=head1 NAME
-perldelta - what is new for perl v5.9.3
+perl593delta - what is new for perl v5.9.3
=head1 DESCRIPTION
=head2 Parsing of C<-f _>
-C<_> is now forced to be a bareword after a filetest operator. This solves
-a number of misparsing issues when a global C<_> subroutine is defined.
+The identifier C<_> is now forced to be a bareword after a filetest
+operator. This solves a number of misparsing issues when a global C<_>
+subroutine is defined.
=head2 C<mkdir()>
=head2 The C<feature> pragma
The C<feature> pragma is used to enable new syntax that would break Perl's
-backward-compatibility with older releases of the language. It's a lexical
+backwards-compatibility with older releases of the language. It's a lexical
pragma, like C<strict> or C<warnings>.
Currently the following new features are available: C<switch> (adds a
Those features are described below.
Note that C<err> low-precedence defined-or operator used to be enabled by
-default, but as a weak keyword. It's now only recognized when explicitely
-turned on.
+default (although as a weak keyword, meaning that any function would
+override it). It's now only recognized when explicitly turned on (and is
+then a regular keyword).
+
+Those features, and the C<feature> pragma itself, have been contributed by
+Robin Houston.
=head2 Switch and Smart Match operator
-XXX
+Perl 5 now has a switch statement. It's available when C<use feature
+'switch'> is in effect. This feature introduces three new keywords,
+C<given>, C<when>, and C<default>:
+
+ given ($foo) {
+ when (/^abc/) { $abc = 1; }
+ when (/^def/) { $def = 1; }
+ when (/^xyz/) { $xyz = 1; }
+ default { $nothing = 1; }
+ }
+
+A more complete description of how Perl matches the switch variable
+against the C<when> conditions is given in L<perlsyn/"Switch statements">.
+
+This kind of match is called I<smart match>, and it's also possible to use
+it outside of switch statements, via the new C<~~> operator (enabled via
+the C<use feature '~~'> directive). See L<perlsyn/"Smart matching in
+detail">.
=head2 C<say()>
-say() is a new built-in, only avaiable when C<use feature 'say'> is in
+say() is a new built-in, only available when C<use feature 'say'> is in
effect, that is similar to print(), but that implicitly appends a newline
to the printed string. See L<perlfunc/say>.
C<CLONE>, C<CLONE_SKIP> is called once per package; however, it is called
just before cloning starts, and in the context of the parent thread. If it
returns a true value, then no objects of that class will be cloned. See
-L<perlmod> for details.
+L<perlmod> for details. (Contributed by Dave Mitchell.)
=head2 C<${^CHILD_ERROR_NATIVE}>
A new internal variable, C<${^CHILD_ERROR_NATIVE}>, gives the native
status returned by the last pipe close, backtick command, successful call
to wait() or waitpid(), or from the system() operator. See L<perlrun> for
-details.
+details. (Contributed by Gisle Aas.)
=head2 Assertions
The support for assertions, introduced in perl 5.9.0, has been improved.
The syntax for the C<-A> command-line switch has changed; it now accepts
an optional module name, defaulting to C<assertions::activate>. See
-L<assertions> and L<perlrun>.
+L<assertions> and L<perlrun>. (Contributed by Salvador Fandiño García.)
=head2 Unicode Character Database 4.1.0
=head2 C<no VERSION>
You can now use C<no> followed by a version number to specify that you
-want to use a version of perl inferior to the specified one.
+want to use a version of perl older than the specified one.
=head2 Recursive sort subs
-You can now use recursive subroutines with sort().
+You can now use recursive subroutines with sort(), thanks to Robin Houston.
=head2 Effect of pragmas in eval
=head2 New B<-E> command-line switch
B<-E> is equivalent to B<-e>, but it implicitly enables all
-optional features.
+optional features (like C<use feature ":5.10">).
+
+=head2 C<chdir>, C<chmod> and C<chown> on filehandles
+
+C<chdir>, C<chmod> and C<chown> can now work on filehandles as well as
+filenames, if the system supports respectively C<fchdir>, C<fchmod> and
+C<fchown>, thanks to a patch provided by Gisle Aas.
+
+=head2 OS groups
+
+C<$(> and C<$)> now return groups in the order where the OS returns them,
+thanks to Gisle Aas. This wasn't previously the case.
=head1 Modules and Pragmata
-=head2 C<feature>
+=head2 New Core Modules
+
+=over 4
+
+=item *
+
+A new pragma, C<feature>, has been added; see above in L</"Core
+Enhancements">.
+
+=item *
+
+C<assertions::compat>, also available on CPAN, allows the use of assertions on
+perl versions prior to 5.9.0 (that is the first one to natively support
+them).
+
+=item *
+
+C<Math::BigInt::FastCalc> is an XS-enabled, and thus faster, version of
+C<Math::BigInt::Calc>.
