X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperldelta.pod;h=d3fbae5b87b232c2dc1eb3ea07fdf2d286a6b256;hb=0a92e3a8032b83483524fad83a5e76cf0cf6aa8d;hp=4ec71c8eb55ae8e51be7af4b985d529df28c4289;hpb=01784f0d790efbb184547612fb96fd8626f5737f;p=p5sagit%2Fp5-mst-13.2.git diff --git a/pod/perldelta.pod b/pod/perldelta.pod index 4ec71c8..d3fbae5 100644 --- a/pod/perldelta.pod +++ b/pod/perldelta.pod @@ -6,22 +6,664 @@ 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 + =head1 Incompatible Changes +=head2 WARNING: This version is not binary compatible with Perl 5.004. + +Starting with Perl 5.004_50 there were many deep and far-reaching changes +to the language internals. If you have dynamically loaded extensions +that you built under perl 5.003 or 5.004, you can continue to use them +with 5.004, but you will need to rebuild and reinstall those extensions +to use them 5.005. See L for detailed instructions on how to +upgrade. + +=head2 Default installation structure has changed + +The new Configure defaults are designed to allow a smooth upgrade from +5.004 to 5.005, but you should read L for a detailed +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. + +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.] + +Some new keywords have been introduced. These are generally expected to +have very little impact on compatibility. See L keyword>, +L keyword>, and L 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 is now a reserved word>. + +=head2 C Source Compatibility + +=item Core sources now require ANSI C compiler + +=item Enabling threads has source compatibility issues + +=head2 Binary Compatibility + +This version is NOT binary compatible with older versions. All extensions +will need to be recompiled. + +=head2 Security fixes may affect compatibility + +A few taint leaks and taint omissions have been corrected. This may lead +to "failure" of scripts that used to work with older versions. Compiling +with -DINCOMPLETE_TAINTS provides a perl with minimal amounts of changes +to the tainting behavior. But note that the resulting perl will have +known insecurities. + +Oneliners with the C<-e> switch do not create temporary files anymore. + +=head2 Relaxed new mandatory warnings introduced in 5.004 + +Many new warnings that were introduced in 5.004 have been made +optional. Some of these warnings are still present, but perl's new +features make them less often a problem. See L. + +=head2 Licensing + +Perl has a new Social Contract for contributors. See F. + +The license included in much of the Perl documentation has changed. +[XXX See where?] + =head1 Core Changes -=head1 Modules -=head2 Required Updates +=head2 Threads + +WARNING: Threading is considered an experimental feature. Details of the +implementation may change without notice. There are known limitations +and and some bugs. + +See L. + +=head2 Compiler + +WARNING: The Compiler and related tools are considered experimental. +Features may change without notice, and there are known limitations +and bugs. + +The Compiler produces three different types of transformations of a +perl program. The C backend generates C code that captures perl's state +just before execution begins. It eliminates the compile-time overheads +of the regular perl interpreter, but the run-time performance remains +comparatively the same. The CC backend generates optimized C code +equivivalent to the code path at run-time. The CC backend has greater +potential for big optimizations, but only a few optimizations are +implemented currently. The Bytecode backend generates a platform +independent bytecode representation of the interpreter's state +just before execution. Thus, the Bytecode back end also eliminates +much of the compilation overhead of the interpreter. + +The compiler comes with several valuable utilities. + +C is an experimental module to detect and warn about suspicious +code, especially the cases that the C<-w> switch does not detect. + +C can be used to demystify perl code, and understand +how perl optimizes certain constructs. + +C generates cross reference reports of all definition and use +of variables, subroutines and formats in a program. + +C show the lexical variables used by a subroutine or file +at a glance. + +C is a simple frontend for compiling perl. + +See C. + +=head2 Regular Expressions + +See L and L. + +=head2 Improved malloc() + +See banner at the beginning of C for details. + +=head2 Quicksort is internally implemented + +See C. + +=head2 Reliable signals + +Two kinds. + +Via C. + +Via switched runtime op loop. [XXX Not yet available.] + +=head2 Reliable stack pointers + +The internals now reallocate the perl stack only at predictable times. +In particular, magic calls never trigger reallocations of the stack, +because all reentrancy of the runtime is handled using a "stack of stacks". +This should improve reliability of cached stack pointers in the internals +and in XSUBs. + +=head2 Behavior of local() on composites is now well-defined + +See L. + +=head2 C<%!