diff options
Diffstat (limited to 'pod/perldelta.pod')
| -rw-r--r-- | pod/perldelta.pod | 233 |
1 files changed, 193 insertions, 40 deletions
diff --git a/pod/perldelta.pod b/pod/perldelta.pod index 0cbba50374..7a371fb586 100644 --- a/pod/perldelta.pod +++ b/pod/perldelta.pod @@ -6,11 +6,19 @@ perldelta - what's new for perl5.005 This document describes differences between the 5.004 release and this one. -[XXX this needs more verbose summaries of the sub topics, instead of just -the "See foo." Scheduled for a second iteration. GSAR] - =head1 About the new versioning system +Perl is now developed on two tracks: a maintenance track that makes +small, safe updates to released production versions with emphasis on +compatibility; and a development track that pursues more aggressive +evolution. Maintenance releases (which should be considered production +quality) have subversion numbers that run from C<1> to C<49>, and +development releases (which should be considered "alpha" quality) run +from C<50> to C<99>. + +Perl 5.005 is the combined product of the new dual-track development +scheme. + =head1 Incompatible Changes =head2 WARNING: This version is not binary compatible with Perl 5.004. @@ -31,31 +39,80 @@ discussion of the changes in order to adapt them to your system. =head2 Perl Source Compatibility When none of the experimental features are enabled, there should be -no user-visible Perl source compatibility issue. +very few user-visible Perl source compatibility issues. If threads are enabled, then some caveats apply. C<@_> and C<$_> become lexical variables. The effect of this should be largely transparent to the user, but there are some boundary conditions under which user will -need to be aware of the issues. [XXX Add e.g. here.] +need to be aware of the issues. For example, C<local(@_)> results in +a "Can't localize lexical variable @_ ..." message. This may be enabled +in a future version. Some new keywords have been introduced. These are generally expected to -have very little impact on compatibility. See L</New C<INIT> keyword>, -L</New C<lock> keyword>, and L</New C<qr//> operator>. +have very little impact on compatibility. See L<New C<INIT> keyword>, +L<New C<lock> keyword>, and L<New C<qr//> operator>. Certain barewords are now reserved. Use of these will provoke a warning if you have asked for them with the C<-w> switch. -See L</C<our> is now a reserved word>. +See L<C<our> is now a reserved word>. =head2 C Source Compatibility +There have been a large number of changes in the internals to support +the new features in this release. + +=over 4 + =item Core sources now require ANSI C compiler +An ANSI C compiler is now B<required> to build perl. See F<INSTALL>. + +=item All Perl global variables must now be referenced with an explicit prefix + +All Perl global variables that are visible for use by extensions now +have a C<PL_> prefix. New extensions should C<not> refer to perl globals +by their unqualified names. To preserve sanity, we provide limited +backward compatibility for globals that are being widely used like +C<sv_undef> and C<na> (which should now be written as C<PL_sv_undef>, +C<PL_na> etc.) + +If you find that your XS extension does not compile anymore because a +perl global is not visible, try adding a C<PL_> prefix to the global +and rebuild. + +It is strongly recommended that all functions in the Perl API that don't +begin with C<perl> be referenced with a C<Perl_> prefix. The bare function +names without the C<Perl_> prefix are supported with macros, but this +support may cease in a future release. + +See L<perlguts/API LISTING>. + =item Enabling threads has source compatibility issues +Perl built with threading enabled requires extensions to use the new +C<dTHR> macro to initialize the handle to access per-thread data. +If you see a compiler error that talks about the variable C<thr> not +being declared (when building a module that has XS code), you need +to add C<dTHR;> at the beginning of the block that elicited the error. + +The API function C<perl_get_sv("@",FALSE)> should be used instead of +directly accessing perl globals as C<GvSV(errgv)>. The API call is +backward compatible with existing perls and provides source compatibility +with threading is enabled. + +See L<API Changes for more information>. + +=back + =head2 Binary Compatibility This version is NOT binary compatible with older versions. All extensions -will need to be recompiled. +will need to be recompiled. Further binaries built with threads enabled +are incompatible with binaries built