-This new module implements the C<feature> pragma; see above in
-L</"Core Enhancements">.
+=item *
+
+C<Compress::Zlib> is an interface to the zlib compression library. It
+comes with a bundled version of zlib, so having a working zlib is not a
+prerequisite to install it. It's used by C<Archive::Tar> (see below).
+
+=item *
+
+C<IO::Zlib> is an C<IO::>-style interface to C<Compress::Zlib>.
-=head2 C<assertions::compat>
+=item *
-=head2 C<Math::BigInt::FastCalc>
+C<Archive::Tar> is a module to manipulate C<tar> archives.
-=head2 C<Compress::Zlib>
+=item *
-=head2 C<IO::Zlib>
+C<Digest::SHA> is a module used to calculate many types of SHA digests,
+has been included for SHA support in the CPAN module.
-=head2 C<Archive::Tar>
+=item *
+
+C<ExtUtils::CBuilder> and C<ExtUtils::ParseXS> have been added.
+
+=back
=head1 Utility Changes
=head2 C<ptar>
+C<ptar> is a pure perl implementation of C<tar>, that comes with
+C<Archive::Tar>.
+
+=head2 C<ptardiff>
+
+C<ptardiff> is a small script used to generate a diff between the contents
+of a tar archive and a directory tree. Like C<ptar>, it comes with
+C<Archive::Tar>.
+
+=head2 C<shasum>
+
+This command-line utility, used to print or to check SHA digests, comes
+with the new C<Digest::SHA> module.
+
+=head2 C<h2xs> enhancements
+
+C<h2xs> implements a new option C<--use-xsloader> to force use of
+C<XSLoader> even in backwards compatible modules.
+
+The handling of authors' names that had apostrophes has been fixed.
+
+Any enums with negative values are now skipped.
+
+=head2 C<perlivp> enhancements
+
+C<perlivp> no longer checks for F<*.ph> files by default. Use the new C<-a>
+option to run I<all> tests.
+
=head1 Documentation
=head2 Perl Glossary
The L<perlglossary> manpage is a glossary of terms used in the Perl
-documentation, technical and otherwise.
+documentation, technical and otherwise, kindly provided by O'Reilly Media,
+Inc.
+
+L<perltodo> now lists a rough roadmap to Perl 5.10.
=head1 Performance Enhancements
=head2 XS-assisted SWASHGET
Some pure-perl code that perl was using to retrieve Unicode properties and
-transliteration mappings has been retrieved in XS.
+transliteration mappings has been reimplemented in XS.
+
+=head2 Constant subroutines
+
+The interpreter internals now support a far more memory efficient form of
+inlineable constants. Storing a reference to a constant value in a symbol
+table is equivalent to a full typeglob referencing a constant subroutine,
+but using about 400 bytes less memory. This proxy constant subroutine is
+automatically upgraded to a real typeglob with subroutine if necessary.
+The approach taken is analogous to the existing space optimisation for
+subroutine stub declarations, which are stored as plain scalars in place
+of the full typeglob.
+
+Several of the core modules have been converted to use this feature for
+their system dependent constants - as a result C<use POSIX;> now takes about
+200K less memory.
+
+=head2 C<PERL_DONT_CREATE_GVSV>
+
+The new compilation flag C<PERL_DONT_CREATE_GVSV>, introduced as an option
+in perl 5.8.8, is turned on by default in perl 5.9.3. It prevents perl
+from creating an empty scalar with every new typeglob. See L<perl589delta>
+for details.
+
+=head2 Weak references are cheaper
-=head2 Constants subroutines
+Weak reference creation is now I<O(1)> rather than I<O(n)>, courtesy of
+Nicholas Clark. Weak reference deletion remains I<O(n)>, but if deletion only
+happens at program exit, it may be skipped completely.
-XXX
+=head2 sort() enhancements
+
+Salvador Fandiño provided improvements to reduce the memory usage of C<sort>
+and to speed up some cases.
=head1 Installation and Configuration Improvements
+=head2 Compilation improvements
+
+Parallel makes should work properly now, although there may still be problems
+if C<make test> is instructed to run in parallel.
+
+Building with Borland's compilers on Win32 should work more smoothly. In
+particular Steve Hay has worked to side step many warnings emitted by their
+compilers and at least one C compiler internal error.
+
+Perl extensions on Windows now can be statically built into the Perl DLL,
+thanks to a work by Vadim Konovalov.
+
=head2 New Or Improved Platforms
Perl is being ported to Symbian OS. See L<perlsymbian> for more
=head2 New probes
-Perl will detect and use internally futimes(2) if available.
+C<Configure> will now detect C<clearenv> and C<unsetenv>, thanks to a
+patch from Alan Burlison. It will also probe for C<futimes> (and use it
+internally if available), and whether C<sprintf> correctly returns the
+length of the formatted string.
