=encoding utf8

=head1 NAME

perldelta - what is new for perl v5.15.4

=head1 DESCRIPTION

This document describes differences between the 5.15.3 release and
the 5.15.4 release.

If you are upgrading from an earlier release such as 5.15.3, first read
L<perl5153delta>, which describes differences between 5.15.3 and
5.15.4.

=head1 Core Enhancements

=head2 $^X converted to an absolute path on FreeBSD, OS X and Solaris

C<$^X> is now converted to an absolute path on OS X, FreeBSD (without
needing F</proc> mounted) and Solaris 10 and 11. This augments the
previous approach of using F</proc> on Linux, FreeBSD and NetBSD
(in all cases, where mounted).

This makes relocatable perl installations more useful on these platforms.
(See "Relocatable @INC" in F<INSTALL>)

=head2 Unicode Symbol Names

Perl now has proper support for Unicode in symbol names.  It used to be
that C<*{$foo}> would ignore the internal UTF8 flag and use the bytes of
the underlying representation to look up the symbol.  That meant that
C<*{"\x{100}"}> and C<*{"\xc4\x80"}> would return the same thing.  All
these parts of Perl have been fixed to account for Unicode:

=over

=item *

Method names (including those passed to C<use overload>)

=item *

Typeglob names (including names of variables, subroutines and filehandles)

=item *

Package names

=item *

Constant subroutine names (not null-clean yet)

=item *

C<goto>

=item *

Symbolic dereferencing

=item *

Second argument to C<bless()> and C<tie()>

=item *

Return value of C<ref()>

=item *

Package names returned by C<caller()>

=item *

Subroutine prototypes

=item *

Attributes

=item *

Various warnings and error messages that mention variable names or values,
methods, etc.

=back

In addition, a parsing bug has been fixed that prevented C<*{é}> from
implicitly quoting the name, but instead interpreted it as C<*{+é}>, which
would cause a strict violation.

C<*{"*a::b"}> automatically strips off the * if it is followed by an ASCII
letter.  That has been extended to all Unicode identifier characters.

C<$é> is now subject to "Used only once" warnings.  It used to be exempt,
as it was treated as a punctuation variable.

Also, single-character Unicode punctuation variables (like $‰) are now
supported [perl #69032].  They are also supported with C<our> and C<my>,
but that is a mistake that will be fixed before 5.16.

=head2 Support for Embedded Nulls

Some parts of Perl did not work correctly with nulls (C<chr 0>) embedded in
strings.  That meant that, for instance, C<< $m = "a\0b"; foo->$m >> would
call the "a" method, instead of the actual method name contained in $m.
These parts of perl have been fixed to support nulls:

=over

=item *

Method names

=item *

Typeglob names (including filehandle names)

=item *

Package names

=item *

Autoloading

=item *

Return value of C<ref()>

=item *

Package names returned by C<caller()>

=item *

Filehandle warnings

=item *

Typeglob elements (C<*foo{"THING\0stuff"}>)

=item *

Signal names

=item *

Various warnings and error messages that mention variable names or values,
methods, etc.

=back

One side effect of these changes is that blessing into "\0" no longer
causes C<ref()> to return false.

=head2 Autoloaded sort Subroutines

Custom sort subroutines can now be autoloaded [perl #30661]:

    sub AUTOLOAD { ... }
    @sorted = sort foo @list; # uses AUTOLOAD

=head2 Improved typemaps for Some Builtin Types

Most XS authors will be aware that there is a longstanding bug
in the OUTPUT typemap for T_AVREF (C<AV*>), T_HVREF (C<HV*>),
T_CVREF (C<CV*>), and T_SVREF (C<SVREF> or C<\$foo>) that requires
manually decrementing the reference count of the return value
instead of the typemap taking care of this. For
backwards-compatibility, this cannot be changed in the default
typemaps. But we now provide additional typemaps
C<T_AVREF_REFCOUNT_FIXED>, etc. that do not exhibit this bug.
Using them in your extension is as simple as having one line
in your C<TYPEMAP> section:

  HV*	T_HVREF_REFCOUNT_FIXED

=head1 Performance Enhancements

=over 4

=item *

C<substr> no longer calculates a value to return when called in void
context.

=back

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over 4

=item *

L<Archive::Tar> has been upgraded from version 1.78 to version 1.80.

=item *

L<base> has been upgraded from version 2.17 to version 2.18.

C<base> no longer sets a module's C<$VERSION> to "-1" when a module it loads
does not define a C<$VERSION>.  This change has been made because "-1" is not
a valid version number under the new "lax" criteria used internally by
C<UNIVERSAL::VERSION>.  (See L<version> for more on "lax" version criteria.)

