=head1 NAME
-perldelta - what's new for perl5.006 (as of 5.005_56)
+perldelta - what's new for perl v5.6 (as of v5.005_61)
=head1 DESCRIPTION
+This is an unsupported alpha release, meant for intrepid Perl developers
+only. The included sources may not even build correctly on some platforms.
+Subscribing to perl5-porters is the best way to monitor and contribute
+to the progress of development releases (see www.perl.org for info).
+
This document describes differences between the 5.005 release and this one.
=head1 Incompatible Changes
=head2 Perl Source Incompatibilities
-None known at this time.
+TODO
=head2 C Source Incompatibilities
=item C<PERL_POLLUTE>
Release 5.005 grandfathered old global symbol names by providing preprocessor
-macros for extension source compatibility. As of release 5.006, these
+macros for extension source compatibility. As of release 5.6, these
preprocessor definitions are not available by default. You need to explicitly
compile perl with C<-DPERL_POLLUTE> to get these definitions. For
extensions still using the old symbols, this option can be
perl Makefile.PL POLLUTE=1
+=item C<PERL_IMPLICIT_CONTEXT>
+
+This new build option provides a set of macros for all API functions
+such that an implicit interpreter/thread context argument is passed to
+every API function. As a result of this, something like C<sv_setsv(foo,bar)>
+amounts to a macro invocation that actually translates to something like
+C<Perl_sv_setsv(my_perl,foo,bar)>. While this is generally expected
+to not have any significant source compatibility issues, the difference
+between a macro and a real function call will need to be considered.
+
+This means that there B<is> a source compatibility issue as a result of
+this if your extensions attempt to use pointers to any of the Perl API
+functions.
+
+Note that the above issue is not relevant to the default build of
+Perl, whose interfaces continue to match those of prior versions
+(but subject to the other options described here).
+
+PERL_IMPLICIT_CONTEXT is automatically enabled whenever Perl is built
+with one of -Dusethreads, -Dusemultiplicity, or both.
+
+See L<perlguts/"The Perl API"> for detailed information on the
+ramifications of building Perl using this option.
+
=item C<PERL_POLLUTE_MALLOC>
Enabling Perl's malloc in release 5.005 and earlier caused
have allowed this behaviour to be suppressed with the HIDEMYMALLOC and
EMBEDMYMALLOC preprocessor definitions.
-As of release 5.006, Perl's malloc family of functions have default names
+As of release 5.6, Perl's malloc family of functions have default names
distinct from the system versions. You need to explicitly compile perl with
C<-DPERL_POLLUTE_MALLOC> to get the older behaviour. HIDEMYMALLOC
and EMBEDMYMALLOC have no effect, since the behaviour they enabled is now
=head2 Binary Incompatibilities
-This release is not binary compatible with the 5.005 release or its
-maintenance versions.
+The default build of this release is binary compatible with the 5.005
+release or its maintenance versions.
+
+The usethreads or usemultiplicity builds are B<not> binary compatible
+with the corresponding builds in 5.005.
=head1 Core Changes
=head2 Lexically scoped warning categories
You can now control the granularity of warnings emitted by perl at a finer
-level using the C<use warning> pragma. See L<warning> for details.
+level using the C<use warnings> pragma. See L<warnings> and L<perllexwarn>
+for details.
=head2 Binary numbers supported
=head2 64-bit support
-Better 64-bit support -- but full support still a distant goal. One
-must Configure with -Duse64bits to get Configure to probe for the
-extent of 64-bit support. Depending on the platform (hints file) more
-or less 64-awareness becomes available. As of 5.005_54 at least
-somewhat 64-bit aware platforms are HP-UX 11 or better, Solaris 2.6 or
-better, IRIX 6.2 or better. Naturally 64-bit platforms like Digital
-Unix and UNICOS also have 64-bit support.
+All platforms that have 64-bit integers either (a) natively as longs
+or ints (b) via special compiler flags (c) using long long are able to
+use "quads" (64-integers) as follows:
+
+=over 4
+
+=item constants in the code
+
+=item arguments to oct() and hex()
+
+=item arguments to print(), printf() and sprintf()
+
+=item pack() and unpack() "q" format
+
+=item in basic arithmetics
+
+=item vec() (but see the below note about bit arithmetics)
+
+=back
+
+Note that unless you have the case (a) you will have to configure
+and compile Perl using the -Duse64bits Configure flag.
+
+Unfortunately bit arithmetics (&, |, ^, ~, <<, >>) are not 64-bit clean.
+
+Last but not least: note that due to Perl's habit of always using
+floating point numbers the quads are still not true integers.
+When quads overflow their limits (0...18_446_744_073_709_551_615 unsigned,
+-9_223_372_036_854_775_808...9_223_372_036_854_775_807 signed), they
+are silently promoted to floating point numbers, after which they will
+start losing precision (their lower digits).
