[ 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 v5.21.6
+perldelta - what is new for perl v5.21.7
=head1 DESCRIPTION
-This document describes differences between the 5.21.5 release and the 5.21.6
+This document describes differences between the 5.21.6 release and the 5.21.7
release.
-If you are upgrading from an earlier release such as 5.21.4, first read
-L<perl5215delta>, which describes differences between 5.21.4 and 5.21.5.
+If you are upgrading from an earlier release such as 5.21.5, first read
+L<perl5216delta>, which describes differences between 5.21.5 and 5.21.6.
=head1 Notice
[ List each enhancement as a =head2 entry ]
-=head2 List form of pipe open implemented for Win32
+=head2 faster array and hash lookups
-The list form of pipe:
+Array and hash lookups (especially nested ones) that use only constants
+or simple variables as keys, are now considerably faster. See
+L</Internal Changes> for more details.
- open my $fh, "-|", "program", @arguments;
+=head2 C<fileno> now works on directory handles
-is now implemented on Win32. It has the same limitations as C<system
-LIST> on Win32, since the Win32 API doesn't accept program arguments
-as a list.
+When the relevant support is available in the operating system, the
+C<fileno> builtin now works on directory handles, yielding the
+underlying file descriptor in the same way as for filehandles. On
+operating systems without such support, C<fileno> on a directory handle
+continues to return the undefined value, as before, but also sets C<$!> to
+indicate that the operation is not supported.
-=head2 Assignment to list repetition
-
-C<(...) x ...> can now be used within a list that is assigned to, as long
-as the left-hand side is a valid lvalue. This allows C<(undef,undef,$foo)
-= that_function()> to be written as C<((undef)x2, $foo) = that_function()>.
-
-=head2 C<close> now sets C<$!>
-
-When an I/O error occurs, the fact that there has been an error is recorded
-in the handle. C<close> returns false for such a handle. Previously, the
-value of C<$!> would be untouched by C<close>, so the common convention of
-writing C<close $fh or die $!> did not work reliably. Now the handle
-records the value of C<$!>, too, and C<close> restores it.
+Currently, this uses either a C<dd_fd> member in the OS C<DIR>
+structure, or a dirfd(3) function as specified by POSIX.1-2008.
=head1 Security
[ List each incompatible change as a =head2 entry ]
+=head2 C<&> and C<\&> prototypes accepts only subs
+
+The C<&> prototype character now accepts only anonymous subs (C<sub {...}>)
+and things beginning with C<\&>. Formerly it erroneously also allowed
+C<undef> and references to array, hashes, and lists. [perl #4539]
+[perl #123062]
+
+The C<\&> prototype was allowing subroutine calls, whereas now it only
+allows subroutines. C<&foo> is permitted. C<&foo()> and C<foo()> are not.
+[perl #77860]
+
+=head2 C<use encoding> is now lexical
+
+The L<encoding> pragma's effect is now limited to lexical scope. This
+pragma is deprecated, but in the meantime, it could adversely affect
+unrelated modules that are included in the same program.
+
+=head2 List slices returning empty lists
+
+List slices return an empty list now only if the original list was empty
+(or if there are no indices). Formerly, a list slice would return an empty
+list if all indices fell outside the original list. [perl #114498]
+
=head1 Deprecations
XXX Any deprecated features, syntax, modules etc. should be listed here.
[ List each other deprecation as a =head2 entry ]
-=head2 Use of non-graphic characters in single-character variable names
+=head2 Setting C<${^ENCODING}> to anything but C<undef>
-The syntax for single-character variable names is more lenient than
-for longer variable names, allowing the one-character name to be a
-punctuation character or even invisible (a non-graphic). Perl v5.20
-deprecated the ASCII-range controls as such a name. Now, all
-non-graphic characters that formerly were allowed are deprecated.
-The practical effect of this occurs only when not under C<S<"use
-utf8">>, and affects just the C1 controls (code points 0x80 through
-0xFF), NO-BREAK SPACE, and SOFT HYPHEN.
+This variable allows Perl scripts to be written in a non-ASCII,
+non-UTF-8 encoding. However, it affects all modules globally, leading
+to wrong answers and segmentation faults. New scripts should be written
+in UTF-8; old scripts should be converted to UTF-8, which is easily done
+with the L<encoding> pragma.
=head1 Performance Enhancements
=item *
-C<(...)x1>, C<("constant")x0> and C<($scalar)x0> are now optimised in list
-context. If the right-hand argument is a constant 1, the repetition
-operator disappears. If the right-hand argument is a constant 0, the whole
-expressions is optimised to the empty list, so long as the left-hand
-argument is a simple scalar or constant. C<(foo())x0> is not optimised.
+Win32 Perl uses 8 KB less of per-process memory than before for every perl
+process of this version. This data is now memory mapped from disk and shared
+between perl processes from the same perl binary.
