Skip copying perlhist.pod entries to blead for BLEAD-POINT releases

[perl5.git] / pod / perldelta.pod

=encoding utf8

=for comment
Stuff that needs to be done still:
70502ce [perl #119101] Extraneous warnings in Parse::ErrorString::Perl
aa8c2dc Fix RT #41461 (with a test).

=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 v5.19.3

=head1 DESCRIPTION

This document describes differences between the 5.19.2 release and the 5.19.3
release.

If you are upgrading from an earlier release such as 5.19.1, first read
L<perl5192delta>, which describes differences between 5.19.1 and 5.19.2.

=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 B<-F> now implies B<-a> and B<-a> implies B<-n>

Previously B<-F> without B<-a> was a no-op, and B<-a> without B<-n> or
B<-p> was a no-op, with this change, if you supply B<-F> then both
B<-a> and B<-n> are implied and if you supply B<-a> then B<-n> is implied.

You can still use B<-p> for its extra behaviour. [perl #116190]

=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

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>, which prints stub
entries to STDOUT.  Results can be pasted in place of the '=head2' entries
below.  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 1.44 to 1.45.

Calling the C<GV> method on C<B::CV> objects created from a lexical
sub would return nonsense, possibly crashing perl. C<GV> now returns
C<undef> for lexical subs. [perl #118525]

Added the C<NAME_HEK> method to return the name of a lexical sub.

=item *

L<bignum> has been upgraded from version 0.35 to 0.36.

L<bigrat> wasn't correctly updating an internal variable when C<use>d
with a C<lib> option.

=item *

L<Carp> has been upgraded from 1.30 to 1.31

L<Carp> now handles objects with string overloads. It also allows objects
to specify how they appear in the stack dump with a C<CARP_TRACE> method,
and also allows the user to specify their own formatter for objects without
C<CARP_TRACE> as well as other references. [perl #92446]

=item *

L<Compress::Raw::Bzip2> has been upgraded from 2.061 to 2.062.

=item *

L<Compress::Raw::Zlib> has been upgraded from 2.061 to 2.062.

=item *

L<Config::Perl::V> has been upgraded from version 0.18 to 0.19.

=item *

L<Data::Dumper> has been upgraded from version 2.147 to 2.148.

The compatbility of the XS implementation with the pure perl version
under C<Useqq> has been improved. [perl #118933]

=item *

L<Devel::Peek> has been upgraded from version 1.12 to 1.13.

The C<SvREFCNT_inc()> and C<SvREFCNT_dec()> functions have been
removed and C<SvREFCNT()> will now work on non-scalars. [perl #117793]

C<Dump> now checks its arguments at compile time.  Both arguments are now
evaluated in scalar context, with exceptions for @arrays and %hashes,
allowing aggregates to be dumped directly.  The first argument is evaluated
in rvalue scalar context, allowing rvalue C<pos> and C<substr> to be
dumped.  

C<fill_mstats> no longer crashes if its argument is not already a string.
[perl #92260]

=item *

L<Encode> has been upgraded from version 2.51 to 2.52.

Encoding "0" with MIME-Headers no longer gets a blank string.

=item *

L<Exporter> has been upgraded from version 5.68 to 5.69.

L<Exporter> would ignore custom C<$SIG{__WARN__}> handlers in
C<Exporter::Heavy>. [perl #39739]

=item *

The IO-Compress module collection has been upgraded from 2.061 to 2.062.

=item *

L<IPC::Cmd> has been upgraded from version 0.82 to 0.84.

C<run_forked> has various fixes/improvements, L<Socket> is only used where
needed and a regression introduced in 0.78 has been fixed.

=item *

L<IPC::Open3> has been upgradded from version 1.14 to 1.15.

C<open3> would leak a zombie process if the child process I/O
redirection or exec() failed. [perl #114722]

=item *

The libnet module collection has been upgraded from version 1.22 to 1.23.

=item *

L<List::Util> has been upgraded from version 1.27 to 1.30

L<List::Util> now includes C<pairgrep>, C<pairmap>, C<pairs>, C<pairkeys>,
C<pairvalues> and C<pairfirst> functions that operate on even-sized lists of
pairs.

=item *

L<parent> has been upgraded from version 0.225 to 0.226.

=item *

L<Socket> has been upgraded from version 2.010 to 2.011.

Handle FreeBSD (or other platforms) returning shorter AF_UNIX sockaddr
structures due to embedded sun_len. [cpan #86613]

=item *

L<Storable> has been upgraded from version 2.45 to 2.46.

Avoid creating temporary objects for STORABLE_attach when they aren't
required. [perl #118907]

=item *

L<Time::Piece> has been upgraded from version 1.21 to 1.22.

=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<perlopentut>

=over 4

=item *

The C<open> tutorial has been completely rewriten by Tom Christiansen, and now
focuses on covering only the basics, rather than providing a comprehensive
reference to all things openable.  This rewrite came as the result of a
vigorous discussion on perl5-porters kicked off by a set of improvements
written by Alexander Hartmaier to the existing C<perlopentut>.  A "more than
you ever wanted to know about C<open>" document may follow in subsequent
versions of perl.

=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 *

L<Argument "%s" treated as 0 in increment (++)|perldiag/"Argument
"%s" treated as 0 in increment (++)">

(W numeric) The indicated string was fed as an argument to the C<++>
operator which expects either a number or a string matching
C</^[a-zA-Z]*[0-9]*\z/>.  See L<perlop/Auto-increment and
Auto-decrement> for details.

