perldelta for open() FETCH fix

[perl5.git] / pod / perldelta.pod

=encoding utf8

=for comment
This has been completed up to 7c5c3d9b except for:
a1da11a30dfa4f3543dcab00834ff535202f5085 (GNU/Hurd hints)
f0d0a205cc02c769ca48d6df00f3eea304ff91d8 (similar)
a058c51605ec2d38bf37f2e2c4f81926e3a90ea9 (Leon Timmermans; setresgid)
928b2f01177c40be013139c657d79c631790a916 (Reini Urban; Errno)

=head1 NAME

[ 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 v5.15.5

=head1 DESCRIPTION

This document describes differences between the 5.15.4 release and
the 5.15.5 release.

If you are upgrading from an earlier release such as 5.15.3, first read
L<perl5154delta>, which describes differences between 5.15.3 and
5.15.4.

=head1 Notice

XXX Any important notices here

=head1 Core Enhancements

XXX New core language features go here. Summarise user-visible core language
enhancements. Particularly prominent performance optimisations could go
here, but most should go in the L</Performance Enhancements> section.

=head2 More consistent C<eval>

The C<eval> operator sometimes treats a string argument as a sequence of
characters and sometimes as a sequence of bytes, depending on the internal
encoding.  The internal encoding is not supposed to make any difference,
but there is code that relies on this inconsistency.

Under C<use v5.15> and higher, the C<unicode_eval> and C<evalbytes>
features resolve this.  The C<unicode_eval> feature causes C<eval $string>
to treat the string always as Unicode.  The C<evalbytes> features provides
a function, itself called C<evalbytes>, which evaluates its argument always
as a string of bytes.

These features also fix oddities with source filters leaking to outer
dynamic scopes.

See L<feature> for more detail.

=head2 C<$[> is back

The C<$[> variable is back again, but is now implemented as a module, so
programs that do not mention it (i.e., most of them), will not incur any
run-time penalty.  In a later release in the 5.15 branch it might be
disabled in the scope of C<use v5.16>.

The new implementation has some bug fixes.  See L<arybase>.

=head1 Security

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.

[ List each security issue as a =head2 entry ]

=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 reports are welcome.

=head2 Certain deprecated Unicode properties are no longer supported by default

Perl should never have exposed certain Unicode properties that are used
by Unicode internally and not meant to be publicly available.  Use of
these has generated deprecated warning messages since Perl 5.12.  The
removed properties are Other_Alphabetic,
Other_Default_Ignorable_Code_Point, Other_Grapheme_Extend,
Other_ID_Continue, Other_ID_Start, Other_Lowercase, Other_Math, and
Other_Uppercase.

Perl may be recompiled to include any or all of them; instructions are
given in
L<perluniprops/Unicode character properties that are NOT accepted by Perl>.


=head2 Dereferencing IO thingies as typeglobs

The C<*{...}> operator, when passed a reference to an IO thingy (as in
C<*{*STDIN{IO}}>), creates a new typeglob containing just that IO object.

Previously, it would stringify as an empty string, but some operators would
treat it as undefined, producing an "uninitialized" warning.

Having a typeglob appear as an empty string is a side effect of the
implementation that has caused various bugs over the years.

The solution was to make it stringify like a normal anonymous typeglob,
like those produced by C<open($foo->{bar}, ...)> [perl #96326].

=head1 Deprecations

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.

[ List each deprecation as a =head2 entry ]

=head2 Don't read the Unicode data base files in F<lib/unicore>

It is now deprecated to directly read the Unicode data base files.
These are stored in the F<lib/unicore> directory.  Instead, you should
use the new functions in L<Unicode::UCD>.  These provide a stable API,
and give complete information.  (This API is, however, subject to change
somewhat during the 5.15 development cycle, as we gain experience and
get feedback from using it.)

Perl may at some point in the future change or remove the files.  The
file most likely for applications to have used is F<lib/unicore/ToDigit.pl>.
L<Unicode::UCD/prop_invmap()> can be used to get at its data instead.

=head1 Performance Enhancements

XXX Changes which enhance performance without changing behaviour go here. There
may well be none in a stable release.

[ List each enhancement as a =item entry ]

=over 4

=item *

Due to changes in L<File::Glob>, Perl's C<glob> function and its
C<< <...> >> equivalent are now much faster.  The splitting of the pattern
into words has been rewritten in C, resulting in speed-ups of 20% in some
cases.

This does not affect VMS, as it does not use File::Glob.

=back

=head1 Modules and Pragmata

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.

[ Within each section, list entries as a =item entry ]

=head2 New Modules and Pragmata

=over 4

=item *

L<arybase> -- this new module implements the C<$[> variable.

