[ 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 ]
-
-=head2 Upgrade to Unicode 6.2
-
-Perl now supports the final version of Unicode 6.2. Earlier releases in
-the 5.17 series supported Unicode 6.2 beta versions. There were no
-substantive changes in the final Unicode 6.2 version from the most
-recent beta, included in Perl 5.17.4. A list of changes from Unicode
-6.1 is at L<http://www.unicode.org/versions/Unicode6.2.0>.
+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:
-
- 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.
-
-[ List each incompatible change as a =head2 entry ]
-
-=head2 New Restrictions in Multi-Character Case-Insensitive Matching in Regular Expression Bracketed Character Classes
-
-Unicode has now withdrawn their previous recommendation for regular
-expressions to automatically handle cases where a single character can
-match multiple characters case-insensitively; for example, the letter
-LATIN SMALL LETTER SHARP S and the sequence C<ss>. This is because
-it turns out to be impracticable to do this correctly in all
-circumstances. Because Perl has tried to do this as best it can, it
-will continue to do so. (We are considering an option to turn it off.)
-However, a new restriction is being added on such matches when they
-occur in [bracketed] character classes. People were specifying
-things such as C</[\0-\xff]/i>, and being surprised that it matches the
-two character sequence C<ss> (since LATIN SMALL LETTER SHARP S occurs in
-this range). This behavior is also inconsistent with the using a
-property instead of a range: C<\p{Block=Latin1}> also includes LATIN
-SMALL LETTER SHARP S, but C</[\p{Block=Latin1}]/i> does not match C<ss>.
-The new rule is that for there to be a multi-character case-insensitive
-match within a bracketed character class, the character must be
-explicitly listed, and not as an end point of a range. This more
-closely obeys the Principle of Least Astonishment. See
-L<perlrecharclass/Bracketed Character Classes>. Note that a bug [perl
-#89774], now fixed as part of this change, prevented the previous
-behavior from working fully.
-
-=head2 Change to Warnings About Lexical Subroutines
-
-The warnings category for lexical subroutines is now
-"experimental::lexical_subs", with two colons, not
-"experimental:lexical_subs";
+=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]
+
+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<Carp> has been upgraded from version 1.26 to 1.27. The C<longmess()> and
-C<shortmess()> functions are now documented.
-
-=item *
-
-L<ExtUtils::CBuilder> has been upgraded from version 0.280208 to 0.280209. A
-list of symbols to export can now be passed to C<link()> when on Windows, as on
-other OSes [perl #115100].
-
-=item *
-
-L<File::Glob> has been upgraded from version 1.17 to 1.18. A
-space-separated list of patterns return long lists of results no longer
-results in memory corruption or crashes. This bug was introduced in Perl
-5.16.0. [perl #114984]
+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
=item *
-The error produced when a module cannot be loaded now includes a hint that
-the module may need to be installed: "Can't locate hopping.pm in @INC (you
-may need to install the hopping module) (@INC contains: ...)"
+XXX Describe change here
=back
entries for each change
Use L<XXX> with program names to get proper documentation linking. ]
-=head3 L<h2xs>
+=head3 L<XXX>
=over 4
=item *
-F<h2xs> no longer produces invalid code for empty defines. [perl #20636]
+XXX
=back
=head2 Discontinued Platforms
-XXX List any platforms that this version of perl no longer compiles on.
-
=over 4
-=item MPE/IX
+=item BeOS
-Support for MPE/IX has been removed.
+Support for BeOS has been removed.
=back
=item *
-Case-insensitive matching inside a [bracketed] character class with a
-multi-character fold, no longer excludes one of the possibilities in the
-circumstances that it used to. [perl #89774].
-
-=item *
-
-C<PL_formfeed> has been removed.
-
-=item *
-
-The regular expression engine no longer reads one byte past the end of the
-target string. While for all internally well-formed scalars this should
-never have been a problem, this change facilitates clever tricks with
-string buffers in CPAN modules. [perl #73542]
-
-=item *
-
-Inside a BEGIN block, C<PL_compcv> now points to the currently-compiling
-subroutine, rather than the BEGIN block itself.
-
-=item *
-
-C<mg_length> has been deprecated.
-
-=item *
-
-C<sv_len> now always returns a byte count and C<sv_len_utf8> a character
-count. Previously, C<sv_len> and C<sv_len_utf8> were both buggy and would
-sometimes returns bytes and sometimes characters. C<sv_len_utf8> no longer
-assumes that its argument is in UTF8. Neither of these creates UTF8 caches
-for tied or overloaded values or for non-PVs any more.
