=encoding utf8 =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 v5.19.1 =head1 DESCRIPTION This document describes differences between the 5.19.0 release and the 5.19.1 release. =head1 Notice XXX Any important notices here =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 section. [ List each enhancement as a =head2 entry ] =head1 Security XXX Any security-related notices go here. In particular, any security vulnerabilities closed should be noted here rather than in the L section. [ List each security issue as a =head2 entry ] =head1 Incompatible Changes XXX For a release on a stable branch, this section aspires to be: 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 below. [ List each incompatible change as a =head2 entry ] =head2 Most regex engine global state eliminated As part of this series of fixes it was necessary to change the API of Perl_re_intuit_start(). See L for more. =head2 Locale decimal point character no longer leaks outside of S> scope This is actually a bug fix, but some code has come to rely on the bug being present, so this change is listed here. The current locale that the program is running under is not supposed to be visible to Perl code except within the scope of a S>. However, until now under certain circumstances, the character used for a decimal point (often a comma) leaked outside the scope. If your code is affected by this change, simply add a S>. =head1 Deprecations 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. XXX Note that deprecated modules should be listed here even if they are listed as an updated module in the L section. =over =item * XXXX =back [ List each other deprecation as a =head2 entry ] =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 a =item entry ] =over 4 =item * Perl has a new copy-on-write mechanism that avoids the need to copy the internal string buffer when assigning from one scalar to another. This makes copying large strings appear much faster. Modifying one of the two (or more) strings after an assignment will force a copy internally. This makes it unnecessary to pass strings by reference for efficiency. This feature was already available in 5.18.0, but wasn't enabled by default. It is the default now, and so you no longer need build perl with the F argument: -Accflags=PERL_NEW_COPY_ON_WRITE It can be disabled (for now) in a perl build with: -Accflags=PERL_NO_COW =back =head1 Modules and Pragmata XXX All changes to installed files in F, F, F and F go here. If Module::CoreList is updated, generate an initial draft of the following sections using F, which prints stub entries to STDOUT. Results can be pasted in place of the '=head2' entries below. A paragraph summary for important changes should then be added by hand. In an ideal world, dual-life modules would have a F file that could be cribbed. [ Within each section, list entries as a =item entry ] =head2 New Modules and Pragmata =over 4 =item * L which provides information on which core and dual-life utilities shipped with each version of L. =back =head2 Updated Modules and Pragmata =over 4 =item * L has been upgraded from version 1.20 to 1.21. C is now deparsed correctly with the B<-p> option. [RT #117081] The B<-l> option no longer puts form feeds in the middle of a line when outputting C and C blocks. [RT #117311] Elements of C<%#>, such as C<$# {foo}> and C<${#}{foo}> are now deparsed correctly. [RT #117531] =item * L has been updated from 1.05 to 1.06 and L from 1.39_10 to 1.40. The call depth allowed by default in the debugger is now 1000 rather than 100. =item * L has been upgraded from version 3.40 to 3.41. C now respects changes to environment variables from which the temporary directory is derived. [RT #88940] =item * L has been upgraded from version 3.26 to 3.28 Memory usage is dramatically reduced. t/harness now uses about 10% of the memory used by 3.26 and earlier. C is always propagated to a test's C<@INC>, even under C<-T>. =item * L has been upgraded from version 0.51 to 0.52. A function, L is now available to do search an inversion list or map for a code point. =back =head2 Removed Modules and Pragmata =over 4 =item * XXX =back =head1 Documentation XXX Changes to files in F go here. Consider grouping entries by file and be sure to link to the appropriate page, e.g. L. =head2 New Documentation XXX Changes which create B files in F go here. =head3 L XXX Description of the purpose of the new file here =head2 Changes to Existing Documentation XXX Changes which significantly change existing files in F go here. However, any changes to F should go in the L section. =head3 L =over =item * C is now documented to handle an expression that evalutes to a code reference as if it was C. This behavior is at least ten years old. =back =head3 L =over =item * Update to mention fc(), \F =back =head3 L =over 4 =item * There is now a L section. =back =head1 Diagnostics 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. XXX New or changed warnings emitted by the core's C code go here. Also include any changes in L that reconcile it to the C code. =head2 New Diagnostics XXX Newly added diagnostic messages go under here, separated into New Errors and New Warnings =head3 New Errors =over 4 =item * XXX L =back =head3 New Warnings =over 4 =item * L L These two deprecation warnings involving C<\N{...