+
+=head2 Large file support
+
+If you have filesystems that support "large files" (files larger than
+2 gigabytes), you may now also be able to create and access them from Perl.
+
+Note that in addition to requiring a proper file system to do this you
+may also need to adjust your per-process (or even your per-system)
+maximum filesize limits before running Perl scripts that try to handle
+large files, especially if you intend to write such files.
+
+Adjusting your file system/system limits is outside the scope of Perl.
+For process limits, you may try to increase the limits using your
+shell's limit/ulimit command before running Perl. The BSD::Resource
+extension (not included with the standard Perl distribution) may also
+be of use.
+
+(Large file support is also related to 64-bit support, for obvious reasons)
=head2 Better syntax checks on parenthesized unary operators
remains unchanged. See L<perlop>.
+=head2 POSIX character class syntax [: :] supported
+
+For example to match alphabetic characters use /[[:alpha:]]/.
+See L<perlre> for details.
+
=head2 Improved C<qw//> operator
The C<qw//> operator is now evaluated at compile time into a true list
The new format type modifier '!' is useful for packing and unpacking
native shorts, ints, and longs. See L<perlfunc/"pack">.
+=head2 pack() and unpack() support counted strings
+
+The template character '#' can be used to specify a counted string
+type to be packed or unpacked. See L<perlfunc/"pack">.
+
=head2 $^X variables may now have names longer than one character
Formerly, $^X was synonymous with ${"\cX"}, but $^XY was a syntax
characters. As before, variables whose names begin with a control
character are always forced to be in package `main'. All such variables
are reserved for future extensions, except those that begin with
-C<^_>, which may be used by user programs and is guaranteed not to
+C<^_>, which may be used by user programs and are guaranteed not to
acquire special meaning in any future version of Perl.
+=head2 C<use attrs> implicit in subroutine attributes
+
+Formerly, if you wanted to mark a subroutine as being a method call or
+as requiring an automatic lock() when it is entered, you had to declare
+that with a C<use attrs> pragma in the body of the subroutine.
+That can now be accomplished with a declaration syntax, like this:
+
+ sub mymethod : locked, method ;
+ ...
+ sub mymethod : locked, method {
+ ...
+ }
+
+F<AutoSplit.pm> and F<SelfLoader.pm> have been updated to keep the attributes
+with the stubs they provide. See L<attributes>.
+
=head1 Significant bug fixes
=head2 E<lt>HANDLEE<gt> on empty files
were opened only for writing will now produce warnings (just as
writing to read-only filehandles does).
+=head2 Buffered data discarded from input filehandle when dup'ed.
+
+C<open(NEW, "E<lt>&OLD")> now discards any data that was previously
+read and buffered in C<OLD>. The next read operation on C<NEW> will
+return the same data as the corresponding operation on C<OLD>.
+Formerly, it would have returned the data from the start of the
+following disk block instead.
+
=head1 Supported Platforms
=over 4
Rhapsody is now supported.
+=item *
+
+EPOC is is now supported (on Psion 5).
+
=back
=head1 New tests
=over 4
-=item op/io_const
+=item lib/attrs
+
+Compatibility tests for C<sub : attrs> vs the older C<use attrs>.
+
+=item lib/io_const
IO constants (SEEK_*, _IO*).
-=item op/io_dir
+=item lib/io_dir
Directory-related IO methods (new, read, close, rewind, tied delete).
-=item op/io_multihomed
+=item lib/io_multihomed
INET sockets with multi-homed hosts.
-=item op/io_poll
+=item lib/io_poll
IO poll().
-=item op/io_unix
+=item lib/io_unix
UNIX sockets.
+=item op/attrs
+
+Regression tests for C<my ($x,@y,%z) : attrs> and <sub : attrs>.
+
=item op/filetest
File test operators.
=over 4
+=item attributes
+
+While used internally by Perl as a pragma, this module also
+provides a way to fetch subroutine and variable attributes.
+See L<attributes>.
+
+=item ByteLoader
+
+The ByteLoader is a dedication extension to generate and run
+Perl bytecode. See L<ByteLoader>.
+
+=item B
+
+The Perl Compiler suite has been extensively reworked for this
+release.
+
+=item Devel::DProf
+
+Devel::DProf, a Perl source code profiler has been added.
+
=item Dumpvalue
Added Dumpvalue module provides screen dumps of Perl data.
=head2 Pragmata
+C<use attrs> is now obsolescent, and is only provided for
+backward-compatibility. It's been replaced by the C<sub : attributes>
+syntax. See L<perlsub/"Subroutine Attributes"> and L<attributes>.
+
C<use utf8> to enable UTF-8 and Unicode support.
