path: root/pod/perldelta.pod

=encoding utf8

=head1 NAME

perldelta - what is new for perl v5.35.5

=head1 DESCRIPTION

This document describes differences between the 5.35.4 release and the 5.35.5
release.

If you are upgrading from an earlier release such as 5.35.3, first read
L<perl5354delta>, which describes differences between 5.35.3 and 5.35.4.

=head1 Core Enhancements

=head2 iterating over multiple values at a time

As of Perl 5.36, you can iterate over multiple values at a time by specifying
a list of lexicals within parentheses. For example,

    for my ($key, $value) (%hash) { ... }
    for my ($left, $right, $gripping) (@moties) { ... }

Attempting to specify a list after C<for my> was previously a syntax error.

For more detail see L<perlsyn/Compound Statements>.

=head1 Incompatible Changes

There are no changes intentionally incompatible with 5.35.4
If any exist, they are bugs, and we request that you submit a
report.  See L</Reporting Bugs> below.

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over 4

=item *

L<B::Concise> has been upgraded from version 1.005 to 1.006.

=item *

L<B::Deparse> has been upgraded from version 1.58 to 1.59.

=item *

L<Digest> has been upgraded from version 1.19 to 1.20.

=item *

L<DynaLoader> has been upgraded from version 1.51 to 1.52.

=item *

L<Encode> has been upgraded from version 3.12 to 3.16.

=item *

L<Errno> has been upgraded from version 1.34 to 1.35.

=item *

L<experimental> has been upgraded from version 0.024 to 0.025.

=item *

L<File::Copy> has been upgraded from version 2.36 to 2.37.

=item *

L<FindBin> has been upgraded from version 1.52 to 1.53.

=item *

L<GDBM_File> has been upgraded from version 1.20 to 1.21.

=item *

L<HTTP::Tiny> has been upgraded from version 0.076 to 0.078.

=item *

L<I18N::Langinfo> has been upgraded from version 0.20 to 0.21.

=item *

L<Module::CoreList> has been upgraded from version 5.20210920 to 5.20211020.

=item *

L<POSIX> has been upgraded from version 1.99 to 2.01.

=item *

L<Scalar::Util> has been upgraded from version 1.56_001 to 1.60.

=item *

L<Test::Simple> has been upgraded from version 1.302185 to 1.302188.

=item *

L<Tie::Handle> has been upgraded from version 4.2 to 4.3.

=item *

L<Tie::Hash> has been upgraded from version 1.05 to 1.06.

=item *

L<Tie::Scalar> has been upgraded from version 1.05 to 1.06.

=item *

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

=item *

L<XS::APItest> has been upgraded from version 1.19 to 1.20.

=back

=head1 Documentation

=head2 Changes to Existing Documentation

We have attempted to update the documentation to reflect the changes
listed in this document.  If you find any we have missed, open an issue
at L<https://github.com/Perl/perl5/issues>.

Additionally, the following selected changes have been made:

=head3 L<perlgov>

=over 4

=item *

The election process has been finetuned to allow the vote to be skipped if there
are no more candidates than open seats.

=item *

A special election is now allowed to be postponed for up to twelve weeks, for
example until a normal election.

=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<panic: newFORLOOP, %s|perldiag/"panic: newFORLOOP, %s">

The parser failed an internal consistency check while trying to parse
a C<foreach> loop.

=back

=head3 New Warnings

=over 4

=item * 

L<for my (...) is experimental|perldiag/"for my (...) is experimental">

This warning is emitted if you use C<for> to iterate multiple values at
a time. This syntax is currently experimental and its behaviour may
change in future releases of Perl.

=back

=head2 Changes to Existing Diagnostics

=over 4

=item * L<'E<sol>' does not take a repeat count in %s|perldiag/"'/' does not take a repeat count in %s">

This warning used to not include the C<in %s>.

=back

=head1 Configuration and Compilation

=over 4

=item *

The Perl C source code now uses some C99 features, which we have verified are
supported by all compilers we target. This means that Perl's headers now
contain some code that is legal in C99 but not C89.

