add note of 789bd8 .. 03d5bc rev ids to UNDERBAR/etc. delta entry

[p5sagit/p5-mst-13.2.git] / pod / perl5132delta.pod

=encoding utf8

=head1 NAME

perldelta - what is new for perl v5.13.2

=head1 DESCRIPTION

This document describes differences between the 5.13.2 release and
the 5.13.1 release.

If you are upgrading from an earlier release such as 5.10, first read
L<perl5120delta>, which describes differences between 5.10 and
5.12.

=head1 Notice

XXX Any important notices here

=head1 Incompatible Changes

=head2 localised tied scalars are tied again.

The change in behaviour in 5.13.1 of localising tied scalar values has
been reverted to the existing 5.12.0 and earlier behaviour (the change for
arrays and hashes remains).

=head1 Core Enhancements

XXX New core language features go here. Summarise user-visible core language
enhancements. Particularly prominent performance optimisations could go
here, but most should go in the L</Performance Enhancements> section.

=head2 Non-destructive substitution

The substitution operator now supports a C</r> option that
copies the input variable, carries out the substitution on
the copy and returns the result.  The original remains unmodified.

  my $old = 'cat';
  my $new = $old =~ s/cat/dog/r;
  # $old is 'cat' and $new is 'dog'

This is particularly useful with C<map>.  See L<perlop> for more examples
(4f4d75, 000c65).

=head2 package block syntax

A package declaration can now contain a code block, in which case the
declaration is in scope only inside that block.  So C<package Foo { ... }>
is precisely equivalent to C<{ package Foo; ... }>.  It also works with
a version number in the declaration, as in C<package Foo 1.2 { ... }>.
See L<perlfunc> (434da3..36f77d, 702646).

=head1 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.

=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.

=head2 New Modules and Pragmata

=head2 Pragmata Changes

=head2 Updated Modules

=head2 Removed Modules and Pragmata

=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>.

=over 4

=item F<XXX>

XXX

=back

=head1 New Documentation

XXX Changes which create B<new> files in F<pod/> go here.

=over 4

=item L<XXX>

XXX

=back

=head1 Changes to Existing Documentation

XXX Changes which significantly change existing files in F<pod/> go here.
Any changes to F<pod/perldiag.pod> should go in L</New or Changed Diagnostics>.

=head2 Replace wrong tr/// table in perlebcdic.pod

perlebcdic.pod contains a helpful table to use in tr/// to convert
between EBCDIC and Latin1/ASCII.  Unfortunately, the table was the
inverse of the one it describes, though the code that used the table
worked correctly for the specific example given.

The table has been changed to its inverse, and the sample code changed
to correspond, as this is easier for the person trying to follow the
instructions since deriving the old table is somewhat more complicated.

The table has also been changed to hex from octal, as that is more the norm
these days, and the recipes in the pod altered to print out leading
zeros to make all the values the same length, as the table that they can
generate has them (5f26d5).

=head2 Document tricks for user-defined casing

perlunicode.pod now contains an explanation of how to override, mangle
and otherwise tweak the way perl handles upper, lower and other case
conversions on unicode data, and how to provide scoped changes to alter
one's own code's behaviour without stomping on anybody else (71648f).

=head2 INSTALL explicitly states the requirement for C89

This was already true but it's now Officially Stated For The Record.

=head1 Performance Enhancements

Only allocate entries for @_ on demand - this not only saves memory per
subroutine defined but should hopefully improve COW behaviour (77bac2).

Multiple small improvements to threads:

=over 4

=item *

Change the internal structured of thread->params from an SV (RV) to an AV
- so we now pass around and store the array directly, rather than creating,
holding and dereferencing a reference to it (78b7eff).

=item *

Change S_ithread_create() params from a single AV* to a pair of SV** pointers.
This saves creating, duplicating and freeing and AV, which is only ever used for
an internal calling convention (4cf5ea).

=item *

Remove redundant hv_exists() calls from ithread_create()'s spec parser (b1faab).

=item *

Skip unnecessary newAV() in ithread_create() (39f3f7).

=item *

Avoid duping pads created for recursion since there's no point pre-allocating
the same memory in the new thread (6de654).

