Merge perl5251delta.pod

1 files changed, 272 insertions, 6 deletions

diff --git a/pod/perl5260delta.pod b/pod/perl5260delta.pod
index 061998b6a1..f77208dfe5 100644
--- a/pod/perl5260delta.pod
+++ b/pod/perl5260delta.pod
@@ -9,6 +9,272 @@ perl5260delta - what is new for perl v5.26.0
 This document describes the differences between the 5.24.0 release and the
 5.26.0 release.
 
+=head1 Core Enhancements
+
+=head2 POSIX::tmpnam() has been removed
+
+The fundamentally unsafe C<tmpnam()> interface was deprecated in
+Perl 5.22.0 and has now been removed.  In its place you can use
+for example the L<File::Temp> interfaces.
+
+=head2 require ::Foo::Bar is now illegal.
+
+Formerly, C<require ::Foo::Bar> would try to read F</Foo/Bar.pm>. Now any
+bareword require which starts with a double colon dies instead.
+
+=head2 Unescaped literal C<"{"> characters in regular expression
+patterns are no longer permissible
+
+You have to now say something like C<"\{"> or C<"[{]"> to specify to
+match a LEFT CURLY BRACKET.  This will allow future extensions to the
+language.  This restriction is not enforced, nor are there current plans
+to enforce it, if the C<"{"> is the first character in the pattern.
+
+These have been deprecated since v5.16, with a deprecation message
+displayed starting in v5.22.
+
+=head2 Literal control character variable names are no longer permissible
+
+A variable name may no longer contain a literal control character under
+any circumstances.  These previously were allowed in single-character
+names on ASCII platforms, but have been deprecated there since Perl
+v5.20.  This affects things like C<$I<\cT>>, where I<\cT> is a literal
+control (such as a C<NAK> or C<NEGATIVE ACKNOWLEDGE> character) in the
+source code.
+
+=head2 C<qr//xx> is no longer permissible
+
+Using more than one C</x> regular expression pattern modifier on a
+single pattern is now forbidden.  This is to allow a future enhancement
+to the language.  This usage has been deprecated since v5.22.
+
+=head2 C<NBSP> is no longer permissible in C<\N{...}>
+
+The name of a character may no longer contain non-breaking spaces.  It
+has been deprecated to do so since Perl v5.22.
+
+=head1 Performance Enhancements
+
+=over 4
+
+=item *
+
+Bareword constant strings are now permitted to take part in constant
+folding. They were originally exempted from constant folding in August 1999,
+during the development of Perl 5.6, to ensure that C<use strict "subs">
+would still apply to bareword constants. That has now been accomplished a
+different way, so barewords, like other constants, now gain the performance
+benefits of constant folding.
+
+This also means that void-context warnings on constant expressions of
+barewords now report the folded constant operand, rather than the operation;
+this matches the behaviour for non-bareword constants.
+
+=back
+
+=head1 Modules and Pragmata
+
+=head2 Updated Modules and Pragmata
+
+=over 4
+
+=item *
+
+L<POSIX> has been upgraded from version 1.65 to 1.69. This remedies several
+defects in making its symbols exportable. [perl #127821]
+The C<POSIX::tmpnam()> interface has been removed,
+see L</"POSIX::tmpnam() has been removed">.
+Trying to import POSIX subs that have no real implementations
+(like C<POSIX::atend()>) now fails at import time, instead of
+waiting until runtime.
+
+=item *
+
+L<threads> has been upgraded from version 2.07 to 2.08. Compatibility
+with 5.8 has been restored.
+
+=back
+
+=head1 Documentation
+
+=head2 Changes to Existing Documentation
+
+=over 4
+
+=item *
+
+Fixed link to Crosby paper on hash complexity attack in L<perlsec>.
+
+=back
+
+=head1 Diagnostics
+
+=head2 New Diagnostics
+
+=head3 New Errors
+
+=over 4
+
+=item *
+
+L<Bareword in require contains "%s"|perldiag/"Bareword in require contains "%s"">
+
+=item *
+
+L<Bareword in require maps to empty filename|perldiag/"Bareword in require maps to empty filename">
+
+=item *
+
+L<Bareword in require maps to disallowed filename "%s"|perldiag/"Bareword in require maps to disallowed filename "%s"">
+
+=item *
+
+L<Bareword in require must not start with a double-colon: "%s"|perldiag/"Bareword in require must not start with a double-colon: "%s"">
+
+=back
+
+=head2 Changes to Existing Diagnostics
+
+=over 4
+
+=item *
+
+Code like C<$x = $x . "a"> was incorrectly failing to yield a
+L<use of uninitialized value|perldiag/"Use of uninitialized value%s">
+warning when C<$x> was a lexical variable with an undefined value. That has
+now been fixed. [perl #127877]
+
+=item *
+
+When the error "Experimental push on scalar is now forbidden" is raised for
+the hash functions C<keys>, C<each>, and C<values>, it is now followed by