C<base> no longer internally skips loading modules it has already loaded and
instead relies on C<require> to inspect C<%INC>.  This fixes a bug when C<base>
is used with code that clear C<%INC> to force a module to be reloaded.

=item *

L<Digest> has been upgraded from version 1.16 to version 1.17.

=item *

L<DynaLoader> has been upgraded from version 1.13 to 1.14.

It stopped exporting its symbols with the ExtUtils::ParseXS changes in
5.15.2.  Now it exports them once more.

=item *

L<ExtUtils::MakeMaker> has been upgraded from version 6.59 to version 6.61_01.

=item *

L<ExtUtils::ParseXS> has been upgraded from version 3.04_04 to version 3.05.

=item *

L<Module::CoreList> has been upgraded from version 2.56 to 2.57.

=item *

L<Module::Load> has been upgraded from version 0.20 to version 0.22.

Resolve possible security problem [http://goo.gl/YzHRU] where a '::' prefixed
module can 'jump' out of @INC

=item *

L<perlfaq> has been upgraded from version 5.0150034 to version 5.0150035.

=item *

L<Unicode::Collate> has been upgraded from version 0.78 to version 0.80.

Locales updated to CLDR 2.0: ar, be, bg, ha, hr, kk, lt.
Newly supported locales: as, fi__phonebook, gu, hi, kn, kok and ln.

=back

=head1 Documentation

=head2 Changes to Existing Documentation

=head3 L<perlfunc>, L<open>

=over 4

=item *

As an accident of history, C<open $fh, "<:", ...> applies the default
layers for the platform (C<:raw> on Unix, C<:crlf> on Windows), ignoring
whatever is declared by L<open.pm|open>.  This seems such a useful feature
it has been documented in L<perlfunc|perlfunc/open> and L<open>.

=back

=head3 L<perlapi>

=over 4

=item *

The HV API has long accepted negative lengths to indicate that the key is
in UTF8.  Now this is documented.

=item *

The C<boolSV()> macro is now documented.

=back

=head3 L<perlguts>

=over 4

=item *

A new section, L<Autoloading with XSUBs|perlguts/Autoloading with XSUBs>,
has been added, which explains the two APIs for accessing the name of the
autoloaded sub.

=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>.

=head2 Changes to Existing Diagnostics

=over 4

=item *

The message,
"Code point 0x%X is not Unicode, no properties match it; all inverse
prop erties do" has been changed to "Code point 0x%X is not Unicode, all
\p{} matches fail; all \P{} matches succeed"

=back

=head1 Testing

=over 4

=item *

F<t/porting/checkcfgvar.t> now tests that all config.sh-style files are
complete. These are used by the various non-*nix to generate their
F<config.h>, and an incomplete input file will generate invalid output.

=back

=head1 Internal Changes

=over 4

=item *

These new functions have been added as part of the work on Unicode symbols:

    HvNAMELEN
    HvNAMEUTF8
    HvENAMELEN
    HvENAMEUTF8
    gv_init_pv
    gv_init_pvn
    gv_init_pvsv
    gv_fetchmeth_pv
    gv_fetchmeth_pvn
    gv_fetchmeth_sv
    gv_fetchmeth_pv_autoload
    gv_fetchmeth_pvn_autoload
    gv_fetchmeth_sv_autoload
    gv_fetchmethod_pv_flags
    gv_fetchmethod_pvn_flags
    gv_fetchmethod_sv_flags
    gv_autoload_pv
    gv_autoload_pvn
    gv_autoload_sv
    newGVgen_flags
    sv_derived_from_pv
    sv_derived_from_pvn
    sv_derived_from_sv
    sv_does_pv
    sv_does_pvn
    sv_does_sv
    whichsig_pv
    whichsig_pvn
    whichsig_sv

The gv_fetchmethod_*_flags functions, like gv_fetchmethod_flags, are
experimental and may change in a future release.

=item *

The following functions were added.  These are I<not> part of the API:

    GvNAMEUTF8
    GvENAMELEN
    GvENAME_HEK
    CopSTASH_flags
    CopSTASH_flags_set
    PmopSTASH_flags
    PmopSTASH_flags_set
    sv_sethek
    HEKfARG

There is also a C<HEKf> macro corresponding to C<SVf>, for
interpolating HEKs in formatted strings.

=item *

C<sv_catpvn_flags> takes a couple of new internal-only flags,
C<SV_CATBYTES> and C<SV_CATUTF8>, which tell it whether the char array to
be concatenated is UTF8.  This allows for more efficient concatenation than
creating temporary SVs to pass to C<sv_catsv>.

