NAME

perl5234delta - what is new for perl v5.23.4

DESCRIPTION

This document describes differences between the 5.23.3 release and the 5.23.4 release.

If you are upgrading from an earlier release such as 5.23.2, first read perl5233delta, which describes differences between 5.23.2 and 5.23.3.

Incompatible Changes

Lexical $_ has been removed

my $_ was introduced in Perl 5.10, and subsequently caused much confusion with no obvious solution. In Perl 5.18.0, it was made experimental on the theory that it would either be removed or redesigned in a less confusing (but backward-incompatible) way. Over the following years, no alternatives were proposed. The feature has now been removed and will fail to compile.

Only blanks and tabs are now allowed within [...] within (?[...]).

The experimental Extended Bracketed Character Classes can contain regular bracketed character classes within them. These differ from regular ones in that white space is generally ignored, unless escaped by preceding it with a backslash. The white space that is ignored is now limited to just tab \t and SPACE characters. Previously, it was any white space. See "Extended Bracketed Character Classes" in perlrecharclass.

Performance Enhancements

• /fixed-substr/ has been made much faster.

  On platforms with a libc memchr() implementation which makes good use of underlying hardware support, patterns which include fixed substrings will now often be much faster; for example with glibc on a recent x86_64 CPU, this:

  $s = "a" x 1000 . "wxyz";
  $s =~ /wxyz/ for 1..30000

  is now about 7 times faster. On systems with slow memchr(), e.g. 32-bit ARM Raspberry Pi, there will be a small or little speedup. Conversely, some pathological cases, such as "ab" x 1000 =~ /aa/ will be slower now; up to 3 times slower on the rPi, 1.5x slower on x86_64.

Modules and Pragmata

Updated Modules and Pragmata

• B has been upgraded from version 1.59 to 1.60.

• bignum has been upgraded from version 0.40 to 0.41.

• Compress::Raw::Bzip2 has been upgraded from version 2.068 to 2.069.

• Compress::Raw::Zlib has been upgraded from version 2.068_01 to 2.069.

• Devel::PPPort has been upgraded from version 3.31 to 3.32.

• DynaLoader has been upgraded from version 1.34 to 1.35.

• Encode has been upgraded from version 2.77 to 2.78.

• experimental has been upgraded from version 0.014 to 0.016.

• ExtUtils::CBuilder has been upgraded from version 0.280223 to 0.280224.

• File::Path has been upgraded from version 2.11 to 2.12.

• if has been upgraded from version 0.0605 to 0.0606.

• IO has been upgraded from version 1.35 to 1.36.

  For an IO::Poll object $poll with no file handles yet in it, $poll->poll(10) now sleeps for up to 10 seconds anyway instead of returning 0 immediately. [cpan #25049]

• The IO-Compress modules have been upgraded from version 2.068 to 2.069.

• Math::BigInt has been upgraded from version 1.999701 to 1.999704.

• Math::BigInt::FastCalc has been upgraded from version 0.31 to 0.34.

• Module::CoreList has been upgraded from version 5.20150920 to 5.20151020.

• Module::Metadata has been upgraded from version 1.000027 to 1.000029.

• Perl::OSType has been upgraded from version 1.008 to 1.009.

• PerlIO::encoding has been upgraded from version 0.21 to 0.22.

  PerlIO::encoding objects are now properly duplicated. [perl #31923]

• POSIX has been upgraded from version 1.57 to 1.58.

  If POSIX::strerror was passed $! as its argument then it accidentally cleared $!. This has been fixed. [perl #126229]

• Socket has been upgraded from version 2.020_01 to 2.020_02.

  Various fixes have been applied to inet_pton for the benefit of MS VC++ builds on Windows. In particular, this restores the build with MS VC++ 6.0.

• Unicode::Normalize has been upgraded from version 1.19 to 1.21.

• warnings has been upgraded from version 1.33 to 1.35.