+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.
-=back
-
-=head1 Selected Bug Fixes
+So this is now a syntax error:
-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>.
+ if (!SvUPGRADE(sv)) { croak(...); }
-[ List each fix as a =item entry ]
+If you have code like that, simply replace it with
-=over 4
+ SvUPGRADE(sv);
-=item *
+or to to avoid compiler warnings with older perls, possibly
-A bug, case-insensitive regex with UTF8-flagged strings, introduced
-earlier in the 5.17 series has been fixed. [perl #114982]
+ (void)SvUPGRADE(sv);
=item *
-Attributes applied to lexical variables no longer leak memory.
-[perl #114764]
+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.
-C<dump>, C<goto>, C<last>, C<next>, C<redo> or C<require> followed by a
-bareword (or version) and then an infix operator is no longer a syntax
-error. It used to be for those infix operators (like C<+>) that have a
-different meaning where a term is expected. [perl #105924]
+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 *
-C<require a::b . 1> and C<require a::b + 1> no longer produce erroneous
-ambiguity warnings. [perl #107002]
-
-=item *
+Copy-on-write no longer uses the SvFAKE and SvREADONLY flags. Hence,
+SvREADONLY indicates a true read-only SV.
-Class method calls are now allowed on any string, and not just strings
-beginning with an alphanumeric character. [perl #105922]
+Use the SvIsCOW macro (as before) to identify a copy-on-write scalar.
=item *
-An empty pattern created with C<qr//> used in C<m///> no longer triggers
-the "empty pattern reuses last pattern" behaviour. C<s///> has not yet
-been fixed. [perl #96230]
+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.
-XXX There is no reason s/// should not be fixed before 5.17.5. Nag sprout.
+The previous behaviour can still be enabled by running F<Configure> with
+B<-Accflags=-DPERL_SAWAMPERSAND>.
-=item *
-
-Tying a hash during iteration no longer results in a memory leak.
-
-=item *
-
-Freeing a tied hash during iteration no longer results in a memory leak.
-
-=item *
-
-List assignment to a tied array or hash that dies on STORE no longer
-results in a memory leak.
+=back
-=item *
+=head1 Selected Bug Fixes
-If the hint hash (C<%^H>) is tied, compile-time scope entry (which copies
-the hint hash) no longer leaks memory if FETCH dies. [perl #107000]
+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 ]
-Constant folding no longer inappropriately triggers the special
-C<split " "> behaviour. [perl #94490]
+=over 4
=item *
-C<defined scalar(@array)>, C<defined do { &foo }>, and similar constructs
-now treat the argument to C<defined> as a simple scalar. [perl #97466]
+C<sort {undef} ...> under fatal warnings no longer crashes. It started
+crashing in Perl 5.16.
=item *
-Running a custom debugging that defines no C<*DB::DB> glob or provides a
-subroutine stub for C<&DB::DB> no longer results in a crash, but an error
-instead. [perl #114990]
+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 *
-C<reset ""> now matches its documentation. C<reset> only resets C<m?...?>
-patterns when called with no argument. An empty string for an argument now
-does nothing. (It used to be treated as no argument.) [perl #97958]
+Numerous memory leaks have been fixed, mostly involving fatal warnings and
+syntax errors.
=item *
-C<printf> with an argument returning an empty list no longer reads past the
-end of the stack, resulting in erratic behaviour. [perl #77094]
+Lexical constants (C<my sub answer () { 42 }>) no longer cause double
+frees.
=item *
-C<--subname> no longer produces erroneous ambiguity warnings.
-[perl #77240]
+Constant subroutine redefinition warns by default, but lexical constants
+were accidentally exempt from default warnings. This has been corrected.
=item *
-C<v10> is now allowed as a label or package name. This was inadvertently
-broken when v-strings were added in Perl 5.6. [perl #56880]
+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 *
-A regression introduced in 5.17.2 has been fixed, which made C</[\@\\]||/>
-result in a "panic" error. [perl #115050]
+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 *
-C<length>, C<pos>, C<substr> and C<sprintf> could be confused by ties,
-overloading, references and typeglobs if the stringification of such
-changed the internal representation to or from UTF8. [perl #114410]
+Two minor bugs involving C<local *ISA> and C<local *Foo::> causing stale
+MRO caches have been fixed.
=item *
-utf8::encode now calls FETCH and STORE on tied variables. utf8::decode now
-calls STORE (it was already calling FETCH).
+Defining a subroutine when its typeglob has been aliased no longer results
+in stale method caches. This bug was introduced in Perl 5.10.
=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