Fix two broken links in perldelta.

[perl5.git] / pod / perl5257delta.pod

=encoding utf8

=head1 NAME

perl5257delta - what is new for perl v5.25.7

=head1 DESCRIPTION

This document describes differences between the 5.25.6 release and the 5.25.7
release.

If you are upgrading from an earlier release such as 5.25.5, first read
L<perl5256delta>, which describes differences between 5.25.5 and 5.25.6.

=head1 Core Enhancements

=head2 Indented Here-documents

This adds a new modifier '~' to here-docs that tells the parser
that it should look for /^\s*$DELIM\n/ as the closing delimiter.

These syntaxes are all supported:

    <<~EOF;
    <<~\EOF;
    <<~'EOF';
    <<~"EOF";
    <<~`EOF`;
    <<~ 'EOF';
    <<~ "EOF";
    <<~ `EOF`;

The '~' modifier will strip, from each line in the here-doc, the
same whitespace that appears before the delimiter.

Newlines will be copied as is, and lines that don't include the
proper beginning whitespace will cause perl to croak.

For example:

    if (1) {
      print <<~EOF;
        Hello there
        EOF
    }

prints "Hello there\n" with no leading whitespace.

=head2 '.' and @INC

Perl now provides a way to build perl without C<.> in @INC by default. If you
want this feature, you can build with -Ddefault_inc_excludes_dot

Because the testing / make process for perl modules do not function well with
C<.> missing from @INC, Perl now supports the environment variable
PERL_USE_UNSAFE_INC=1 which makes Perl behave as it previously did, returning
C<.> to @INC in all child processes.

WARNING: PERL_USE_UNSAFE_INC has been provided during the perl 5.25 development
cycle and is not guaranteed to function in perl 5.26.

=head2 create a safer utf8_hop() called utf8_hop_safe()

Unlike utf8_hop(), utf8_hop_safe() won't navigate before the beginning or after
the end of the supplied buffer.

=head2 Fix taint handling in list assignment

commit v5.25.6-79-gb09ed99 reworked list assignment, and
accidentally broke taint handling at the same time.

=head2 @{^CAPTURE}, %{^CAPTURE}, and %{^CAPTURE_ALL}

@{^CAPTURE} exposes the capture buffers of the last match as an array. So $1 is
${^CAPTURE}[0].

%{^CAPTURE} is the equivalent to %+ (ie named captures)

%{^CAPTURE_ALL} is the equivalent to %- (ie all named captures).

=head2 op.c: silence compiler warning in fold_constants()

    op.c: In function ‘S_fold_constants’:
    op.c:4374:28: warning: argument ‘o’ might be clobbered by ‘longjmp’ or ‘vfork’ [-Wclobbered]
     S_fold_constants(pTHX_ OP *o)
                                ^

This warning has been silenced.

=head1 Performance Enhancements

=over 4

=item *

Reduce cost of SvVALID().

=item *

C<$ref1 = $ref2> has been optimized.

=item *

Array and hash assignment are now faster, e.g.

    (..., @a) = (...);
    (..., %h) = (...);

especially when the RHS is empty.

=item *

Reduce the number of odd special cases for the SvSCREAM flag.

=item *

Avoid sv_catpvn() in do_vop() when unneeded.

=item *

Enhancements in Regex concat COW implementation.

=item *

Speed up AV and HV clearing/undeffing.

=item *

Better optimise array and hash assignment

=back

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over 4

=item *

L<podlators> has been upgraded from version 4.08 to 4.09.

=item *

L<Archive::Tar> has been upgraded from version 2.14 to 2.18.

=item *

L<B> has been upgraded from version 1.64 to 1.65.

=item *

L<Data::Dumper> has been upgraded from version 2.162 to 2.165.

The XS implementation now supports Deparse.

=item *

L<Devel::Peek> has been upgraded from version 1.25 to 1.26.

=item *

L<DynaLoader> has been upgraded from version 1.39 to 1.40.

=item *

L<Errno> has been upgraded from version 1.26 to 1.27.

Document that using C<%!> loads Errno for you.

=item *

L<File::Spec> has been upgraded from version 3.65 to 3.66.

=item *

L<Hash::Util> has been upgraded from version 0.21 to 0.22.

=item *

L<JSON::PP> has been upgraded from version 2.27400_01 to 2.27400_02.

=item *

L<List::Util> has been upgraded from version 1.46 to 1.46_02.

=item *

L<Math::BigInt> has been upgraded from version 1.999726(_01) to 1.999727.

There have also been some core customizations.

=item *

L<Math::Complex> has been upgraded from version 1.59 to 1.5901.

=item *

L<Module::CoreList> has been upgraded from version 5.20161020 to 5.20161120.

=item *

L<mro> has been upgraded from version 1.19 to 1.20.

