CVE-2016-2381

=head1 Incompatible Changes

=head2 The C<autoderef> feature has been removed

The experimental C<autoderef> feature (which allowed calling C<push>, C<pop>, C<shift>, C<unshift>, C<splice>, C<keys>, C<values>, and C<each> on a scalar argument) has been deemed unsuccessful. It has now been removed; trying to use the feature (or to disable the C<experimental::autoderef> warning it previously triggered) now yields an exception.

=head2 Lexical $_ has been removed

C<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.

=head2 C<qr/\b{wb}/> is now tailored to Perl expectations

This is now more suited to be a drop-in replacement for plain C<\b>, but giving better results for parsing natural language. Previously it strictly followed the current Unicode rules which calls for it to match between each white space character. Now it doesn't generally match within spans of white space, behaving like C<\b> does. See L<perlrebackslash/\b{wb}>

=head2 Regular expression compilation errors

Some regular expression patterns that had runtime errors now don't compile at all.

Almost all Unicode properties using the C<\p{}> and C<\P{}> regular expression pattern constructs are now checked for validity at pattern compilation time, and invalid ones will cause the program to not compile. In earlier releases, this check was often deferred until run time. Whenever an error check is moved from run- to compile time, erroneous code is caught 100% of the time, whereas before it would only get caught if and when the offending portion actually gets executed, which for unreachable code might be never.

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

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

=head2 Nested declarations are now disallowed

A C<my>, C<our>, or C<state> declaration is no longer allowed inside of another C<my>, C<our>, or C<state> declaration.

For example, these are now fatal: my ($x, my($y)); our (my $x);

Lperl #125587 ]|https://rt.perl.org/Ticket/Display.html?id=125587>

Lperl #121058 ]|https://rt.perl.org/Ticket/Display.html?id=121058>

=head2 The C</\C/> character class has been removed.

This regular expression character class was deprecated in v5.20.0 and has produced a deprecation warning since v5.22.0. It is now a compile-time error. If you need to examine the individual bytes that make up a UTF8-encoded character, then use C<utf8::encode()> on the string (or a copy) first.

=head2 C<chdir('')> no longer chdirs home

Using C<chdir('')> or C<chdir(undef)> to chdir home has been deprecated since perl v5.8, and will now fail. Use C<chdir()> instead.

=head2 ASCII characters in variable names must now be all visible

It was legal until now on ASCII platforms for variable names to contain non-graphical ASCII control characters (ordinals 0 through 31, and 127, which are the C0 controls and C<DELETE>). This usage has been deprecated since v5.20, and as of now causes a syntax error. The variables these names referred to are special, reserved by Perl for whatever use it may choose, now, or in the future. Each such variable has an alternative way of spelling it. Instead of the single non-graphic control character, a two character sequence beginning with a caret is used, like C<$^]> and C<${^GLOBAL_PHASE}>. Details are at L<perlvar>. It remains legal, though unwise and deprecated (raising a deprecation warning), to use certain non-graphic non-ASCII characters in variables names when not under S<C<use utf8>>. No code should do this, as all such variables are reserved by Perl, and Perl doesn't currently define any of them (but could at any time, without notice).

=head2 An off by one issue in C<$Carp::MaxArgNums> has been fixed

C<$Carp::MaxArgNums> is supposed to be the number of arguments to display. Prior to this version, it was instead showing C<$Carp::MaxArgNums> + 1 arguments, contrary to the documentation.

=head2 Only blanks and tabs are now allowed within C<[...]> within C<(?[...])>.

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 C<\t> and SPACE characters. Previously, it was any white space. See L<perlrecharclass/Extended Bracketed Character Classes>.

=head1 Deprecations

=head2 Using code points above the platform's C<IV_MAX> is now deprecated

Unicode defines code points in the range C<0..0x10FFFF>. Some standards at one time defined them up to 2**31 - 1, but Perl has allowed them to be as high as anything that will fit in a word on the platform being used. However, use of those above the platform's C<IV_MAX> is broken in some constructs, notably C<tr///>, regular expression patterns involving quantifiers, and in some arithmetic and comparison operations, such as being the upper limit of a loop. Now the use of such code points raises a deprecation warning, unless that warning category is turned off. C<IV_MAX> is typically 2**31 -1 on 32-bit platforms, and 2**63-1 on 64-bit ones.