}> were incorrectly implemented. They did not warn by default (now they do) and could not be made fatal via C 'deprecated'> (now they can). =back =head2 Changes to Existing Diagnostics XXX Changes (i.e. rewording) of diagnostic messages go here =over 4 =item * XXX Describe change here =back =head1 Utility Changes XXX Changes to installed programs such as F and F go here. Most of these are built within the directories F and F. [ List utility changes as a =head3 entry for each utility and =item entries for each change Use L with program names to get proper documentation linking. ] =head3 F enhancements The git bisection tool F has had many enhancements. =over 4 =item * Can optionally run the test case with a timeout. =item * Can now run in-place in a clean git checkout. =item * Can run the test case under C. =item * Can apply user supplied patches and fixes to the source checkout before building. =item * Now has fixups to enable building several more historical ranges of bleadperl, which can be useful for pinpointing the origins of bugs or behaviour changes. =back It is provided as part of the source distribution but not installed because it is not self-contained as it relies on being run from within a git checkout. Note also that it makes no attempt to fix tests, correct runtime bugs or make something useful to install - its purpose is to make minimal changes to get any historical revision of interest to build and run as close as possible to "as-was", and thereby make C easy to use. =head1 Configuration and Compilation XXX Changes to F, F, F, 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 section, instead. [ List changes as a =item entry ]. =over 4 =item * XXX =back =head1 Testing XXX Any significant changes to the testing of a freshly built perl should be listed here. Changes which create B files in F go here as do any large changes to the testing harness (e.g. when parallel testing was added). Changes to existing files in F aren't worth summarizing, although the bugs that they represent may be covered elsewhere. [ List each test improvement as a =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 a =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 directories, or new subdirectories and F files at the top level of the source tree. =over 4 =item XXX-some-platform XXX =back =head2 Discontinued Platforms XXX List any platforms that this version of perl no longer compiles on. =over 4 =item DG/UX DG/UX was a Unix sold by Data General. The last release was in April 2001. It only runs on Data General's own hardware. =item XXX-some-platform XXX =back =head2 Platform-Specific Notes 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 section. =over 4 =item Mixed-endian platforms The code supporting C and C operations on mixed endian platforms has been removed. We believe that Perl has long been unable to build on mixed endian architectures (such as PDP-11s), so we don't think that this change will affect any platforms which are able to build v5.18.0. =item Windows The BUILD_STATIC and ALL_STATIC makefile options for linking some or (nearly) all extensions statically (into perl519.dll, and into a separate perl-static.exe too) were broken for MinGW builds. This has now been fixed. The ALL_STATIC option has also been improved to include the Encode and Win32 extensions (for both VC++ and MinGW builds). =back =head1 Internal Changes XXX Changes which affect the interface available to C code go here. Other significant internal changes for future core maintainers should be noted as well. =over 4 =item * Perl's new copy-on-write mechanism (which is now enabled by default), allows any C scalar to be automatically upgraded to a copy-on-write scalar when copied. A reference count on the string buffer is stored in the string buffer itself. For example: $ perl -MDevel::Peek -e'$a="abc"; $b = $a; Dump $a; Dump $b' SV = PV(0x260cd80) at 0x2620ad8 REFCNT = 1 FLAGS = (POK,IsCOW,pPOK) PV = 0x2619bc0 "abc"\0 CUR = 3 LEN = 16 COW_REFCNT = 1 SV = PV(0x260ce30) at 0x2620b20 REFCNT = 1 FLAGS = (POK,IsCOW,pPOK) PV = 0x2619bc0 "abc"\0 CUR = 3 LEN = 16 COW_REFCNT = 1 Note that both scalars share the same PV buffer and have a COW_REFCNT greater than zero. This means that XS code which wishes to modify the C buffer of an SV should call C or similar first, to ensure a valid (and unshared) buffer, and to call C afterwards. This in fact has always been the case (for example hash keys were already copy-on-write); this change just spreads the COW behaviour to a wider variety of SVs. One important difference is that before 5.18.0, shared hash-key scalars used to have the C flag set; this is no longer the case. This new behaviour can still be disabled by running F with B<-Accflags=-DPERL_NO_COW>. This option will probably be removed in Perl 5.22. =item * C is now a constant. The switch this variable provided (to enable/disable the pre-match copy depending on whether C<$&> had been seen) has been removed and replaced with copy-on-write, eliminating a few bugs. The previous behaviour can still be enabled by running F with B<-Accflags=-DPERL_SAWAMPERSAND>. =item * The functions C, C and C have been removed. It is unclear why these functions were ever marked as I, part of the API. XS code can't call them directly, as it can't rely on them being compiled. Unsurprisingly, no code on CPAN references them. =item * The signature of the C regex function has changed; the function pointer C in the regex engine plugin structure has also changed accordingly. A new parameter, C has been added; this has the same meaning as the same-named parameter in C. Previously intuit would try to guess the start of the string from the passed SV (if any), and would sometimes get it wrong (e.g. with an overloaded SV). =item * XS code may use various macros to change the case of a character or code point (for example C). Only a couple of these were documented until now; and now they should be used in preference to calling the underlying functions. See L. =item * The code dealt rather inconsistently with uids and gids. Some places assumed that they could be safely stored in UVs, others in IVs, others in ints. Four new macros are introduced: SvUID(), sv_setuid(), SvGID(), and sv_setgid() =back =head1 Selected Bug Fixes XXX Important bug fixes in the core language are summarized here. Bug fixes in files in F and F are best summarized in L. [ List each fix as a =item entry ] =over 4 =item * The OP allocation code now returns correctly aligned memory in all cases for C. Previously it could return memory only aligned to a 