C<use caller 'encoding'> allows modules to inherit pragmatic attributes
from the caller's context. C<encoding> is currently the only supported
attribute.
-Lexical warnings pragma, C<use warning;>, to control optional warnings.
+Lexical warnings pragma, C<use warnings;>, to control optional warnings.
C<use filetest> to control the behaviour of filetests (C<-r> C<-w> ...).
Currently only one subpragma implemented, "use filetest 'access';",
=head1 New Diagnostics
+=item "my sub" not yet implemented
+
+(F) Lexically scoped subroutines are not yet implemented. Don't try that
+yet.
+
+=item %s package attribute may clash with future reserved word: %s
+
+(W) A lowercase attribute name was used that had a package-specific handler.
+That name might have a meaning to Perl itself some day, even though it
+doesn't yet. Perhaps you should use a mixed-case attribute name, instead.
+See L<attributes>.
+
=item /%s/: Unrecognized escape \\%c passed through
(W) You used a backslash-character combination which is not recognized
you intended only to read from the file, use "E<lt>". See
L<perlfunc/open>.
+=item Invalid %s attribute: %s
+
+The indicated attribute for a subroutine or variable was not recognized
+by Perl or by a user-supplied handler. See L<attributes>.
+
+=item Invalid %s attributes: %s
+
+The indicated attributes for a subroutine or variable were not recognized
+by Perl or by a user-supplied handler. See L<attributes>.
+
+=item Invalid separator character %s in attribute list
+
+(F) Something other than a comma or whitespace was seen between the
+elements of an attribute list. If the previous attribute
+had a parenthesised parameter list, perhaps that list was terminated
+too soon. See L<attributes>.
+
=item Missing command in piped open
(W) You used the C<open(FH, "| command")> or C<open(FH, "command |")>
construction, but the command was missing or blank.
+=item Missing name in "my sub"
+
+(F) The reserved syntax for lexically scoped subroutines requires that they
+have a name with which they can be found.
+
=item Unrecognized escape \\%c passed through
(W) You used a backslash-character combination which is not recognized
by Perl.
+=item Unterminated attribute parameter in attribute list
+
+(F) The lexer saw an opening (left) parenthesis character while parsing an
+attribute list, but the matching closing (right) parenthesis
+character was not found. You may need to add (or remove) a backslash
+character to get your parentheses to balance. See L<attributes>.
+
+=item Unterminated attribute list
+
+(F) The lexer found something other than a simple identifier at the start
+of an attribute, and it wasn't a semicolon or the start of a
+block. Perhaps you terminated the parameter list of the previous attribute
+too soon. See L<attributes>.
+
=item defined(@array) is deprecated
(D) defined() is not usually useful on arrays because it checks for an
undefined I<scalar> value. If you want to see if the hash is empty,
just use C<if (%hash) { # not empty }> for example.
+=item Invalid separator character %s in subroutine attribute list
+
+(F) Something other than a comma or whitespace was seen between the
+elements of a subroutine attribute list. If the previous attribute
+had a parenthesised parameter list, perhaps that list was terminated
+too soon.
+
+=item Unterminated attribute parameter in subroutine attribute list
+
+(F) The lexer saw an opening (left) parenthesis character while parsing a
+subroutine attribute list, but the matching closing (right) parenthesis
+character was not found. You may need to add (or remove) a backslash
+character to get your parentheses to balance.
+
+=item Unterminated subroutine attribute list
+
+(F) The lexer found something other than a simple identifier at the start
+of a subroutine attribute, and it wasn't a semicolon or the start of a
+block. Perhaps you terminated the parameter list of the previous attribute
+too soon.
+
+=item /%s/ should probably be written as "%s"
+
+(W) You have used a pattern where Perl expected to find a string,
+like in the first argument to C<join>. Perl will treat the true
+or false result of matching the pattern against $_ as the string,
+which is probably not what you had in mind.
+
+=item /%s/ should probably be written as "%s"
+
+(W) You have used a pattern where Perl expected to find a string,
+like in the first argument to C<join>. Perl will treat the true
+or false result of matching the pattern against $_ as the string,
+which is probably not what you had in mind.
+
=head1 Obsolete Diagnostics
Todo.
=head1 Configuration Changes
+=head2 installusrbinperl
+
You can use "Configure -Uinstallusrbinperl" which causes installperl
to skip installing perl also as /usr/bin/perl. This is useful if you
prefer not to modify /usr/bin for some reason or another but harmful
because many scripts assume to find Perl in /usr/bin/perl.
+=head2 SOCKS support
+
+You can use "Configure -Dusesocks" which causes Perl to probe
+for the SOCKS proxy protocol library, http://www.socks.nec.com/
+
=head1 BUGS
If you find what you think is a bug, you might check the headers of