=head2 Doing bitwise operations on strings containing code points above 0xFF is deprecated

The string bitwise operators treat their operands as strings of bytes, and values beyond 0xFF are nonsensical in this context. To operate on encoded bytes, first encode the strings. To operate on code points' numeric values, use C<split> and C<map ord>. In the future, this warning will be replaced by an exception.

=head2 C<sysread()>, C<syswrite()>, C<recv()> and C<send()> are deprecated on :utf8 handles

The C<sysread()>, C<recv()>, C<syswrite()> and C<send()> operators are deprecated on handles that have the C<:utf8> layer, either explicitly, or implicitly, eg., with the C<:encoding(UTF-16LE)> layer.

Both C<sysread()> and C<recv()> currently use only the C<:utf8> flag for the stream, ignoring the actual layers. Since C<sysread()> and C<recv()> do no UTF-8 validation they can end up creating invalidly encoded scalars.

Similarly, C<syswrite()> and C<send()> use only the C<:utf8> flag, otherwise ignoring any layers. If the flag is set, both write the value UTF-8 encoded, even if the layer is some different encoding, such as the example above.

Ideally, all of these operators would completely ignore the C<:utf8> state, working only with bytes, but this would result in silently breaking existing code. To avoid this a future version of perl will throw an exception when any of C<sysread()>, C<recv()>, C<syswrite()> or C<send()> are called on handle with the C<:utf8> layer.

=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 *

Many languages, such as Chinese, are caseless. Perl now knows about most common ones, and skips much of the work when a program tries to change case in them (like C<ucfirst()>) or match caselessly (C<qr//i>). This will speed up a program, such as a web server, that can operate on multiple languages, while it is operating on a caseless one.

=item *

C</fixed-substr/> has been made much faster.

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

=item *

Faster addition, subtraction and multiplication.

Since 5.8.0, arithmetic became slower due to the need to support 64-bit integers. To deal with 64-bit integers, a lot more corner cases need to be checked, which adds time. We now detect common cases where there is no need to check for those corner cases, and special-case them.

=item *

Preincrement, predecrement, postincrement, and postdecrement have been made faster by internally splitting the functions which handled multiple cases into different functions.

=item *

Creating Perl debugger data structures (see L<perldebguts/"Debugger Internals">) for XSUBs and const subs has been removed. This removed one glob/scalar combo for each unique C<.c> file that XSUBs and const subs came from. On startup (C<perl -e"0">) about half a dozen glob/scalar debugger combos were created. Loading XS modules created more glob/scalar combos. These things were being created regardless of whether the perl debugger was being used, and despite the fact that it can't debug C code anyway

=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 than before.

=item *

Single arguments in list assign are now slightly faster: ($x) = (...); (...) = ($x);

=item *

Less peak memory is now used when compiling regular expression patterns.

=back

=head1 Modules and Pragmata

=head2 Updated Modules and Pragmata

=over

=item *

L<arybase> has been upgraded from version 0.10 to 0.11.

=item *

L<Attribute::Handlers> has been upgraded from version 0.97 to 0.99.

=item *

L<autodie> has been upgraded from version 2.26 to 2.29.

=item *

L<autouse> has been upgraded from version 1.08 to 1.11.

=item *

L<B> has been upgraded from version 1.58 to 1.62.

=item *

L<B::Deparse> has been upgraded from version 1.35 to 1.37.

=item *

L<base> has been upgraded from version 2.22 to 2.23.

=item *

L<Benchmark> has been upgraded from version 1.2 to 1.22.

=item *

L<bignum> has been upgraded from version 0.39 to 0.42.

=item *

L<bytes> has been upgraded from version 1.04 to 1.05.

=item *

L<Carp> has been upgraded from version 1.36 to 1.40.

=item *

L<Compress::Raw::Bzip2> has been upgraded from version 2.068 to 2.069.

=item *

L<Compress::Raw::Zlib> has been upgraded from version 2.068 to 2.069.

=item *

L<Config::Perl::V> has been upgraded from version 0.24 to 0.25.

=item *

L<CPAN::Meta> has been upgraded from version 2.150001 to 2.150005.

=item *

L<CPAN::Meta::Requirements> has been upgraded from version 2.132 to 2.140.

=item *

L<CPAN::Meta::YAML> has been upgraded from version 0.012 to 0.018.

=item *

L<Data::Dumper> has been upgraded from version 2.158 to 2.160.

=item *

L<Devel::Peek> has been upgraded from version 1.22 to 1.23.