=item *
-C<substr> assignment is now optimised into 4-argument C<substr> at the end
-of a subroutine (or as the argument to C<return>). Previously, this
-optimisation only happened in void context.
+If method and class names are known at compile time, hashes are precomputed
+to speed up run-time method lookup. Also, compound method names like
+C<SUPER::new> are parsed at compile time, to save having to parse them at
+run time.
=back
=item *
-L<B::Deparse> has been upgraded from version 1.29 to 1.30.
+L<B> has been upgraded from version 1.53 to 1.54.
+
+Nulled COPs are now of class C<B::COP>, rather than C<B::OP>.
+
+B::REGEXP objects now provide a C<qr_anoncv> method for accessing the
+implicit CV associated with C<qr//> things containing code blocks.
-It now deparses C<+sub : attr { ... }> correctly at the start of a
-statement. Without the initial C<+>, C<sub> would be a statement label.
+B::PMOP now provides a C<pmregexp> method returning a B::REGEXP object.
+
+Two new classes, B::PADNAME and B::PADNAMELIST, have been introduced.
=item *
-L<DynaLoader> has been upgraded from version 1.27 to 1.28.
+L<B::Deparse> has been upgraded from version 1.30 to 1.31.
+
+BEGIN blocks at the end of the enclosing scope are now deparsed in the
+right place. [perl #77452]
+
+BEGIN blocks were sometimes deparsed as __ANON__, but are now always called
+BEGIN.
+
+Lexical subroutines are now fully deparsed. [perl #116553]
+
+Deparsing of C<$lexical =~ //> was accidentally broken in 1.30 (perl
+5.21.6), omitting the C<$lexical =~>, but has now been fixed.
+
+C<Anything =~ y///r> with C</r> no longer omits the left-hand operand.
+
+The op trees that make up regexp code blocks are now deparsed for real.
+Formerly, the original string that made up the regular expression was used.
+That caused problems with C<qr/(?{<<heredoc})/> and multiline code blocks,
+which were deparsed incorrectly. [perl #123217] [perl #115256]
+
+C<$;> at the end of a statement no longer loses its semicolon.
+[perl #123357]
+
+Some cases of subroutine declarations stored in the stash in shorthand form
+were being omitted.
+
+Non-ASCII characters are now consistently escaped in strings, instead of
+some of the time. (There are still outstanding problems with regular
+expressions and identifiers that have not been fixed.)
+
+When prototype sub calls are deparsed with C<&> (e.g., under the B<-P>
+option), C<scalar> is now added where appropriate, to force the scalar
+context implied by the prototype.
+
+C<require(foo())>, C<do(foo())>, C<goto(foo())> and similar constructs with
+loop controls are now deparsed correctly. The outer parentheses are not
+optional.
+
+Whitespace is no longer escaped in regular expressions, because it was
+getting erroneously escaped within C<(?x:...)> sections.
+
+C<sub foo { foo() }> is now deparsed with those mandatory parentheses.
+
+C</@array/> is now deparsed as a regular expression, and not just
+C<@array>.
+
+C</@{-}/>, C</@{+}/> and C<$#{1}> are now deparsed with the braces, which
+are mandatory in these cases.
+
+In deparsing feature bundles, B::Deparse was emitting C<no feature;> first
+instead of C<no feature ':all';>. This has been fixed.
+
+C<chdir FH> is now deparsed without quotation marks.
+
+C<\my @a> is now deparsed without parentheses. (Parenthese would flatten
+the array.)
=item *
-L<IO::Socket> has been upgraded from version 1.37 to 1.38.
+L<ExtUtils::ParseXS> has been upgraded from version 3.26 to 3.27.
+
+Only declare C<file> unused if we actually define it.
+
+Improve generated C<RETVAL> code generation to avoid repeated
+references to C<ST(0)>. [perl #123278]
+
+Broaden and document the C</OBJ$/> to C</REF$/> typemap optimization
+for the C<DESTROY> method. [perl #123418]
+
+=item *
-Document the limitations of the isconnected() method. [perl #123096]
+The PathTools module collection has been upgraded from 3.52 to 3.53.
+
+Don't turn leading C<//> into C</> on Cygwin. [perl #122635]
+
+=item *
+
+L<Locale::Maketext> has been upgraded from version 1.25 to 1.26.
+
+=item *
+
+L<XSLoader> has been upgraded from version 0.19 to 0.20
+
+Don't test twice for bootstrap file.
=back
However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
section.
-=head3 L<perldata/Identifier parsing>
+=head3 L<XXX>
=over 4
=item *
-The syntax of single-character variable names has been brought
-up-to-date and more fully explained.
