=encoding utf8
+=for to-do
+23b7025ebc definitely needs to be summarised.
+
=head1 NAME
-perldelta - what is new for perl v5.17.4
+[ 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 v5.17.7
=head1 DESCRIPTION
-This document describes differences between the 5.17.3 release and the 5.17.4
+This document describes differences between the 5.17.6 release and the 5.17.7
release.
-If you are upgrading from an earlier release such as 5.17.2, first read
-L<perl5173delta>, which describes differences between 5.17.2 and 5.17.3.
-
-=head1 Core Enhancements
-
-=head2 Latest Unicode 6.2 beta is included
-
-This is supposed to be the final data for 6.2, unless glitches are
-found. The earlier experimental 6.2 beta data has been reverted, and
-this used instead. Not all the changes that were proposed for 6.2 and
-that were in the earlier beta versions are actually going into 6.2. In
-particular, there are no changes from 6.1 in the General_Category of any
-characters. 6.2 does revise the C<\X> handling for the REGIONAL
-INDICATOR characters that were added in Unicode 6.0. Perl now for the
-first time fully handles this revision.
-
-=head2 New DTrace probes
-
-The following new DTrace probes have been added:
-
-=over 4
-
-=item C<op-entry>
-
-=item C<loading-file>
-
-=item C<loaded-file>
-
-=back
-
-=head2 C<${^LAST_FH}>
-
-This new variable provides access to the filehandle that was last read.
-This is the handle used by C<$.> and by C<tell> and C<eof> without
-arguments.
-
-=head2 Looser here-doc parsing
+If you are upgrading from an earlier release such as 5.17.5, first read
+L<perl5176delta>, which describes differences between 5.17.5 and 5.17.6.
-Here-doc terminators no longer require a terminating newline character when
-they occur at the end of a file. This was already the case at the end of a
-string eval [perl #65838].
+=head1 Notice
-=head2 New mechanism for experimental features
+XXX Any important notices here
-Newly-added experimental features will now require this incantation:
-
- no warnings "experimental:feature_name";
- use feature "feature_name"; # would warn without the prev line
-
-There is a new warnings category, called "experimental", containing
-warnings that the L<feature> pragma emits when enabling experimental
-features.
-
-Newly-added experimental features will also be given special warning IDs,
-which consist of "experimental:" followed by the name of the feature. (The
-plan is to extend this mechanism eventually to all warnings, to allow them
-to be enabled or disabled individually, and not just by category.)
-
-By saying
-
- no warnings "experimental:feature_name";
-
-you are taking responsibility for any breakage that future changes to, or
-removal of, the feature may cause.
-
-=head2 Lexical subroutines
-
-This new feature is still considered experimental. To enable it, use the
-mechanism described above:
-
- use 5.018;
- no warnings "experimental:lexical_subs";
- use feature "lexical_subs";
+=head1 Core Enhancements
-You can now declare subroutines with C<state sub foo>, C<my sub foo>, and
-C<our sub foo>. (C<state sub> requires that the "state" feature be
-enabled, unless you write it as C<CORE::state sub foo>.)
+=head2 $&, $` and $' are no longer slow
-C<state sub> creates a subroutine visible within the lexical scope in which
-it is declared. The subroutine is shared between calls to the outer sub.
+These three infamous variables have been redeemed and no longer slow down
+your program when used. Hence, the /p regular expression flag now does
+nothing.
-C<my sub> declares a lexical subroutine that is created each time the
-enclosing block is entered. C<state sub> is generally slightly faster than
-C<my sub>.
+=head1 Security
-C<our sub> declares a lexical alias to the package subroutine of the same
-name.
+XXX Any security-related notices go here. In particular, any security
+vulnerabilities closed should be noted here rather than in the
+L</Selected Bug Fixes> section.
-See L<perlsub/Lexical Subroutines>.
+[ List each security issue as a =head2 entry ]
=head1 Incompatible Changes
-=head2 Here-doc parsing
-
-The body of a here-document inside a quote-like operator now always begins
-on the line after the "<<foo" marker. Previously, it was documented to
-begin on the line following the containing quote-like operator, but that
-was only sometimes the case [perl #114040].
+=head2 readline() with C<$/ = \N> now reads N characters, not N bytes
-=head2 Stricter parsing of substitution replacement
+Previously, when reading from a stream with I/O layers such as
+C<encoding>, the readline() function, otherwise known as the C<< <> >>
+operator, would read I<N> bytes from the top-most layer. [perl #79960]
-It is no longer possible to abuse the way the parser parses C<s///e> like
-this:
+Now, I<N> characters are read instead.