4-byte boundary, which is not correct for an ithreads build with 64 bit IVs on some 32 bit platforms. Notably, this caused the build to fail completely on sparc GNU/Linux. [RT #118055] =item * The debugger's C command been fixed. It was broken in the v5.18.0 release. The C command is aliased to the names C and C - all now work again. =item * C<@_> is now correctly visible in the debugger, fixing a regression introduced in v5.18.0's debugger. [RT #118169] =item * Evaluating large hashes in scalar context is now much faster, as the number of used chains in the hash is now cached for larger hashes. Smaller hashes continue not to store it and calculate it when needed, as this saves one IV. That would be 1 IV overhead for every object built from a hash. [RT #114576] =item * Fixed a small number of regexp constructions that could either fail to match or crash perl when the string being matched against was allocated above the 2GB line on 32-bit systems. [RT #118175] =item * Perl v5.16 inadvertently introduced a bug whereby calls to XSUBs that were not visible at compile time were treated as lvalues and could be assigned to, even when the subroutine was not an lvalue sub. This has been fixed. [RT #117947] =item * In Perl v5.18.0 dualvars that had an empty string for the string part but a non-zero number for the number part starting being treated as true. In previous versions they were treated as false, the string representation taking precedeence. The old behaviour has been restored. [RT #118159] =item * Since Perl v5.12, inlining of constants that override built-in keywords of the same name had countermanded C, causing subsequent mentions of the constant to use the built-in keyword instead. This has been fixed. =item * Lexical constants (C) no longer crash when inlined. =item * Parameter prototypes attached to lexical subroutines are now respected when compiling sub calls without parentheses. Previously, the prototypes were honoured only for calls I parentheses. [RT #116735] =item * Syntax errors in lexical subroutines in combination with calls to the same subroutines no longer cause crashes at compile time. =item * The warning produced by C<-l $handle> now applies to IO refs and globs, not just to glob refs. That warning is also now UTF8-clean. [RT #117595] =item * Various memory leaks involving the parsing of the C<(?[...])> regular expression construct have been fixed. =item * C<(?[...])> now allows interpolation of precompiled patterns consisting of C<(?[...])> with bracketed character classes inside (C<$pat = S S>). Formerly, the brackets would confuse the regular expression parser. =item * The "Quantifier unexpected on zero-length expression" warning message could appear twice starting in Perl v5.10 for a regular expression also containing alternations (e.g., "a|b") triggering the trie optimisation. =item * C no longer leaks memory. =item * C and C followed by a keyword prefixed with C now treat it as a keyword, and not as a subroutine or module name. [RT #24482] =item * Through certain conundrums, it is possible to cause the current package to be freed. Certain operators (C, C, C, C) could not cope and would crash. They have been made more resilient. [RT #117941] =item * Aliasing filehandles through glob-to-glob assignment would not update internal method caches properly if a package of the same name as the filehandle existed, resulting in filehandle method calls going to the package instead. This has been fixed. =item * C<./Configure -de -Dusevendorprefix> didn't default [RT #64126] =item * The C warning was listed in L as an C-category warning, but was enabled and disabled by the C category. On the other hand, the C category controlled its fatal-ness. It is now entirely handled by the C category. =item * The "Replacement list is longer that search list" warning for C and C no longer occurs in the presence of the C flag. [RT #118047] =item * Perl v5.18 inadvertently introduced a bug whereby interpolating mixed up- and down-graded UTF-8 strings in a regex could result in malformed UTF-8 in the pattern: specifically if a downgraded character in the range C<\x80..\xff> followed a UTF-8 string, e.g. utf8::upgrade( my $u = "\x{e5}"); utf8::downgrade(my $d = "\x{e5}"); /$u$d/ [RT #118297] =back =head1 Known Problems XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any tests that had to be Ced for the release would be noted here. Unfixed platform specific bugs also go here. [ List each fix as a =item entry ] =over 4 =item * XXX =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 v5.19.1..HEAD =head1 Reporting Bugs If you find what you think is a bug, you might check the articles recently posted to the comp.lang.perl.misc newsgroup and the perl bug database at http://rt.perl.org/perlbug/ . There may also be information at http://www.perl.org/ , the Perl Home Page. If you believe you have an unreported bug, please run the L program included with your release. Be sure to trim your bug down to a tiny but sufficient test case. Your bug report, along with the output of C, will be sent off to perlbug@perl.org to be analysed by the Perl porting team. If the bug you are reporting has security implications, which make it inappropriate to send to a publicly archived mailing list, then please send it to perl5-security-report@perl.org. This points to a closed subscription unarchived mailing list, which includes all the core committers, who will be able to help assess the impact of issues, figure out a resolution, and help co-ordinate the release of patches to mitigate or fix the problem across all platforms on which Perl is supported. Please only use this address for security issues in the Perl core, not for modules independently distributed on CPAN. =head1 SEE ALSO The F file for an explanation of how to view exhaustive details on what changed. The F file for how to build Perl. The F file for general stuff. The F and F files for copyright information. =cut