> is transparently tied to the L module + +See L, and L. + +=head2 Pseudo-hashes are supported + +See L. + +=head2 C is supported + +See L. + +=head2 Slice notation on glob elements is supported + +[XXX See what?] + +=head2 Keywords can be globally overridden + +See L. + +=head2 C<$^E> is meaningful on Win32 + +See L. + +=head2 C optimized + +C is now optimized into a counting loop. It does +not try to allocate a 1000000-size list anymore. + +=head2 C can be used as implicitly quoted package name + +[XXX See what?] + +=head2 C tests existence of a package + +[XXX See what?] + +=head2 Better locale support + +See L. + +=head2 Experimental support for 64-bit platforms + +Perl5 has always had 64-bit support on systems with 64-bit longs. +Starting with 5.005, the beginnings of experimental support for systems +with 32-bit long and 64-bit 'long long' integers has been added. +If you add -DUSE_LONG_LONG to your ccflags in config.sh (or manually +define it in perl.h) then perl will be built with 'long long' support. +There will be many compiler warnings, and the resultant perl may not +work on all systems. There are many other issues related to +third-party extensions and libraries. This option exists to allow +people to work on those issues. + +=head2 prototype() returns useful results on builtins + +See L. + +=head2 Extended support for exception handling + +C 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. [XXX there's nothing +about this in perlfunc/eval yet.] + +=head2 Re-blessing in DESTROY() supported for chaining DESTROY() methods + +See L. + +=head2 All C format conversions are handled internally + +See L. + +=head2 New C keyword + +C subs are like C and C, but they get run just before +the perl runtime begins execution. e.g., the Perl Compiler makes use of +C blocks to initialize and resolve pointers to XSUBs. + +[XXX Needs to be documented in perlsub or perlmod.] + +=head2 New C keyword + +The C keyword is the fundamental synchronization primitive +in threaded perl. When threads are not enabled, it is currently a noop. + +To minimize impact on source compatibility this keyword is "weak", i.e., any +user-defined subroutine of the same name overrides it, unless a C +has been seen. + +=head2 New C operator + +The C operator, which is syntactically similar to the other quote-like +operators, is used to create precompiled regular expressions. This compiled +form can now be explicitly passed around in variables, and interpolated in +other regular expressions. See L. + +=head2 C is now a reserved word + +=head2 Tied arrays are now fully supported + +See L. + +=head2 Tied handles support is better + +Several missing hooks have been added. There is also a new base class for +TIEARRAY implementations. See L. + +=head2 4th argument to substr + +substr() can now both return and replace in one operation. The optional +4th argument is the replacement string. See L. + +=head2 Negative LENGTH argument to splice + +Splice() with a negative LENGTH argument now work similar to what the +LENGTH did for substr(). Previously a negative LENGTH was treated as +0. See L. + + +=head1 Supported Platforms + +Configure has many incremental improvements. Site-wide policy for building +perl can now be made persistent, via Policy.sh. Configure also records +the command-line arguments used in F. + +=head2 New Platforms + +BeOS is now supported. See L. + +DOS is now supported under the DJGPP tools. See L. + +MPE/iX is now supported. See L. + +=head2 Changes in existing support + +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.] + +VMS configuration system has been rewritten. See L. + +OpenBSD better supported. [XXX what others?] + +=head1 Modules and Pragmata + +=head2 New Modules + +=over + +=item B + +Perl compiler and tools. See [XXX what?]. + +=item Data::Dumper + +A module to pretty print Perl data. See L. + +=item Errno + +A module to look up errors more conveniently. See L. + +=item File::Spec + +A portable API for file operations. - XXX Any??? +=item ExtUtils::Installed + +Query and manage installed modules. + +=item ExtUtils::Packlist + +Manipulate .packlist files. + +=item Fatal + +Make functions/builtins succeed or die. + +=item IPC::SysV + +Constants and other support infrastructure for System V IPC operations +in perl. + +=item Test + +A framework for writing testsuites. + +=item Tie::Array + +Base class for tied arrays. + +=item Tie::Handle + +Base class for tied handles. + +=item Thread + +Perl thread creation, manipulation, and support. + +=item attrs + +Set subroutine attributes. + +=item fields + +Compile-time class fields. + +=item re + +Various pragmata to control behavior of regular expressions. + +=back + +=head2 Changes in existing modules + +=over + +=item CGI + +CGI has been updated to version 2.42. + +=item POSIX + +POSIX now has its own platform-specific