- %_=(_,"Just another ");
- $_="Perl hacker,\n";
- s//_}->{_/e;print
+There is no change in behaviour when reading from streams with no
+extra layers, since bytes map exactly to characters.
-=head2 Interaction of lexical and default warnings
+=head2 Lexical subroutine warnings have moved
-Turning on any lexical warnings used first to disable all default warnings
-if lexical warnings were not already enabled:
+The warning about the use of an experimental feature emitted when lexical
+subroutines (added in 5.17.4) are used now happens when the subroutine
+itself is declared, not when the "lexical_subs" feature is activated via
+C<use feature>.
- $*; # deprecation warning
- use warnings "void";
- $#; # void warning; no deprecation warning
+This stops C<use feature ':all'> from warning, but causes
+C<my sub foo; my sub bar> to warn twice.
-Now, the debugging, deprecated, glob, inplace and malloc warnings
-categories are left on when turning on lexical warnings (unless they are
-turned off by C<no warnings>, of course).
+=head2 Overridden C<glob> is now passed one argument
-This may cause deprecation warnings to occur in code that used to be free
-of warnings.
+C<glob> overrides used to be passed a magical undocumented second argument
+that identified the caller. Nothing on CPAN was using this, and it got in
+the way of a bug fix, so it was removed. If you really need to identify
+the caller, see L<Devel::Callsite> on CPAN.
-Those are the only categories consisting only of default warnings. Default
-warnings in other categories are still disabled by C<use warnings
-"category">, as we do not yet have the infrastructure for controlling
-individual warnings.
+=head1 Deprecations
-=head2 C<state sub> and C<our sub>
+XXX Any deprecated features, syntax, modules etc. should be listed here. In
+particular, deprecated modules should be listed here even if they are listed as
+an updated module in the L</Modules and Pragmata> section.
-Due to an accident of history, C<state sub> and C<our sub> were equivalent
-to a plain C<sub>, so one could even create an anonymous sub with
-C<our sub { ... }>. These are now disallowed outside of the "lexical_subs"
-feature. Under the "lexical_subs" feature they have new meanings described
-in L<perlsub/Lexical Subroutines>.
+[ List each deprecation as a =head2 entry ]
-=head2 C<gv_fetchmeth_*> and SUPER
+=head2 Lexical $_ is now deprecated
-The various C<gv_fetchmeth_*> XS functions used to treat a package whose
-named ended with ::SUPER specially. A method lookup on the Foo::SUPER
-package would be treated as a SUPER method lookup on the Foo package. This
-is no longer the case. To do a SUPER lookup, pass the Foo stash and the
-GV_SUPER flag.
-
-=head1 Performance Enhancements
+Since it was introduced in Perl 5.10, it has caused much confusion with no
+obvious solution:
-=over 4
+=over
=item *
-Speed up in regular expression matching against Unicode properties. The
-largest gain is for C<\X>, the Unicode "extended grapheme cluster". The
-gain for it is about 35% - 40%. Bracketed character classes, e.g.,
-C<[0-9\x{100}]> containing code points above 255 are also now faster.
+Various modules (e.g., List::Util) expect callback routines to use the
+global $_. C<use List::Util 'first'; my $_; first { $_ == 1 } @list> does
+not work as one would expect.
=item *
-On platforms supporting it, several former macros are now implemented as static
-inline functions. This should speed things up slightly on non-GCC platforms.
+A C<my $_> declaration earlier in the same file can cause confusing closure
+warnings.
=item *
-Apply the optimisation of hashes in boolean context, such as in C<if> or C<and>,
-to constructs in non-void context.
+The "_" subroutine prototype character allows called subroutines to access
+your lexical $_, so it is not really private after all.
=item *
-Extend the optimisation of hashes in boolean context to C<scalar(%hash)>,
-C<%hash ? ... : ...>, and C<sub { %hash || ... }>.
+Nevertheless, subroutines with a "(@)" prototype and methods cannot access
+the caller's lexical $_, unless they are written in XS.
=item *
-When making a copy of the string being matched against (so that $1, $& et al
-continue to show the correct value even if the original string is subsequently
-modified), only copy that substring of the original string needed for the
-capture variables, rather than copying the whole string.
