[ 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 v5.27.1
+perldelta - what is new for perl v5.27.6
=head1 DESCRIPTION
-This document describes differences between the 5.27.0 release and the 5.27.1
+This document describes differences between the 5.27.5 release and the 5.27.6
release.
-If you are upgrading from an earlier release such as 5.26.0, first read
-L<perl5270delta>, which describes differences between 5.26.0 and 5.27.0.
+If you are upgrading from an earlier release such as 5.27.4, first read
+L<perl5275delta>, which describes differences between 5.27.4 and 5.27.5.
=head1 Notice
[ List each enhancement as a =head2 entry ]
+=head2 Initialisation of aggregate state variables
+
+A persistent lexical array or hash variable can now be initialized,
+by an expression such as C<state @a = qw(x y z)>. Initialization of a
+list of persistent lexical variables is still not possible.
+
+=head2 Full-size inode numbers
+
+On platforms where inode numbers are of a type larger than perl's native
+integer numerical types, L<stat|perlfunc/stat> will preserve the full
+content of large inode numbers by returning them in the form of strings of
+decimal digits. Exact comparison of inode numbers can thus be achieved by
+comparing with C<eq> rather than C<==>. Comparison with C<==>, and other
+numerical operations (which are usually meaningless on inode numbers),
+work as well as they did before, which is to say they fall back to
+floating point, and ultimately operate on a fairly useless rounded inode
+number if the real inode number is too big for the floating point format.
+
=head1 Security
XXX Any security-related notices go here. In particular, any security
[ List each incompatible change as a =head2 entry ]
-=head2 Comma-less variable lists in formats are no longer allowed
-
-Omitting the commas between variables passed to formats is no longer
-allowed. This has been deprecated since perl 5.000.
+=head2 Yada-yada is now strictly a statement
-=head2 The C<:locked> and C<:unique> attributes have been removed
+By the time of its initial stable release in Perl 5.12, the C<...>
+(yada-yada) operator was explicitly intended to serve as a statement,
+not an expression. However, the original implementation was confused
+on this point, leading to inconsistent parsing. The operator was
+accidentally accepted in a few situations where it did not serve as a
+complete statement, such as
-These have been no-ops and deprecated since perl 5.12 and 5.10,
-respectively.
+ ... . "foo";
+ ... if $a < $b;
-=head2 C<\N{}> with nothing between the braces is now illegal.
-
-This has been deprecated since Perl 5.24.
+The parsing has now been made consistent, permitting yada-yada only as
+a statement. Affected code can use C<do{...}> to put a yada-yada into
+an arbitrary expression context.
=head1 Deprecations
XXX Any deprecated features, syntax, modules etc. should be listed here.
-=head2 Some uses of unescaped C<"{"> are no longer fatal
-
-Perl 5.26.0 fatalized some uses of an unescaped left brace, but an
-exception was made at the last minute, specifically crafted to be a
-minimal change to allow GNU Autoconf to work. This code is heavily
-depended upon, and continues to use the deprecated usage. Its use of an
-unescaped left brace is one where we have no intention of repurposing
-C<"{"> to be something other than itself.
-
-That exception is now generalized to include various other such cases
-where the C<"{"> will not be repurposed. This is to get real experience
-with this more complicated change now, in case we need to issue a dot
-release if we find other things like Autoconf that are important to work
-around.
-
-Note that these uses continue to raise a deprecation message.
-
=head2 Module removals
XXX Remove this section if inapplicable.
XXX Changes which enhance performance without changing behaviour go here.
There may well be none in a stable release.
-[ List each enhancement as a =item entry ]
+[ List each enhancement as an =item entry ]
=over 4
=item *
-XXX
+Many string concatenation expressions are now considerably faster, due
+to the introduction internally of a C<multiconcat> opcode which combines
+multiple concatenations, and optionally a C<=> or C<.=>, into a single
+action. For example, apart from retrieving C<$s>, C<$a> and C<$b>, this
+whole expression is now handled as a single op:
+
+ $s .= "a=$a b=$b\n"
+
+As a special case, if the LHS of an assign is a lexical variable or
+C<my $s>, the op itself handles retrieving the lexical variable, which
+is faster.
+
+In general, the more the expression includes a mix of constant strings and
+variable expressions, the longer the expression, and the more it mixes
+together non-utf8 and utf8 strings, the more marked the performance
+improvement. For example on a C<x86_64> system, this code has been
+benchmarked running four times faster:
+
+ my $s;
+ my $a = "ab\x{100}cde";
+ my $b = "fghij";
+ my $c = "\x{101}klmn";
+
+ for my $i (1..10_000_000) {
+ $s = "\x{100}wxyz";
+ $s .= "foo=$a bar=$b baz=$c";
+ }
+
+In addition, C<sprintf> expressions which have a constant format
+containing only C<%s> and C<%%> format elements, and which have a fixed
+number of arguments, are now also optimised into a C<multiconcat> op.
=back
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 ]
+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 Removal of use vars
+
+=over 4
+
+The usage of "use vars" has been discouraged since the introduction of our in
+Perl 5.6.0. Where possible the usage of this pragma has now been removed from
+the Perl source code.
+
+=back
=head2 New Modules and Pragmata
=item *
-L<XXX> has been upgraded from version A.xx to B.yy.
