=head1 NAME
-[ 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.
-
-=head1 Notice
-
-XXX Any important notices here
+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 Core Enhancements
-XXX New core language features go here. Summarize user-visible core language
-enhancements. Particularly prominent performance optimisations could go
-here, but most should go in the L</Performance Enhancements> section.
-
-[ 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.
-
-=head1 Security
-
-XXX Any security-related notices go here. In particular, any security
-vulnerabilities closed should be noted here rather than in the
-L</Selected Bug Fixes> section.
-
-[ List each security issue as a =head2 entry ]
-
-=head1 Incompatible Changes
+=head2 Mixed Unicode scripts are now detectable
-XXX For a release on a stable branch, this section aspires to be:
+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
- There are no changes intentionally incompatible with 5.XXX.XXX
- If any exist, they are bugs, and we request that you submit a
- report. See L</Reporting Bugs> below.
+ qr/(?script_run: \d+ \b )/x
-[ List each incompatible change as a =head2 entry ]
+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.
-=head2 Yada-yada is now strictly a statement
+=head2 String- and number-specific bitwise ops are no longer experimental
-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
+The new string-specific (C<&. |. ^. ~.>) and number-specific (C<& | ^ ~>)
+bitwise operators introduced in Perl 5.22 are no longer experimental.
+Because the number-specific ops are spelled the same way as the existing
+operators that choose their behaviour based on their operands, these
+operators must still be enabled via the "bitwise" feature, in either of
+these two ways:
- ... . "foo";
- ... if $a < $b;
+ use feature "bitwise";
-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.
+ use v5.28; # "bitwise" now included
-=head2 Subroutines no longer need typeglobs
+They are also now enabled by the B<-E> command-line switch.
-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.
+The "bitwise" feature no longer emits a warning. Existing code that
+disables the "experimental::bitwise" warning category that the feature
+previously used will continue to work.
-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.
+One caveat that module authors ought to be aware of is that the numeric
+operators now pass a fifth TRUE argument to overload methods. Any methods
+that check the number of operands may croak if they do not expect so many.
+XS authors in particular should be aware that this:
-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.
+ SV *
+ bitop_handler (lobj, robj, swap)
-[perl #129916] [perl #132252]
+may need to be changed to this:
-=head1 Deprecations
+ SV *
+ bitop_handler (lobj, robj, swap, ...)
-XXX Any deprecated features, syntax, modules etc. should be listed here.
-
-=head2 Module removals
-
-XXX Remove this section if inapplicable.
-
-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.
-Distributions on CPAN which require these modules will need to list them as
-prerequisites.
-
-The core versions of these modules will now issue C<"deprecated">-category
-warnings to alert you to this fact. To silence these deprecation warnings,
-install the modules in question from CPAN.
-
-Note that these are (with rare exceptions) fine modules that you are encouraged
-to continue to use. Their disinclusion from core primarily hinges on their
-necessity to bootstrapping a fully functional, CPAN-capable Perl installation,
-not usually on concerns over their design.
-
-=over
-
-=item XXX
-
-XXX Note that deprecated modules should be listed here even if they are listed
-as an updated module in the L</Modules and Pragmata> section.
+=head1 Incompatible Changes
-=back
+=head2 Smartmatch and switch reversion
-[ List each other deprecation as a =head2 entry ]
+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 Performance Enhancements
-XXX Changes which enhance performance without changing behaviour go here.
-There may well be none in a stable release.
-
-[ List each enhancement as an =item entry ]
-
=over 4
=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
=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 Removal of use vars
+=head2 New Modules and Pragmata
=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.
+=item *
+
+XXX Remove this section if not applicable.
=back
-=head2 New Modules and Pragmata
+=head2 Updated Modules and Pragmata
=over 4
=item *
-XXX
+L<XXX> has been upgraded from version A.xx to B.yy.
-=back
+If there was something important to note about this change, include that here.
-=head2 Updated Modules and Pragmata
+=item *
-=over 4
+L<Unicode::UCD> has been upgraded from version 0.69 to 0.70.
