path: root/pod/perldelta.pod

=encoding utf8

=head1 NAME

perldelta - what is new for perl v5.23.8

=head1 DESCRIPTION

This document describes differences between the 5.23.7 release and the 5.23.8
release.

If you are upgrading from an earlier release such as 5.23.6, first read
L<perl5237delta>, which describes differences between 5.23.6 and 5.23.7.

=head1 Core Enhancements

=head2 More fields provided to C<sigaction> callback with C<SA_SIGINFO>

When passing the C<SA_SIGINFO> flag to L<sigaction|POSIX/sigaction>, the
C<errno>, C<status>, C<uid>, C<pid>, C<addr> and C<band> fields are now
included in the hash passed to the handler, if supported by the
platform.

=head1 Security

=head2 Set proper umask before calling C<mkstemp(3)>

In 5.22 perl started setting umask to 0600 before calling C<mkstemp(3)>
and restoring it afterwards. This wrongfully tells open(2) to strip
the owner read and write bits from the given mode before applying it,
rather than the intended negation of leaving only those bits in place.

Systems that use mode 0666 in C<mkstemp(3)> (like old versions of
glibc) create a file with permissions 0066, leaving world read and
write permissions regardless of current umask.

This has been fixed by using umask 0177 instead. [perl #127322]

=head1 Incompatible Changes

=head2 C<qr/\N{}/> now disallowed under C<use re "strict">

An empty C<\N{}> makes no sense, but for backwards compatibility is
silently accepted as doing nothing.  But now this is a fatal error under
the experimental feature L<re/'strict' mode>.

=head1 Performance Enhancements

=over 4

=item *

The overhead of scope entry and exit has been considerably reduced, so
for example subroutine calls, loops and basic blocks are all faster now.
This empty function call now takes about a third less time to execute:

    sub f{} f();

=item *

On Win32, C<stat>ing or C<-X>ing a path, if the file or directory does not
exist, is now 3.5x faster on a SSD (or any drive) than before.

=back

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over 4

=item *

F<cpan/podlators/> has been upgraded from version 4.04 to 4.06.

=item *

The PathTools module collection has been upgraded from version 3.62
to 3.63.

=item *

L<DynaLoader> has been upgraded from version 1.37 to 1.38.

DynaLoader now always looks for bootstrap files having the same base name as
the module for which the bootstrap code is being run. Previously, and only on
platforms that use C<mod2fname> to produce unique loadable library names,
L<DynaLoader> would look for the bootstrap file using a base name that matched
the loadable library and not find it.

=item *

L<Encode> has been upgraded from version 2.78 to 2.80.

=item *

L<ExtUtils::CBuilder> has been upgraded from version 0.280224 to 0.280225.

=item *

L<ExtUtils::MakeMaker> has been upgraded from version 7.10 to 7.10_01.

=item *

L<File::Spec> has been upgraded from version 3.62 to 3.63.

=item *

L<IPC::SysV> has been upgraded from version 2.04 to 2.05.

=item *

L<Module::CoreList> has been upgraded from version 5.20160120 to 5.20160121.

=item *

L<ODBM_File> has been upgraded from version 1.12 to 1.13.

=item *

L<PerlIO::encoding> has been upgraded from version 0.23 to 0.24.

=item *

L<POSIX> has been upgraded from version 1.59 to 1.63.

It can now export constants for the C<code> value in the hash passed to the
L<sigaction|POSIX/sigaction> handler when using the C<SA_SIGINFO> flag.

These previously deprecated functions are now removed: C<isalnum>,
C<isalpha>, C<iscntrl>, C<isdigit>, C<isgraph>, C<islower>, C<isprint>,
C<ispunct>, C<isspace>, C<isupper>, and C<isxdigit>.

=item *

L<Storable> has been upgraded from version 2.54 to 2.55.

=item *

L<Time::HiRes> has been upgraded from version 1.9728 to 1.9730.

It can now export Linux-specific and FreeBSD-specific C<clock_gettime()>
constants. It also now has emulation for OS X C<clock_nanosleep()>,
C<clock_gettime()>, and C<clock_getres()>.

=back

=head1 Documentation

=head2 Changes to Existing Documentation

=head3 L<perlguts>

=over 4

=item *

A new section has been added, L<perlguts/"Dynamic Scope and the Context
Stack">, which explains how the perl context stack works.

=back

=head3 L<perlmodlib>

=over 4

=item *

We now recommend contacting the module-authors list or PAUSE in seeking
guidance on the naming of modules.

=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>.

