[ List each enhancement as a =head2 entry ]
+=head2 Experimental C Backtrace API
+
+Starting from Perl 5.21.1, on some platforms Perl supports retrieving
+the C level backtrace (similar to what symbolic debuggers like gdb do).
+
+The backtrace returns the stack trace of the C call frames,
+with the symbol names (function names), the object names (like "perl"),
+and if it can, also the source code locations (file:line).
+
+The supported platforms are Linux and OS X (some *BSD might work at
+least partly, but they have not yet been tested).
+
+The feature needs to be enabled with C<Configure -Dusecbacktrace>.
+
+Also included is a C API to retrieve backtraces.
+
+See L<perlhacktips/"C backtrace"> for more information.
+
=head2 C<qr/foo/x> now ignores any Unicode pattern white space
The C</x> regular expression modifier allows the pattern to contain
If any exist, they are bugs, and we request that you submit a
report. See L</Reporting Bugs> below.
+=head2 S<C<"use encoding">> now is a fatal error
+
+The C<encoding> pragma has been deprecated since v5.18, and its use now
+is a fatal error.
+
=head2 C<\N{}> with a sequence of multiple spaces is now a fatal error.
This has been deprecated since v5.18.
'bytes' pragma causes the UTF-8 flag to not be set, just as in previous
Perl releases. This resolves [perl #112208].
+=head2 MAD build option has been removed
+
+MAD = Misc Attribute Decoration; unmaintained attempt at preserving
+the Perl parse tree more faithfully so that automatic conversion of
+Perl 5 to Perl 6 would have been easier.
+
+This build-time configuration option had been unmaintained for years,
+and had probably seriously diverged on both Perl 5 and Perl 6 sides.
+
=head1 Deprecations
XXX Any deprecated features, syntax, modules etc. should be listed here.
regular space, and so should not be allowed. See
L<charnames/CUSTOM ALIASES>.
+=head2 A literal C<"{"> should now be escaped in a pattern
+
+If you want a literal left curly bracket (also called a left brace) in a
+regular expression pattern, you should now escape it by either
+preceding it with a backslash (C<"\{">) or enclosing it within square
+brackets C<"[{]">, or by using C<\Q>; otherwise a deprecation warning
+will be raised. This was first announced as forthcoming in the v5.16
+release; it will allow future extensions to the language to happen.
+
=head2 Module removals
XXX Remove this section if inapplicable.
=item *
+L<Data::Dumper> has been upgraded from version 2.151 to 2.152.
+
+Changes to resolve Coverity issues.
+
+XS dumps incorrectly stored the name of code references stored in a
+GLOB.
+L<[perl #122070]|https://rt.perl.org/Ticket/Display.html?id=122070>
+
+=item *
+
L<Encode> has been upgraded from version 2.60_01 to 2.62.
B<piconv> now has better error handling when the encoding name is nonexistent,
=item *
+L<Hash::Util> has been upgraded from version 0.16 to 0.17.
+
+Minor bug fixes and documentation fixes to Hash::Util::hash_stats()
+
+=item *
+
The libnet collection of modules has been upgraded from version 1.25 to 1.27.
There are only whitespace changes to the installed files.
=item *
-L<perl5db.pl> has been upgraded from version 1.44 to 1.45.
+L<OS2::Process> has been upgraded from version 1.09 to 1.10.
=item *
-A mismatch between the documentation and the code in utf8::downgrade()
-was fixed in favour of the documentation. The optional second argument
-is now correctly treated as a perl boolean (true/false semantics) and
-not as an integer.
-
-=item *
+L<perl5db.pl> has been upgraded from version 1.44 to 1.45.
fork() in the debugger under C<tmux> will now create a new window for
the forked process. L<[perl
restores it when you restart your program with C<R> or <rerun>. L<[perl
#121509]|https://rt.perl.org/Ticket/Display.html?id=121509>
+=item *
+
+L<PerlIO::encoding> has been upgraded from version 0.18 to 0.19.
+
+No changes in behaviour.
