path: root/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 v5.19.9

=head1 DESCRIPTION

This document describes differences between the 5.19.8 release and the 5.19.9
release.

If you are upgrading from an earlier release such as 5.19.7, first read
L<perl5198delta>, which describes differences between 5.19.7 and 5.19.8.

=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.

=head2 UTF-8 locales now supported better under C<S<use locale>>

A UTF-8 locale is one in which the character set is Unicode and the
encoding is UTF-8.  Now, the POSIX C<LC_CTYPE> category operations under
such a locale (within the scope of C<S<use locale>>), which include case
changing (like C<lc()>, C<"\U">), and character classification (C<\w>,
C<\D>, C<qr/[[:punct:]]/> work just as if not under locale, except taint
rules are followed.  Prior to this, Perl only handled single-byte
locales.  This resolves [perl #56820].

=head2 C<S<use locale>> now compiles on systems without locale ability

Previously doing this caused the program to not compile.  Within its
scope the program behaves as if in the "C" locale.  Thus programs
written for platforms that support locales can run on locale-less
platforms without change.  Attempts to change the locale away from the
"C" locale will, of course, fail.

=head2 PERL_DEBUG_READONLY_COW

On some operating systems Perl can be compiled in such a way that any
attempt to modify string buffers shared by multiple SVs will crash.  This
way XS authors can test that their modules handle copy-on-write scalars
correctly.  See L<perlguts/"Copy on Write"> for detail.

This feature was actually added in 5.19.8, but was unintentionally omitted
from its delta document.

=head2 C<-DL> runtime option now added for tracing locale setting

This is designed for Perl core developers to aid in field debugging bugs
regarding locales.

=head2 Subroutine signatures

Declarative syntax to unwrap argument list into lexical variables.
C<sub foo ($a,$b) {...}> checks the number of arguments and puts the
arguments into lexical variables.  Signatures are not equivalent to
the existing idiom of C<sub foo { my($a,$b) = @_; ... }>.  Signatures
are only available by enabling a non-default feature, and generate
warnings about being experimental.  The syntactic clash with
prototypes is managed by disabling the short prototype syntax when
signatures are enabled.

See L<perlsub/Signatures> for details.

=head2 More locale initialization fallback options

If there was an error with locales during Perl start-up, it immediately
gave up and tried to use the C<"C"> locale.  Now it first tries using
other locales given by the environment variables, as detailed in
L<perllocale/ENVIRONMENT>.  For example, if C<LC_ALL> and C<LANG> are
both set, and using the C<LC_ALL> locale fails, Perl will now try the
C<LANG> locale, and only if that fails, will it fall back to C<"C">.  On
Windows machines, Perl will try, ahead of using C<"C">, the system
default locale if all the locales given by environment variables fail.

=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

=head2 Tainting happens under more circumstances; now conforms to documentation

When changing the case of a string (C<lc>, C<"\U">, I<etc>.), within the
scope of C<use locale>, the result is now tainted no matter what the
contents of the string were, as the documentation (L<perlsec>,
L<perllocale/SECURITY>) indicates it should.   Previously, if the string
contained no characters whose case change could be affected by the
locale, the result would not be tainted.  For example, the result of
C<uc()> on an empty string or one containing only above-Latin1 code
points is now tainted.  This leads to more consistent tainting results.

=head2 Quote-like escape changes

The character after C<\c> in a double-quoted string ("..." or qq(...))
or regular expression must now be a printable character and may not be
C<{>.

A literal C<{> after C<\B> or C<\b> is now fatal.

These were deprecated in perl v5.14.

=head1 Deprecations

=over 4

=item *

Setting C<$/> to a reference to zero or a reference to a negative integer is
now deprecated, and will behave B<exactly> as though it was set to C<undef>.
If you want slurp behavior set C<$/> to C<undef> explicitly.

=item *

Setting C<$/> to a reference to a non integer is now forbidden and will
throw an error. Perl has never documented what would happen in this
context and while it used to behave the same as setting C<$/> to
the address of the references in future it may behave differently, so we
have forbidden this usage.

=item *

Use of any of these functions in the C<POSIX> module is now deprecated:
C<isalnum>, C<isalpha>, C<iscntrl>, C<isdigit>, C<isgraph>, C<islower>,
C<isprint>, C<ispunct>, C<isspace>, C<isupper>, and C<isxdigit>.  The
functions are buggy and don't work on UTF-8 encoded strings.  See their
entries in L<POSIX> for more information.

A warning is raised on the first call to any of them from each place in
the code that they are called.  (Hence a repeated statement in a loop
will raise just the one warning.)

