Make a new perldelta for 5.17.8-to-be

1 files changed, 175 insertions, 253 deletions

diff --git a/pod/perldelta.pod b/pod/perldelta.pod
index 0b74681407..71325ef6c8 100644
--- a/pod/perldelta.pod
+++ b/pod/perldelta.pod
@@ -2,195 +2,140 @@
 
 =head1 NAME
 
-perldelta - what is new for perl v5.17.7
+[ 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 v5.17.8
 
 =head1 DESCRIPTION
 
-This document describes differences between the 5.17.6 release and the 5.17.7
+This document describes differences between the 5.17.7 release and the 5.17.8
 release.
 
-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.
-
-=head1 Core Enhancements
-
-=head2 $&, $` and $' are no longer slow
-
-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.
+If you are upgrading from an earlier release such as 5.17.6, first read
+L<perl5177delta>, which describes differences between 5.17.6 and 5.17.7.
 
-=head1 Security
+=head1 Notice
 
-=head2 C<Storable> security warning in documentation
+XXX Any important notices here
 
-The documentation for C<Storable> now includes a section which warns readers
-of the danger of accepting Storable documents from untrusted sources. The
-short version is that deserializing certain types of data can lead to loading
-modules and other code execution. This is documented behavior and wanted
-behavior, but this opens an attack vector for malicious entities.
+=head1 Core Enhancements
 
-=head2 C<Locale::Maketext> allowed code injection via a malicious template
+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</Performance Enhancements> section.
 
-If users could provide a translation string to Locale::Maketext, this could be
-used to invoke arbitrary Perl subroutines available in the current process.
+[ List each enhancement as a =head2 entry ]
 
-This has been fixed, but it is still possible to invoke any method provided by
-C<Locale::Maketext> itself or a subclass that you are using. One of these
-methods in turn will invoke the Perl core's C<sprintf> subroutine.
+=head1 Security
 
-In summary, allowing users to provide translation strings without auditing
-them is a bad idea.
+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.
 
-This vulnerability is documented in CVE-2012-6329.
+[ List each security issue as a =head2 entry ]
 
 =head1 Incompatible Changes
 
-=head2 readline() with C<$/ = \N> now reads N characters, not N bytes
-
-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]
+XXX For a release on a stable branch, this section aspires to be:
 
-Now, I<N> characters are read instead.
+    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</Reporting Bugs> below.
 
-There is no change in behaviour when reading from streams with no
-extra layers, since bytes map exactly to characters.
+[ List each incompatible change as a =head2 entry ]
 
-=head2 Lexical subroutine warnings have moved
-
-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>.
-
-This stops C<use feature ':all'> from warning, but causes
-C<my sub foo; my sub bar> to warn twice.
+=head1 Deprecations
 
-=head2 Overridden C<glob> is now passed one argument
+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.
 
-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.
+[ List each deprecation as a =head2 entry ]
 
-=head1 Deprecations
+=head1 Performance Enhancements
 
-=head2 Lexical $_ is now deprecated
+XXX Changes which enhance performance without changing behaviour go here.
+There may well be none in a stable release.
 
-Since it was introduced in Perl 5.10, it has caused much confusion with no
-obvious solution:
+[ List each enhancement as a =item entry ]
 
-=over
+=over 4
 
 =item *
 
-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.
+XXX
 
-=item *
+=back
 
-A C<my $_> declaration earlier in the same file can cause confusing closure
-warnings.
+=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.
 
-The "_" subroutine prototype character allows called subroutines to access
-your lexical $_, so it is not really private after all.
+[ Within each section, list entries as a =item entry ]
 
-=item *
+=head2 New Modules and Pragmata
 
-Nevertheless, subroutines with a "(@)" prototype and methods cannot access
-the caller's lexical $_, unless they are written in XS.
+=over 4
 
 =item *
 
-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 $_.
+XXX
 
 =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>.
-
-=head1 Performance Enhancements
+=head2 Updated Modules and Pragmata
 
 =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.
+L<XXX> has been upgraded from version A.xx to B.yy.
 