hints files. + +=item DB_File + +DB_File supports version 2.x of Berkeley DB. See C. + +=item MakeMaker + +MakeMaker now supports writing empty makefiles, provides a way to +specify that site umask() policy should be honored. There is also +better support for manipulation of .packlist files, and getting +information about installed modules. + +Extensions that have both architecture-dependent and +architecture-independent files are now always installed completely in +the architecture-dependent locations. Previously, the shareable parts +were shared both across architectures and across perl versions and were +therefore liable to be overwritten with newer versions that might have +subtle incompatibilities. + +=item CPAN + +[XXX What?] + +=item Cwd + +Cwd::cwd is faster on most platforms. + +=item Benchmark + +Keeps better time. + +=back =head1 Utility Changes -=head1 C Language API Changes +h2ph and related utilities have been vastly overhauled. + +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 +submit patches for perl. + +=head1 New Diagnostics + +=over + +=item Ambiguous call resolved as CORE::%s(), qualify as such or use & + +(W) A subroutine you have declared has the same name as a Perl keyword, +and you have used the name without qualification for calling one or the +other. Perl decided to call the builtin because the subroutine is +not imported. + +To force interpretation as a subroutine call, either put an ampersand +before the subroutine name, or qualify the name with its package. +Alternatively, you can import the subroutine (or pretend that it's +imported with the C pragma). + +To silently interpret it as the Perl operator, use the C prefix +on the operator (e.g. C) or by declaring the subroutine +to be an object method (see L). + +=item Bad index while coercing array into hash + +(F) The index looked up in the hash found as the 0'th element of a +pseudo-hash is not legal. Index values must be at 1 or greater. +See L. + +=item Bareword "%s" refers to nonexistent package + +(W) You used a qualified bareword of the form C, but +the compiler saw no other uses of that namespace before that point. +Perhaps you need to predeclare a package? + +=item Can't call method "%s" on an undefined value + +(F) You used the syntax of a method call, but the slot filled by the +object reference or package name contains an undefined value. +Something like this will reproduce the error: + + $BADREF = 42; + process $BADREF 1,2,3; + $BADREF->process(1,2,3); + +=item Can't coerce array into hash + +(F) You used an array where a hash was expected, but the array has no +information on how to map from keys to array indices. You can do that +only with arrays that have a hash reference at index 0. + +=item Can't goto subroutine from an eval-string + +(F) The "goto subroutine" call can't be used to jump out of an eval "string". +(You can use it to jump out of an eval {BLOCK}, but you probably don't want to.) + +=item Can't use %%! because Errno.pm is not available + +(F) The first time the %! hash is used, perl automatically loads the +Errno.pm module. The Errno module is expected to tie the %! hash to +provide symbolic names for C<$!> errno values. + +=item Cannot find an opnumber for "%s" + +(F) A string of a form C was given to prototype(), but +there is no builtin with the name C. + +=item Character class syntax [. .] is reserved for future extensions + +(W) Within regular expression character classes ([]) the syntax beginning +with "[." and ending with ".]" is reserved for future extensions. +If you need to represent those character sequences inside a regular +expression character class, just quote the square brackets with the +backslash: "\[." and ".\]". + +=item Character class syntax [: :] is reserved for future extensions + +(W) Within regular expression character classes ([]) the syntax beginning +with "[:" and ending with ":]" is reserved for future extensions. +If you need to represent those character sequences inside a regular +expression character class, just quote the square brackets with the +backslash: "\[:" and ":\]". + +=item Character class syntax [= =] is reserved for future extensions + +(W) Within regular expression character classes ([]) the syntax +beginning with "[=" and ending with "=]" is reserved for future extensions. +If you need to represent those character sequences inside a regular +expression character class, just quote the square brackets with the +backslash: "\[=" and "=\]". + +=item %s: Eval-group in insecure regular expression + +(F) Perl detected tainted data when trying to compile a regular expression +that contains the C<(?{ ... })> zero-width assertion, which is unsafe. +See L, and L. + +=item %s: Eval-group not allowed, use re 'eval' + +(F) A regular expression contained the C<(?{ ... })> zero-width assertion, +but that construct is only allowed when the C pragma is +in effect. See L. + +=item %s: Eval-group not allowed at run time + +(F) Perl tried to compile a regular expression containing the C<(?