[ 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 v5.27.6
+perldelta - what is new for perl v5.27.8
=head1 DESCRIPTION
-This document describes differences between the 5.27.5 release and the 5.27.6
+This document describes differences between the 5.27.7 release and the 5.27.8
release.
-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.
+If you are upgrading from an earlier release such as 5.27.6, first read
+L<perl5277delta>, which describes differences between 5.27.6 and 5.27.7.
=head1 Notice
[ List each enhancement as a =head2 entry ]
-=head2 Initialisation of aggregate state variables
+=head2 Close-on-exec flag set atomically
-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.
+When opening a file descriptor, perl now generally opens it with its
+close-on-exec flag already set, on platforms that support doing so.
+This improves thread safety, because it means that an C<exec> initiated
+by one thread can no longer cause a file descriptor in the process
+of being opened by another thread to be accidentally passed to the
+executed program.
-=head2 Full-size inode numbers
+Additionally, perl now sets the close-on-exec flag more reliably, whether
+it does so atomically or not. Most file descriptors were getting the
+flag set, but some were being missed.
-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.
+=head2 Mixed Unicode scripts are now detectable
+
+A mixture of scripts, such as Cyrillic and Latin, in a string is often
+the sign of a spoofing attack. A new regular expression construct
+now allows for easy detection of these. For example, you can say
+
+ qr/(?script_run: \d+ \b )/x
+
+And the digits matched will all be from the same set of 10. You won't
+get a look-alike digit from a different script that has a different
+value than what it appears to be.
=head1 Security
[ List each incompatible change as a =head2 entry ]
-=head2 Yada-yada is now strictly a statement
-
-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
-
- ... . "foo";
- ... if $a < $b;
-
-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.
-
-=head2 Subroutines no longer need typeglobs
+=head2 Smartmatch and switch reversion
-Perl 5.22.0 introduced an optimization allowing subroutines to be stored in
-packages as simple sub refs, not requiring a full typeglob (thus
-potentially saving large amounts of memeory). However, the optimization
-was flawed: it only applied to the main package.
-
-This optimization has now been extended to all packages. This may break
-compatibility with introspection code that looks inside stashes and expects
-everything in them to be a typeglob.
-
-When this optimization happens, the typeglob still notionally exists, so
-accessing it will cause the stash entry to be upgraded to a typeglob. The
-optimization does not apply to XSUBs or exported subroutines, and calling a
-method will undo it, since method calls cache things in typeglobs.
-
-[perl #129916] [perl #132252]
-
-=head2 Sort algorithm can no longer be specified
-
-Since Perl 5.8, the L<sort> pragma has had subpragmata C<_mergesort>,
-C<_quicksort>, and C<_qsort> that can be used to specify which algorithm
-perl should use to implement the L<sort|perlfunc/sort> builtin.
-This was always considered a dubious feature that might not last,
-hence the underscore spellings, and they were documented as not being
-portable beyond Perl 5.8. These subpragmata have now been deleted,
-and any attempt to use them is an error. The L<sort> pragma otherwise
-remains, and the algorithm-neutral C<stable> subpragma can be used to
-control sorting behaviour.
+The changes to the experimental smart match operator (C<~~>) and switch
+(C<given>/C<when>) constructs that were made in Perl 5.27.7 have been
+reverted due to the extent of the trouble caused to CPAN modules.
+It is expected that smartmatch will be changed again in the future,
+but preceded by some kind of explicit deprecation.
=head1 Deprecations
=head2 Module removals
-XXX Remove this section if inapplicable.
+XXX Remove this section if not applicable.
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.
=item *
-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.
-
-=item *
-
-Subroutines in packages no longer need to be stored in typeglobs, saving
-large amounts of memory. See L</Subroutines no longer need typeglobs>
-under L</Incompatible Changes>, above.
+The performance of pattern matching C<[[:ascii:]]> and C<[[:^ascii:]]>
+has been improved significantly except on EBCDIC platforms.
=back
[ 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.
-
-This had a slight effect (for the better) on the output of WARNING_BITS in B::Deparse.
-
-=back
-
=head2 New Modules and Pragmata
=over 4
=item *
-XXX
+XXX Remove this section if not applicable.
=back
=item *
-L<Carp> has been upgraded from version 1.43 to 1.44.