=back

=head2 Updated Modules and Pragmata

=over 4

=item *

L<Archive::Extract> has been upgraded from version 0.56 to version 0.58.

=item *

L<B::Deparse> has been upgraded from version 1.08 to 1.08.

It now correctly deparses C<CORE::do>, C<CORE::glob> and slices of empty
lists.

=item *

L<CGI> has been upgraded from version 3.55 to version 3.58.

Use public and documented FCGI.pm API in CGI::Fast
CGI::Fast was using an FCGI API that was deprecated and removed from
documentation more than ten years ago. Usage of this deprecated API with
FCGI >= 0.70 or FCGI <= 0.73 introduces a security issue.
L<https://rt.cpan.org/Public/Bug/Display.html?id=68380>
L<http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2011-2766>

=item *

L<Compress::Raw::Bzip2> has been upgraded from version 2.037 to version 2.042.

=item *

L<Compress::Raw::Zlib> has been upgraded from version 2.037 to version 2.042.

=item *

L<Compress::Zlib> has been upgraded from version 2.037 to version 2.042.

=item *

L<CPANPLUS> has been upgraded from version 0.9111 to version 0.9112.

=item *

L<CPANPLUS::Dist::Build> has been upgraded from version 0.58 to version 0.60.

=item *

L<Digest::SHA> has been upgraded from version 5.62 to version 5.63.

Added code to allow very large data inputs all at once, which had previously been
limited to several hundred megabytes at a time

=item *

L<ExtUtils::MakeMaker> has been upgraded from version 6.61_01 to version 6.63_02.

=item *

L<File::Glob> has been upgraded from version 1.13 to 1.14.

It has a new C<:bsd_glob> export tag, intended to replace C<:glob>.  Like
C<:glob> it overrides C<glob> with a function that does not split the glob
pattern into words, but, unlike C<:glob>, it iterates properly in scalar
context, instead of returning the last file.

There are other changes affecting Perl's own C<glob> operator (which uses
File::Glob internally, except on VMS).  See L</Performance Enhancements>
and L</Selected Bug Fixes>.

=item *

L<HTTP::Tiny> has been upgraded from version 0.013 to version 0.016.

Adds additional shorthand methods for all common HTTP verbs,
a C<post_form()> method for POST-ing x-www-form-urlencoded data and
a C<www_form_urlencode()> utility method.

=item *

L<perlfaq> has been upgraded from version 5.0150035 to version 5.0150036.

=item *

L<Socket> as been upgraded from version 1.94_01 to 1.94_02.

It has new functions and constants for handling IPv6 sockets:

    pack_ipv6_mreq
    unpack_ipv6_mreq
    IPV6_ADD_MEMBERSHIP
    IPV6_DROP_MEMBERSHIP
    IPV6_MTU
    IPV6_MTU_DISCOVER
    IPV6_MULTICAST_HOPS
    IPV6_MULTICAST_IF
    IPV6_MULTICAST_LOOP
    IPV6_UNICAST_HOPS
    IPV6_V6ONLY

=item *

L<Storable> has been upgraded from version 2.32 to 2.33.

The ability to add a fake entry to %INC to prevent Log::Agent from loading
has been restored.  In version 2.27 (included with perl 5.14.0), Storable
starting producing an error instead.

=item *

L<Unicode::Collate> has been upgraded from version 0.80 to version 0.85.

Locales updated to CLDR 2.0: mk, mt, nb, nn, ro, ru, sk, sr, sv, uk,
zh__pinyin, zh__stroke
Newly supported locales: bn, fa, ml, mr, or, pa, sa, si, si__dictionary,
sr_Latn, sv__reformed, ta, te, th, ur, wae.

=item *

L<Unicode::UCD> has been upgraded from version 0.36 to version 0.37.
This adds four new functions:  C<prop_aliases()>, and
C<prop_value_aliases()> which are used to find all the Unicode-approved
synonyms for property names, or to convert from one name to another;
C<prop_invlist> which returns all the code points matching a given
Unicode binary property; and C<prop_invmap> which returns the complete
specification of a given Unicode property.

=back

=head2 Removed Modules and Pragmata

=over 4

=item *

XXX

=back

=head1 Documentation

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>.

=head2 New Documentation

XXX Changes which create B<new> files in F<pod/> go here.

=head3 L<XXX>

XXX Description of the purpose of the new file here

=head2 Changes to Existing Documentation

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 *

XXX Description of the change here

=back

=head1 Diagnostics

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>.

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.

[ Within each section, list entries as a =item entry that links to perldiag,
  e.g.