=item *

L<Net::Ping> has been upgraded from version 2.51 to 2.55.

Remove sudo from 500_ping_icmp.t.

Avoid stderr noise in tests

Check for echo in new Net::Ping tests.

=item *

L<Opcode> has been upgraded from version 1.38 to 1.39.

=item *

L<POSIX> has been upgraded from version 1.73 to 1.75.

=item *

L<Scalar::Util> has been upgraded from version 1.46 to 1.46_02.

=item *

L<Storable> has been upgraded from version 2.58 to 2.59.

=item *

L<Term::ANSIColor> has been upgraded from version 4.05 to 4.06.

=item *

L<Test::Simple> has been upgraded from version 1.302059 to 1.302062.

=item *

L<threads> has been upgraded from version 2.09 to 2.10.

=item *

L<Time::HiRes> has been upgraded from version 1.9740_01 to 1.9740_03.

Now uses clockid_t.

=item *

L<Unicode::Collate> has been upgraded from version 1.14 to 1.18.

=item *

L<Unicode::Normalize> is now maintained by p5p and has been moved to dist/

=item *

L<Unicode::UCD> has been upgraded from version 0.66 to 0.67.

=item *

L<XS::Typemap> has been upgraded from version 0.14 to 0.15.

=back

=head1 Documentation

=head2 Changes to Existing Documentation

=head3 L<perlfunc>

=over 4

=item *

Defined on aggregates is no longer allowed. Perlfunc was still reporting it as
deprecated, and that it will be deleted in the future.

=back

=head3 L<perldata>

=over 4

=item *

Use of single character variables, with the variable name a non printable
character in the range \x80-\xFF is no longer allowed. Update the docs to
reflect this.

=back

=head3 L<perlobj>

=over 4

=item *

Added a section on calling methods using their fully qualified names.

=item *

Do not discourage manual @ISA.

=back

=head3 L<perlop>

=over 4

=item *

Clarify behavior single quote regexps.

=back

=head3 L<perllocale>

=over 4

=item *

Some locales aren't compatible with Perl.  Note the potential bad
consequences of using them.

=back

=head3 L<perldiag>

=over 4

=item *

Deprecations are to be marked with a D.
C<"%s() is deprecated on :utf8 handles"> use a deprecation message, and as
such, such be marked C<"(D deprecated)"> and not C<"(W deprecated)">.

=back

=head3 L<perlguts>

=over 4

=item *

add pTHX_ to magic method examples.

=back

=head3 L<perlvar>

=over 4

=item *

Document @ISA. Was documented other places, not not in perlvar.

=back

=head3 L<perlootut>

=over 4

=item *

Tidy the document.

=item *

Mention Moo more.

=back

=head3 L<perlhack>

=over 4

=item *

Document Tab VS Space.

=back

=head3 L<perlre>

=over 4

=item *

Several minor enhancements to the documentation.

=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 *

Improve error for missing tie() package/method. This brings the error messages
in line with the ones used for normal method calls, despite not using
call_method().

=item *

Make the sysread()/syswrite/() etc :utf8 handle warnings default. These
warnings were under 'deprecated' previously.

=item *

'do' errors now refer to 'do' (not 'require').

=back

=head1 Utility Changes

=over 4

=item *

Porting/pod_lib.pl

Removed spurious executable bit.

Account for possibility of DOS file endings.

=item *

perf/benchmarks

Tidy file, rename some symbols.

=item *

Porting/checkAUTHORS.pl

Replace obscure character range with \w.

=item *

t/porting/regen.t

try to be more helpful when tests fail.

=item *

utils/h2xs.PL

Avoid infinite loop for enums.

=back

=head1 Configuration and Compilation

=over 4

=item *

Remove "Warning: perl appears in your path"

This install warning is more or less obsolete, since most platforms already
*will* have a /usr/bin/perl or similar provided by the OS.

=item *

Reduce verbosity of "make install.man"

Previously, two progress messages were emitted for each manpage: one by
installman itself, and one by the function in install_lib.pl that it calls to
actually install the file. Disabling the second of those in each case saves
over 750 lines of unhelpful output.

=item *

Cleanup for clang -Weverything support. [perl 129961]

=item *

Configure: signbit scan was assuming too much, stop assuming negative 0.

=item *

Various compiler warnings have been silenced.

=item *

Several smaller changes have been made to remove impediments to compiling under
C++11.

=back

=head1 Testing

=over 4

=item *

XS-APItest/t/utf8.t: Several small fixes and enhancements.

=item *

Tests for locales were erroneously using locales incompatible with Perl.

=back

=head1 Platform Support

=head2 Platform-Specific Notes

=over 4

=item Darwin

don't treat -Dprefix=/usr as special, instead require an extra option
-Ddarwin_distribution to produce the same results.

=item POSIX

Finish removing POSIX deprecated functions.