=item *

L<Devel::PPPort> has been upgraded from version 3.31 to 3.32.

=item *

L<Dumpvalue> has been upgraded from version 1.17 to 1.18.

=item *

L<DynaLoader> has been upgraded from version 1.32 to 1.38.

=item *

L<Encode> has been upgraded from version 2.72 to 2.80.

=item *

L<encoding> has been upgraded from version 2.14 to 2.17.

=item *

L<encoding::warnings> has been upgraded from version 0.11 to 0.12.

=item *

L<English> has been upgraded from version 1.09 to 1.10.

=item *

L<Errno> has been upgraded from version 1.23 to 1.25.

=item *

L<experimental> has been upgraded from version 0.013 to 0.016.

=item *

L<ExtUtils::CBuilder> has been upgraded from version 0.280221 to 0.280225.

=item *

L<ExtUtils::Embed> has been upgraded from version 1.32 to 1.33.

=item *

L<ExtUtils::MakeMaker> has been upgraded from version 7.04_01 to 7.10_01.

=item *

L<ExtUtils::ParseXS> has been upgraded from version 3.28 to 3.31.

=item *

L<ExtUtils::Typemaps> has been upgraded from version 3.28 to 3.31.

=item *

L<feature> has been upgraded from version 1.40 to 1.42.

=item *

L<fields> has been upgraded from version 2.17 to 2.23.

=item *

L<File::Copy> has been upgraded from version 2.30 to 2.31.

=item *

L<File::Find> has been upgraded from version 1.29 to 1.34.

=item *

L<File::Glob> has been upgraded from version 1.24 to 1.26.

=item *

L<File::Path> has been upgraded from version 2.09 to 2.12_01.

=item *

L<File::Spec> has been upgraded from version 3.56 to 3.63.

=item *

L<Filter::Util::Call> has been upgraded from version 1.54 to 1.55.

=item *

L<Getopt::Long> has been upgraded from version 2.45 to 2.48.

=item *

L<Hash::Util> has been upgraded from version 0.18 to 0.19.

=item *

L<Hash::Util::FieldHash> has been upgraded from version 1.15 to 1.19.

=item *

L<HTTP::Tiny> has been upgraded from version 0.054 to 0.056.

=item *

L<I18N::Langinfo> has been upgraded from version 0.12 to 0.13.

=item *

L<if> has been upgraded from version 0.0604 to 0.0606.

=item *

L<IO> has been upgraded from version 1.35 to 1.36.

=item *

IO-Compress has been upgraded from version 2.068 to 2.069.

=item *

L<IPC::Open3> has been upgraded from version 1.18 to 1.20.

=item *

L<IPC::SysV> has been upgraded from version 2.04 to 2.06_01.

=item *

L<List::Util> has been upgraded from version 1.41 to 1.42_02.

=item *

L<locale> has been upgraded from version 1.06 to 1.08.

=item *

L<Locale::Codes> has been upgraded from version 3.34 to 3.37.

=item *

L<Math::BigInt> has been upgraded from version 1.9997 to 1.999715.

=item *

L<Math::BigInt::FastCalc> has been upgraded from version 0.31 to 0.40.

=item *

L<Math::BigRat> has been upgraded from version 0.2608 to 0.260802.

=item *

L<Module::CoreList> has been upgraded from version 5.20150520 to 5.20160506.

=item *

L<Module::Metadata> has been upgraded from version 1.000026 to 1.000031.

=item *

L<mro> has been upgraded from version 1.17 to 1.18.

=item *

L<ODBM_File> has been upgraded from version 1.12 to 1.14.

=item *

L<Opcode> has been upgraded from version 1.32 to 1.34.

=item *

L<parent> has been upgraded from version 0.232 to 0.234.

=item *

L<Parse::CPAN::Meta> has been upgraded from version 1.4414 to 1.4417.

=item *

L<Perl::OSType> has been upgraded from version 1.008 to 1.009.

=item *

L<perlfaq> has been upgraded from version 5.021009 to 5.021010.

=item *

L<PerlIO::encoding> has been upgraded from version 0.21 to 0.24.

=item *

L<PerlIO::mmap> has been upgraded from version 0.014 to 0.016.

=item *

L<PerlIO::scalar> has been upgraded from version 0.22 to 0.24.

=item *

L<PerlIO::via> has been upgraded from version 0.15 to 0.16.

=item *

podlators has been upgraded from version 2.28 to 4.07.