  =item *

  L<Invalid version object|perldiag/"Invalid version object">
]

=head2 New Diagnostics

XXX Newly added diagnostic messages go here

=head3 New Errors

=over 4

=item *

XXX L<message|perldiag/"message">

=back

=head3 New Warnings

=over 4

=item *

L<length() used on %s|perldiag/length() used on %s>

This new warning occurs when C<length> is used on an array or hash, instead
of C<scalar(@array)> or C<scalar(keys %hash)>.

=item *

L<$[ used in %s (did you mean $] ?)|perldiag/"$[ used in %s (did you mean $] ?)">

This new warning exists to catch the mistaken use of C<$[> in version
checks.  C<$]>, not C<$[>, contains the version number.  C<$[> in a numeric
comparison is almost always wrong.

=back

=head2 Changes to Existing Diagnostics

XXX Changes (i.e. rewording) of diagnostic messages go here

=over 4

=item *

The uninitialized warning for C<y///r> when C<$_> is implicit and undefined
now mentions the variable name, just like the non-/r variation of the
operator.

=item *

The "Applying pattern match..." or similar warning produced when an array
or hash is on the left-hand side of the C<=~> operator now mentions the
name of the variable.

=back

=head1 Utility Changes

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>.

[ 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 *

F<pod/buildtoc>, used by the build process to build L<perltoc>, has been
refactored and simplified. It now only contains code to build L<perltoc>;
the code to regenerate Makefiles has been moved to F<Porting/pod_rules.pl>.
It's a bug if this change has any material affect on the build process.

=back

=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.

[ List changes as a =item entry ].

=over 4

=item *

XXX

=back

=head1 Testing

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 summarising, although the bugs
that they represent may be covered elsewhere.

[ List each test improvement as a =item entry ]

=over 4

=item *

XXX

=back

=head1 Platform Support

XXX Any changes to platform support should be listed in the sections below.

[ Within the sections, list each platform as a =item entry with specific
changes as paragraphs below it. ]

=head2 New Platforms

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.

=over 4

=item XXX-some-platform

XXX

=back

=head2 Discontinued Platforms

XXX List any platforms that this version of perl no longer compiles on.

=over 4

=item XXX-some-platform

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

=head1 Internal Changes

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.

[ List each change as a =item entry ]

=over 4

=item *

C<PL_curstash> is now reference-counted.

=back

=head1 Selected Bug Fixes

XXX Important bug fixes in the core language are summarised here.
Bug fixes in files in F<ext/> and F<lib/> are best summarised in
L</Modules and Pragmata>.

[ List each fix as a =item entry ]

=over 4

=item *

Perl now holds an extra reference count on the package that code is
currently compiling in.  This means that the following code no longer crashes [perl #101486]:

    package Foo;
    BEGIN {*Foo:: = *Bar::}
    sub foo;

=item *

F<dumpvar.pl>, and consequently the C<x> command in the debugger, have been
fixed to handle objects blessed into classes whose names contain "=".  The
contents of such objects used not to be dumped [perl #101814].

=item *

The C<x> repetition operator no longer crashes on 64-bit builds with large
repeate counts [perl #94560].

=item *

A fix to C<glob> under miniperl (used to configure modules when perl itself
is built) in Perl 5.15.3 stopped C<< <~> >> from returning the home
directory, because it cleared %ENV before calling csh.  Now C<$ENV{HOME}>
is preserved.  This fix probably does not affect anything.  If
L<File::Glob> fails to load for some reason, Perl reverts to using csh.
So it would apply in that case.

=item *

On OSes other than VMS, Perl's C<glob> operator (and the C<< <...> >> form)
use L<File::Glob> underneath.  L<File::Glob> splits the pattern into words,
before feeding each word to its C<bsd_glob> function.

There were several inconsistencies in the way the split was done.  Now
quotation marks (' and ") are always treated as shell-style word delimiters
(that allow whitespace as part of a word) and backslashes are always
preserved, unless they exist to escape quotation marks.  Before, those
would only sometimes be the case, depending on whether the pattern
contained whitespace.  Also, escaped whitespace at the end of the pattern
is no longer stripped [perl #40470].

=item *

C<CORE::glob> now works as a way to call the default globbing function.  It
used to respect overrides, despite the C<CORE::> prefix.

=item *

In 5.14, C</[[:lower:]]/i> and C</[[:upper:]]/i> no longer matched the
opposite case.  This has been fixed [perl #101970].

=item *

A regular expression match with an overloaded object on the right-hand side
would in some cases stringify the object too many times.

=item *

The C-level C<pregcomp> function could become confused as to whether the
pattern was in UTF8 if the pattern was an overloaded, tied, or otherwise
magical scalar [perl #101940].