+
+The function C<num> now accepts an optional parameter to help in
+diagnosing error returns.
=item *
-L<Carp> has been upgraded from version 1.43 to 1.44.
+L<XSLoader> has been upgraded from version 0.29 to 0.30.
-If a package on the call stack contains a constant named C<ISA>, Carp no
-longer throws a "Not a GLOB reference" error.
+Platforms that use C<mod2fname> to edit the names of loadable libraries now look for
+bootstrap (.bs) files under the correct, non-edited name.
=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).
+L<Socket> has been upgraded from version 2.020_04 to 2.027.
=back
XXX Changes to files in F<pod/> go here. Consider grouping entries by
file and be sure to link to the appropriate page, e.g. L<perlfunc>.
-=head2 New Documentation
-
-XXX Changes which create B<new> files in F<pod/> go here.
-
-=head3 L<XXX>
-
-XXX Description of the purpose of the new file here
-
=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.
-
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<perlembed>
=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.
+An example in L<perlembed> used the string value of C<ERRSV> as a
+format string when calling croak(). If that string contains format
+codes such as C<%s> this could crash the program.
-=item *
+This has been changed to a call to croak_sv().
-XXX Description of the change here
+An alternative could have been to supply a trivial format string:
-=back
+ croak("%s", SvPV_nolen(ERRSV));
-=head1 Diagnostics
+or as a special case for C<ERRSV> simply:
-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>.
-
-XXX New or changed warnings emitted by the core's C<C> code go here. Also
-include any changes in L<perldiag> that reconcile it to the C<C> code.
-
-=head2 New Diagnostics
+ croak(NULL);
-XXX Newly added diagnostic messages go under here, separated into New Errors
-and New Warnings
+=back
-=head3 New Errors
+=head3 L<perlfunc>
=over 4
=item *
-XXX L<message|perldiag/"message">
+Improve the documentation of C<each> with a slightly more
+explicit description of the sharing of iterator state, and with
+caveats regarding the fragility of while-each loops. [perl #132644]
=back
-=head3 New Warnings
+=head3 L<perlfunc>, L<perlop>, L<perlsyn>
=over 4
=item *
-XXX L<message|perldiag/"message">
+Improve the documentation of while condition magic in various
+places. [perl #132644]
=back
-=head2 Changes to Existing Diagnostics
-
-XXX Changes (i.e. rewording) of diagnostic messages go here
+=head3 L<perlrun>
=over 4
=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
+Clarify the documentation of B<< -m >>. [perl #131518]
=back
-=head1 Utility Changes
+=head1 Diagnostics
-XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
-Most of these are built within the directory F<utils>.
+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>.
-[ List utility changes as a =head2 entry for each utility and =item
-entries for each change
-Use L<XXX> with program names to get proper documentation linking. ]
+=head2 New Diagnostics
-=head2 L<XXX>
+=head3 New Errors
=over 4
=item *
-XXX
-
-=back
+L<Can't "goto" into a binary or list expression|perldiag/"Can't E<quot>gotoE<quot> into a binary or list expression">
-=head1 Configuration and Compilation
+Use of C<goto> to jump into the parameter of a binary or list operator has
+been prohibited, to prevent crashes and stack corruption. [perl #130936]
-XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
-go here. Any other changes to the Perl build process should be listed here.
-However, any platform-specific changes should be listed in the
-L</Platform Support> section, instead.
+=back
-[ List changes as an =item entry ].
+=head2 Changes to Existing Diagnostics
=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
+The C<< Unable to flush stdout >> error message was missing a trailing
+newline. [debian #875361]
=back
=head1 Testing
-XXX Any significant changes to the testing of a freshly built perl should be
-listed here. Changes which create B<new> files in F<t/> go here as do any
-large changes to the testing harness (e.g. when parallel testing was added).
-Changes to existing files in F<t/> aren't worth summarizing, although the bugs
-that they represent may be covered elsewhere.
-
-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
=item *
-XXX
-
-=back
-
-=head1 Platform Support
-
-XXX Any changes to platform support should be listed in the sections below.