=item *

L<Pod::Functions> has been upgraded from version 1.09 to 1.10.

=item *

L<Pod::Perldoc> has been upgraded from version 3.25 to 3.25_02.

=item *

L<Pod::Simple> has been upgraded from version 3.29 to 3.32.

=item *

L<Pod::Usage> has been upgraded from version 1.64 to 1.68.

=item *

L<POSIX> has been upgraded from version 1.53 to 1.65.

=item *

L<Scalar::Util> has been upgraded from version 1.41 to 1.42_02.

=item *

L<SDBM_File> has been upgraded from version 1.13 to 1.14.

=item *

L<SelfLoader> has been upgraded from version 1.22 to 1.23.

=item *

L<Socket> has been upgraded from version 2.018 to 2.020_03.

=item *

L<Storable> has been upgraded from version 2.53 to 2.56.

=item *

L<strict> has been upgraded from version 1.09 to 1.11.

=item *

L<Term::ANSIColor> has been upgraded from version 4.03 to 4.04.

=item *

L<Term::Cap> has been upgraded from version 1.15 to 1.17.

=item *

L<Test> has been upgraded from version 1.26 to 1.28.

=item *

L<Test::Harness> has been upgraded from version 3.35 to 3.36.

=item *

L<Thread::Queue> has been upgraded from version 3.05 to 3.09.

=item *

L<threads> has been upgraded from version 2.01 to 2.07.

=item *

L<threads::shared> has been upgraded from version 1.48 to 1.51.

=item *

L<Tie::File> has been upgraded from version 1.01 to 1.02.

=item *

L<Tie::Scalar> has been upgraded from version 1.03 to 1.04.

=item *

L<Time::HiRes> has been upgraded from version 1.9726 to 1.9733.

=item *

L<Time::Piece> has been upgraded from version 1.29 to 1.31.

=item *

L<Unicode::Collate> has been upgraded from version 1.12 to 1.14.

=item *

L<Unicode::Normalize> has been upgraded from version 1.18 to 1.25.

=item *

L<Unicode::UCD> has been upgraded from version 0.61 to 0.64.

=item *

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

=item *

L<utf8> has been upgraded from version 1.17 to 1.19.

=item *

L<version> has been upgraded from version 0.9909 to 0.9916.

=item *

L<warnings> has been upgraded from version 1.32 to 1.36.

=item *

L<Win32> has been upgraded from version 0.51 to 0.52.

=item *

L<Win32API::File> has been upgraded from version 0.1202 to 0.1203.

=item *

L<XS::Typemap> has been upgraded from version 0.13 to 0.14.

=item *

L<XSLoader> has been upgraded from version 0.20 to 0.21.

=back

=head1 Documentation

=head2 Changes to Existing Documentation

=head3 L<perlapi>

=over 4

=item *

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

=back

=head3 L<perlcall>

=over 4

=item *

A number of cleanups have been made to perlcall, including:

=over 4

=item *

use C<EXTEND(SP, n)> and C<PUSHs()> instead of C<XPUSHs()> where applicable and update prose to match

=item *

add POPu, POPul and POPpbytex to the "complete list of POP macros" and clarify the documentation for some of the existing entries, and a note about side-effects

=item *

add API documentation for POPu and POPul

=item *

use ERRSV more efficiently

=item *

approaches to thread-safety storage of SVs.

=back

=back

=head3 L<perlfunc>

=over 4

=item *

The documentation of C<hex> has been revised to clarify valid inputs.

=item *

Better explain meaning of negative PIDs in C . Lperl #127080 ]|https://rt.perl.org/Ticket/Display.html?id=127080>

=item *

General cleanup: there's more consistency now (in POD usage, grammar, code examples), better practices in code examples (use of C<my>, removal of bareword filehandles, dropped usage of C<&> when calling subroutines, ...), etc.

=back

=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<perllocale>

=over 4

=item *

A stronger caution about using locales in threaded applications is given. Locales are not thread-safe, and you can get wrong results or even segfaults if you use them there.

=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

=head3 L<perlop>

=over 4

=item *

The documentation of C<qx//> now describes how C<$?> is affected.

=back

=head3 L<perlpolicy>

=over 4

=item *

This note has been added to perlpolicy: While civility is required, kindness is encouraged; if you have any doubt about whether you are being civil, simply ask yourself, "Am I being kind?" and aspire to that.

=back

=head3 L<perlreftut>

=over 4

=item *

Fix some examples to be L<strict> clean.