=back

=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 ]

=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 *

Code like:

  my $x; # or @x, %x
  my $y;

is now optimized to:

  my ($x, $y);

In combination with the padrange optimization, this means longer
uninitialized my variable statements are also optimized, so:

  my $x; my @y; my %z;

becomes:

  my ($x, @y, %z);

[perl #121077]

=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<autodie> has been upgraded from version 2.22 to 2.23.

C<autodie> no longer weakens strict by allowing undeclared variables
with the same name as built-ins.  [cpan #74246]

C<use autodie qw( foo ! foo);> now correctly insists that we have
hints for foo.

=item *

L<B::Concise> has been upgraded from version 0.991 to 0.992.

Remove the obsolete C<DEREFed> flag.

=item *

L<B::Deparse> has been upgraded from version 1.24 to 1.25.

It now knows how to handle whitespace in prototypes.  Previously, it could
loop infinitely.  [perl #121050]

=item *

L<CGI> has been upgraded from version 3.64 to 3.65.

=item *

L<Compress::Raw::Bzip2> has been upgraded from version 2.063 to 2.064.

Handle non-PVs better.  [cpan #91558]

=item *

L<Compress::Raw::Zlib> has been upgraded from version 2.063 to 2.065.

Handle non-PVs better.  [cpan #91558]

Z_OK instead of Z_BUF_ERROR.  [cpan #92521]

Resolve a C++ build failure in core.  [cpan #92657]

=item *

L<Devel::Peek> has been upgraded from version 1.15 to 1.16.

Devel::Peek::SvREFCNT() now ensures it has been passed a reference, as
specified by its prototype.

=item *

L<Digest::SHA> has been upgraded from version 5.85 to 5.86.

Improved the performance of hexadecimal output functions.

=item *

L<ExtUtils::MakeMaker> has been upgraded from version 6.86 to 6.88.

Improved support for Android and other minor changes.

=item *

L<File::Fetch> has been upgraded from version 0.46 to 0.48.

Force curl to be IPv4 only during testing on NetBSD.

=item *

The IO-Compress module collection has been upgraded from version 2.063
to 2.064.

Android support.

=item *

L<IO::Socket::IP>, tentatively introduced in L<Perl 5.19.8|perl5198delta>,
has been upgraded from 0.26 to 0.28.

=item *

L<IPC::Cmd> has been upgraded from version 0.90 to 0.92.

=item *

The libnet module collection has been upgraded from version 1.24 to 1.25.

The creation of L<Net::FTP> dataconnections now honour the requested timeout,
errors from C<Net::Cmd::response()> are now handled in C<Net::FTP::pasv_wait()>
and a warning from C<Net::Domain::domainname()> on Android is now stopped.

=item *

L<List::Util> has been upgraded from version 1.37 to 1.38.

A backwards-compatibility issue with older perls has been fixed.  [cpan #92363]

=item *

L<Locale::Codes> has been upgraded from version 3.28 to 3.29.

=item *

L<Module::Build> has been upgraded from version 0.4204 to 0.4205.

Fix license code regression for artistic license.

Don't swallow ExtUtils::CBuilder loading errors.

Handle testing on cross-compile builds.

Protect against platforms without getpw{nam,uid}.

=item *

L<Module::Load> has been upgraded from version 0.28 to 0.30.

Prevent uninitialized warnings during testing.

=item *

L<Module::Load::Conditional> has been upgraded from version 0.60 to 0.62.

=item *

L<mro> has been upgraded from version 1.14 to 1.15.

Use HEKfARG() instead of creating and throwing away SVs.

=item *

The PathTools module collection has been upgraded from version 3.45 to
3.46.

Improved support for Android.

C<< File::Spec::Unix->tmpdir >> now consistently returns an absolute
path, unless in taint mode.  [perl #120593]

=item *

L<Pod::Escapes> has been upgraded from version 1.04 to 1.05.

Now strict and warning clean.  Several minor documentation updates.

=item *

L<Pod::Parser> has been upgraded from version 1.61 to 1.62.

=item *

L<threads> has been upgraded from version 1.91 to 1.92.

Synchronization with CPAN release.

=item *

L<version> has been upgraded from version 0.9907 to 0.9908.

=item *

L<warnings> has been upgraded from version 1.21 to 1.22.

C<< use warnings "FATAL"; >> now implies C<< "all" >>, and similarly
for C<< use warnings "NONFATAL" >>.  [perl #120977]

=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<perlfunc>

=over 4

=item *

L<perlfunc/exec>'s handling of arguments is now more clearly
documented.

=back

=head3 L<perlguts>

=over 4

=item *

New sections on L<Read-Only Values|perlguts/"Read-Only Values"> and
L<Copy on Write|perlguts/"Copy on Write"> have been added.  They were
actually added in 5.19.8 but accidentally omitted from its delta document.

