perldelta for c65b7c4d

[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 v5.21.7

=head1 DESCRIPTION

This document describes differences between the 5.21.6 release and the 5.21.7
release.

If you are upgrading from an earlier release such as 5.21.5, first read
L<perl5216delta>, which describes differences between 5.21.5 and 5.21.6.

=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 C<fileno> now works on directory handles

When the relevant support is available in the operating system, the
C<fileno> builtin now works on directory handles, yielding the
underlying file descriptor in the same way as for filehandles. On
operating systems without such support, C<fileno> on a directory handle
continues to return the undefined value, as before, but also sets C<$!> to
indicate that the operation is not supported.

Currently, this uses either a C<dd_fd> member in the OS C<DIR>
structure, or a dirfd(3) function as specified by POSIX.1-2008.

=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 ]

=head2 C<&> and C<\&> prototypes accepts only subs

The C<&> prototype character now accepts only anonymous subs (C<sub {...}>)
and things beginning with C<\&>.  Formerly it erroneously also allowed
C<undef> and references to array, hashes, and lists.  [perl #4539]
[perl #123062]

The C<\&> prototype was allowing subroutine calls, whereas now it only
allows subroutines.  C<&foo> is permitted.  C<&foo()> and C<foo()> are not.
[perl #77860]

=head2 C<use encoding> is now lexical

The L<encoding> pragma's effect is now limited to lexical scope.  This
pragma is deprecated, but in the meantime, it could adversely affect
unrelated modules that are included in the same program.

=head2 List slices returning empty lists

List slices return an empty list now only if the original list was empty
(or if there are no indices).  Formerly, a list slice would return an empty
list if all indices fell outside the original list.  [perl #114498]

=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 ]

=head2 Setting C<${^ENCODING}> to anything but C<undef>

This variable allows Perl scripts to be written in a non-ASCII,
non-UTF-8 encoding.  However, it affects all modules globally, leading
to wrong answers and segmentation faults.  New scripts should be written
in UTF-8; old scripts should be converted to UTF-8, which is easily done
with the L<encoding> pragma.

=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 *

Win32 Perl uses 8 KB less of per-process memory than before for every perl
process of this version. This data is now memory mapped from disk and shared
between perl processes from the same perl binary.

=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<B> has been upgraded from version 1.53 to 1.54.

Nulled COPs are now of class C<B::COP>, rather than C<B::OP>.

B::REGEXP objects now provide a C<qr_anoncv> method for accessing the
implicit CV associated with C<qr//> things containing code blocks.

B::PMOP now provides a C<pmregexp> method returning a B::REGEXP object.

Two new classes, B::PADNAME and B::PADNAMELIST, have been introduced.

=item *

L<B::Deparse> has been upgraded from version 1.30 to 1.31.

BEGIN blocks at the end of the enclosing scope are now deparsed in the
right place.  [perl #77452]

Lexical subroutines are now fully deparsed.  [perl #116553]

Deparsing of C<$lexical =~ //> was accidentally broken in 1.30 (perl
5.21.6), omitting the C<$lexical =~>, but has now been fixed.

C<Anything =~ y///r> with C</r> no longer omits the left-hand operand.

The op trees that make up regexp code blocks are now deparsed for real.
Formerly, the original string that made up the regular expression was used.
That caused problems with C<qr/(?{<<heredoc})/> and multiline code blocks,
which were deparsed incorrectly.  [perl #123217] [perl #115256]

C<$;> at the end of a statement no longer loses its semicolon.
[perl #123357]

Some cases of subroutine declarations stored in the stash in shorthand form
were being omitted.

Non-ASCII characters are now consistently escaped in strings, instead of
some of the time.  (There are still outstanding problems with regular
expressions and identifiers that have not been fixed.)

When prototype sub calls are deparsed with C<&> (e.g., under the B<-P>
option), C<scalar> is now added where appropriate, to force the scalar
context implied by the prototype.

=item *

L<ExtUtils::ParseXS> has been upgraded from version 3.26 to 3.27.

Only declare C<file> unused if we actually define it.

Improve generated C<RETVAL> code generation to avoid repeated
references to C<ST(0)>.  [perl #123278]

=item *

The PathTools module collection has been upgraded from 3.52 to 3.53.

Don't turn leading C<//> into C</> on Cygwin. [perl #122635]

=item *

L<Locale::Maketext> has been upgraded from version 1.25 to 1.26.

=item *

L<XSLoader> has been upgraded from version 0.19 to 0.20

Don't test twice for bootstrap file.

=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 *

XXX L<message|perldiag/"message">

=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 *

"Variable %s will not stay shared" has been changed to say "Subroutine"
when it is actually a lexical sub that will not stay shared.

=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

=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

=head3 Win32

=over

=item *

Intel C builds are now always built with C99 mode on.

=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 PADNAME and PADNAMELIST types are now separate types, and no longer
simply aliases for SV and AV.  [perl #123223]

=item *

Pad names are now always UTF8.  The C<PadnameUTF8> macro always returns
true.  Previously, this was effectively the case already, but any support
for two different internal representations of pad names has now been
removed.

=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 *

On Win32, restoring in a child pseudo-process a variable that was
C<local()>ed in a parent pseudo-process before the C<fork> happened caused
memory corruption and a crash in the child pseudo-process (and therefore OS
process).  [perl #40565]

=item *

Calling C<write> on a format with a C<^**> field could produce a panic
in sv_chop() if there were insufficient arguments or if the variable
used to fill the field was empty.  [perl #123245]

=item *

Non-ASCII lexical sub names (use in error messages) on longer have extra
junk on the end.

=item *

The C<\@> subroutine prototype no longer flattens parenthesized arrays
(taking a reference to each element), but takes a reference to the array
itself.  [perl #47363]

=item *

A block containing nothing except a C-style C<for> loop could corrupt the
stack, causing lists outside the block to lose elements or have elements
overwritten.  This could happen with C<map { for(...){...} } ...> and with
lists containing C<do { for(...){...} }>.  [perl #123286]

=item *

C<scalar()> now propagates lvalue context, so that
C<for(scalar($#foo)) { ... }> can modify C<$#foo> through C<$_>.

=item *

C<qr/@array(?{block})/> no longer dies with "Bizarre copy of ARRAY".
[#123344]

=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 v5.21.6..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
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