-
-This is a big win for code like
-
- $&;
- $_ = 'x' x 1_000_000;
- 1 while /(.)/;
-
-Also, when pessimizing if the code contains C<$`>, C<$&> or C<$'>, record the
-presence of each variable separately, so that the determination of the substring
-range is based on each variable separately. So performance-wise,
+But even XS routines cannot access a lexical $_ declared, not in the
+calling subroutine, but in an outer scope, iff that subroutine happened not
+to mention $_ or use any operators that default to $_.
- $&; /x/
-
-is now roughly equivalent to
-
- /(x)/
-
-whereas previously it was like
-
- /^(.*)(x)(.*)$/
+=back
+=head2 Various XS-callable functions are now deprecated
+
+The following functions will be removed from a future version of Perl,
+and should not be used. With participating C compilers (e.g., gcc),
+compiling any file that uses any of these will generate a warning.
+These were not intended for public use; there are equivalent, faster,
+macros for most of them. See L<perlapi/Character classes>:
+C<is_uni_ascii>,
+C<is_uni_ascii_lc>,
+C<is_uni_blank>,
+C<is_uni_blank_lc>,
+C<is_uni_cntrl>,
+C<is_uni_cntrl_lc>,
+C<is_uni_idfirst_lc>,
+C<is_uni_space>,
+C<is_uni_space_lc>,
+C<is_uni_xdigit>,
+C<is_uni_xdigit_lc>,
+C<is_utf8_ascii>,
+C<is_utf8_blank>,
+C<is_utf8_cntrl>,
+C<is_utf8_idcont>,
+C<is_utf8_idfirst>,
+C<is_utf8_perl_space>,
+C<is_utf8_perl_word>,
+C<is_utf8_posix_digit>,
+C<is_utf8_space>,
+C<is_utf8_xdigit>.
+C<is_utf8_xidcont>,
+C<is_utf8_xidfirst>,
+C<to_uni_lower_lc>,
+C<to_uni_title_lc>,
and
+C<to_uni_upper_lc>.
- $&; $'; /x/
-
-is now roughly equivalent to
-
- /(x)(.*)$/
-
-etc.
-
-=back
+=head1 Performance Enhancements
-=head1 Modules and Pragmata
+XXX Changes which enhance performance without changing behaviour go here.
+There may well be none in a stable release.
-=head2 Updated Modules and Pragmata
+[ List each enhancement as a =item entry ]
=over 4
=item *
-L<Archive::Tar> has been upgraded from version 1.88 to 1.90. This adds
-documentation fixes.
+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.
-=item *
-
-L<B> has been upgraded from version 1.37 to 1.38. This makes the module work
-with the new pad API.
-
-=item *
+=back
-L<B::Concise> has been upgraded from version 0.92 to 0.93. This adds support
-for the new C<OpMAYBE_TRUEBOOL> and C<OPpTRUEBOOL> flags.
+=head1 Modules and Pragmata
-=item *
+XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
+go here. If Module::CoreList is updated, generate an initial draft of the
+following sections using F<Porting/corelist-perldelta.pl>, 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<Changes> file that could be
+cribbed.
-L<B::Deparse> has been upgraded from version 1.16 to 1.17. This suppresses
-trailing semicolons in formats.
+[ Within each section, list entries as a =item entry ]
-=item *
+=head2 New Modules and Pragmata
-L<CPANPLUS> has been upgraded from version 0.9130 to 0.9131. This resolves
-issues with the SQLite source engine.
+=over 4
=item *
-L<DB_File> has been upgraded from version 1.826 to 1.827. The main Perl module
-no longer uses the C<"@_"> construct.
+XXX
-=item *
-
-L<Devel::Peek> has been upgraded from version 1.09 to 1.10. This fixes
-compilation with C++ compilers and makes the module work with the new pad API.
+=back
-=item *
+=head2 Updated Modules and Pragmata
-L<DynaLoader> has been upgraded from version 1.15 to 1.16. This fixes warnings
-about using C<CODE> sections without an C<OUTPUT> section.
+=over 4
=item *
-L<ExtUtils::ParseXS> has been upgraded from version 3.17 to 3.18. This avoids a
-bogus warning for initialised XSUB non-parameters [perl #112776].
+L<File::DosGlob> has been upgraded from version 1.08 to 1.09. The internal
+cache of file names that it keeps for each caller is now freed when that
+caller is freed. This means
+C<< use File::DosGlob 'glob'; eval 'scalar <*>' >> no longer leaks memory.