+
+=item *
+
+L<PerlIO::mmap> has been upgraded from version 0.012 to 0.013.
+
+No changes in behaviour.
+
+=item *
+
+L<PerlIO::scalar> has been upgraded from version 0.18 to 0.19.
+
+No changes in behaviour.
+
+=item *
+
L<Unicode::Collate> has been upgraded from version 1.04 to 1.07.
Version 0.67's improved discontiguous contractions is invalidated by default
=item *
-L<Hash::Util> has been upgraded from version 0.16 to 0.17.
-
-Minor bug fixes and documentation fixes to Hash::Util::hash_stats()
-
+A mismatch between the documentation and the code in utf8::downgrade()
+was fixed in favour of the documentation. The optional second argument
+is now correctly treated as a perl boolean (true/false semantics) and
+not as an integer.
=back
L<[perl #121523]|https://rt.perl.org/Ticket/Display.html?id=121523>
+=item *
+
+Note that C<exec LIST> and C<system LIST> may fall back to the shell on
+Win32. Only C<exec PROGRAM LIST> and C<system PROGRAM LIST> indirect object
+syntax will reliably avoid using the shell.
+
+This has also been noted in L<perlport>.
+
+L<[perl #122046]|https://rt.perl.org/Ticket/Display.html?id=122046>
+
=back
=head3 L<perlapi>
L<[perl #121869]|https://rt.perl.org/Ticket/Display.html?id=121869>
+=item *
+
+Clarify where C<NUL> may be embedded or is required to terminate a string.
+
+=item *
+
+Previously missing documentation due to formatting errors are now included.
+
+=item *
+
+Entries are now organized into groups rather than by file where they are found.
+
+=item *
+
+Alphabetical sorting of entries is now handled by the POD generator to make
+entries easier to find when scanning.
+
=back
=head3 L<perlhacktips>
=item *
+<> should be quotes
+
+This warning has been changed to
+L<< <> at require-statement should be quotes|perldiag/"<> at require-statement should be quotes" >>
+to make the issue more identifiable.
+
+=item *
+
L<Unsuccessful %s on filename containing newline|perldiag/"Unsuccessful %s on filename containing newline">
This warning is now only produced when the newline is at the end of
XXX
+=item OpenBSD
+
+On OpenBSD, Perl will now default to using the system C<malloc> due to the
+security features it provides. Perl's own malloc wrapper has been in use
+since v5.14 due to performance reasons, but the OpenBSD project believes
+the tradeoff is worth it and would prefer that users who need the speed
+specifically ask for it.
+
+L<[perl #122000]|https://rt.perl.org/Ticket/Display.html?id=122000>.
+
=back
=head1 Internal Changes
developing v5.21. Send email to L<mailto:perl5-porters@perl.org> for
guidance.
+=item *
+
+A new macro L<C<isUTF8_CHAR>|perlapi/isUTF8_CHAR> has been written which
+efficiently determines if the string given by its parameters begins
+with a well-formed UTF-8 encoded character.
+
=back
=head1 Selected Bug Fixes
Many issues have been detected by L<Coverity|http://www.coverity.com/> and
fixed.
+=item *
+
+system() and friends should now work properly on more Android builds.
+
+Due to an oversight, the value specified through -Dtargetsh to Configure
+would end up being ignored by some of the build process. This caused perls
+cross-compiled for Android to end up with defective versions of system(),
+exec() and backticks: the commands would end up looking for C</bin/sh>
+instead of C</system/bin/sh>, and so would fail for the vast majority
+of devices, leaving C<$!> as C<ENOENT>.
+
+=item *
+
+C<qr(...\(...\)...)>,
+C<qr[...\[...\]...]>,
+and
+C<qr{...\{...\}...}>
+now work. Previously it was impossible to escape these three
+left-characters with a backslash within a regular expression pattern
+where otherwise they would be considered metacharacters, and the pattern
+opening delimiter was the character, and the closing delimiter was its
+mirror character.
+
=back
=head1 Known Problems
https://perl5.git.perl.org / perl5.git / blobdiff