+XXX Description of the change here
=back
=item *
-L<Use of literal non-graphic characters in variable names is deprecated|perldiag/"Use of literal non-graphic characters in variable names is deprecated">
-
-=item *
-
-A new C<locale> warning category has been created, with the following warning
-messages currently in it:
-
-=over 4
-
-=item *
-
-L<Locale '%s' may not work well.%s|perldiag/Locale '%s' may not work well.%s>
-
-=item *
-
-L<Can't do %s("%s") on non-UTF-8 locale; resolved to "%s".|perldiag/Can't do %s("%s") on non-UTF-8 locale; resolved to "%s".>
-
-=back
-
-=item *
-
-L<Warning: unable to close filehandle %s properly: %s|perldiag/"Warning: unable to close filehandle %s properly: %s">
+XXX L<message|perldiag/"message">
=back
=item *
-L<Quantifier unexpected on zero-length expression in regex mE<sol>%sE<sol>|perldiag/"Quantifier unexpected on zero-length expression in regex m/%s/">.
-
-This message has had the S<"<-- HERE"> marker removed, as it was always
-placed at the end of the regular expression, regardless of where the
-problem actually occurred. [perl #122680]
+"Variable %s will not stay shared" has been changed to say "Subroutine"
+when it is actually a lexical sub that will not stay shared.
=back
=item *
-F<Configure> with C<-Dmksymlinks> should now be faster. [perl #122002]
+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</Modules and Pragmata> section.
-
-=over 4
-
-=item XXX-some-platform
-
-XXX
-
-=back
-
=head3 Win32
-=over 4
-
-=item *
-
-In the experimental C<:win32> layer, a crash in C<open> was fixed. Also
-opening C</dev/null>, which works the Win32 Perl's normal C<:unix> layer, was
-implemented for C<:win32>.
-L<[perl #122224]|https://rt.perl.org/Ticket/Display.html?id=122224>
+=over
=item *
-A new makefile option, C<USE_LONG_DOUBLE>, has been added to the Windows
-dmake makefile for gcc builds only. Set this to "define" if you want perl to
-use long doubles to give more accuracy and range for floating point numbers.
+Intel C builds are now always built with C99 mode on.
=back
=item *
-C<screaminstr> has been removed. Although marked as public API, it is
-undocumented and has no usage in modern perl versions on CPAN Grep. Calling it
-has been fatal since 5.17.0.
+The PADNAME and PADNAMELIST types are now separate types, and no longer
+simply aliases for SV and AV. [perl #123223]
+
+=item *
+
+Pad names are now always UTF8. The C<PadnameUTF8> macro always returns
+true. Previously, this was effectively the case already, but any support
+for two different internal representations of pad names has now been
+removed.
=item *
-C<newDEFSVOP>, C<block_start>, C<block_end> and C<intro_my> have been added
-to the API.
+The C<OP_SIBLING> and C<OP_HAS_SIBLING> macros added in an earlier 5.21.x
+release have been renamed C<OpSIBLING> and C<OpHAS_SIBLING>, following the
+existing convention.
=item *
-The internal C<convert> function in F<op.c> has been renamed
-C<op_convert_list> and added to the API.
+A new op class, C<UNOP_AUX>, has been added. This is a subclass of
+C<UNOP> with an C<op_aux> field added, which points to an array of unions
+of C<UV>, C<SV*> etc. It is intended for where an op needs to store more data
+than a simple C<op_sv> or whatever. Currently the only op of this type is
+C<OP_MULTIDEREF> (see below).
=item *
-C<sv_magic> no longer forbids "ext" magic on read-only values. After all,
-perl can't know whether the custom magic will modify the SV or not.
-[perl #123103]
+A new op has been added, C<OP_MULTIDEREF>, which performs one or more
+nested array and hash lookups where the key is a constant or simple
+variable. For example the expression C<$a[0]{$k}[$i]>, which previously
+involved ten C<rv2Xv>, C<Xelem>, C<gvsv> and C<const> ops is now performed
+by a single C<multideref> op. It can also handle C<local>, C<exists> and
+C<delete>. A non-simple index expression, such as C<[$i+1]> is still done
+using C<aelem/helem>, and single-level array lookup with a small constant
+index is still done using C<aelemfast>.
=back
=item *
-fchmod() and futimes() now set C<$!> when they fail due to being
-passed a closed file handle. [perl #122703]
+On Win32, restoring in a child pseudo-process a variable that was
+C<local()>ed in a parent pseudo-process before the C<fork> happened caused
+memory corruption and a crash in the child pseudo-process (and therefore OS
+process). [perl #40565]
=item *
-Perl now comes with a corrected Unicode 7.0 for the erratum issued on
-October 21, 2014 (see L<http://www.unicode.org/errata/#current_errata>),
-dealing with glyph shaping in Arabic.