=item *
-L<File::Copy> has been upgraded from version 2.23 to 2.24. C<copy()> no longer
-zeros files when copying into the same directory, and also now fails (as it has
-long been documented to do) when attempting to copy a file over itself.
+L<File::Glob> has been upgraded from version 1.18 to 1.19. File::Glob has
+had exactly the same fix as File::DosGlob. Since it is what Perl's own
+C<glob> operator itself uses (except on VMS), this means
+C<< eval 'scalar <*>' >> no longer leaks.
=item *
-L<File::Find> has been upgraded from version 1.21 to 1.22. This fixes
-inconsistent unixy path handling on VMS.
-
-=item *
+L<GDBM_File> has been upgraded from version 1.14 to 1.15. The undocumented
+optional fifth parameter to C<TIEHASH> has been removed. This was intended
+to provide control of the callback used by C<gdbm*> functions in case of
+fatal errors (such as filesystem problems), but did not work (and could
+never have worked). No code on CPAN even attempted to use it. The callback
+is now always the previous default, C<croak>. Problems on some platforms with
+how the C<C> C<croak> function is called have also been resolved.
-L<IPC::Open3> has been upgraded from version 1.12 to 1.13. The C<open3()>
-function no longer uses C<POSIX::close()> to close file descriptors since that
-breaks the ref-counting of file descriptors done by PerlIO in cases where the
-file descriptors are shared by PerlIO streams, leading to attempts to close the
-file descriptors a second time when any such PerlIO streams are closed later on.
+=back
-=item *
+=head2 Removed Modules and Pragmata
-L<Locale::Codes> has been upgraded from version 3.22 to 3.23. It includes some
-new codes.
+=over 4
=item *
-L<Module::CoreList> has been upgraded from version 2.71 to 2.73. This restores
-compatibility with older versions of perl and cleans up the corelist data for
-various modules.
-
-=item *
+XXX
-L<Opcode> has been upgraded from version 1.23 to 1.24 to reflect the removal of
-the boolkeys opcode and the addition of the clonecv, introcv and padcv
-opcodes.
+=back
-=item *
+=head1 Documentation
-L<Socket> has been upgraded from version 2.004 to 2.006.
-C<unpack_sockaddr_in()> and C<unpack_sockaddr_in6()> now return just the IP
-address in scalar context, and C<inet_ntop()> now guards against incorrect
-length scalars being passed in.
+XXX Changes to files in F<pod/> go here. Consider grouping entries by
+file and be sure to link to the appropriate page, e.g. L<perlfunc>.
-=item *
+=head2 New Documentation
-L<Storable> has been upgraded from version 2.38 to 2.39. This contains Various
-bugfixes, including compatibility fixes for older versions of Perl and vstring
-handling.
+XXX Changes which create B<new> files in F<pod/> go here.
-=item *
+=head3 L<XXX>
-L<Sys::Syslog> has been upgraded from version 0.31 to 0.32. This includes
-several documentation and bug fixes.
+XXX Description of the purpose of the new file here
-=item *
+=head2 Changes to Existing Documentation
-L<threads::shared> has been upgraded from version 1.40 to 1.41. This adds the
-option to warn about or ignore attempts to clone structures that can't be
-cloned, as opposed to just unconditionally dying in that case.
+XXX Changes which significantly change existing files in F<pod/> go here.
+However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
+section.
-=item *
+=head3 L<perlapi/Character classes>
-L<version> has been upgraded from version 0.99 to 0.9901.
+=over 4
=item *
-L<XSLoader> has been upgraded from version 0.15 to 0.16.
+There are quite a few macros callable from XS modules that classify
+characters into things like alphabetic, punctuation, etc. More of these
+are now documented, including ones which work on characters whose code
+points are outside the Latin-1 range.
=back
including warnings and fatal error messages. For the complete list of
diagnostic messages, see L<perldiag>.
+XXX New or changed warnings emitted by the core's C<C> code go here. Also
+include any changes in L<perldiag> that reconcile it to the C<C> code.