+L<Carp> has been upgraded from version 1.43 to 1.44.
+
+If a package on the call stack contains a constant named C<ISA>, Carp no
+longer throws a "Not a GLOB reference" error.
=back
=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>.
+
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<XXX>
+Additionally, the following selected changes have been made:
+
+=head3 L<perldiag/Variable length lookbehind not implemented in regex m/%s/>
+
+This now gives more ideas as to workarounds to the issue that was
+introduced in Perl 5.18 (but not documented explicitly in its perldelta)
+for the fact that some Unicode C</i> rules cause a few sequences such as
+
+ (?<!st)
+
+to be considered variable length, and hence disallowed.
=over 4
=item *
+The section on reference counting in L<perlguts> has been heavily revised,
+to describe references in the way a programmer needs to think about them
+rather than in terms of the physical data structures.
+
+=item *
+
XXX Description of the change here
=back
=item *
+The diagnostic C<Initialization of state variables in list context
+currently forbidden> has changed to C<Initialization of state variables
+in list currently forbidden>, because list-context initialization of
+single aggregate state variables is now permitted.
+
+=item *
+
XXX Describe change here
=back
However, any platform-specific changes should be listed in the
L</Platform Support> section, instead.
-[ List changes as a =item entry ].
+[ List changes as an =item entry ].
=over 4
-=item *
+=item New probes
-XXX
+=over 2
+
+=item HAS_BUILTIN_ADD_OVERFLOW
+
+=item HAS_BUILTIN_MUL_OVERFLOW
+
+=item HAS_BUILTIN_SUB_OVERFLOW
+
+=item HAS_THREAD_SAFE_NL_LANGINFO_L
+
+=item HAS_LOCALECONV_L
+
+=item HAS_MBRLEN
+
+=item HAS_MBRTOWC
+
+=item HAS_MEMRCHR
+
+=item HAS_NANOSLEEP
+
+=item HAS_STRNLEN
+
+=item HAS_STRTOLD_L
+
+=item I_WCHAR
+
+=back
=back
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 ]
+XXX If there were no significant test changes, say this:
+
+Tests were added and changed to reflect the other additions and changes
+in this release.
+
+XXX If instead there were significant changes, say this:
+
+Tests were added and changed to reflect the other additions and
+changes in this release. Furthermore, these significant changes were
+made:
+
+[ List each test improvement as an =item entry ]
=over 4
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
+[ Within the sections, list each platform as an =item entry with specific
changes as paragraphs below it. ]
=head2 New Platforms
significant internal changes for future core maintainers should be noted as
well.
-[ List each change as a =item entry ]
+[ List each change as an =item entry ]
=over 4
=item *
-The C<PL_statbuf> interpreter variable has been removed.
+A new optimisation phase has been added to the compiler,
+C<optimize_optree()>, which does a top-down scan of a complete optree
+just before the peephole optimiser is run. This phase is not currently
+hookable.
=item *
-The deprecated function C<to_utf8_case()>, accessible from XS code, has
-been removed.
+An C<OP_MULTICONCAT> op has been added. At C<optimize_optree()> time, a
+chain of C<OP_CONCAT> and C<OP_CONST> ops, together optionally with an
+C<OP_STRINGIFY> and/or C<OP_SASSIGN>, are combined into a single
+C<OP_MULTICONCAT> op. The op is of type C<UNOP_AUX>, and the aux array
+contains the argument count, plus a pointer to a constant string and a set
+of segment lengths. For example with
+
+ my $x = "foo=$foo, bar=$bar\n";
+
+the constant string would be C<"foo=, bar=\n"> and the segment lengths
+would be (4,6,1). If the string contains characters such as C<\x80>, whose
+representation changes under utf8, two sets of strings plus lengths are
+precomputed and stored.
+
+=item *
+
+Direct access to L<C<PL_keyword_plugin>|perlapi/PL_keyword_plugin> is not
+safe in the presence of multithreading. A new
+L<C<wrap_keyword_plugin>|perlapi/wrap_keyword_plugin> function has been
+added to allow XS modules to safely define custom keywords even when
+loaded from a thread, analoguous to L<C<PL_check>|perlapi/PL_check> /
+L<C<wrap_op_checker>|perlapi/wrap_op_checker>.
=back
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 ]
+[ List each fix as an =item entry ]
=over 4
=item *
-XXX
+C<stat()>, C<lstat()>, and file test operators now fail if given a
+filename containing a nul character, in the same way that C<open()>
+already fails.
+
+=item *
+
+The in-place reverse optimisation now correctly strengthens weak
+references using the L<C<sv_rvunweaken()>|perlapi/sv_rvunweaken>
+API function.
+
+=item *
+
+Fixed a read before buffer when parsing a range starting with C<\N{}>
+at the beginning of the character set for the transliteration
+operator. [perl #132245]
+
+=item *
+
+Fixed a leaked SV when parsing an empty C<\N{}> at compile-time.
+[perl #132245]
=back
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 ]
+[ List each fix as an =item entry ]
=over 4
XXX Generate this with:
- perl Porting/acknowledgements.pl v5.25.5..HEAD
+ perl Porting/acknowledgements.pl v5.27.5..HEAD
=head1 Reporting Bugs
https://perl5.git.perl.org / perl5.git / blobdiff