=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 directories F<utils> and F<x2p>.

[ List utility changes as a =head3 entry for each utility and =item
entries for each change
Use L<XXX> with program names to get proper documentation linking. ]

=head3 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

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

=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 *

C<sv_pos_b2u_flags> has been added to the API.  It is similar to
C<sv_pos_b2u>, but supports long strings on 64-bit platforms.

=item *

C<PL_exit_flags> can now be used by perl embedders or other XS code to
have perl warn or abort() on an attempted exit. [perl #52000]

=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 *

Autovivifying a subroutine stub via C<\&$glob> started causing crashes in
Perl 5.18.0 if the $glob was merely a copy of a real glob, i.e., a scalar
that had had a glob assigned to it.  This has been fixed [perl #119051].

=item *

On 64-bit platforms C<pos> can now be set to a value higher than 2**31-1
[perl #72766].

=item *

Perl used to leak an implementation detail when it came to referencing the
return values of certain operators.  C<for ($a+$b) { warn \$_; warn \$_ }>
used to display two different memory addresses, because the C<\> operator
was copying the variable.  Under threaded builds, it would also happen for
constants (C<for(1) { ... }>).  This has been fixed [perl #21979, #78194,
#89188, #109746, #114838, #115388].

=item *

The range operator C<..> was returning the same modifiable scalars with
each call, unless it was the only thing in a C<foreach> loop header.  This
meant that changes to values within the list returned would be visible the
next time the operator was executed [perl #3105].

=item *

Constant folding and subroutine inlining no longer cause operations that
would normally return new modifiable scalars to return read-only values
instead.

=item *

Closures of the form C<sub () { $some_variable }> are no longer inlined,
causing changes to the variable to be ignored by callers of the subroutine
[perl #79908].

=item *

Return values of certain operators such as C<ref> would sometimes be shared
between recursive calls to the same subroutine, causing the inner call to
modify the value returned by C<ref> in the outer call.  This has been
fixed.

=item *

C<__PACKAGE__> and constants returning a package name or hash key are now
consistently read-only.  In various previous Perl releases, they have
become mutable under certain circumstances.

=item *

C</$qr/p> was broken in Perl 5.18.0; the C</p> flag was ignored.  This has
been fixed [perl #118213].

=item *

Starting in v5.18.0, a construct like C</[#](?{})/x> would have its C<#>
incorrectly interpreted as a comment.  The code block would be skipped,
unparsed.  This has been corrected.

=item *

Starting in Perl 5.001, a regular expression like C</[#$a]/x> or
C</[#]$a/x> would have its C<#> incorrectly interpreted as a comment, so
the variable would not interpolate.  This has been corrected [perl #45667].

=item *

On non-threaded builds, setting C<${"_<filename"}> to a reference or
typeglob no longer causes C<__FILE__> and some error messages to produce a
corrupt string, and no longer prevents C<#line> directives in string evals
from providing the source lines to the debugger.  Threaded builds were
unaffected.

=item *

Enabling "used once" warnings no longer causes crashes on stash
circularities created at compile time (C<*Foo::Bar::Foo:: = *Foo::>).

=item *

Undef constants used in hash keys (C<use constant u => undef; $h{+u}>) no
longer produce "uninitialized" warnings at compile time.

=item *

Modifying a substitution target inside the substitution replacement no
longer causes crashes.

=item *

The first statement inside a string eval used to use the wrong pragma setting sometimes during constant folding.  C<eval 'uc chr 0xe0'> would randomly choose between Unicode, byte, and locale semantics.  This has been
fixed.

=item *

The handling of return values of @INC filters (subroutines returned by
subroutines in @INC) has been fixed in various ways.  Previously tied
variables were mishandled, and setting $_ to a reference or typeglob could
result in crashes.

=item *

The C<SvPVbyte> XS function has been fixed to work with tied scalars
returning something other than a string.  It used to return utf8 in those
cases where C<SvPV> would.

=item *

Perl 5.18.0 inadvertently made dereferenced regular expressions
S<(C<${ qr// }>)> false as booleans.  This has been fixed.

=item *

Perl 5.18.0 inadvertently made C<--> and C<++> crash on dereferenced
regular expressions, and stopped C<++> from flattening vstrings.

=item *

C<bless> no longer dies with "Can't bless non-reference value" if its first
argument is a tied reference.

=item *

C<reset> with an argument no longer skips copy-on-write scalars, regular
expressions, typeglob copies, and vstrings.  Also, when encountering those
or read-only values, it no longer skips any array or hash with the same
name.

=item *

C<reset> with an argument now skips scalars aliased to typeglobs
(C<for $z (*foo) { reset "z" }>).  Previously it would corrupt memory or
crash.

=item *

C<ucfirst> and C<lcfirst> were not respecting the bytes pragma.  This was a
regression from v5.12 [perl #117355].

=item *

The use of C<\G> in regular expressions, where it's not at the start of
the pattern, is now slightly less buggy (although it is still somewhat
problematic).

=item *

Where a regular expression included code blocks (C</(?{...})/>), and where
the use of constant overloading triggered a re-compilation of the code block,
the second compilation didn't see its outer lexical scope. This was a
regression in 5.18.0.

=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 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 v5.19.2..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
http://rt.perl.org/perlbug/ .  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