+L<XXX> has been upgraded from version A.xx to B.yy.
-If a package on the call stack contains a constant named C<ISA>, Carp no
-longer throws a "Not a GLOB reference" error.
+If there was something important to note about this change, include that here.
=item *
-L<File::Copy> has been upgraded from version 2.32 to 2.33. It will now use
-Time::HiRes utime where available (RT #132401).
-
-=item *
+L<Unicode::UCD> has been upgraded from version 0.69 to 0.70.
-To address a security vulnerability in older versions of the 'zlib' library
-(which is bundled with Compress-Raw-Zlib), L<Compress::Raw::Zlib> has been
-upgraded to CPAN version 2.075.
+The function C<num> now accepts an optional parameter to help in
+diagnosing error returns.
=back
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.
+=head3 L<XXX>
=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 *
-
-The section "Truth and Falsehood" in L<perlsyn> has been removed from
-that document, where it didn't belong, and merged into the existing
-paragraph on the same topic in L<perldata>.
-
-=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
=over 4
-=item C89 requirement
-
-Perl has been documented as requiring a C89 compiler to build since October
-1998. A variety of simplifications have now been made to Perl's internals to
-rely on the features specified by the C89 standard. We believe that this
-internal change hasn't altered the set of platforms that Perl builds on, but
-please report a bug if Perl now has new problems building on your platform.
-
-=item New probes
-
-=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
+=item *
-=back
+XXX
=back
=over 4
-=item Windows
+=item XXX-some-platform
-Visual C++ compiler version detection has been improved to work on non-English
-language systems.
+XXX
=back
=item *
-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 *
-
-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=$bar\n";
-
-the constant string would be C<"foo=, bar=\n"> and the segment lengths
-would be (4,6,1). If the string contains characters such as C<\x80>, whose
-representation changes under utf8, two sets of strings plus lengths are
-precomputed and stored.
-
-=item *
-
-Direct access to L<C<PL_keyword_plugin>|perlapi/PL_keyword_plugin> is not
-safe in the presence of multithreading. A new
-L<C<wrap_keyword_plugin>|perlapi/wrap_keyword_plugin> function has been
-added to allow XS modules to safely define custom keywords even when
-loaded from a thread, analoguous to L<C<PL_check>|perlapi/PL_check> /
-L<C<wrap_op_checker>|perlapi/wrap_op_checker>.
+XXX
=back
=item *
-C<stat()>, C<lstat()>, and file test operators now fail if given a
-filename containing a nul character, in the same way that C<open()>
-already fails.
-
-=item *
-
-C<stat()>, C<lstat()>, and file test operators now reliably set C<$!> when
-failing due to being applied to a closed or otherwise invalid file handle.
-
-=item *
-
-File test operators for Unix permission bits that don't exist on a
-particular platform, such as C<-k> (sticky bit) on Windows, now check that
-the file being tested exists before returning the blanket false result,
-and yield the appropriate errors if the argument doesn't refer to a file.
-
-=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]
-
-=item *
-
-Calling C<do $path> on a directory or block device now yields a meaningful
-error code in C<$!>. [perl #125774]
-
-=item *
-
-Lexical sub declarations in C<do> blocks such as C<do { my sub lex; 123 }>
-could corrupt the stack, erasing items already on the stack in the
-enclosing statement. This has been fixed. [perl #132442]
+XXX
=back
XXX
+=item *
+
+The bugfix for [perl #2754] in Perl 5.27.7 turned out to cause so much
+trouble on CPAN [perl #132577] that it is being postponed. The bug has
+been restored, so C<exit(0)> in a C<UNITCHECK> or C<CHECK> block now
+once again permits the main program to run, and C<exit(0)> in a C<BEGIN>
+block once again permits C<INIT> blocks to run before exiting. The bug
+will be fixed again for Perl 5.30.
+
=back
=head1 Errata From Previous Releases
=head1 Obituary
-XXX If any significant core contributor has died, we've added a short obituary
-here.
+XXX If any significant core contributor or member of the CPAN community has
+died, add a short obituary here.
=head1 Acknowledgements
XXX Generate this with:
- perl Porting/acknowledgements.pl v5.27.5..HEAD
+ perl Porting/acknowledgements.pl v5.27.7..HEAD
=head1 Reporting Bugs
https://perl5.git.perl.org / perl5.git / blobdiff