This may cause problems for some XS modules that unconditionally add
C<-Werror=declaration-after-statement> to their C compiler flags if compiling
with gcc or clang. Earlier versions of Perl support long obsolete compilers
that are strict in rejecting certain C99 features, particularly mixed
declarations and code, and hence it makes sense for XS module authors to audit
that their code does not violate this. However, doing this is now only
possible on these earlier versions of Perl, hence these modules need to be
changed to only add this flag for C<<$] < 5.035005>>.

=back

=head1 Testing

Tests were added and changed to reflect the other additions and
changes in this release.  Furthermore, these significant changes were
made:

=over 4

=item * t/op/for-many.t was added

This tests for looping of multiple values as the same time

=back

=head1 Platform Support

=head2 Discontinued Platforms

=over 4

=item NetWare

Support code for Novell NetWare has been removed.  NetWare was a
server operating system by Novell.  The port was last updated in July
2002, and the platform itself in May 2009.

Unrelated changes accidentally broke the build for the NetWare port in
September 2009, and in 12 years no-one has reported this.

=back

=head2 Platform-Specific Notes

=over 4

=item Windows

Support for old MSVC++ (pre-VC12) has been removed

These did not support C99 and hence can no longer be used to compile perl.

=back

=head1 Internal Changes

=over 4

=item *

Memory for hash iterator state (C<struct xpvhv_aux>) is now allocated as part
of the hash body, instead of as part of the block of memory allocated for the
main hash array.

Nothing else changes - memory for this structure is still allocated only when
needed, is still accessed via the C<HvAUX()> macro, and the macro should only
be called when C<SvOOK()> is true. Hashes are still always of type C<SVt_PVHV>,
hash bodies are still allocated from arenas, and the address of the hash
doesn't change, because the address is the pointer to the head structure, which
never moves.

Internally, a second arena (the arena with index 1) is used to allocate larger
bodies with space for C<struct xpvhv_aux>, the body "upgraded", and the "head"
structure updated to reflect this (much the same way that the bodies of scalars
are upgraded). We already re-purpose arenas - arena with index 0 is used for
C<HE *>s.

None of this affects documented public XS interfaces. The only code changes are
in F<hv.c> and F<sv.c>. As the rest of the core itself uses these macros but
needed no changes, likely no code on CPAN will be affected either.

=back

=head1 Selected Bug Fixes

=over 4

=item *

Calling C<untie> on a tied hash that is partway through iteration now frees the
iteration state immediately.

Iterating a tied hash causes perl to store a copy of the current hash key to
track the iteration state, with this stored copy passed as the second parameter
to C<NEXTKEY>. This internal state is freed immediately when tie hash iteration
completes, or if the hash is destroyed, but due to an implementation oversight,
it was not freed if the hash was untied. In that case, the internal copy of the
key would persist until the earliest of

=over 4

=item 1

C<tie> was called again on the same hash

=item 2

The (now untied) hash was iterated (ie passed to any of C<keys>, C<values> or
C<each>)

=item 3

The hash was destroyed.

=back

This inconsistency is now fixed - the internal state is now freed immediately by
C<untie>.

As the precise timing of this behaviour can be observed with pure Perl code
(the timing of C<DESTROY> on objects returned from C<FIRSTKEY> and C<NEXTKEY>)
it's just possible that some code is sensitive to it.

=item *

The C<Internals::getcwd()> function added for bootstrapping miniperl
in perl 5.30.0 is now only available in miniperl. [github #19122]

=back

=head1 Acknowledgements

Perl 5.35.5 represents approximately 4 weeks of development since Perl
5.35.4 and contains approximately 32,000 lines of changes across 380 files
from 22 authors.

Excluding auto-generated files, documentation and release tools, there were
approximately 17,000 lines of changes to 260 .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 5.35.5:

Andrew Fresh, Chris 'BinGOs' Williams, Dagfinn Ilmari Mannsåker, Dan Book,
Dan Kogai, David Mitchell, E. Choroba, Hugo van der Sanden, James E Keenan,
Karl Williamson, Leon Timmermans, Matthew Horsfall, Nicholas Clark, Olaf
Alders, Paul Evans, Ricardo Signes, Richard Leach, Sergey Poznyakoff, Steve
Hay, TAKAI Kousuke, Tomasz Konojacki, Tony Cook.

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