and therefore it can only be placed inside an
actual method (or method-like expression, such as a field initializer
expression).

=item *

L<get_layers: unknown argument '%s'|perldiag/"get_layers: unknown argument '%s'">

(F) You called PerlIO::get_layers() with an unknown argument. Legal
arguments are provided in key/value pairs, with the keys being one
of C<input>, C<output> or C<detail>, followed by a boolean.

=item

L<UNIVERSAL does not export anything|perldiag/"UNIVERSAL does not export anything">

(F) You asked UNIVERSAL to export something, but UNIVERSAL is the
base class for all classes and contains not exportable symbols.

=back

=head3 New Warnings

=over 4

=item *

L<< Forked open '%s' not meaningful in <>|perldiag/"Forked open '%s' not meaningful in <>" >>

(S inplace) You had C<|-> or C<-|> in C<@ARGV> and tried to use C<< <>
>> to read from it.

Previously this would fork and produce a confusing error message. [L<GH #21176|https://github.com/Perl/perl5/issues/21176>]

=back

=head1 Configuration and Compilation

=over 4

=item *

C<microperl>, long broken and of unclear present purpose, has been removed
as promised in L<Perl 5.18|perl5180delta/Future Deprecations>.

=back

=head1 Testing

Tests were added and changed to reflect the other additions and changes
in this release.

=head1 Platform Support

=head2 Platform-Specific Notes

=over 4

=item Serenity OS

Out of the box support for Serenity OS was added.

=item Windows

Workaround a bug in most 32-bit Mingw builds, where the generated
code, including the code in the gcc support library, assumes 16-byte
stack alignment, which 32-bit Windows does not preserve. [L<GH #21313|https://github.com/Perl/perl5/issues/21313>]

=back

=head1 Internal Changes

=over 4

=item *

C<PERL_RC_STACK> build option added.

This new build option is highly experimental and is not enabled by
default.  Perl can be built with it by using the F<Configure> option
C<-Accflags='-DPERL_RC_STACK'>. 

It makes the argument stack bump the reference count of SVs pushed onto
it. It is functional, but currently slow and incomplete.

See L<perlguts|perlguts/"Reference-counted argument stack">.

=item *

Functions L<perlapi/sv_strftime_tm> and L<perlapi/sv_strftime_ints> have
been added to the public API.  These transparently handle UTF-8 for you.
One takes as input a libc S<C<struct tm>> and the other takes integers
specifying the time, in the same form as L<POSIX/strftime>.

=back

=head1 Selected Bug Fixes

=over 4

=item *

C<use 5.36;> or later didn't enable the post parse reporting of L<Name
"%s::%s" used only once: possible typo|perldiag/"Name "%s::%s" used
only once: possible typo"> warnings when enabling warnings.
[L<GH #21271|https://github.com/Perl/perl5/issues/21271>]

=item *

Fix a crash or assertion when cleaning up a closure that refers to an
outside C<our> sub.  [L<GH #21067|https://github.com/Perl/perl5/issues/21067>]

=item *

Fixed a number of issues where C<I32> was used as a string offset or
size rather than C<SSize_t> or C<STRLEN>/C<size_t> [L<GH #21012|https://github.com/Perl/perl5/issues/21012>]

=over

=item *

C<~$str> when C<$str> was more than 2GB in size would do nothing or
produce an incomplete result.

=item *

String repeat, C<$str x $count>, didn't handle C<$str> over 2GB in
size, throwing an error.  Now such strings are repeated.

=item *

Complex substitution after the 2GB point in a string could access
incorrect or invalid offsets in the string.

=item *

sv_utf8_decode() would truncate the SVs pos() value.  This wasn't
visible via utf8::decode().

=item *

When compiling a constant folded hash key, the length was truncated
when creating the shared SV.  Since hash keys over 2GB are not
supported, throw a compilation error instead.

=back

=item *

msgrcv() incorrectly called get magic on the buffer SV and failed to
call set magic on completion. [L<GH #21012|https://github.com/Perl/perl5/issues/21012>]

=item *

msgrcv() used the size parameter to resize the buffer before
validating it. [L<GH #21012|https://github.com/Perl/perl5/issues/21012>]

=item *

Inheriting from a class that was hierarchically an ancestor of the new
class, eg. C< class A::B :isa(A) { ... } >, would not attempt to load
the parent class. [L<GH #21332|https://github.com/Perl/perl5/issues/21332>]

=back

=head1 Acknowledgements

Perl 5.39.2 represents approximately 4 weeks of development since Perl
5.39.1 and contains approximately 38,000 lines of changes across 510 files
from 24 authors.

Excluding auto-generated files, documentation and release tools, there were
approximately 27,000 lines of changes to 370 .pm, .t, .c and .h files.

Perl continues to flourish into its fourth decade thanks to a vibrant
community of users and developers. The following people are known to have
contributed the improvements that became Perl 5.39.2:

Beckett Normington, Dagfinn Ilmari Mannsåker, David Golden, David Mitchell,
Elvin Aslanov, Erik Huelsmann, Greg Kennedy, H.Merijn Brand, James E Keenan,
James Raspass, Karen Etheridge, Karl Williamson, Leon Timmermans, Lukas Mai,
Nicolas Mendoza, Nicolas R, OpossumPetya, Paul Evans, Raul E Rangel, Ricardo
Signes, Richard Leach, Steve Hay, Tony Cook, Yves Orton.

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 perl bug database
at L<https://github.com/Perl/perl5/issues>.  There may also be information at
L<http://www.perl.org/>, the Perl Home Page.

If you believe you have an unreported bug, please open an issue at
L<https://github.com/Perl/perl5/issues>.  Be sure to trim your bug down to a
tiny but sufficient test case.

If the bug you are reporting has security implications which make it
inappropriate to send to a public issue tracker, then see
L<perlsec/SECURITY VULNERABILITY CONTACT INFORMATION>
for details of how to report the issue.

=head1 Give Thanks

If you wish to thank the Perl 5 Porters for the work we had done in Perl 5,
you can do so by running the C<perlthanks> program:

    perlthanks

This will send an email to the Perl 5 Porters list with your show of thanks.

=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