{ ... })> +zero-width assertion at run time, as it would when the pattern contains +interpolated values. Since that is a security risk, it is not allowed. +If you insist, you may still do this by explicitly building the pattern +from an interpolated string at run time and using that in an eval(). +See L. + +=item Explicit blessing to '' (assuming package main) + +(W) You are blessing a reference to a zero length string. This has +the effect of blessing the reference into the package main. This is +usually not what you want. Consider providing a default target +package, e.g. bless($ref, $p or 'MyPackage'); + +=item Illegal hex digit ignored + +(W) You may have tried to use a character other than 0 - 9 or A - F in a +hexadecimal number. Interpretation of the hexadecimal number stopped +before the illegal character. + +=item No such array field + +(F) You tried to access an array as a hash, but the field name used is +not defined. The hash at index 0 should map all valid field names to +array indices for that to work. + +=item No such field "%s" in variable %s of type %s + +(F) You tried to access a field of a typed variable where the type +does not know about the field name. The field names are looked up in +the %FIELDS hash in the type package at compile time. The %FIELDS hash +is usually set up with the 'fields' pragma. + +=item Out of memory during ridiculously large request + +(F) You can't allocate more than 2^31+"small amount" bytes. This error +is most likely to be caused by a typo in the Perl program. e.g., C<$arr[time]> +instead of C<$arr[$time]>. + +=item Range iterator outside integer range + +(F) One (or both) of the numeric arguments to the range operator ".." +are outside the range which can be represented by integers internally. +One possible workaround is to force Perl to use magical string +increment by prepending "0" to your numbers. + +=item Recursive inheritance detected while looking for method '%s' in package '%s' + +(F) More than 100 levels of inheritance were encountered while invoking a +method. Probably indicates an unintended loop in your inheritance hierarchy. + +=item Reference found where even-sized list expected + +(W) You gave a single reference where Perl was expecting a list with +an even number of elements (for assignment to a hash). This +usually means that you used the anon hash constructor when you meant +to use parens. In any case, a hash requires key/value B. + + %hash = { one => 1, two => 2, }; # WRONG + %hash = [ qw/ an anon array / ]; # WRONG + %hash = ( one => 1, two => 2, ); # right + %hash = qw( one 1 two 2 ); # also fine + +=item Undefined value assigned to typeglob + +(W) An undefined value was assigned to a typeglob, a la C<*foo = undef>. +This does nothing. It's possible that you really mean C. + +=item Use of reserved word "%s" is deprecated + +(D) The indicated bareword is a reserved word. Future versions of perl +may use it as a keyword, so you're better off either explicitly quoting +the word in a manner appropriate for its context of use, or using a +different name altogether. The warning can be suppressed for subroutine +names by either adding a C<&> prefix, or using a package qualifier, +e.g. C<&our()>, or C. + +=item perl: warning: Setting locale failed. + +(S) The whole warning message will look something like: + + perl: warning: Setting locale failed. + perl: warning: Please check that your locale settings: + LC_ALL = "En_US", + LANG = (unset) + are supported and installed on your system. + perl: warning: Falling back to the standard locale ("C"). + +Exactly what were the failed locale settings varies. In the above the +settings were that the LC_ALL was "En_US" and the LANG had no value. +This error means that Perl detected that you and/or your system +administrator have set up the so-called variable system but Perl could +not use those settings. This was not dead serious, fortunately: there +is a "default locale" called "C" that Perl can and will use, the +script will be run. Before you really fix the problem, however, you +will get the same error message each time you run Perl. How to really +fix the problem can be found in L section B. + +=back + + +=head1 Obsolete Diagnostics + +=over + +=item Can't mktemp() + +(F) The mktemp() routine failed for some reason while trying to process +a B<-e> switch. Maybe your /tmp partition is full, or clobbered. + +=item Can't write to temp file for B<-e>: %s + +(F) The write routine failed for some reason while trying to process +a B<-e> switch. Maybe your /tmp partition is full, or clobbered. + +=item Cannot open temporary file + +(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 If you find what you think is a bug, you might check the headers of @@ -46,3 +688,5 @@ The F file for general stuff. The F and F files for copyright information. =head1 HISTORY + +=cut