=head2 New Diagnostics

=head3 New Errors

=over 4

=item *

L<<< Sequence (?PE<lt>... not terminated in regex; marked by E<lt>-- HERE in mE<sol>%sE<sol>
|perldiag/"Sequence (?PE<lt>... not terminated in regex; marked by <-- HERE in mE<sol>%sE<sol>" >>>

=item *

L<Sequence (?PE<gt>... not terminated in regex; marked by E<lt>-- HERE in mE<sol>%sE<sol>
|perldiag/"Sequence (?PE<gt>... not terminated in regex; marked by <-- HERE in mE<sol>%sE<sol>">

=item *

L<Empty \%c in regex; marked by E<lt>-- HERE in mE<sol>%sE<sol>
|perldiag/"Empty \%c in regex; marked by <-- HERE in mE<sol>%sE<sol>">

=back

=head3 New Warnings

=over 4

=item *

L<Assuming NOT a POSIX class since %s in regex; marked by E<lt>-- HERE in mE<sol>%sE<sol>|
perldiag/Assuming NOT a POSIX class since %s in regex; marked by <-- HERE in mE<sol>%sE<sol>>

=back

=head1 Configuration and Compilation

=over 4

=item *

The GNU Make makefile for Win32 now supports parallel builds.  [perl #126632]

=item *

You can now build perl with MSVC++ on Win32 using GNU Make.  [perl #126632]

=item *

Bison 3.0 is now supported.

=back

=head1 Platform Support

=head2 Platform-Specific Notes

=over 4

=item VMS

=over

=item *

For those C<%ENV> elements based on the CRTL environ array, we've always
preserved case when setting them but did look-ups only after upcasing the
key first, which made lower- or mixed-case entries go missing. This problem
has been corrected by making C<%ENV> elements derived from the environ array
case-sensitive on look-up as well as case-preserving on store.

=item *

Environment look-ups for C<PERL5LIB> and C<PERLLIB> previously only
considered logical names, but now consider all sources of C<%ENV> as
determined by C<PERL_ENV_TABLES> and as documented in L<perlvms/%ENV>.

=back

=item Win32

Builds using Microsoft Visual C++ 2003 and earlier no longer produce
an "INTERNAL COMPILER ERROR" message.  [perl #126045]

=back

=head1 Internal Changes

=over 4

=item *

The implementation of perl's context stack system, and its internal API,
have been heavily reworked. Note that no significant changes have been
made to any external APIs, but XS code which relies on such internal
details may need to be fixed. The main changes are:

=over 4

=item *

The C<PUSHBLOCK()>, C<POPSUB()> etc. macros have been replaced with static
inline functions such as C<cx_pushblock()>, C<cx_popsub()> etc. These use
function args rather than implicitly relying on local vars such as
C<gimme> and C<newsp> being available. Also their functionality has
changed: in particular, C<cx_popblock()> no longer decrements
C<cxstack_ix>. The ordering of the steps in the C<pp_leave*> functions
involving C<cx_popblock()>, C<cx_popsub()> etc. has changed. See the new
documentation, L<perlguts/"Dynamic Scope and the Context Stack">, for
details on how to use them.

=item *

Various macros, which now consistently have a CX_ prefix, have been added:

  CX_CUR(), CX_LEAVE_SCOPE(), CX_POP()

or renamed:

  CX_POP_SAVEARRAY(), CX_DEBUG(), CX_PUSHSUBST(), CX_POPSUBST()

=item *

C<cx_pushblock()> now saves C<PL_savestack_ix> and C<PL_tmps_floor>, so
C<pp_enter*> and C<pp_leave*> no longer do

  ENTER; SAVETMPS; ....; LEAVE

=item *

C<cx_popblock()> now also restores C<PL_curpm>.

=item *

In C<dounwind()> for every context type, the current savestack frame is
now processed before each context is popped; formerly this was only done
for sub-like context frames. This action has been removed from
C<cx_popsub()> and placed into its own macro, C<CX_LEAVE_SCOPE(cx)>, which
must be called before C<cx_popsub()> etc.

C<dounwind()> now also does a C<cx_popblock()> on the last popped frame
(formerly it only did the C<cx_popsub()> etc. actions on each frame).

=item *

The temps stack is now freed on scope exit; previously, temps created
during the last statement of a block wouldn't be freed until the next
C<nextstate> following the block (apart from an existing hack that did
this for recursive subs in scalar context); and in something like
C<f(g())>, the temps created by the last statement in C<g()> would
formerly not be freed until the statement following the return from
C<f()>.

=item *

Most values that were saved on the savestack on scope entry are now
saved in suitable new fields in the context struct, and saved and
restored directly by C<cx_pushfoo()> and C<cx_popfoo()>, which is much
faster.

=item *

Various context struct fields have been added, removed or modified.

=item *

The handling of C<@_> in C<cx_pushsub()> and C<cx_popsub()> has been
considerably tidied up, including removing the C<argarray> field from the
context struct, and extracting out some common (but rarely used) code into
a separate function, C<clear_defarray()>. Also, useful subsets of
C<cx_popsub()> which had been unrolled in places like C<pp_goto> have been
gathered into the new functions C<cx_popsub_args()> and
C<cx_popsub_common()>.