  The warnings::enabled example now actually uses warnings::enabled. [perl #126051]

Documentation

Changes to Existing Documentation

perlapi

• The process of using undocumented globals has been documented, namely, that one should send email to perl5-porters@perl.org first to get the go-ahead for documenting and using an undocumented function or global variable.

perlsub

• Updated to note that anonymous subroutines can have signatures.

perltie

• The usage of FIRSTKEY and NEXTKEY has been clarified.

perlvar

• The specific true value of $!{E...} is now documented, noting that it is subject to change and not guaranteed.

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 perldiag.

New Diagnostics

New Errors

• Can't find Unicode property definition "%s" in regex;

• Character following \p must be '{' or a single-character Unicode property name in regex;

• Illegal user-defined property name

Changes to Existing Diagnostics

• Can't modify non-lvalue subroutine call of &%s

  This error now reports the name of the non-lvalue subroutine you attempted to use as an lvalue.

Configuration and Compilation

• Using the NO_HASH_SEED define in combination with the default hash algorithm PERL_HASH_FUNC_ONE_AT_A_TIME_HARD resulted in a fatal error while compiling the interpreter, since Perl 5.17.10. This has been fixed.

• If you had Configure hints for d_procselfexe or procselfexe, they were probably broken by the AmigaOS changes in Perl 5.23.3. This has been now fixed. [perl #126152]

Platform Support

Platform-Specific Notes

IRIX

• Under some circumstances IRIX stdio fgetc() and fread() set the errno to ENOENT, which made no sense according to either IRIX or POSIX docs. Errno is now cleared in such cases. [perl #123977]

• Problems when multiplying long doubles by infinity have been fixed. [perl #126396]

MacOS X

• Until now OS X builds of perl have specified a link target of 10.3 (Panther, 2003) but have not specified a compiler target. From now on, builds of perl on OS X 10.6 or later (Snow Leopard, 2008) by default capture the current OS X version and specify that as the explicit build target in both compiler and linker flags, thus preserving binary compatibility for extensions built later regardless of changes in OS X, SDK, or compiler and linker versions. To override the default value used in the build and preserved in the flags, specify export MACOSX_DEPLOYMENT_TARGET=10.N before configuring and building perl, where 10.N is the version of OS X you wish to target. In OS X 10.5 or earlier there is no change to the behavior present when those systems were current; the link target is still OS X 10.3 and there is no explicit compiler target.

VMS

• Perl now implements its own killpg by scanning for processes in the specified process group, which may not mean exactly the same thing as a Unix process group, but allows us to send a signal to a parent (or master) process and all of its sub-processes. At the perl level, this means we can now send a negative pid like so:

  kill SIGKILL, -$pid;

  to signal all processes in the same group as $pid.

Win32

• A new build option USE_NO_REGISTRY has been added to the makefiles. This option is off by default, meaning the default is to do Windows registry lookups. This option stops Perl from looking inside the registry for anything. For what values are looked up in the registry see perlwin32. Internally, in C, the name of this option is WIN32_NO_REGISTRY.

• The behavior of Perl using HKEY_CURRENT_USER\Software\Perl and HKEY_LOCAL_MACHINE\Software\Perl to lookup certain values, including %ENV vars starting with PERL has changed. Previously, the 2 keys were checked for entries at all times through Perl processes life time even if they did not exist. For performance reasons, now, if the root key (i.e. HKEY_CURRENT_USER\Software\Perl or HKEY_LOCAL_MACHINE\Software\Perl) does not exist at process start time, it will not be checked again for %ENV override entries for the remainder of the Perl processes life. This more closely matches Unix behaviour in that the environment is copied or inherited on startup and changing the variable in the parent process or another process or editing .bashrc will not change the environmental variable in other existing, running, processes.

• One glob fetch was removed for each -X or stat call whether done from Perl code or internally from Perl's C code. The glob being looked up was ${^WIN32_SLOPPY_STAT} which is a special variable. This makes -X and stat slightly faster.