without. This should largely be +transparent to the user, as all binary incompatible configurations have +their own unique architecture name, and extension binaries get installed at +unique locations. This allows coexistence of several configurations in +the same directory hierarchy. See F<INSTALL>. =head2 Security fixes may affect compatibility @@ -78,24 +135,25 @@ features make them less often a problem. See L<New Diagnostics>. Perl has a new Social Contract for contributors. See F<Porting/Contract>. The license included in much of the Perl documentation has changed. -[XXX See where?] +See L<perl> and the individual perl man pages listed therein. =head1 Core Changes =head2 Threads -WARNING: Threading is considered an experimental feature. Details of the +WARNING: Threading is considered an B<experimental> feature. Details of the implementation may change without notice. There are known limitations -and and some bugs. +and some bugs. These are expected to be fixed in future versions. See L<README.threads>. =head2 Compiler -WARNING: The Compiler and related tools are considered experimental. +WARNING: The Compiler and related tools are considered B<experimental>. Features may change without notice, and there are known limitations -and bugs. +and bugs. Since the compiler is fully external to perl, the default +configuration will build and install it. The Compiler produces three different types of transformations of a perl program. The C backend generates C code that captures perl's state @@ -125,10 +183,87 @@ at a glance. C<perlcc> is a simple frontend for compiling perl. -See C<ext/B/README>. +See C<ext/B/README>, L<B>, and the respective compiler modules. =head2 Regular Expressions +Perl's regular expression engine has been seriously overhauled, and +many new constructs are supported. Several bugs have been fixed. + +Here is an itemized summary: + +=over 4 + +=item Many new and improved optimizations + +Changes in the RE engine: + + Unneeded nodes removed; + Substrings merged together; + New types of nodes to process (SUBEXPR)* and similar expressions + quickly, used if the SUBEXPR has no side effects and matches + strings of the same length; + better optimizations by lookup for constant substrings; + Better search for constants substrings anchored by $ ; + +Changes in Perl code using RE engine: + + more optimizations to s/longer/short/; + study() was not working; + /blah/ may be optimized to an analogue of index() if $& $` $' not seen; + Unneeded copying of matched-against string removed; + Only matched part of the string is copying if $` $' were not seen; + +=item Many bug fixes + +Note that only the major bug fixes are listed here. See F<Changes> for others. + + Backtracking might not restore start of $3. + No feedback if max count for * or + on "complex" subexpression + was reached, similarly (but at compile time) for {3,34567} + Primitive restrictions on max count introduced to decrease a + possibility of a segfault; + (ZERO-LENGTH)* could segfault; + (ZERO-LENGTH)* was prohibited; + Long RE were not allowed; + /RE/g could skip matches at the same position after a + zero-length match; + +=item New regular expression constructs + +The following new syntax elements are supported: + + (?<=RE) + (?<!RE) + (?{ CODE }) + (?i-x) + (?i:RE) + (?(COND)YES_RE|NO_RE) + (?>RE) + \z + +=item New operator for precompiled regular expressions + +See L<New C<qr//> operator>. + +=item Other improvements + + better debugging output (possibly with colors), even from non-debugging Perl; + RE engine code now looks like C, not like assembler; + behaviour of RE modifiable by `use re' directive; + Improved documentation; + Test suite significantly extended; + Syntax [:^upper:] etc., reserved inside character classes; + +=item Incompatible changes + + (?i) localized inside enclosing group; + $( is not interpolated into RE any more; + /RE/g may match at the same position (with non-zero length) + after a zero-length match (bug fix). + +=back + See L<perlre> and L<perlop>. =head2 Improved malloc() @@ -137,15 +272,24 @@ See banner at the beginning of C<malloc.c> for details. =head2 Quicksort is internally implemented +Perl now contains its own highly optimized qsort() routine. The new qsort() +is resistant to inconsistent comparison functions, so Perl's C<sort()> will +not provoke coredumps any more when given poorly written sort subroutines. +(Some C library C<qsort()>s that were being used before used to have this +problem.) In our testing, the new C<qsort()> required the minimal number +of pair-wise compares on