+
=head2 New Diagnostics
-=head3 New Warnings
+XXX Newly added diagnostic messages go under here, separated into New Errors
+and New Warnings
+
+=head3 New Errors
=over 4
=item *
-L<Experimental "%s" subs not enabled|perldiag/"Experimental "%s" subs not enabled">
+XXX L<message|perldiag/"message">
-(F) To use lexical subs, you must first enable them:
+=back
- no warnings 'experimental:lexical_subs';
- use feature 'lexical_subs';
- my sub foo { ... }
+=head3 New Warnings
-=item *
+=over 4
-L<Subroutine "&%s" is not available|perldiag/"Subroutine "&%s" is not available">
+=item *
-(W closure) During compilation, an inner named subroutine or eval is
-attempting to capture an outer lexical subroutine that is not currently
-available. This can happen for one of two reasons. First, the lexical
-subroutine may be declared in an outer anonymous subroutine that has not
-yet been created. (Remember that named subs are created at compile time,
-while anonymous subs are created at run-time.) For example,
+XXX L<message|perldiag/"message">
- sub { my sub a {...} sub f { \&a } }
+=back
-At the time that f is created, it can't capture the current the "a" sub,
-since the anonymous subroutine hasn't been created yet. Conversely, the
-following won't give a warning since the anonymous subroutine has by now
-been created and is live:
+=head2 Changes to Existing Diagnostics
- sub { my sub a {...} eval 'sub f { \&a }' }->();
+XXX Changes (i.e. rewording) of diagnostic messages go here
-The second situation is caused by an eval accessing a variable that has
-gone out of scope, for example,
+=over 4
- sub f {
- my sub a {...}
- sub { eval '\&a' }
- }
- f()->();
+=item *
-Here, when the '\&a' in the eval is being compiled, f() is not currently
-being executed, so its &a is not available for capture.
+L<Constant(%s): Call to &{$^H{%s}} did not return a defined value|perldiag/Constant(%s): Call to &{$^H{%s}} did not return a defined value>
-=item *
+Constant overloading that returns C<undef> results in this error message.
+For numeric constants, it used to say "Constant(undef)". "undef" has been
+replaced with the number itself.
-L<"%s" subroutine &%s masks earlier declaration in same %s|perldiag/"%s" subroutine &%s masks earlier declaration in same %s>
+=back
-(W misc) A "my" or "state" subroutine has been redeclared in the
-current scope or statement, effectively eliminating all access to
-the previous instance. This is almost always a typographical error.
-Note that the earlier subroutine will still exist until the end of
-the scope or until all closure references to it are destroyed.
+=head1 Utility Changes
-=item *
+XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
+Most of these are built within the directories F<utils> and F<x2p>.
-L<The %s feature is experimental|perldiag/"The %s feature is experimental">
+[ List utility changes as a =head3 entry for each utility and =item
+entries for each change
+Use L<XXX> with program names to get proper documentation linking. ]
-(S experimental) This warning is emitted if you enable an experimental
-feature via C<use feature>. Simply suppress the warning if you want
-to use the feature, but know that in doing so you are taking the risk
-of using an experimental feature which may change or be removed in a
-future Perl version:
+=head3 L<XXX>
- no warnings "experimental:lexical_subs";
- use feature "lexical_subs";
+=over 4
=item *
-L<sleep(%u) too large|perldiag/"sleep(%u) too large">
-
-(W overflow) You called C<sleep> with a number that was larger than it can
-reliably handle and C<sleep> probably slept for less time than requested.
+XXX
=back
-=head2 Changes to Existing Diagnostics
-
-=over 4
+=head1 Configuration and Compilation
-=item *
+XXX Changes to F<Configure>, F<installperl>, F<installman>, 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</Platform Support> section, instead.
-L<vector argument not supported with alpha versions|perldiag/vector argument not supported with alpha versions>
+[ List changes as a =item entry ].
-This warning was not suppressable, even with C<no warnings>. Now it is
-suppressible, and has been moved from the "internal" category to the
-"printf" category.
+=over 4
=item *
-C<< Can't do {n,m} with n > m in regex; marked by <-- HERE in m/%s/ >>
-
-This fatal error has been turned into a warning that reads:
+XXX
-L<< Quantifier {n,m} with n > m can't match in regex | perldiag/Quantifier {n,m} with n > m can't match in regex >>
+=back
-(W regexp) Minima should be less than or equal to maxima. If you really want
-your regexp to match something 0 times, just put {0}.
+=head1 Testing
-=back
+XXX Any significant changes to the testing of a freshly built perl should be
+listed here. Changes which create B<new> files in F<t/> go here as do any
+large changes to the testing harness (e.g. when parallel testing was added).
+Changes to existing files in F<t/> aren't worth summarizing, although the bugs
+that they represent may be covered elsewhere.
