[ 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 v5.17.5
+perldelta - what is new for perl v5.17.7
=head1 DESCRIPTION
-This document describes differences between the 5.17.4 release and the 5.17.5
+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 5.17.3, first read
-L<perl5174delta>, which describes differences between 5.17.3 and 5.17.4.
+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 Notice
=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</Performance Enhancements> section.
+=head2 $&, $` and $' are no longer slow
-[ List each enhancement as a =head2 entry ]
+These three infamous variables have been redeemed and no longer slow down
+your program when used. Hence, the /p regular expression flag now does
+nothing.
=head1 Security
=head1 Incompatible Changes
-XXX For a release on a stable branch, this section aspires to be:
+=head2 readline() with C<$/ = \N> now reads N characters, not N bytes
- 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.
+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]
-[ List each incompatible change as a =head2 entry ]
+Now, I<N> characters are read instead.
+
+There is no change in behaviour when reading from streams with no
+extra layers, since bytes map exactly to characters.
+
+=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
[ List each deprecation as a =head2 entry ]
+=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
XXX Changes which enhance performance without changing behaviour go here.
=item *
-XXX
+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.
=back
=item *
-L<XXX> has been upgraded from version A.xx to B.yy.
+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.
=back
However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
section.
-=head3 L<XXX>
+=head3 L<perlapi/Character classes>
=over 4
=item *
-XXX Description of the change here
+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
=head2 Discontinued Platforms
-XXX List any platforms that this version of perl no longer compiles on.
-
=over 4
-=item XXX-some-platform
+=item BeOS
-XXX
+Support for BeOS has been removed.
=back
=item *
-XXX
+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.
+
+So this is now a syntax error:
+
+ if (!SvUPGRADE(sv)) { croak(...); }
+
+If you have code like that, simply replace it with
+
+ SvUPGRADE(sv);
+
+or to to avoid compiler warnings with older perls, possibly
+
+ (void)SvUPGRADE(sv);
+
+=item *
+
+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.
+
+This breaks a few XS modules by allowing copy-on-write scalars to go
+through code paths that never encountered them before.
+
+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 *
+
+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 *
+
+C<PL_sawampersand> is now a constant. The switch this variable provided
+(to enable/disable the pre-match copy depending on whether C<$&> had been
+seen) has been removed and replaced with copy-on-write, eliminating a few
+bugs.
+
+The previous behaviour can still be enabled by running F<Configure> with
+B<-Accflags=-DPERL_SAWAMPERSAND>.
=back
=item *
-XXX
+C<sort {undef} ...> under fatal warnings no longer crashes. It started
+crashing in Perl 5.16.
+
+=item *
+
+Stashes blessed into each other
+(C<bless \%Foo::, 'Bar'; bless \%Bar::, 'Foo'>) no longer result in double
+frees. This bug started happening in Perl 5.16.
+
+=item *
+
+Numerous memory leaks have been fixed, mostly involving fatal warnings and
+syntax errors.
+
+=item *
+
+Lexical constants (C<my sub answer () { 42 }>) no longer cause double
+frees.
+
+=item *
+
+Constant subroutine redefinition warns by default, but lexical constants
+were accidentally exempt from default warnings. This has been corrected.
+
+=item *
+
+Some failed regular expression matches such as C<'f' =~ /../g> were not
+resetting C<pos>. Also, "match-once" patterns (C<m?...?g>) failed to reset
+it, too, when invoked a second time [perl #23180].
+
+=item *
+
+Accessing C<$&> 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 *
+
+Several bugs involving C<local *ISA> and C<local *Foo::> causing stale
+MRO caches have been fixed.
+
+=item *
+
+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 *
+
+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
XXX Generate this with:
- perl Porting/acknowledgements.pl v5.17.4..HEAD
+ perl Porting/acknowledgements.pl v5.17.6..HEAD
=head1 Reporting Bugs
https://perl5.git.perl.org / perl5.git / blobdiff