average, among all known C<qsort()> implementations. + See C<perlfunc/sort>. =head2 Reliable signals -Two kinds. +Perl's signal handling is susceptible to random crashes, because signals +arrive asynchronously, and the Perl runtime is not reentrant at arbitrary +times. -Via C<Thread::Signal>. - -Via switched runtime op loop. [XXX Not yet available.] +However, one experimental implementation of reliable signals is available +when threads are enabled. See C<Thread::Signal>. Also see F<INSTALL> for +how to build a Perl capable of threads. =head2 Reliable stack pointers @@ -186,11 +330,18 @@ not try to allocate a 1000000-size list anymore. =head2 C<Foo::> can be used as implicitly quoted package name -[XXX See what?] +Barewords caused unintuitive behavior when a subroutine with the same +name as a package happened to be defined. Thus, C<new Foo @args>, +use the result of the call to C<Foo()> instead of C<Foo> being treated +as a literal. The recommended way to write barewords in the indirect +object slot is C<new Foo:: @args>. Note that the method C<new()> is +called with a first argument of C<Foo>, not C<Foo::> when you do that. =head2 C<exists $Foo::{Bar::}> tests existence of a package -[XXX See what?] +It was impossible to test for the existence of a package without +actually creating it before. Now C<exists $Foo::{Bar::}> can be +used to test if the C<Foo::Bar> namespace has been created. =head2 Better locale support @@ -216,8 +367,7 @@ See L<perlfunc/prototype>. C<die()> now accepts a reference value, and C<$@> gets set to that value in exception traps. This makes it possible to propagate -exception objects. See L<perlfunc/eval>. [XXX there's nothing -about this in perlfunc/eval yet.] +exception objects. This is an undocumented B<experimental> feature. =head2 Re-blessing in DESTROY() supported for chaining DESTROY() methods @@ -233,8 +383,6 @@ C<INIT> subs are like C<BEGIN> and C<END>, but they get run just before the perl runtime begins execution. e.g., the Perl Compiler makes use of C<INIT> blocks to initialize and resolve pointers to XSUBs. -[XXX Needs to be documented in perlsub or perlmod.] - =head2 New C<lock> keyword The C<lock> keyword is the fundamental synchronization primitive @@ -253,6 +401,9 @@ other regular expressions. See L<perlop>. =head2 C<our> is now a reserved word +Calling a subroutine with the name C<our> will now provoke a warning when +using the C<-w> switch. + =head2 Tied arrays are now fully supported See L<Tie::Array>. @@ -319,12 +470,11 @@ MPE/iX is now supported. See L<README.mpeix>. Win32 support has been vastly enhanced. Support for Perl Object, a C++ encapsulation of Perl. GCC and EGCS are now supported on Win32. -[XXX Perl Object needs a big explanation elsewhere, and a pointer to -that location here.] +See F<README.win32>, aka L<perlwin32>. VMS configuration system has been rewritten. See L<README.vms>. -OpenBSD better supported. [XXX what others?] +The hints files for most Unix platforms have seen incremental improvements. =head1 Modules and Pragmata @@ -334,7 +484,7 @@ OpenBSD better supported. [XXX what others?] =item B -Perl compiler and tools. See [XXX what?]. +Perl compiler and tools. See L<B>. =item Data::Dumper @@ -427,7 +577,7 @@ subtle incompatibilities. =item CPAN -[XXX What?] +See <perlmodinstall> and L<CPAN>. =item Cwd @@ -447,21 +597,20 @@ perlcc, a new experimental front end for the compiler is available. The crude GNU configure emulator is now called configure.gnu. -=head1 API Changes - -=head2 Incompatible Changes - -=head2 Deprecations, Extensions - -=head2 C++ Support - =head1 Documentation Changes Config.pm now has a glossary of variables. -Porting/patching.pod has detailed instructions on how to create and +F<Porting/patching.pod> has detailed instructions on how to create and submit patches for perl. +L<perlport> specifies guidelines on how to write portably. + +L<perlmodinstall> describes how to fetch and install modules from C<CPAN> +sites. + +Some more Perl traps are documented now. See L<perltrap>. + =head1 New Diagnostics =over @@ -691,7 +840,6 @@ a B<-e> switch. Maybe your /tmp partition is full, or clobbered. (F) The create routine failed for some reason while trying to process a B<-e> switch. Maybe your /tmp partition is full, or clobbered. - =back =head1 BUGS @@ -719,4 +867,9 @@ The F<Artistic> and F<Copying> files for copyright information. =head1 HISTORY +Written by Gurusamy Sarathy <F<gsar@umich.edu>>, with many contributions +from The Perl Porters. + +Send omissions or corrections to <F<perlbug@perl.com>>. + =cut |