perldelta for f75dfdbdb9d5

[perl5.git] / pod / perldelta.pod

=encoding utf8

=head1 NAME

perldelta - what is new for perl v5.29.6

=head1 DESCRIPTION

This document describes differences between the 5.29.5 release and the 5.29.6
release.

If you are upgrading from an earlier release such as 5.29.4, first read
L<perl5295delta>, which describes differences between 5.29.4 and 5.29.5.

=head1 Core Enhancements

=head2 The upper limit C<"n"> specifiable in a regular expression
quantifier of the form C<"{m,n}"> has been doubled to 65534

The meaning of an unbounded upper quantifier C<"{m,}"> remains unchanged.
It matches 2**31 - 1 times on most platforms, and more on ones where a C
language short variable is more than 4 bytes long.

The text above is what perl5294delta should have said.  Instead it said
"The maximum number of times a pattern can match has been doubled to 65535"
That statement was wrong.  Try to forget you ever saw it.

=head1 Security

=head2 [CVE-2018-18312] Heap-buffer-overflow write in S_regatom (regcomp.c)

A crafted regular expression could cause heap-buffer-overflow write during
compilation, potentially allowing arbitrary code execution. (This was 
actually fixed in 5.29.4, but not announced as a security fix at the time).

L<[perl #133423]|https://rt.perl.org/Ticket/Display.html?id=133423>

=head1 Performance Enhancements

=over 4

=item *

Optimization of C<IV> to C<UV> conversions.
L<[perl #133677]|https://rt.perl.org/Ticket/Display.html?id=133677>.

=item *

Speed up of the integer stringification algorithm by processing
two digits at a time instead of one.
L<[perl #133691]|https://rt.perl.org/Ticket/Display.html?id=133691>.

=item *

Improvements based on LGTM analysis and recommendation.
(L<https://lgtm.com/projects/g/Perl/perl5/alerts/?mode=tree>). 
L<[perl #133686]|https://rt.perl.org/Ticket/Display.html?id=133686>.
L<[perl #133699]|https://rt.perl.org/Ticket/Display.html?id=133699>.

=item *

Code optimizations in F<regcomp.c>, F<regcomp.h>, F<regexec.c>.

=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.

The list of new and updated modules is modified automatically as part of
preparing a Perl release, so the only reason to manually add entries here is if
you're summarising the important changes in the module update. (Also, if the
manually-added details don't match the automatically-generated ones, the
release manager will have to investigate the situation carefully.)

[ Within each section, list entries as an =item entry ]

=head2 New Modules and Pragmata

=over 4

=item *

XXX Remove this section if not applicable.

=back

=head2 Updated Modules and Pragmata

=over 4

=item *

L<Config::Perl::V>. has been upgraded from version 0.30 to 0.31. This was due
to a new configuration variable that has influence on binary compatibility:
C<USE_THREAD_SAFE_LOCALE>.

=item *

L<threads::shared> has been upgraded from version 1.58 to 1.59.

=item *

L<Test::Simple> has been upgraded from version 1.302140 to 1.302141.

=item *

L<File::Find> has been upgraded from 1.34 to 1.35.
C<$File::Find::dont_use_nlink> now defaults to 1 on all platforms.

=item *

L<XXX> has been upgraded from version A.xx to B.yy.

If there was something important to note about this change, include that here.

=back

=head2 Removed Modules and Pragmata

=over 4

=item *

XXX

=back

=head1 Documentation

=head2 Changes to Existing Documentation

We have attempted to update the documentation to reflect the changes
listed in this document.  If you find any we have missed, send email
to L<perlbug@perl.org|mailto:perlbug@perl.org>.

Additionally, the following selected changes have been made:

=head3 L<perlfunc>

=over 4

=item *

Clarification of behaviour of C<reset EXPR>.

=back

=head3 L<perlreref>

=over 4

=item *

Clarification of the syntax of /(?(cond)yes)/.