 =back
 
-=head1 Modules and Pragmata
-
-=head2 Updated Modules and Pragmata
+=head2 Removed Modules and Pragmata
 
 =over 4
 
 =item *
 
-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.
+XXX
 
-=item *
-
-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.
+=back
 
-=item *
+=head1 Documentation
 
-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.
+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<Module::CoreList> has been upgraded from version 2.78 to 2.79.
+XXX Changes which create B<new> files in F<pod/> go here.
 
-=back
+=head3 L<XXX>
 
-=head1 Documentation
+XXX Description of the purpose of the new file here
 
 =head2 Changes to Existing Documentation
 
-=head3 L<perlapi/Character classes>
+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.
+
+=head3 L<XXX>
 
 =over 4
 
 =item *
 
-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.
+XXX Description of the change here
 
 =back
 
@@ -200,229 +145,206 @@ 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<perldiag>.
 
-=head2 Changes to Existing Diagnostics
+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
+
+XXX Newly added diagnostic messages go under here, separated into New Errors
+and New Warnings
+
+=head3 New Errors
 
 =over 4
 
 =item *
 
-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>
-
-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.
+XXX L<message|perldiag/"message">
 
 =back
 
-=head1 Internal Changes
+=head3 New Warnings
 
 =over 4
 
 =item *
 
-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.
+XXX L<message|perldiag/"message">
 
-So this is now a syntax error:
+=back
 
-    if (!SvUPGRADE(sv)) { croak(...); }
+=head2 Changes to Existing Diagnostics
 
-If you have code like that, simply replace it with
+XXX Changes (i.e. rewording) of diagnostic messages go here
 
-    SvUPGRADE(sv);
+=over 4
 
-or to to avoid compiler warnings with older perls, possibly
+=item *
 
-    (void)SvUPGRADE(sv);
+XXX Describe change here
 
-=item *
+=back
 
-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.
+=head1 Utility Changes
 
-This breaks a few XS modules by allowing copy-on-write scalars to go
-through code paths that never encountered them before.
+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>.
 
-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.
+[ 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. ]
+
+=head3 L<XXX>
+
+=over 4
 
 =item *
 
-Copy-on-write no longer uses the SvFAKE and SvREADONLY flags.  Hence,
-SvREADONLY indicates a true read-only SV.
+XXX
 
-Use the SvIsCOW macro (as before) to identify a copy-on-write scalar.
+=back
 
-=item *
+=head1 Configuration and Compilation
+
+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.
 
-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.
+[ List changes as a =item entry ].
 
-The previous behaviour can still be enabled by running F<Configure> with
-B<-Accflags=-DPERL_SAWAMPERSAND>.
+=over 4
 
 =item *
 
-PL_glob_index is gone.
+XXX
 
 =back
 
-=head1 Selected Bug Fixes
+=head1 Testing
 
-=over 4
+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.
 
-=item *
+[ List each test improvement as a =item entry ]
 
-C<sort {undef} ...> under fatal warnings no longer crashes.  It started
-crashing in Perl 5.16.
+=over 4
 
 =item *
 
-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.
+XXX
 
-=item *
+=back
 
-Numerous memory leaks have been fixed, mostly involving fatal warnings and
-syntax errors.
+=head1 Platform Support
 
-=item *
+XXX Any changes to platform support should be listed in the sections below.
 
-Lexical constants (C<my sub answer () { 42 }>) no longer cause double
-frees.
+[ Within the sections, list each platform as a =item entry with specific
+changes as paragraphs below it. ]
 
-=item *
+=head2 New Platforms
 
-Constant subroutine redefinition warns by default, but lexical constants
-were accidentally exempt from default warnings.  This has been corrected.
+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.
 