=item OS X

OS X El Capitan doesn't implement the clock_gettime() or clock_getres() APIs,
emulate them as necessary.

=item macOS

Deprecated syscall(2) on macOS 10.12.

=item EBCDIC

Several tests have been updated to work (or be skipped) on EBCDIC platforms.

=item HP-UX

L<Net::Ping> UDP test is skipped on HP-UX.

=item VMS

Move _pDEPTH and _aDEPTH after config.h otherwise DEBUGGING may not be defined
yet.

VAXC has not been a possibility for a good long while, and the versions of the
DEC/Compaq/HP/VSI C compiler that report themselves as "DEC" in a listing file
are 15 years or more out-of-date and can be safely desupported.

=item VMS And Win32

Fix some breakage, add 'undef' value for default_inc_excludes_dot in build
scripts.

=item Linux

Drop support for Linux a.out Linux has used ELF for over twenty years.

=item NetBSD-VAX

Test fixes and minor updates.

Account for lack of C<inf>, C<nan>, and C<-0.0> support.

=item Win32

fp definitions have been updated.

=item OpenBSD 6

OpenBSD 6 still does not support returning pid, gid or uid with SA_SIGINFO.
Make sure this is accounted for.

=item FreeBSD

t/uni/overload.t: Skip hanging test on FreeBSD.

=back

=head1 Internal Changes

=over 4

=item *

The meanings of some internal SV flags have been changed

OPpRUNTIME, SVpbm_VALID, SVpbm_TAIL, SvTAIL_on, SvTAIL_off, SVrepl_EVAL,
SvEVALED

=item *

Change C<hv_fetch(…, "…", …, …)> to C<hv_fetchs(…, "…", …)>

The dual-life dists all use Devel::PPPort, so they can use this function even
though it was only added in 5.10.

=back

=head1 Selected Bug Fixes

=over 4

=item *

Handle SvIMMORTALs in LHS of list assign. [perl #129991]

=item *

[perl #130010] a5540cf breaks texinfo

This involved user-defined Unicode properties.

=item *

Fix error message for unclosed C<\N{> in regcomp.

An unclosed C<\N{> could give the wrong error message
C<"\N{NAME} must be resolved by the lexer">.

=item *

List assignment in list context where the LHS contained aggregates and
where there were not enough RHS elements, used to skip scalar lvalues.
Previously, C<(($a,$b,@c,$d) = (1))> in list context returned C<($a)>; now
it returns C<($a,$b,$d)>. C<(($a,$b,$c) = (1))> is unchanged: it still
returns C<($a,$b,$c)>. This can be seen in the following:

    sub inc { $_++ for @_ }
    inc(($a,$b,@c,$d) = (10))

Formerly, the values of C<($a,$b,$d)> would be left as C<(11,undef,undef)>;
now they are C<(11,1,1)>.

=item *

[perl 129903]

The basic problem is that code like this: /(?{ s!!! })/ can trigger infinite
recursion on the C stack (not the normal perl stack) when the last successful
pattern in scope is itself. Since the C stack overflows this manifests as an
untrappable error/segfault, which then kills perl.

We avoid the segfault by simply forbidding the use of the empty pattern when it
would resolve to the currently executing pattern.

=item *

[perl 128997] Avoid reading beyond the end of the line buffer when there's a
short UTF-8 character at the end.

=item *

[perl 129950] fix firstchar bitmap under utf8 with prefix optimisation.

=item *

[perl 129954] Carp/t/arg_string.t: be liberal in f/p formats.

=item *

[perl 129928] make do "a\0b" fail silently instead of throwing.

=item *

[perl 129130] make chdir allocate the stack it needs.

=back

=head1 Acknowledgements

Perl 5.25.7 represents approximately 4 weeks of development since Perl 5.25.6
and contains approximately 83,000 lines of changes across 630 files from 26
authors.

Excluding auto-generated files, documentation and release tools, there were
approximately 13,000 lines of changes to 340 .pm, .t, .c and .h files.

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 5.25.7:

Aaron Crane, Abigail, Andrew Fresh, Andy Lester, Aristotle Pagaltzis, Chad
Granum, Chris 'BinGOs' Williams, Craig A. Berry, Dagfinn Ilmari Mannsåker, Dan
Collins, Dave Rolsky, David Mitchell, Hauke D, H.Merijn Brand, Hugo van der
Sanden, James E Keenan, Jarkko Hietaniemi, Karl Williamson, Lukas Mai, Matthew
Horsfall, Nicolas R., Stefan Seifert, Steve Hay, Todd Rinaldo, Tony Cook, Yves
Orton.

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 perl bug database
at L<https://rt.perl.org/> .  There may also be information at
L<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 see
L<perlsec/SECURITY VULNERABILITY CONTACT INFORMATION>
for details of how to report the issue.

=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