path: root/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 v5.23.8

=head1 DESCRIPTION

This document describes differences between the 5.23.7 release and the 5.23.8
release.

If you are upgrading from an earlier release such as 5.23.6, first read
L<perl5237delta>, which describes differences between 5.23.6 and 5.23.7.

=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 More fields provided to C<sigaction> callback with C<SA_SIGINFO>

When passing the C<SA_SIGINFO> flag to L<sigaction|POSIX/sigaction>, the
C<errno>, C<status>, C<uid>, C<pid>, C<addr> and C<band> fields are now
included in the hash passed to the handler, if supported by the
platform.

=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 *

The overhead of scope entry and exit has been considerably reduced, so
for example subroutine calls, loops and basic blocks are all faster now.
This empty function call now takes about a third less time to execute:

    sub f{} f();

=item *

On Win32, C<stat>ing or C<-X>ing a path, if the file or directory does not exist
is now 3.5x faster on a SSD (or any drive) than before.

=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 *

F<cpan/podlators/> has been upgraded from version 4.04 to 4.06.

=item *

L<POSIX> has been upgraded from version 1.59 to 1.60.

It can now export constants for the C<code> value in the hash passed to the
L<sigaction|POSIX/sigaction> handler when using the C<SA_SIGINFO> flag.

=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<perlguts>

=over 4

=item *

A new section has been added, L<perlguts/"Dynamic Scope and the Context
Stack">, which explains how the perl context stack works.

=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 *

L<Sequence (?PE<lt>... not terminated in regex; marked by S<<-- HERE> in mE<sol>%sE<sol>
|perldiag/"Sequence (?PE<lt>... not terminated in regex; marked by <-- HERE in mE<sol>%sE<sol>">

=item *

L<Sequence (?PE<gt>... not terminated in regex; marked by S<<-- HERE> in mE<sol>%sE<sol>
|perldiag/Sequence (?PE<gt>... not terminated in regex; marked by <-- HERE in mE<sol>%sE<sol>>

=back

=head3 New Warnings

=over 4

=item *

L<Assuming NOT a POSIX class since %s in regex; marked by E<lt>-- HERE in mE<sol>%sE<sol>|
perldiag/Assuming NOT a POSIX class since %s in regex; marked by <-- HERE in mE<sol>%sE<sol>>

=back

=head2 Changes to Existing Diagnostics

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

=over 4

=item *

XXX Describe change here

=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

=item *

The GNU Make makefile for Win32 now supports parallel builds.  [perl #126632]

=item *

You can now build perl with MSVC++ on Win32 using GNU Make.  [perl #126632]

=back

=head1 Platform Support

=head2 Platform-Specific Notes

=over 4

=item VMS

=over

=item *

For those C<%ENV> elements based on the CRTL environ array, we've always
preserved case when setting them but did look-ups only after upcasing the
key first, which made lower- or mixed-case entries go missing. This problem
has been corrected by making C<%ENV> elements derived from the environ array
case-sensitive on look-up as well as case-preserving on store.

=item *

Environment look-ups for C<PERL5LIB> and C<PERLLIB> previously only
considered logical names, but now consider all sources of C<%ENV> as
determined by C<PERL_ENV_TABLES> and as documented in L<perlvms/%ENV>.

=back

=back

=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

Builds using Microsoft Visual C++ 2003 and earlier no longer produce
an "INTERNAL COMPILER ERROR" message.  [perl #126045]

=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 *

The implementation of perl's context stack system, and its internal API,
have been heavily reworked. Note that no significant changes have been
made to any external APIs, but XS code which relies on such internal
details may need to be fixed. The main changes are:

=over 4

=item *

The C<PUSHBLOCK()>, C<POPSUB()> etc. macros have been replaced with static
inline functions such as C<cx_pushblock()>, C<cx_popsub()> etc. These use
function args rather than implicitly relying on local vars such as
C<gimme> and C<newsp> being available. Also their functionality has
changed: in particular, C<cx_popblock()> no longer decrements
C<cxstack_ix>. The ordering of the steps in the C<pp_leave*> functions
involving C<cx_popblock()>, C<cx_popsub()> etc. has changed. See the new
documentation, L<perlguts/"Dynamic Scope and the Context Stack">, for
details on how to use them.

=item *

Various macros, which now consistently have a CX_ prefix, have been added:

 CX_CUR(), CX_LEAVE_SCOPE(), CX_POP()

or renamed:

 CX_POP_SAVEARRAY(), CX_DEBUG(), CX_PUSHSUBST() ,CX_POPSUBST()

=item *

C<cx_pushblock()> now saves C<PL_savestack_ix> and C<PL_tmps_floor>, so
CMpp_enter*> and C<pp_leave*> no longer do

  ENTER; SAVETMPS; ....; LEAVE

=item *

C<cx_popblock()> now also restores C<PL_curpm>.