-=item *
+=over 4
 
-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 XXX-some-platform
 
-=item *
+XXX
 
-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].
+=back
 
-=item *
+=head2 Discontinued Platforms
 
-Several bugs involving C<local *ISA> and C<local *Foo::> causing stale
-MRO caches have been fixed.  
+XXX List any platforms that this version of perl no longer compiles on.
 
-=item *
+=over 4
 
-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 XXX-some-platform
 
-=item *
+XXX
 
-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.
+=back
 
-=item *
+=head2 Platform-Specific Notes
 
-Under some circumstances, C<local *method=...> would fail to reset method
-caches upon scope exit.
+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.
 
-=item *
+=over 4
 
-C</[.foo.]/> is no longer an error, but produces a warning (as before) and
-is treated as C</[.fo]/> [perl #115818].
+=item XXX-some-platform
 
-=item *
+XXX
 
-C<goto $tied_var> now calls FETCH before deciding what type of goto
-(subroutine or label) this is.
+=back
 
-=item *
+=head1 Internal Changes
 
-Renaming packages through glob assignment
-(C<*Foo:: = *Bar::; *Bar:: = *Baz::>) in combination with C<m?...?> and
-C<reset> no longer makes threaded builds crash.
+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.
 
-=item *
+[ List each change as a =item entry ]
 
-An earlier release in the 5.17.x series could crash if user code prevented
-_charnames from loading via C<$INC{'_charnames.pm'}++>.
+=over 4
 
 =item *
 
-A number of bugs related to assigning a list to hash have been fixed. Many of
-these involve lists with repeated keys like C<(1, 1, 1, 1)>.
+XXX
 
-=over 8
+=back
 
-=item -
+=head1 Selected Bug Fixes
 
-The expression C<scalar(%h = (1, 1, 1, 1))> now returns C<4>, not C<2>.
+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>.
 
-=item -
+[ List each fix as a =item entry ]
 
-The return value of C<%h = (1, 1, 1)> in list context was wrong. Previously
-this would return C<(1, undef, 1)>, now it returns C<(1, undef)>.
+=over 4
 
-=item -
+=item *
 
-Perl now issues the same warning on C<($s, %h) = (1, {})> as it does for
-C<(%h) = ({})>, "Reference found where even-sized list expected".
+XXX
 
-=item -
+=back
 
-A number of additional edge cases in list assignment to hashes were
-corrected. For more details see commit 23b7025ebc.
+=head1 Known Problems
 
-=back
+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.
 
-=back
+[ List each fix as a =item entry ]
 
-=head1 Known Problems
+=over 4
 
-There may be a failure in the F<t/op/require_errors.t> test if you run the
-test suite as the root user.
+=item *
 
-=head1 Acknowledgements
+XXX
 
-Perl 5.17.7 represents approximately 4 weeks of development since Perl 5.17.6
-and contains approximately 30,000 lines of changes across 490 files from 26
-authors.
+=back
 
-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 5.17.7:
+=head1 Obituary
 
-Alexandr Ciornii, Bob Ernst, Brian Carlson, Chris 'BinGOs' Williams, Craig A.
-Berry, Daniel Dragan, Dave Rolsky, David Mitchell, Father Chrysostomos, Hugo
-van der Sanden, James E Keenan, Joel Berger, Karl Williamson, Lukas Mai, Martin
-Hasch, Matthew Horsfall, Nicholas Clark, Ricardo Signes, Ruslan Zakirov, Sergey
-Alekseev, Steffen Müller, Sullivan Beck, Sven Strickroth, Sébastien
-Aperghis-Tramoni, Tony Cook, Yves Orton.
+XXX If any significant core contributor has died, we've added a short obituary
+here.
 
-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.
+=head1 Acknowledgements
 
-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.
+XXX Generate this with:
 
-For a more complete list of all of Perl's historical contributors, please see
-the F<AUTHORS> file in the Perl source distribution.
+  perl Porting/acknowledgements.pl v5.17.7..HEAD
 
 =head1 Reporting Bugs