• During miniperl's process startup, during the build process, 4 to 8 IO calls related to the process starting .pl and the buildcustomize.pl file were removed from the code opening and executing the first 1 or 2 .pl files.

Internal Changes

• "sv_backoff" in perlapi had its return type changed from int to void. It previously has always returned 0 since Perl 5.000 stable but that was undocumented. Although sv_backoff is marked as public API, XS code is not expected to be impacted since the proper API call would be through public API sv_setsv(sv, &PL_sv_undef), or quasi-public SvOOK_off, or non-public SvOK_off calls, and the return value of sv_backoff was previously a meaningless constant that can be rewritten as (sv_backoff(sv),0).

• The EXTEND and MEXTEND macros have been improved to avoid various issues with integer truncation and wrapping. In particular, some casts formerly used within the macros have been removed. This means for example that passing an unsigned nitems argument is likely to raise a compiler warning now (it's always been documented to require a signed value; formerly int, lately SSize_t).

Selected Bug Fixes

• There were places in regular expression patterns where comments ((?#...)) weren't allowed, but should have been. This is now fixed. [perl #116639]

• Some regressions from Perl 5.20 have been fixed, in which some syntax errors in (?[...]) constructs within regular expression patterns could cause a segfault instead of a proper error message. [perl #126180] [perl #126404]

• Another problem with (?[...]) constructs has been fixed wherein things like \c] could cause panics. [perl #126181]

• Some problems with attempting to extend the perl stack to around 2G or 4G entries have been fixed. This was particularly an issue on 32-bit perls built to use 64-bit integers, and was easily noticeable with the list repetition operator, e.g.

  @a = (1) x $big_number

  Formerly perl may have crashed, depending on the exact value of $big_number; now it will typically raise an exception. [perl #125937]

• In a regex conditional expression (?(condition)yes-pattern|no-pattern), if the condition is (?!) then perl failed the match outright instead of matching the no-pattern. This has been fixed. [perl #126222]

• The special backtracking control verbs (*VERB:ARG) now all allow an optional argument and set REGERROR/REGMARK appropriately as well. [perl #126186]

• Several bugs, including a segmentation fault, have been fixed with the bounds checking constructs (introduced in Perl 5.22) \b{gcb}, \b{sb}, \b{wb}, \B{gcb}, \B{sb}, and \B{wb}. All the \B{} ones now match an empty string; none of the \b{} ones do. [perl #126319]

Errata From Previous Releases

• (This was actually done in Perl 5.23.2, but the perldelta entry got missed.) The way that OP_AASSIGN handles assignment with potentially common values (e.g. ($a,$b) = ($b, $a) has changed. In particular the OPpASSIGN_COMMON flag has been replaced with three more specific flags:

  OPpASSIGN_COMMON_AGG
  OPpASSIGN_COMMON_RC1
  OPpASSIGN_COMMON_SCALAR

  and the runtime now sometimes does a mark and sweep using the SVf_BREAK to detect common elements.

Acknowledgements

Perl 5.23.4 represents approximately 4 weeks of development since Perl 5.23.3 and contains approximately 21,000 lines of changes across 360 files from 21 authors.

Excluding auto-generated files, documentation and release tools, there were approximately 15,000 lines of changes to 250 .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 5.23.4:

Chris 'BinGOs' Williams, Craig A. Berry, Dagfinn Ilmari Mannsåker, Daniel Dragan, David Mitchell, Doug Bell, Father Chrysostomos, H.Merijn Brand, Jarkko Hietaniemi, Karen Etheridge, Karl Williamson, Nicholas Clark, Peter Martini, Rafael Garcia-Suarez, Reini Urban, Ricardo Signes, Steve Hay, Tony Cook, Victor Adam, Vincent Pit, Yves Orton.

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 AUTHORS file in the Perl source distribution.

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 https://rt.perl.org/ . 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 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 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.

SEE ALSO

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

The INSTALL file for how to build Perl.

The README file for general stuff.

The Artistic and Copying files for copyright information.

cpanm sort

perl -MCPAN -e shell
install sort