+Calling C<write> on a format with a C<^**> field could produce a panic
+in sv_chop() if there were insufficient arguments or if the variable
+used to fill the field was empty. [perl #123245]
=item *
-op_free() no longer crashes due to a stack overflow when freeing a
-deeply recursive op tree. [perl #108276]
+Non-ASCII lexical sub names (use in error messages) on longer have extra
+junk on the end.
=item *
-scalarvoid() would crash due to a stack overflow when processing a
-deeply recursive op tree. [perl #108276]
+The C<\@> subroutine prototype no longer flattens parenthesized arrays
+(taking a reference to each element), but takes a reference to the array
+itself. [perl #47363]
=item *
-In Perl 5.20.0, C<$^N> accidentally had the internal UTF8 flag turned off
-if accessed from a code block within a regular expression, effectively
-UTF8-encoding the value. This has been fixed. [perl #123135]
+A block containing nothing except a C-style C<for> loop could corrupt the
+stack, causing lists outside the block to lose elements or have elements
+overwritten. This could happen with C<map { for(...){...} } ...> and with
+lists containing C<do { for(...){...} }>. [perl #123286]
=item *
-A failed C<semctl> call no longer overwrites existing items on the stack,
-causing C<(semctl(-1,0,0,0))[0]> to give an "uninitialized" warning.
+C<scalar()> now propagates lvalue context, so that
+C<for(scalar($#foo)) { ... }> can modify C<$#foo> through C<$_>.
=item *
-C<else{foo()}> with no space before C<foo> is now better at assigning the
-right line number to that statement. [perl #122695]
+C<qr/@array(?{block})/> no longer dies with "Bizarre copy of ARRAY".
+[#123344]
=item *
-Sometimes the assignment in C<@array = split> gets optimised and C<split>
-itself writes directly to the array. This caused a bug, preventing this
-assignment from being used in lvalue context. So
-C<(@a=split//,"foo")=bar()> was an error. (This bug probably goes back to
-Perl 3, when the optimisation was added.) This optimisation, and the bug,
-started to happen in more cases in 5.21.5. It has now been fixed.
-[perl #123057]
-
-=item *
+C<eval '$variable'> in nested named subroutines would sometimes look up a
+global variable even with a lexical variable in scope.
-When argument lists that fail the checks installed by subroutine
-signatures, the resulting error messages now give the file and line number
-of the caller, not of the called subroutine. [perl #121374]
+In perl 5.20.0, C<sort CORE::fake> where 'fake' is anything other than a
+keyword started chopping of the last 6 characters and treating the result
+as a sort sub name. The previous behaviour of treating "CORE::fake" as a
+sort sub name has been restored. [perl #123410]
=item *
-Flip-flop operators (C<..> and C<...> in scalar context) used to maintain
-a separate state for each recursion level (the number of times the
-enclosing sub was called recursively), contrary to the documentation. Now
-each closure has one internal state for each flip-flop. [perl #122829]
-
-=item *
-
-C<use>, C<no>, statement labels, special blocks (C<BEGIN>) and pod are now
-permitted as the first thing in a C<map> or C<grep> block, the block after
-C<print> or C<say> (or other functions) returning a handle, and within
-C<${...}>, C<@{...}>, etc. [perl #122782]
-
-=item *
-
-The repetition operator C<x> now propagates lvalue context to its left-hand
-argument when used in contexts like C<foreach>. That allows
-C<for(($#that_array)x2) { ... }> to work as expected if the loop modifies
-$_.
-
-=item *
-
-C<(...) x ...> in scalar context used to corrupt the stack if one operand
-were an object with "x" overloading, causing erratic behaviour.
-[perl #121827]
+Outside of C<use utf8>, a single-character Latin-1 lexical variable is
+disallowed. The error message for it, "Can't use global $foo...", was
+giving garbage instead of the variable name.
=back
=item *
-Starting in 5.21.6, accessing L<perlapi/CvPADLIST> in an XSUB is forbidden.
-CvPADLIST has be reused for a different internal purpose for XSUBs. Guard all
-CvPADLIST expressions with C<CvISXSUB()> if your code doesn't already block
-XSUB CV*s from going through optree CV* expecting code.
+XXX
=back
=item *
-Due to a mistake in the string-copying logic, copying the value of a state
-variable could instead steal the value and undefine the variable. This
-bug, introduced in 5.20, would happen mostly for long strings (1250 chars
-or more), but could happen for any strings under builds with copy-on-write
-disabled. [perl #123029]
-
-This bug was actually fixed in 5.21.5, but it was not until after that
-release that this bug, and the fact that it had been fixed, were
-discovered.
+XXX Add anything here that we forgot to add, or were mistaken about, in
+the perldelta of a previous release.
=back
XXX Generate this with:
- perl Porting/acknowledgements.pl v5.21.5..HEAD
+ perl Porting/acknowledgements.pl v5.21.6..HEAD
=head1 Reporting Bugs
https://perl5.git.perl.org / perl5.git / blobdiff