=head2 Module auxiliary files
=head2 Calling CORE::require()
CORE::require() and CORE::do() were always parsed as require() and do()
-when they were overriden. This is now fixed.
+when they were overridden. This is now fixed.
=head2 Subscripts of slices
Using the sprintf() function with some formats could lead to a buffer
overflow in some specific cases. This has been fixed, along with several
-other bugs, notably in bound checking.
+other bugs, notably in bounds checking.
-In related fixes, a format string injection vulnerability has been fixed
-in Sys::Syslog.
+In related fixes, it was possible for badly written code that did not follow
+the documentation of C<Sys::Syslog> to have formatting vulnerabilities.
+C<Sys::Syslog> has been changed to protect people from poor quality third
+party code.
+
+=head2 no warnings 'category' works correctly with -w
+
+Previously when running with warnings enabled globally via C<-w>, selective
+disabling of specific warning categories would actually turn off all warnings.
+This is now fixed; now C<no warnings 'io';> will only turn off warnings in the
+C<io> class. Previously it would erroneously turn off all warnings.
=head2 Smaller fixes
=item *
+Trailing spaces are now trimmed from C<$!> and C<$^E>.
+
+=item *
+
+Operations that require perl to read a process's list of groups, such as reads
+of C<$(> and C<$)>, now dynamically allocate memory rather than using a
+fixed sized array. The fixed size array could cause C stack exhaustion on
+systems configured to use large numbers of groups.
+
+=item *
+
C<PerlIO::scalar> now works better with non-default C<$/> settings.
=item *
-You can now use the C<x> operator to demultiply a C<qw//> list. This used
-to raise a syntax error.
+The C<x> repetition operator is now able to operate on C<qw//> lists. This
+used to raise a syntax error.
=item *
=item *
-C<//g> matches used to loop infinitely on tainted data.
+Perl will now use the C library calls C<unsetenv> and C<clearenv> if present
+to delete keys from C<%ENV> and delete C<%ENV> entirely, thanks to a patch
+from Alan Burlison.
=back
character, unless when the C<bytes> pragma is in effect, where the low
eight bytes of the value are used.
+=item *
+
+Some case insensitive matches between UTF-8 encoded data and 8 bit regexps,
+and vice versa, could give malformed character warnings. These have been
+fixed by Dave Mitchell and Yves Orton.
+
+=item *
+
+C<lcfirst> and C<ucfirst> could corrupt the string for certain cases where
+the length UTF-8 encoding of the string in lower case, upper case or title
+case differed. This was fixed by Nicholas Clark.
+
=back
=head1 New or Changed Diagnostics
$r = do {my @a; \$#a};
$$r = 503;
+=head2 Non-string passed as bitmask
+
+This is a new warning, produced when number has been passed as a argument to
+select(), instead of a bitmask.
+
+ # Wrong, will now warn
+ $rin = fileno(STDIN);
+ ($nfound,$timeleft) = select($rout=$rin, undef, undef, $timeout);
+
+ # Should be
+ $rin = '';
+ vec($rin,fileno(STDIN),1) = 1;
+ ($nfound,$timeleft) = select($rout=$rin, undef, undef, $timeout);
+
=head2 Search pattern not terminated or ternary operator parsed as search pattern
This syntax error indicates that the lexer couldn't find the final
my $x; our $x; # warns
our $x; my $x; # warns
-On the other hand, the following :
+On the other hand, the following:
our $x; our $x;
=head1 Changed Internals
-XXX consting
+In general, the source code of perl has been refactored, tied up, and
+optimized in many places. Also, memory management and allocation has been
+improved in a couple of points.
+
+Andy Lester supplied many improvements to determine which function
+parameters and local variables could actually be declared C<const> to the C
+compiler. Steve Peters provided new C<*_set> macros and reworked the core to
+use these rather than assigning to macros in LVALUE context.
+
+Dave Mitchell improved the lexer debugging output under C<-DT>.
A new file, F<mathoms.c>, has been added. It contains functions that are
no longer used in the perl core, but that remain available for binary or
source compatibility reasons. However, those functions will not be
-compiled in if you add C<-DNO_MATHOM> in the compiler flags.
+compiled in if you add C<-DNO_MATHOMS> in the compiler flags.
The C<AvFLAGS> macro has been removed.
+The C<av_*()> functions, used to manipulate arrays, no longer accept null
+C<AV*> parameters.
+
=head2 B:: modules inheritance changed
The inheritance hierarchy of C<B::> modules has changed; C<B::NV> now
inherits from C<B::SV> (it used to inherit from C<B::IV>).
-=head1 Known Problems
-
-=head2 Platform Specific Problems
-
=head1 Reporting Bugs
If you find what you think is a bug, you might check the articles
https://perl5.git.perl.org / perl5.git / blobdiff