[perl5.git] / pod / perldelta.pod

=for todo
b47a847f62 win32/win32sck.c: dont close() a freed socket os handle
35e037e846 Commit 1735f6f started to escape all...
9b4bdfd44e fix chop formats with non PV vars

=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 v5.19.6

=head1 DESCRIPTION

This document describes differences between the 5.19.5 release and the 5.19.6
release.

If you are upgrading from an earlier release such as 5.19.4, first read
L<perl5195delta>, which describes differences between 5.19.4 and 5.19.5.

=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 $a and $b warnings exemption

The special variables $a and $b, used in C<sort>, are now exempt from "used
once" warnings, even where C<sort> is not used.  This makes it easier for
CPAN modules to provide functions using $a and $b for similar purposes.
[perl #120462]

=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 L<Package::Constants>

=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 *

Constant hash key lookups (C<$hash{key}> as opposed to C<$hash{$key}>) have
long had the internal hash value computed at compile time, to speed up
lookup.  This optimisation has only now been applied to hash slices as
well.

=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 1.46 to 1.47.

C<< B::PMOP->precomp >> now preserves the internal UTF8 flag correctly, so
chr 256 remains chr 256, instead of turning into "\xc4\x80".  This allows
L<B::Deparse> to deparse Unicode regular expression correctly.
[perl #120182]

C<< B::HV->ARRAY >> now preserves the UTF8 flag on returned hash keys.
[perl #120535]

=item *

L<B::Concise> has been upgraded from version 0.99 to 0.991.

B<-debug> output now includes C<op_other> pointers.

=item *

L<B::Deparse> has been upgraded from version 1.23 to 1.24.

C<s//\(3)/e> is now deparsed in a way that does not issue warnings when
parsed again.  [perl #119807]

C<glob(my $x)> is now deparsed correctly, rather than as C<< <my $x> >> or
similar.

C<CORE::glob> is now deparsed correctly with the CORE:: prefix when there
is a subroutine named "glob".

=item *

L<IO::Select> has been upgraded from version 1.21 to 1.22.

Removing a closed file handle from an IO::Select object now correctly
updates its internal state and returns the correct value.  [perl #75156]

=item *

L<Module::CoreList> has been upgraded from version 3.00 to 3.01.

The list of Perl versions covered has been updated.

=item *

L<PerlIO::scalar> has been upgraded from version 0.17 to 0.18.

A bug fix in 0.17 caused references to be stringified as soon as a handle
to it was opened, even if it was opened only for reading.  It also croaked
on read-only references.  This has been fixed.  [perl #119529]

=item *

L<Tie::StdHandle> has been upgraded from version 4.3 to 4.4.

It no longer prints C<$\> twice.  [perl #120202]

It no longer ignores the offset passed to C<syswrite>.

=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 *

L<%%s[%s] in scalar context better written as $%s[%s]|perldiag/"%%s[%s] in scalar context better written as $%s[%s]">:

This warning now occurs for any C<%array[$index]> or C<%hash{key}> known to
be in scalar context at compile time.  Previously it was worded "Scalar
value %%s[%s] better written as $%s[%s]".

=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 *

F<ext/File-Find/t/find.t> has been converted from manual C<print>
statements to Test::More functions.  Each test now has a description.
[perl #120503]

=back

=head1 Platform Support

=head2 New Platforms

=over 4

=item Synology

Synology ships its NAS boxes with a lean Linux distribution (DSM) on relative
cheap CPU's (like the Marvell Kirkwood mv6282 - ARMv5tel or Freescale QorIQ
P1022 ppc - e500v2) not meant for workstations or development. These boxes
should build now. The basic problems are the non-standard location for tools.

=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 Windows

Support for building with Visual C++ 2013 has been added.  There are currently
two possible test failures (see L<perlwin32/"Testing Perl on Windows">) which
will hopefully be resolved soon.

=item WinCE

Perl can now be built in one shot with no user intervention on WinCE by running
C<nmake -f Makefile.ce all>.

Support for building with EVC (Embedded Visual C++) 4 has been restored.  Perl
can also be built using Smart Devices for Visual C++ 2005 or 2008.

=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 *

Compiling with C<-Accflags=-PERL_BOOL_AS_CHAR> now allows C99 and C++
compilers to emulate the aliasing of C<bool> to C<char> that perl does for
C89 compilers.  [perl #120314]

=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 *

Perl 5.18.0 accidentally disallowed C<-bareword> under C<use strict> and
C<use integer>.  This has been fixed.  [perl #120288]

=item *

C<-a> at the start of a line (or a hyphen with any single letter that is
not a filetest operator) no longer produces an erroneous 'Use of "-a"
without parentheses is ambiguous' warning.  [perl #120288]

=item *

Lvalue context is now properly propagated into bare blocks and C<if> and
C<else> blocks in lvalue subroutines.  Previously, arrays and hashes would
sometimes incorrectly be flattened when returned in lvalue list context, or
"Bizarre copy" errors could occur.  [perl #119797]

=item *

Lvalue context is now propagated to the branches of C<||> and C<&&> (and
their alphabetic equivalents, C<or> and C<and>).  This means
C<foreach (pos $x || pos $y) {...}> now allows C<pos> to be modified
through $_.