=back

Eliminated xhv_fill from struct xpvhv: This saves 1 IV per hash and on some
systems will cause struct xpvhv to become cache aligned. To avoid this
memory saving causing a slowdown elsewhere, boolean use of HvFILL now
calls HvTOTALKEYS instead (which is equivalent) - so while the fill data when
actually required is now calculated on demand, the cases when this needs to
be done should be few and far between (f4431c .. fcd245).

=head1 Installation and Configuration Improvements

XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
go here.

=head2 Configuration improvements

XXX

=head2 Compilation improvements

Fix CCINCDIR and CCLIBDIR for mingw64 cross compiler to correctly be under
$(CCHOME)\mingw\include and \lib rather than immediately below $(CCHOME).

This means the 'incpath', 'libpth', 'ldflags', 'lddlflags' and
'ldflags_nolargefiles' values in Config.pm and Config_heavy.pl are now
set correctly (23ae7f).

=head2 Platform Specific Changes

=over 4

=item XXX-some-platform

XXX

=back

=head1 Selected Bug Fixes

Timely cleanup of SVs that are cloned into a new thread but then discovered
to be orphaned (i.e. their owners are -not- cloned) (e42956)

Don't accidentally clone lexicals in scope within active stack frames in
the parent when creating a child thread (RT #73086) (05d04d).

Avoid loading feature.pm when 'no 5.13.2;' or similar is encountered (faee19).

Trap invalid use of SvIVX on SVt_REGEXP when assertions are on (e77da3)

Don't stamp on $DB::single, $DB::trace and $DB::signal if they already have
values when $^P is assigned to (RT #72422) (4c0f30).

chop now correctly handles perl's extended UTF-8 (RT #73246) (65ab92)

=over 4

=item *

Overloading now works properly in conjunction with tied variables. What
formerly happened was that most ops checked their arguments for overloading
I<before> checking for magic, so for example an overloaded object returned
by a tied array access would usually be treated as not overloaded
(RT #57012) (6f1401, ed3b9b, 6a5f8c .. 24328f).

=back

=head1 New or Changed Diagnostics

XXX New or changed warnings emitted by the core's C<C> code go here.

=over 4

=item C<XXX>

XXX

=back

=head1 Changed Internals

XXX Changes which affect the interface available to C<XS> code go here.

=over 4

=item *

The C<find_rundefsvoffset> function has been deprecated. It appeared that
its design was insufficient to reliably get the lexical C<$_> at run-time.

Use the new C<find_rundefsv> function or the C<UNDERBAR> macro instead.
They directly return the right SV representing C<$_>, whether it's lexical
or dynamic (789bd8 .. 03d5bc).

=item *

The following new functions or macros have been added to the public API:
C<SvNV_nomg>,  C<sv_2nv_flags>, C<find_rundefsv>.

=item *

The C<UNDERBAR> macro now calls C<find_rundefsv>. C<dUNDERBAR> is now a
noop but should still be used to ensure past and future compatibility.

=back

=head1 New Tests

XXX Changes which create B<new> files in F<t/> go here. Changes to
existing files in F<t/> aren't worth summarising, although the bugs that
they represent may be.

=over 4

=item F<XXX>

XXX

=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, unless
they were specific to a particular platform (see below).

This is a list of some significant unfixed bugs, which are regressions
from either 5.XXX.XXX or 5.XXX.XXX.

=over 4

=item *

XXX

=back

=head1 Deprecations

XXX Add any new known deprecations here.

The following items are now deprecated.

=over 4

=item *

Omitting a space between a regex pattern or pattern modifiers and the following
word is deprecated.  For example, C<< m/foo/sand $bar >> will still be parsed
as C<< m/foo/s and $bar >> but will issue a warning.

=back

=head1 Platform Specific Notes

XXX Any changes specific to a particular platform. VMS and Win32 are the usual
stars here. It's probably best to group changes under the same section layout
as the main perldelta

=head1 Obituary

XXX If any significant core contributor has died, we've added a short obituary
here.

=head1 Acknowledgements

XXX The list of people to thank goes here.

Your humble release manager would like to specifically call out
Karl Williamson for making the tests a better place to be, and Shlomi
Fish for a passel of tiny incremental docfixes of the sort that don't get
made often enough.

=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 B<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 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