+the more helpful message, "Type of arg 1 to whatever must be hash or
+array". [perl #127976]
+
+=item *
+
+C<undef *_; shift> or C<undef *_; pop> inside a subroutine, with no
+argument to C<shift> or C<pop>, began crashing in Perl 5.14.0, but has now
+been fixed.
+
+=item *
+
+C<< "string$scalar-E<gt>$*" >> now correctly prefers concat overloading to
+string overloading if C<< $scalar-E<gt>$* >> returns an overloaded object,
+bringing it into consistency with C<$$scalar>.
+
+=item *
+
+C<< /@0{0*-E<gt>@*/*0 >> and similar contortions used to crash, but no longer
+do, but merely produce a syntax error. [perl #128171]
+
+=item *
+
+C<do> or C<require> with a reference or typeglob which, when stringified,
+contains a null character started crashing in Perl 5.20.0, but has now been
+fixed. [perl #128182]
+
+=back
+
+=head1 Utility Changes
+
+=head2 L<perlbug>
+
+=over 4
+
+=item *
+
+Long lines in the message body are now wrapped at 900 characters, to stay
+well within the 1000-character limit imposed by SMTP mail transfer agents.
+This is particularly likely to be important for the list of arguments to
+C<Configure>, which can readily exceed the limit if, for example, it names
+several non-default installation paths. This change also adds the first unit
+tests for perlbug. [perl #128020]
+
+=back
+
+=head1 Configuration and Compilation
+
+=over 4
+
+=item *
+
+C<Configure> now builds C<miniperl> and C<generate_uudmap> if you
+invoke it with C<-Dusecrosscompiler> but not C<-Dtargethost=somehost>.
+This means you can supply your target platform C<config.sh>, generate
+the headers and proceed to build your cross-target perl.  [perl #127234]
+
+=item *
+
+Builds with C<-Accflags=-DPERL_TRACE_OPS> now only dump the operator
+counts when the environment variable C<PERL_TRACE_OPS> to be set to a
+non-zero integer.  This allows C<make test> to pass on such a build.
+
+=item *
+
+When building with GCC 6 and link-time optimization (the C<-flto> option to
+C<gcc>), C<Configure> was treating all probed symbols as present on the
+system, regardless of whether they actually exist. This has been fixed.
+[perl #128131]
+
+=item *
+
+The F<t/test.pl> library is used for internal testing of Perl itself, and
+also copied by several CPAN modules. Some of those modules must work on
+older versions of Perl, so F<t/test.pl> must in turn avoid newer Perl
+features. Compatibility with Perl 5.8 was inadvertently removed some time
+ago; it has now been restored. [perl #128052]
+
+=item *
+
+The build process no longer emits an extra blank line before building each
+"simple" extension (those with only F<*.pm> and F<*.pod> files).
+
+=back
+
+=head1 Internal Changes
+
+=over 4
+
+=item *
+
+Perl is now built with the C<PERL_OP_PARENT> compiler define enabled by
+default. To disable it, use the C<PERL_NO_OP_PARENT> compiler define.
+This flag alters how the C<op_sibling> field is used in C<OP> structures,
+and has been available optionally since perl 5.22.0.
+
+See L<perl5220delta/"Internal Changes"> for more details of what this
+build option does.
+
+=back
+
+=head1 Selected Bug Fixes
+
+=over 4
+
+=item *
+
+Expressions containing an C<&&> or C<||> operator (or their synonyms C<and>
+and C<or>) were being compiled incorrectly in some cases. If the left-hand
+side consisted of either a negated bareword constant or a negated C<do {}>
+block containing a constant expression, and the right-hand side consisted of
+a negated non-foldable expression, one of the negations was effectively
+ignored. The same was true of C<if> and C<unless> statement modifiers,
+though with the left-hand and right-hand sides swapped. This long-standing
+bug has now been fixed. [perl #127952]
+
+=item *
+
+C<reset> with an argument no longer crashes when encountering stash entries
+other than globs. [perl #128106]
+
+=item *
+
+Assignment of hashes to, and deletion of, typeglobs named C<*::::::> no
+longer causes crashes. [perl #128086]
+
+=back
+
 =head1 Known Problems
 
 =over 4
@@ -22,22 +288,22 @@ advice if needed.  Below is a subset of these modules:
 
 =over 4
 
-=item L<Algorithm::Permute>
+=item * L<Algorithm::Permute>
 
-=item L<Coro>
+=item * L<Coro>
 
 L<Coro> and perl v5.22.0 were already incompatible due to a change in the perl,
 and the reworking on the perl context stack creates a further incompatibility.
 perl5-porters has L<discussed the issue on the mailing
 list|http://www.nntp.perl.org/group/perl.perl5.porters/2016/05/msg236174.html>.
 
-=item L<Data::Alias>
+=item * L<Data::Alias>
 
-=item L<RPerl>
+=item * L<RPerl>
 
-=item L<Scope::Upper>
+=item * L<Scope::Upper>
 
-=item L<TryCatch>
+=item * L<TryCatch>
 
 =back