=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 *

Added L<Setting $E<sol> to a %s reference is forbidden|perldiag/"Setting $E<sol> to a %s reference is forbidden">

=item *

XXX L<message|perldiag/"message">

=back

=head3 New Warnings

=over 4

=item *

Added L<Setting $E<sol> to a reference to %s as a form of slurp is deprecated, treating as undef|perldiag/"Setting $E<sol> to a reference to %s as a form of slurp is deprecated, treating as undef">

=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 *

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 *

The cross-compilation model has been renovated.
There's several new options, and some backwards-incompatible changes:

We now build binaries for miniperl and generate_uudmap to be used on the host, rather than running
every miniperl call on the target; this means that, short of 'make test',
we no longer need access to the target system once Configure is done.
You can provide already-built binaries through the C<hostperl> and
C<hostgenerate> options to Configure.

Additionally, if targeting an EBCDIC platform from an ASCII host,
or viceversa, you'll need to run Configure with C<-Uhostgenerate>, to
indicate that generate_uudmap should be run on the target.

Finally, there's also a way of having Configure end early, right after
building the host binaries, by cross-compiling without specifying a
C<targethost>.

The incompatible changes include no longer using xconfig.h, xlib, or
Cross.pm, so canned config files and Makefiles will have to be updated.

=item *

Related to the above, there is now a way of specifying the location of sh
(or equivalent) on the target system: C<targetsh>.

For example, Android has its sh in /system/bin/sh, so if cross-compiling
from a more normal Unixy system with sh in /bin/sh, "targetsh" would end
up as /system/bin/sh, and "sh" as /bin/sh.

=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 Android

Perl can now be built for Android, either natively or through
cross-compilation, for all three currently available architectures (ARM,
MIPS, and x86), on a wide range of versions.

=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 VMS

Skip access checks on remotes in opendir().  [perl #121002]

=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 Regexp Engine Changes That Affect The Pluggable Regex Engine Interface

Many flags that used to be exposed via regexp.h and used to populate the
extflags member of struct regexp have been removed. These fields were
technically private to Perl's own regexp engine and should not have been
exposed there in the first place.

The affected flags are:

    RXf_NOSCAN
    RXf_CANY_SEEN
    RXf_GPOS_SEEN
    RXf_GPOS_FLOAT
    RXf_ANCH_BOL
    RXf_ANCH_MBOL
    RXf_ANCH_SBOL
    RXf_ANCH_GPOS

As well as the follow flag masks:

    RXf_ANCH_SINGLE
    RXf_ANCH

All have been renamed to PREGf_ equivalents and moved to regcomp.h.

The behavior previously achieved by setting one or more of the RXf_ANCH_
flags (via the RXf_ANCH mask) have now been replaced by a *single* flag bit
in extflags:

    RXf_IS_ANCHORED

pluggable regex engines which previously used to set these flags should
now set this flag ALONE.

=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 *

Backticks (C< `` > or C< qx// >) combined with multiple threads on
Win32 could result in output sent to stdout on one thread being
captured by backticks of an external command in another thread.

This could occur for pseudo-forked processes too, as Win32's
pseudo-fork is implemented in terms of threads.  [perl #77672]

=item *

C<< open $fh, ">+", undef >> no longer leaks memory when TMPDIR is set
but points to a directory a temporary file cannot be created in.  [perl
#120951]

=item *

C<$^R> wasn't available outside of the regular expression that
initialized it.  [perl #121070]

=item *

Fixed a regular expression bug introduced in 5.19.5 where \S, \W etc
could fail for above ASCII.  [perl #121144]

=item *

A large set of fixes and refactoring for re_intuit_start() was merged,
the highlights are:

=over

=item *

Fixed a panic when compiling the regular expression
C</\x{100}[xy]\x{100}{2}/>.

=item *

Fixed a performance regression when performing a global pattern match
against a UTF-8 string.  [perl #120692]

=item *

Fixed another performance issue where matching a regular expression
like C</ab.{1,2}x/> against a long UTF-8 string would unnecessarily
calculate byte offsets for a large portion of the string. [perl
#120692]

=back

=item *

C< for ( $h{k} || '' ) > no longer auto-vivifies C<$h{k}>.  [perl
#120374]

=item *

On Windows machines, Perl now emulates the POSIX use of the environment
for locale initialization.  Previously, the environment was ignored.
See L<perllocale/ENVIRONMENT>.

=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 perl5180delta.pod

This pod file contains a statement saying that C<RXf_SPLIT> (and its alias
C<RXf_PMf_SPLIT>) and C<RXf_SKIPWHITE> were no longer used and #defined
to 0. This was the case for a short period, but the change was reverted
before Perl 5.18 was released. As such it was not true in Perl 5.18.x,
and is also not true now. Both flags continue to be used. The incorrect
entry has been removed from C<perl5180delta.pod> in this 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 v5.19.9..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