perl #126396 IRIX longdouble infinity issues

[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 v5.23.4

=head1 DESCRIPTION

This document describes differences between the 5.23.3 release and the 5.23.4
release.

If you are upgrading from an earlier release such as 5.23.2, first read
L<perl5233delta>, which describes differences between 5.23.2 and 5.23.3.

=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 ]

=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

=head2 Lexical $_ has been removed

C<my $_> was introduced in Perl 5.10, and subsequently caused much confusion
with no obvious solution.  In Perl 5.18.0, it was made experimental on the
theory that it would either be removed or redesigned in a less confusing (but
backward-incompatible) way.  Over the following years, no alternatives were
proposed.  The feature has now been removed and will fail to compile.

=head2 Only blanks and tabs are now allowed within C<[...]> within C<(?[...])>.

The experimental Extended Bracketed Character Classes can contain regular
bracketed character classes within them.  These differ from regular ones in
that white space is generally ignored, unless escaped by preceding it with a
backslash.  The white space that is ignored is now limited to just tab C<\t>
and SPACE characters.  Previously, it was any white space.  See
L<perlrecharclass/Extended Bracketed Character Classes>.

=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.

=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 *

L<Character following \p must be '{' or a single-character Unicode property name in regex;|perldiag/"Character following \%c must be '{' or a single-character Unicode property name in regex; marked by <-- HERE in m/%s/">

=item *

L<perldiag/"Illegal user-defined property name">

=back

=head3 New Warnings

=over 4

=item *

XXX L<message|perldiag/"message">

=back

=head2 Changes to Existing Diagnostics

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

=over 4

=item *

L<"Can't modify non-lvalue subroutine call of &%s"|perldiag/"Can't modify non-lvalue subroutine call of &%s">

This error now reports the name of the non-lvalue subroutine you attempted to
use as an lvalue.

=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 *

Using the C<NO_HASH_SEED> define in combination with the default hash algorithm
C<PERL_HASH_FUNC_ONE_AT_A_TIME_HARD> resulted in a fatal error while compiling
the interpreter, since Perl 5.17.10.  This has been fixed.

=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 XXX-some-platform

XXX

=item Win32

=over

=item *

A new build option C<USE_NO_REGISTRY> has been added to the makefiles.  This
option is off by default, meaning the default is to do Windows registry
lookups.  This option stops Perl from looking inside the registry for anything.
For what values are looked up in the registry see L<perlwin32>.  Internally, in
C, the name of this option is C<WIN32_NO_REGISTRY>.

=item *

The behavior of Perl using C<HKEY_CURRENT_USER\Software\Perl> and
C<HKEY_LOCAL_MACHINE\Software\Perl> to lookup certain values, including C<%ENV>
vars starting with C<PERL> has changed.  Previously, the 2 keys were checked
for entries at all times through Perl processes life time even if they did not
exist.  For performance reasons, now, if the root key (i.e.
C<HKEY_CURRENT_USER\Software\Perl> or C<HKEY_LOCAL_MACHINE\Software\Perl>) does
not exist at process start time, it will not be checked again for C<%ENV>
override entries for the remainder of the Perl processes life.  This more
closely matches Unix behaviour in that the environment is copied or inherited
on startup and changing the variable in the parent process or another process
or editing <.bashrc> will not change the environmental variable in other
existing, running, processes.

=item *

One glob fetch was removed for each C<-X> or C<stat> call whether done from
Perl code or internally from Perl's C code.  The glob being looked up was
C<${^WIN32_SLOPPY_STAT}> which is a special variable.  This makes C<-X> and
C<stat> slightly faster.

=item *

During miniperl's process startup, during the build process, 4 to 8 IO calls
related to the process starting F<.pl> and the F<buildcustomize.pl> file were
removed from the code opening and executing the first 1 or 2 F<.pl> files.

=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 *

L<perlapi/sv_backoff> had its return type changed from C<int> to C<void>.  It
previously has always returned C<0> since Perl 5.000 stable but that was
undocumented.  Although C<sv_backoff> is marked as public API, XS code is not
expected to be impacted since the proper API call would be through public API
C<sv_setsv(sv, &PL_sv_undef)>, or quasi-public C<SvOOK_off>, or non-public
C<SvOK_off> calls, and the return value of C<sv_backoff> was previously a
meaningless constant that can be rewritten as C<(sv_backoff(sv),0)>.

=item *

The C<EXTEND> and C<MEXTEND> macros have been improved to avoid various issues
with integer truncation and wrapping.  In particular, some casts formerly used
within the macros have been removed.  This means for example that passing an
unsigned nitems arg is likely to raise a compiler warning now (it's always been
documented to require a signed value; formerly int, lately SSize_t).

=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 *

There were places in regular expression patterns where comments (C<(?#...)>)
weren't allowed, but should have been.  This is now fixed.
L<[perl #116639]|https://rt.perl.org/Ticket/Display.html?id=116639>

=item *

A regression from perl Perl 5.20 has been fixed, in which some syntax errors in
L<C<(?[...])>|perlrecharclass/Extended Bracketed Character Classes> constructs
within regular expression patterns could cause a segfault instead of a proper
error message.
L<[perl #126180]|https://rt.perl.org/Ticket/Display.html?id=126180>

=item *

Some problems with attempting to extend the perl stack to around 2G or 4G
entries have been fixed.  This was particularly an issue on 32-bit perls built
to use 64-bit integers, and was easily noticeable with the list repetition
operator, e.g.

    @a = (1) x $big_number

Formerly perl may have crashed, depending on the exact value of C<$big_number>;
now it will typically raise an exception.
L<[perl #125937]|https://rt.perl.org/Ticket/Display.html?id=125937>

=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 *

(This was actually done in Perl 5.23.2, but the perldelta entry got missed.)
The way that C<OP_AASSIGN> handles assignment with potentially common values
(e.g. C<($a,$b) = ($b, $a)> has changed.  In particular the C<OPpASSIGN_COMMON>
flag has been replaced with three more specific flags:

    OPpASSIGN_COMMON_AGG
    OPpASSIGN_COMMON_RC1
    OPpASSIGN_COMMON_SCALAR

and the runtime now sometimes does a mark and sweep using the C<SVf_BREAK> to
detect common elements.

=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 v5.23.3..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