=item *

For XS AUTOLOAD subs, $AUTOLOAD is set once more, as it was in 5.6.0.  This
is in addition to setting C<SvPVX(cv)>, for compatibility with 5.8 to 5.14.
See L<perlguts/Autoloading with XSUBs>.

=item *

Perl now checks whether the array (the linearised isa) returned by a MRO
plugin begins with the name of the class itself, for which the array was
created, instead of assuming that it does.  This prevents the first element
from being skipped during method lookup.  It also means that
C<mro::get_linear_isa> may return an array with one more element than the
MRO plugin provided [perl #94306].

=back

=head1 Selected Bug Fixes

=over 4

=item *

In Perl 5.14.0, C<$tainted ~~ @array> stopped working properly.  Sometimes
it would erroneously fail (when C<$tainted> contained a string that occurs
in the array I<after> the first element) or erroneously succeed (when
C<undef> occurred after the first element) [perl #93590].

=item *

Perl 5.15.0 introduced a minor regression, in that an object referenced by
a deleted hash element would be able to access the freed element from its
DESTROY method, causing panic errors [perl #99660].

=item *

Functions in the CORE package can now be called as methods.  That used to
work only when they had been called or referenced already.  So
C<< "foo"->CORE::ucfirst >> returns Foo.

=item *

C<use> and C<require> are no longer affected by the I/O layers active in
the caller's scope (enabled by L<open.pm|open>) [perl #96008].

=item *

Errors that occur when methods cannot be found during overloading now
mention the correct package name, as they did in 5.8.x, instead of
erroneously mentioning the "overload" package, as they have since 5.10.0.

=item *

Undefining C<%overload::> no longer causes a crash.

=item *

C<our $::é; $é> (which is invalid) no longer produces the "Compilation
error at lib/utf8_heavy.pl..." error message, which it started emitting in
5.10.0 [perl #99984].

=item *

A minor regression, introduced Perl 5.15.0, has been fixed in which some
regular expression Unicode property matches (C<\p{...}>) matched
non-Unicode code points.

=item *

In case-insensitive regular expression pattern matching, no longer on
UTF-8 encoded strings does the scan for the start of match only look at
the first possible position.  This caused matches such as
C<"f\x{FB00}" =~ /ff/i> to fail.

=item *

On 64-bit systems, C<read()> now understands large string offsets beyond
the 32-bit range.

=item *

Errors that occur when processing subroutine attributes no longer cause the
subroutine's op tree to leak.

=item *

C<sort> now works once more with custom sort routines that are XSUBs.  It
stopped working in 5.10.0.

=item *

C<sort> with a constant for a custom sort routine, although it produces
unsorted results, no longer crashes.  It started crashing in 5.10.0.

=item *

Warnings produced when a custom sort routine returns a non-numeric value
now contain "in sort"; e.g., "Use of uninitialized value in sort".

=item *

C<< sort { $a <=> $b } >>, which is optimised internally, now produces
"uninitialized" warnings for NaNs (not-a-number values), since C<< <=> >>
returns C<undef> for those.  This brings it in line with
S<C<< sort { 1; $a <=> $b } >>> and other more complex cases, which are not
optimised [perl #94390].

=item *

C<..> and C<...> in list context now call FETCH only once on tied
arguments, instead of three or four times [perl #53554].

=item *

C<..> and C<...> in list context now mention the name of the variable in
"uninitialized" warnings for string (as opposed to numeric) ranges.

=back

=head1 Acknowledgements

Perl 5.15.4 represents approximately 1 month of development since Perl 5.15.3
and contains approximately 31,000 lines of changes across 350 files from 23
authors.

Perl continues to flourish into its third decade thanks to a vibrant community
of users and developers. The following people are known to have contributed the
improvements that became Perl 5.15.4:

Alan Haggai Alavi, Brian Fraser, Chip Salzenberg, Chris 'BinGOs' Williams, Dave
Rolsky, David Golden, David Mitchell, Dennis Kaarsemaker, Eric Brine, Father
Chrysostomos, Florian Ragwitz, George Greer, Gerard Goossen, H.Merijn Brand,
Jim Cromie, John P. Linderman, Karl Williamson, Nicholas Clark, Reini Urban,
Steffen Müller, Stevan Little, Thorsten Glaser, Tony Cook.

The list above is almost certainly incomplete as it is automatically generated
from version control history. In particular, it does not include the names of
the (very much appreciated) contributors who reported issues to the Perl bug
tracker.

Many of the changes included in this version originated in the CPAN modules
included in Perl's core. We're grateful to the entire CPAN community for
helping Perl to flourish.

For a more complete list of all of Perl's historical contributors, please see
the F<AUTHORS> file in the Perl source distribution.

=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