=item *

C<*DB::DB = sub {} if 0> no longer stops Perl's debugging mode from finding
C<DB::DB> subs declared thereafter.

=item *

C<stat> and C<readline> remember the last handle used; the former
for the special C<_> filehandle, the latter for C<${^LAST_FH}>.
C<eval "*foo if 0"> where *foo was the last handle passed to C<stat>
or C<readline> could cause that handle to be forgotten if the
handle were not opened yet.  This has been fixed.

=item *

Various cases of C<delete $::{a}>, C<delete $::{ENV}> etc. causing a crash
have been fixed.  [perl #54044]

=item *

Assigning another typeglob to C<*^R> no longer makes the regular expression
engine crash.

=item *

C<%{'_<...'}> hashes now set breakpoints on the corresponding C<@{'_<...'}>
rather than whichever array C<@DB::dbline> is aliased to.  [perl #119799]

=item *

Setting C<$!> to EACCESS before calling C<require> could affect
C<require>'s behaviour.  This has been fixed.

=item *

The "Can't use \1 to mean $1 in expression" warning message now only occurs
on the right-hand (replacement) part of a substitution.  Formerly it could
happen in code embedded in the left-hand side, or in any other quote-like
operator.

=item *

The C<\N> regular expression escape, when used without the curly braces (to
mean C<[^\n]>), was ignoring a following C<*> if followed by whitespace
under /x.  It had been this way since C<\N> to mean C<[^\n]> was introduced
in 5.12.0.

=item *

Blessing into a reference (C<bless $thisref, $thatref>) has long been
disallowed, but magical scalars for the second like C<$/> and those tied
were exempt.  They no longer are.  [perl #119809]

=item *

Blessing into a reference was accidentally allowed in 5.18 if the class
argument were a blessed reference with stale method caches (i.e., whose
class had had subs defined since the last method call).  They are
disallowed once more, as in 5.16.

=item *

An undefined lexical sub used as an inherited method no longer crashes.

=item *

C<< $x->{key} >> where $x was declared as C<my Class $x> no longer crashes
if a Class::FIELDS subroutine stub has been declared.

=item *

C<@$obj{'key'}> and C<${$obj}{key}> used to be exempt from compile-time
field checking ("No such class field"; see L<fields>) but no longer are.

=item *

That compile-time field checking also applies now to the C<%$obj{'key'}>
syntax, added recently in Perl 5.19.4.

=item *

A nonexistent array element with a large index passed to a subroutine that
ties the array and then tries to access the element no longer results in a
crash.

=item *

Declaring a subroutine stub named NEGATIVE_INDICES no longer makes negative
array indices crash when the current package is a tied array class.

=item *

Declaring a C<require>, C<glob>, or C<do> subroutine stub in the
CORE::GLOBAL:: package no longer makes compilation of calls to the
corresponding functions crash.

=item *

Aliasing CORE::GLOBAL:: functions to constants stopped working in Perl 5.10
but has now been fixed.

=item *

When C<`...`> or C<qx/.../> calls a C<readpipe> override, double-quotish
interpolation now happens, as is the case when there is no override.
Previously, the presence of an override would make these quote-like
operators act like C<q{}>, suppressing interpolation.  [perl #115330]

=item *

C<<<`...`> here-docs (with backticks as the delimiters) now call
C<readpipe> overrides.  [perl #119827]

=item *

The presence of a lexical sub named "CORE" no longer stops the CORE::
prefix from working.

=item *

C<&CORE::exit()> and C<&CORE::die()> now respect L<vmsish> hints.

=item *

Undefining a glob that triggers a DESTROY method that undefines the same
glob is now safe.  It used to produce "Attempt to free unreferenced glob
pointer" warnings and leak memory.

=item *

If subroutine redefinition (C<eval 'sub foo{}'> or C<newXS> for XS code)
triggers a DESTROY method on the sub that is being redefined, and that
method assigns a subroutine to the same slot (C<*foo = sub {}>), C<$_[0]>
is no longer left pointing to a freed scalar.  Now DESTROY is delayed until
the new subroutine has been installed.

=item *

C<s///>, C<tr///> and C<y///> now work when a wide character is used as the
delimiter.  [perl #120463]

=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 *

C<do CORE()> used to call a sub named "CORE" and treat its return value as
a file name to execute.  A bug fix inadvertently caused it to be
interpreted as the deprecated "do-SUB" construct.  (Yes, C<do
I<bareword>()> is inconsistent.)  This will likely be changed back.

=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 v5.19.5..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