=item *

In C<dounwind()> for every context type, the current savestack frame is
now processed before each context is popped; formerly this was only done
for sub-like context frames. This action has been removed from
C<cx_popsub()> and placed into its own macro, C<CX_LEAVE_SCOPE(cx)>, which
must be called before C<cx_popsub()> etc.

C<dounwind()> now also does a C<cx_popblock()> on the last popped frame
(formerly it only did the C<cx_popsub()> etc. actions on each frame).

=item *

The temps stack is now freed on scope exit; previously, temps created
during the last statement of a block wouldn't be freed until the next
C<nextstate> following the block (apart from an existing hack that did
this for recursive subs in scalar context); and in something like
C<f(g())>, the temps created by the last statement in C<g()> would
formerly not be freed until the statement following the return from
C<f()>.

=item *

Most values that were saved on the savestack on scope entry are now
saved in suitable new fields in the context struct, and saved and
restored directly by C<cx_pushfoo()> and C<cx_popfoo()>, which is much
faster.

=item *

Various context struct fields have been added, removed or modified.

=item *

The handling of C<@_> in C<cx_pushsub()> and C<cx_popsub()> has been
considerably tidied up, including removing the C<argarray> field from the
context struct, and extracting out some common (but rarely used) code into
a separate function, C<clear_defarray()>. Also, useful subsets of
C<cx_popsub()> which had been unrolled in places like C<pp_goto> have been
gathered into the new functions C<cx_popsub_args()> and
C<cx_popsub_common()>.

=item *

C<pp_leavesub> and C<pp_leavesublv> now use the same function as the rest
of the C<pp_leave*>'s to process return args.

=item *

C<CXp_FOR_PAD> and C<CXp_FOR_GV> flags have been added, and
C<CXt_LOOP_FOR> has been split into C<CXt_LOOP_LIST>, C<CXt_LOOP_ARY>.

=item *

Some variables formerly declared by C<dMULTICALL> (but not documented) have
been removed.

=back


=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 *

Line numbers larger than 2**31-1 but less than 2**32 are no longer
returned by caller() as negative numbers.  [perl #126991]

=item *

C<< unless ( I<assignment> ) >> now properly warns when syntax
warnings are enabled.  [perl #127122]

=item *

Setting an C<ISA> glob to an array reference now properly adds
C<isaelem> magic to any existing elements.  Previously modifying such
an element would not update the ISA cache, so method calls would call
the wrong function.  Perl would also crash if the C<ISA> glob was
destroyed, since new code added in 5.23.7 would try to release the
C<isaelem> magic from the elements.  [perl #127351]

=item *

If a here-doc was found while parsing another operator, the parser had
already read end of file, and the here-doc was not terminated, perl
could produce an assertion or a segmentation fault.  This now reliably
complains about the unterminated here-doc.  [perl #125540]

=item *

untie() would sometimes return the last value returned by the UNTIE()
handler as well as it's normal value, messing up the stack.  [perl
#126621]

=item *

Fixed an operator precedence problem when C< castflags & 2> is true.
[perl #127474]

=item *

Caching of DESTROY methods could result in a non-pointer or a
non-STASH stored in the SvSTASH() slot of a stash, breaking the B
STASH() method.  The DESTROY method is now cached in the MRO metadata
for the stash.  [perl #126410]

=item *

The AUTOLOAD method is now called when searching for a DESTROY method,
and correctly sets C<$AUTOLOAD> too.  [perl #124387]  [perl #127494]

=item *

Avoid parsing beyond the end of the buffer when processing a C<#line>
directive with no filename.  [perl #127334]

=item *

Perl now raises a warning when a regular expression pattern looks like
it was supposed to contain a POSIX class, like C<qr/[[:alpha:]]/>, but
there was some slight defect in its specification which causes it to
instead be treated as a regular bracketed character class.  An example
would be missing the second colon in the above like this:
C<qr/[[:alpha]]/>.  This compiles to match a sequence of two characters.
The second is C<"]">, and the first is any of: C<"[">, C<":">, C<"a">,
C<"h">, C<"l">, or C<"p">.   This is unlikely to be the intended
meaning, and now a warning is raised.  No warning is raised unless the
specification is very close to one of the 14 legal POSIX classes.  (See
L<perlrecharclass/POSIX Character Classes>.)
[perl #8904]

=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 v5.23.7..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
L<https://rt.perl.org/> .  There may also be information at
L<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