-
-[ Within the sections, list each platform as an =item entry with specific
-changes as paragraphs below it. ]
-
-=head2 New Platforms
-
-XXX List any platforms that this version of perl compiles on, that previous
-versions did not. These will either be enabled by new files in the F<hints/>
-directories, or new subdirectories and F<README> files at the top level of the
-source tree.
-
-=over 4
+Allow override of watchdog timer count in F<re/pat_psycho.t>.
-=item XXX-some-platform
-
-XXX
+This test can take a long time to run, so there is a timer to keep
+this in check (currently, 5 minutes). This commit adds checking
+the environment variable C<< PERL_TEST_TIME_OUT_FACTOR >>; if set,
+the time out setting is multiplied by its value.
=back
-=head2 Discontinued Platforms
+=head1 Platform Support
-XXX List any platforms that this version of perl no longer compiles on.
+=head2 Platform-Specific Notes
=over 4
-=item XXX-some-platform
-
-XXX
+=item Cygwin
-=back
+A build with the quadmath library can now be done on Cygwin.
-=head2 Platform-Specific Notes
+=item FreeBSD
-XXX List any changes for specific platforms. This could include configuration
-and compilation changes or changes in portability/compatibility. However,
-changes within modules for platforms should generally be listed in the
-L</Modules and Pragmata> section.
+FreeBSD's F<< /usr/share/mk/sys.mk >> specifies C<< -O2 >> for
+architectures other than arm and mips. By default, compile perl
+with the same optimization levels.
-=over 4
+=item VMS
-=item XXX-some-platform
+Several fix-ups for F<configure.com>, marking function VMS has
+(or doesn't have).
-XXX
=back
-=head1 Internal Changes
-
-XXX Changes which affect the interface available to C<XS> code go here. Other
-significant internal changes for future core maintainers should be noted as
-well.
-
-[ List each change as an =item entry ]
+=head1 Selected Bug Fixes
=over 4
=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.
+The C<printf> format specifier C<%.0f> no longer rounds incorrectly
+[perl #47602], and now shows the correct sign for a negative zero.
=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.
+Fixed a use after free bug in pp_list introduced in 5.27.1. [perl #131954]
=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
-
-=head1 Selected Bug Fixes
+Don't stringify numeric first arguments to
+C<< system() >> on Windows or VMS. [perl #132633]
-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>.
+=item *
-[ List each fix as an =item entry ]
-
-=over 4
-
-=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.
+Fixed an issue where the error C<< Scalar value @arrayname[0] better
+written as $arrayname >> would give an error C<< Cannot printf Inf with 'c' >>
+when arrayname starts with C<< Inf >>. [perl #132645]
=item *
-The in-place reverse optimisation now correctly strengthens weak
-references using the L<C<sv_rvunweaken()>|perlapi/sv_rvunweaken>
-API function.
+The Perl implementation of C<< getcwd() >> in C<< Cwd >> in the PathTools
+distribution now behaves the same as XS implementation on errors: it
+returns an error, and sets C<< $! >>. [perl #132648]
=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]
+Fixed argument counting in multiconcat when concatenating adjacent constants.
+[perl #132646]
=item *
-Fixed a leaked SV when parsing an empty C<\N{}> at compile-time.
-[perl #132245]
+Vivify array elements when putting them on the stack.
+Fixes [perl #8910] (reported in April 2002).
=item *
-Calling C<do $path> on a directory or block device now yields a meaningful
-error code in C<$!>. [perl #125774]
+Fixed parsing of braced subscript after parens. Fixes [perl #8045]
+(reported in December 2001).
=back
=head1 Known Problems
-XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
-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 an =item entry ]
-
-=over 4
-
-=item *
-
-XXX
-
-=back
-
-=head1 Errata From Previous Releases
-
=over 4
=item *
-XXX Add anything here that we forgot to add, or were mistaken about, in
-the perldelta of a previous release.
+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 Obituary
-
-XXX If any significant core contributor has died, we've added 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