=item *

C<pp_leavesub> and C<pp_leavesublv> now use the same function as the rest
of the C<pp_leave*>'s to process return args.

=item *

C<CXp_FOR_PAD> and C<CXp_FOR_GV> flags have been added, and
C<CXt_LOOP_FOR> has been split into C<CXt_LOOP_LIST>, C<CXt_LOOP_ARY>.

=item *

Some variables formerly declared by C<dMULTICALL> (but not documented) have
been removed.

=back

=back

=head1 Selected Bug Fixes

=over 4

=item *

Line numbers larger than 2**31-1 but less than 2**32 are no longer
returned by caller() as negative numbers.  [perl #126991]

=item *

C<< unless ( I<assignment> ) >> now properly warns when syntax
warnings are enabled.  [perl #127122]

=item *

Setting an C<ISA> glob to an array reference now properly adds
C<isaelem> magic to any existing elements.  Previously modifying such
an element would not update the ISA cache, so method calls would call
the wrong function.  Perl would also crash if the C<ISA> glob was
destroyed, since new code added in 5.23.7 would try to release the
C<isaelem> magic from the elements.  [perl #127351]

=item *

If a here-doc was found while parsing another operator, the parser had
already read end of file, and the here-doc was not terminated, perl
could produce an assertion or a segmentation fault.  This now reliably
complains about the unterminated here-doc.  [perl #125540]

=item *

untie() would sometimes return the last value returned by the UNTIE()
handler as well as it's normal value, messing up the stack.  [perl
#126621]

=item *

Fixed an operator precedence problem when C< castflags & 2> is true.
[perl #127474]

=item *

Caching of DESTROY methods could result in a non-pointer or a
non-STASH stored in the SvSTASH() slot of a stash, breaking the B
STASH() method.  The DESTROY method is now cached in the MRO metadata
for the stash.  [perl #126410]

=item *

The AUTOLOAD method is now called when searching for a DESTROY method,
and correctly sets C<$AUTOLOAD> too.  [perl #124387]  [perl #127494]

=item *

Avoid parsing beyond the end of the buffer when processing a C<#line>
directive with no filename.  [perl #127334]

=item *

Perl now raises a warning when a regular expression pattern looks like
it was supposed to contain a POSIX class, like C<qr/[[:alpha:]]/>, but
there was some slight defect in its specification which causes it to
instead be treated as a regular bracketed character class.  An example
would be missing the second colon in the above like this:
C<qr/[[:alpha]]/>.  This compiles to match a sequence of two characters.
The second is C<"]">, and the first is any of: C<"[">, C<":">, C<"a">,
C<"h">, C<"l">, or C<"p">.   This is unlikely to be the intended
meaning, and now a warning is raised.  No warning is raised unless the
specification is very close to one of the 14 legal POSIX classes.  (See
L<perlrecharclass/POSIX Character Classes>.)
[perl #8904]

=item *

Certain regex patterns involving a complemented POSIX class in an
inverted bracketed character class, and matching something else
optionally would improperly fail to match.  An example of one that could
fail is C</qr/_?[^\Wbar]\x{100}/>.  This has been fixed.
[perl #127537]

=item *

Perl 5.22 added support to the C99 hexadecimal floating point notation,
but sometimes misparses hex floats. This had been fixed.
[perl #127183]

=back

=head1 Acknowledgements

Perl 5.23.8 represents approximately 4 weeks of development since Perl 5.23.7
and contains approximately 30,000 lines of changes across 350 files from 23
authors.

Excluding auto-generated files, documentation and release tools, there were
approximately 14,000 lines of changes to 210 .pm, .t, .c and .h files.

Perl continues to flourish into its third decade thanks to a vibrant community
of users and developers. The following people are known to have contributed the
improvements that became Perl 5.23.8:

Aaron Crane, Chris 'BinGOs' Williams, Craig A. Berry, Dagfinn Ilmari
Mannsåker, Daniel Dragan, David Mitchell, Ed J, Herbert Breunung, H.Merijn
Brand, James E Keenan, Jarkko Hietaniemi, Karl Williamson, Lukas Mai, Niko
Tyni, Pip Cet, Ricardo Signes, Sawyer X, Sisyphus, Stevan Little, Steve Hay,
Todd Rinaldo, Tom Hukins, Tony Cook.

The list above is almost certainly incomplete as it is automatically generated
from version control history. In particular, it does not include the names of
the (very much appreciated) contributors who reported issues to the Perl bug
tracker.

Many of the changes included in this version originated in the CPAN modules
included in Perl's core. We're grateful to the entire CPAN community for
helping Perl to flourish.

For a more complete list of all of Perl's historical contributors, please see
the F<AUTHORS> file in the Perl source distribution.

=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
L<https://rt.perl.org/> .  There may also be information at
L<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