=item *

A regression has been fixed that was introduced in 5.14, in C</i>
regular expression matching, in which a match improperly fails if the
pattern is in UTF-8, the target string is not, and a Latin-1 character
precedes a character in the string that should match the pattern.  [perl
#101710]

=item *

C<@{"..."} = reverse ...> started crashing in 5.15.3.  This has been fixed.

=item *

C<ref> in a tainted expression started producing an "sv_upgrade" error in
5.15.4.  This has been fixed.

=item *

Weak references to lexical hashes going out of scope were not going stale
(becoming undefined), but continued to point to the hash.

=item *

Weak references to lexical variables going out of scope are now broken
before any magical methods (e.g., DESTROY on a tie object) are called.
This prevents such methods from modifying the variable that will be seen
the next time the scope is entered.

=item *

A C<keys> optimisation in Perl 5.12.0 to make it faster on empty hashes
caused C<each> not to reset the iterator if called after the last element
was deleted.  This has been fixed.

=item *

The C<#line 42 foo> directive used not to update the arrays of lines used
by the debugger if it occurred in a string eval.  This was partially fixed
in 5.14, but it only worked for a single C<#line 42 foo> in each eval.  Now
it works for multiple.

=item *

String eval used not to localise C<%^H> when compiling its argument if it
was empty at the time the C<eval> call itself was compiled.  This could
lead to scary side effects, like C<use re "/m"> enabling other flags that
the surrounding code was trying to enable for its caller [perl #68750].

=item *

Creating a BEGIN block from XS code (via C<newXS> or C<newATTRSUB>) would,
on completion, make the hints of the current compiling code the current
hints.  This could cause warnings to occur in a non-warning scope.

=item *

C<eval $string> and C<require> no longer localise hints (C<$^H> and C<%^H>)
at run time, but only during compilation of the $string or required file.
This makes C<BEGIN { $^H{foo}=7 }> equivalent to
C<BEGIN { eval '$^H{foo}=7' }> [perl #70151].

=item *

When subroutine calls are intercepted by the debugger, the name of the
subroutine or a reference to it is stored in C<$DB::sub>, for the debugger
to access.  In some cases (such as C<$foo = *bar; undef *bar; &$foo>)
C<$DB::sub> would be set to a name that could not be used to find the
subroutine, and so the debugger's attempt to call it would fail.  Now the
check to see whether a reference is needed is more robust, so those
problems should not happen anymore [rt.cpan.org #69862].

=item *

Localising a tied scalar that returns a typeglob no longer stops it from
being tied till the end of the scope.

=item *

When C<open> is called with three arguments, the third being a file handle
(as in C<< open $fh, ">&", $fh2 >>), if the third argument is tied or a
reference to a tied variable, FETCH is now called exactly once, instead of
0, 2, or 3 times (all of which could occur in various circumstances).

=back

=head1 Known Problems

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, unless
they were specific to a particular platform (see below).

This is a list of some significant unfixed bugs, which are regressions
from either 5.XXX.XXX or 5.XXX.XXX.

[ List each fix as a =item entry ]

=over 4

=item *

XXX

=back

=head1 Obituary

XXX If any significant core contributor has died, we've added a short obituary
here.

=head1 Acknowledgements

XXX Generate this with:

  perl Porting/acknowledgements.pl v5.15.4..HEAD

=head1 Reporting Bugs

If you find what you think is a bug, you might check the articles
recently posted to the comp.lang.perl.misc newsgroup and the perl
bug database at http://rt.perl.org/perlbug/ .  There may also be
information at http://www.perl.org/ , the Perl Home Page.

If you believe you have an unreported bug, please run the L<perlbug>
program included with your release.  Be sure to trim your bug down
to a tiny but sufficient test case.  Your bug report, along with the
output of C<perl -V>, will be sent off to perlbug@perl.org to be
analysed by the Perl porting team.

If the bug you are reporting has security implications, which make it
inappropriate to send to a publicly archived mailing list, then please send
it to perl5-security-report@perl.org. This points to a closed subscription
unarchived mailing list, which includes
all the core committers, who will be able
to help assess the impact of issues, figure out a resolution, and help
co-ordinate the release of patches to mitigate or fix the problem across all
platforms on which Perl is supported. Please only use this address for
security issues in the Perl core, not for modules independently
distributed on CPAN.

=head1 SEE ALSO

The F<Changes> file for an explanation of how to view exhaustive details
on what changed.

The F<INSTALL> file for how to build Perl.

The F<README> file for general stuff.

The F<Artistic> and F<Copying> files for copyright information.

=cut