=back

=head3 L<perlop>

=over

=item *

We no longer have null (empty line) here doc terminators, so 
L<perlop> should not refer to them.

=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 *

Under C<< -Dr >> (or C<< use re 'Debug' >>) the compiled regex engine
program is displayed. It used two different spellings for I<< infinity >>,
C<< INFINITY >>, and C<< INFTY >>. It now uses the latter exclusively,
as that spelling has been around the longest.

=back

=head1 Utility Changes

=head2 L<xsubpp>

=over 4

=item *

The generated prototype (with C<< PROTOTYPES: ENABLE >>) would include
C<< OUTLIST >> parameters, but these aren't arguments to the perl function.
This has been rectified.
L<[perl #133654]|https://rt.perl.org/Ticket/Display.html?id=133654>.

=back

=head1 Testing

Tests were added and changed to reflect the other additions and
changes in this release.  Furthermore, these significant changes were
made:

=over 4

=item *

Some tests in F<< t/io/eintr.t >> caused the process to hang on
pre-16 Darwin. These tests are skipped for those version of Darwin.

=back

=head1 Platform Support

=head2 Platform-Specific Notes

=over 4

=item Cygwin

Cygwin doesn't make C<< cuserid >> visible.

=item Win32 Mingw

C99 math functions are now available.

=back

=head1 Internal Changes

=over 4

=item *

Two new regnodes have been introduced C<< EXACT_ONLY8 >>, and
C<< EXACTFU_ONLY8 >>. They're equivalent to C<< EXACT >> and C<< EXACTFU >>,
except that they contain a code point which requires UTF-8 to
represent/match. Hence, if the target string isn't UTF-8, we know
it can't possibly match, without needing to try.

=item *

C<< print_bytes_for_locale() >> is now defined if C<< DEBUGGING >>,
Prior, it didn't get defined unless C<< LC_COLLATE >> was defined
on the platform.

=back

=head1 Selected Bug Fixes

=over 4

=item *

If an in-place edit is still in progress during global destruction and
the process exit code (as stored in C<$?>) is zero, perl will now
treat the in-place edit as successful, replacing the input file with
any output produced.

This allows code like:

  perl -i -ne 'print "Foo"; last'

to replace the input file, while code like:

  perl -i -ne 'print "Foo"; die'

will not.  Partly resolves
L<[perl #133659]|https://rt.perl.org/Ticket/Display.html?id=133659>.

=item *

A regression in 5.28 caused the following code to fail

 close(STDIN); open(CHILD, "|wc -l")'

because the child's stdin would be closed on exec. This has now been fixed.

=item *

Fixed an issue where compiling a regexp containing both compile-time
and run-time code blocks could lead to trying to compile something
which is invalid syntax.

=item *

Fixed build failures with C<< -DNO_LOCALE_NUMERIC >> and
C<< -DNO_LOCALE_COLLATE >>.
L<[perl #133696]|https://rt.perl.org/Ticket/Display.html?id=133696>.

=item *

Prevent the tests in F<< ext/B/t/strict.t >> from being skipped.
L<[perl #133713]|https://rt.perl.org/Ticket/Display.html?id=133713>.

=item *

C<< /di >> nodes ending or beginning in I<s> are now C<< EXACTF >>. We do not
want two C<< EXACTFU >> to be joined together during optimization,
and to form a C<< ss >>, C<< sS >>, C<< Ss >> or C<< SS >> sequence;
they are the only multi-character sequences which may match differently
under C<< /ui >> and C<< /di >>. 

=back

=head1 Acknowledgements

XXX Generate this with:

  perl Porting/acknowledgements.pl v5.29.5..HEAD

=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 Give Thanks

If you wish to thank the Perl 5 Porters for the work we had done in Perl 5,
you can do so by running the C<perlthanks> program:

    perlthanks

This will send an email to the Perl 5 Porters list with your show of thanks.

=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