-=head1 Configuration and Compilation
+[ List each test improvement as a =item entry ]
=over 4
=item *
-F<Configure> will now correctly detect C<isblank()> when compiling with a C++
-compiler.
+XXX
=back
=head1 Platform Support
-=head2 Discontinued Platforms
+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<hints/>
+directories, or new subdirectories and F<README> files at the top level of the
+source tree.
=over 4
-=item VM/ESA
+=item XXX-some-platform
-Support for VM/ESA has been removed. The port was tested on 2.3.0, which
-IBM ended service on in March 2002. 2.4.0 ended service in June 2003, and
-was superseded by Z/VM. The current version of Z/VM is V6.2.0, and scheduled
-for end of service on 2015/04/30.
+XXX
=back
-=head2 Platform-Specific Notes
+=head2 Discontinued Platforms
=over 4
-=item Win32
+=item BeOS
-Fixed a problem where perl could crash while cleaning up threads (including the
-main thread) in threaded debugging builds on Win32 and possibly other platforms
-[perl #114496].
+Support for BeOS has been removed.
-A rare race condition that would lead to L<sleep|perlfunc/sleep> taking more
-time than requested, and possibly even hanging, has been fixed [perl #33096].
-
-=item Solaris
+=back
-In Configure, avoid running sed commands with flags not supported on Solaris.
+=head2 Platform-Specific Notes
-=item Darwin
+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</Modules and Pragmata> section.
-Stop hardcoding an alignment on 8 byte boundaries to fix builds using
--Dusemorebits.
+=over 4
-=item VMS
+=item XXX-some-platform
-Fix linking on builds configured with -Dusemymalloc=y.
+XXX
=back
=head1 Internal Changes
-=over 4
-
-=item *
+XXX Changes which affect the interface available to C<XS> code go here. Other
+significant internal changes for future core maintainers should be noted as
+well.
-The APIs for accessing lexical pads have changed considerably.
+[ List each change as a =item entry ]
-C<PADLIST>s are now longer C<AV>s, but their own type instead. C<PADLIST>s now
-contain a C<PAD> and a C<PADNAMELIST> of C<PADNAME>s, rather than C<AV>s for the
-pad and the list of pad names. C<PAD>s, C<PADNAMELIST>s, and C<PADNAME>s are to
-be accessed as such though the newly added pad API instead of the plain C<AV>
-and C<SV> APIs. See L<perlapi> for details.
+=over 4
=item *
-In the regex API, the numbered capture callbacks are passed an index
-indicating what match variable is being accessed. There are special
-index values for the C<$`, $&, $&> variables. Previously the same three
-values were used to retrieve C<${^PREMATCH}, ${^MATCH}, ${^POSTMATCH}>
-too, but these have now been assigned three separate values. See
-L<perlreapi/Numbered capture callbacks>.
+SvUPGRADE() is no longer an expression. Originally this macro (and its
+underlying function, sv_upgrade()) were documented as boolean, although
+in reality they always croaked on error and never returned false. In 2005
+the documentation was updated to specify a void return value, but
+SvUPGRADE() was left always returning 1 for backwards compatibility. This
+has now been removed, and SvUPGRADE() is now a statement with no return
+value.
-=item *
+So this is now a syntax error:
-C<PL_sawampersand> was previously a boolean indicating that any of
-C<$`, $&, $&> had been seen; it now contains three one-bit flags
-indicating the presence of each of the variables individually.
+ if (!SvUPGRADE(sv)) { croak(...); }
-=back
+If you have code like that, simply replace it with
-=head1 Selected Bug Fixes
+ SvUPGRADE(sv);
-=over 4
+or to to avoid compiler warnings with older perls, possibly
+
+ (void)SvUPGRADE(sv);
=item *
-The error "Can't localize through a reference" had disappeared in 5.16.0
-when C<local %$ref> appeared on the last line of an lvalue subroutine.
-This error disappeared for C<\local %$ref> in perl 5.8.1. It has now
-been restored.
+Perl has a new copy-on-write mechanism that allows any SvPOK scalar to be
+upgraded to a copy-on-write scalar. A reference count on the string buffer
+is stored in the string buffer itself.
-=item *
+This breaks a few XS modules by allowing copy-on-write scalars to go
+through code paths that never encountered them before.
-The parsing of here-docs has been improved significantly, fixing several
-parsing bugs and crashes and one memory leak, and correcting wrong
-subsequent line numbers under certain conditions.
+This behaviour can still be disabled by running F<Configure> with
+B<-Accflags=-DPERL_NO_COW>. This option will probably be removed in Perl
+5.20.
=item *
-Inside an eval, the error message for an unterminated here-doc no longer
-has a newline in the middle of it [perl #70836].
+Copy-on-write no longer uses the SvFAKE and SvREADONLY flags. Hence,
+SvREADONLY indicates a true read-only SV.
+
+Use the SvIsCOW macro (as before) to identify a copy-on-write scalar.
=item *
-A substitution inside a substitution pattern (C<s/${s|||}//>) no longer
-confuses the parser.
+C<PL_sawampersand> is now a constant. The switch this variable provided
+(to enable/disable the pre-match copy depending on whether C<$&> had been
+seen) has been removed and replaced with copy-on-write, eliminating a few
+bugs.
+
+The previous behaviour can still be enabled by running F<Configure> with
+B<-Accflags=-DPERL_SAWAMPERSAND>.
=item *
-It may be an odd place to allow comments, but C<s//"" # hello/e> has
-always worked, I<unless> there happens to be a null character before the
-first #. Now it works even in the presence of nulls.
+PL_glob_index is gone.
-=item *
+=back
-An invalid range in C<tr///> or C<y///> no longer results in a memory leak.
+=head1 Selected Bug Fixes
-=item *
+XXX Important bug fixes in the core language are summarized here. Bug fixes in
+files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
-String eval no longer treats a semicolon-delimited quote-like operator at
-the very end (C<eval 'q;;'>) as a syntax error.
+[ List each fix as a =item entry ]
+
+=over 4
=item *
-C<< warn {$_ => 1} + 1 >> is no longer a syntax error. The parser used to
-get confused with certain list operators followed by an anonymous hash and
-then an infix operator that shares its form with a unary operator.
+C<sort {undef} ...> under fatal warnings no longer crashes. It started
+crashing in Perl 5.16.
=item *
-C<(caller $n)[6]> (which gives the text of the eval) used to return the
-actual parser buffer. Modifying it could result in crashes. Now it always
-returns a copy. The string returned no longer has "\n;" tacked on to the
-end. The returned text also includes here-doc bodies, which used to be
-omitted.
+Stashes blessed into each other
+(C<bless \%Foo::, 'Bar'; bless \%Bar::, 'Foo'>) no longer result in double
+frees. This bug started happening in Perl 5.16.
=item *
-Reset the utf8 position cache when accessing magical variables to avoid the
-string buffer and the utf8 position cache to get out of sync
-[perl #114410].
+Numerous memory leaks have been fixed, mostly involving fatal warnings and
+syntax errors.
=item *
-Various cases of get magic being called twice for magical utf8 strings have been
-fixed.
+Lexical constants (C<my sub answer () { 42 }>) no longer cause double
+frees.
=item *
-This code (when not in the presence of C<$&> etc)
+Constant subroutine redefinition warns by default, but lexical constants
+were accidentally exempt from default warnings. This has been corrected.
- $_ = 'x' x 1_000_000;
- 1 while /(.)/;
+=item *
-used to skip the buffer copy for performance reasons, but suffered from C<$1>
-etc changing if the original string changed. That's now been fixed.
+Some failed regular expression matches such as C<'f' =~ /../g> were not
+resetting C<pos>. Also, "match-once" patterns (C<m?...?g>) failed to reset
+it, too, when invoked a second time [perl #23180].
=item *
-Perl doesn't use PerlIO anymore to report out of memory messages, as PerlIO
-might attempt to allocate more memory.
+Accessing C<$&> after a pattern match now works if it had not been seen
+before the match. I.e., this applies to C<${'&'}> (under C<no strict>) and
+C<eval '$&'>. The same applies to C<$'> and C<$`> [perl #4289].
=item *
-In a regular expression, if something is quantified with C<{n,m}>
-where C<S<n E<gt> m>>, it can't possibly match. Previously this was a fatal error,
-but now is merely a warning (and that something won't match). [perl #82954].
+Several bugs involving C<local *ISA> and C<local *Foo::> causing stale
+MRO caches have been fixed.
=item *
-It used to be possible for formats defined in subroutines that have
-subquently been undefined and redefined to close over variables in the
-wrong pad (the newly-defined enclosing sub), resulting in crashes or
-"Bizarre copy" errors.
+Defining a subroutine when its typeglob has been aliased no longer results
+in stale method caches. This bug was introduced in Perl 5.10.
=item *
-Redefinition of XSUBs at run time could produce warnings with the wrong
-line number.
+Localising a typeglob containing a subroutine when the typeglob's package
+has been deleted from its parent stash no longer produces an error. This
+bug was introduced in Perl 5.14.
=item *
-The %vd sprintf format does not support version objects for alpha versions.
-It used to output the format itself (%vd) when passed an alpha version, and
-also emit an "Invalid conversion in printf" warning. It no longer does,
-but produces the empty string in the output. It also no longer leaks
-memory in this case.
+Under some circumstances, C<local *method=...> would fail to reset method
+caches upon scope exit.
=item *
-A bug fix in an earlier 5.17.x release caused C<no a a 3> (a syntax error)
-to result in a bad read or assertion failure, because an op was being freed
-twice.
+C</[.foo.]/> is no longer an error, but produces a warning (as before) and
+is treated as C</[.fo]/> [perl #115818].
=item *
-C<< $obj->SUPER::method >> calls in the main package could fail if the
-SUPER package had already been accessed by other means.
+C<goto $tied_var> now calls FETCH before deciding what type of goto
+(subroutine or label) this is.
=item *
-Stash aliasing (C<*foo:: = *bar::>) no longer causes SUPER calls to ignore
-changes to methods or @ISA or use the wrong package.
+Renaming packages through glob assignment
+(C<*Foo:: = *Bar::; *Bar:: = *Baz::>) in combination with C<m?...?> and
+C<reset> no longer makes threaded builds crash.
=item *
-Method calls on packages whose names end in ::SUPER are no longer treated
-as SUPER method calls, resulting in failure to find the method.
-Furthermore, defining subroutines in such packages no longer causes them to
-be found by SUPER method calls on the containing package [perl #114924].
+An earlier release in the 5.17.x series could crash if user code prevented
+_charnames from loading via C<$INC{'_charnames.pm'}++>.
=back
=head1 Known Problems
+XXX Descriptions of platform agnostic bugs we know we can't fix go here. Any
+tests that had to be C<TODO>ed for the release would be noted here. Unfixed
+platform specific bugs also go here.
+
+[ List each fix as a =item entry ]
+
=over 4
=item *
-Changes in the lexical pad API break some CPAN modules.
-
-To avoid having to patch those modules again later if we change pads from AVs
-into their own types, APIs for accessing the contents of pads have been added.
+XXX
=back
+=head1 Obituary
+
+XXX If any significant core contributor has died, we've added a short obituary
+here.
+
=head1 Acknowledgements
-Perl 5.17.4 represents approximately 4 weeks of development since Perl 5.17.3
-and contains approximately 82,000 lines of changes across 360 files from 37
-authors.
-
-Perl continues to flourish into its third decade thanks to a vibrant community
-of users and developers. The following people are known to have contributed the
-improvements that became Perl 5.17.4:
-
-Abhijit Menon-Sen, Andy Dougherty, Aristotle Pagaltzis, Chris 'BinGOs'
-Williams, Colin Kuskie, Craig A. Berry, Daniel Dragan, David Golden, David
-Leadbeater, David Mitchell, David Nicol, Dominic Hargreaves, Father
-Chrysostomos, Florian Ragwitz, H.Merijn Brand, James E Keenan, Jerry D. Hedden,
-Jesse Luehrs, John Peacock, Karen Etheridge, Karl Williamson, Leon Timmermans,
-Michael G Schwern, Nicholas Clark, Peter Martini, Rafael Garcia-Suarez, Ricardo
-Signes, Shawn M Moore, Shlomi Fish, Steffen Müller, Steve Hay, Sullivan Beck,
-Sébastien Aperghis-Tramoni, Tony Cook, Vincent Pit, Yves Orton.
-
-The list above is almost certainly incomplete as it is automatically generated
-from version control history. In particular, it does not include the names of
-the (very much appreciated) contributors who reported issues to the Perl bug
-tracker.
-
-Many of the changes included in this version originated in the CPAN modules
-included in Perl's core. We're grateful to the entire CPAN community for
-helping Perl to flourish.
-
-For a more complete list of all of Perl's historical contributors, please see
-the F<AUTHORS> file in the Perl source distribution.
+XXX Generate this with:
+
+ perl Porting/acknowledgements.pl v5.17.6..HEAD
=head1 Reporting Bugs
https://perl5.git.perl.org / perl5.git / blobdiff