=back

=head3 L<perlrebackslash>

=over 4

=item *

Clarify that in languages like Japanese and Thai, dictionary lookup is required to determine word boundaries.

=back

=head3 L<perlsub>

=over 4

=item *

Updated to note that anonymous subroutines can have signatures.

=back

=head3 L<perlsyn>

=over 4

=item *

Fixed a broken example where C<=> was used instead of C<==> in conditional in do/while example.

=back

=head3 L<perltie>

=over 4

=item *

The usage of C<FIRSTKEY> and C<NEXTKEY> has been clarified.

=back

=head3 L<perlunicode>

=over 4

=item *

Discourage use of 'In' as a prefix signifying the Unicode Block property.

=back

=head3 L<perlvar>

=over 4

=item *

The documentation of C was reworded to clarify that it is not just for syntax errors in C . Lperl #124034 ]|https://rt.perl.org/Ticket/Display.html?id=124034>

=item *

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

=item *

Use of C<$OLD_PERL_VERSION> is now discouraged.

=back

=head3 L<perlxs>

=over 4

=item *

The documentation of C<PROTOTYPES> has been corrected; they are I<disabled> by default, not I<enabled>.

=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<%s must not be a named sequence in transliteration operator|perldiag/"%s must not be a named sequence in transliteration operator">

=item *

L<Can't find Unicode property definition "%s" in regex;|perldiag/"Can't find Unicode property definition "%s" in regex; marked by <-- HERE in m/%s/">

=item *

L<Can't redeclare "%s" in "%s"|perldiag/"Can't redeclare "%s" in "%s"">

=item *

L<Character following \p must be '{' or a single-character Unicode property name in regex;|perldiag/"Character following \%c must be '{' or a single-character Unicode property name in regex; marked by <-- HERE in m/%s/">

=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>">

=item *

L<Illegal user-defined property name|perldiag/"Illegal user-defined property name">

=item *

L<Invalid number '%s' for -C option.|perldiag/"Invalid number '%s' for -C option.">

=item *

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

=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>">

=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>>

=item *

L<%s() is deprecated on :utf8 handles|perldiag/"%s() is deprecated on :utf8 handles">

=back

=head2 Changes to Existing Diagnostics

=over 4

=item *

Accessing the C part of a glob as C instead of C is no longer deprecated. It is discouraged to encourage uniformity (so that, for example, one can grep more easily) but it will not be removed. Lperl #127060 ]|https://rt.perl.org/Ticket/Display.html?id=127060>

=item *

The diagnostic C<< Hexadecimal float: internal error >> has been changed to C<< Hexadecimal float: internal error (%s) >> to include more information.

=item *

L<Can't modify non-lvalue subroutine call of &%s|perldiag/"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.

=item *

When running out of memory during an attempt the increase the stack size, previously, perl would die using the cryptic message C<< panic: av_extend_guts() negative count (-9223372036854775681) >>. This has been fixed to show the prettier message: L<< Out of memory during stack extend|perldiag/"Out of memory during %s extend" >>

=back

=head1 Configuration and Compilation

=over 4

=item *

C<Configure> now acts as if the C<-O> option is always passed, allowing command line options to override saved configuration. This should eliminate confusion when command line options are ignored for no obvious reason. C<-O> is now permitted, but ignored.

=item *

Bison 3.0 is now supported.

=item *

F no longer probes for F by default. Originally this was the "New Math" library, but the name has been re-used by the GNOME NetworkManager. Lperl #127131 ]|https://rt.perl.org/Ticket/Display.html?id=127131>

=item *

Added F<Configure> probes for C<newlocale>, C<freelocale>, and C<uselocale>.

=item *

C<< PPPort.so/PPPort.dll >> no longer get installed, as they are not used by C<< PPPort.pm >>, only by its test files.

=item *

It is now possible to specify which compilation date to show on C<< perl -V >> output, by setting the macro C<< PERL_BUILD_DATE >>.

=item *

Using the C<NO_HASH_SEED> define in combination with the default hash algorithm C<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.

=item *

F<Configure> should handle spaces in paths a little better.

=item *

No longer generate EBCDIC POSIX-BC tables. We don't believe anyone is using Perl and POSIX-BC at this time, and by not generating these tables it saves time during development, and makes the resulting tar ball smaller.

=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 *

The Win32 miniperl now has a real C<getcwd> which increases build performance resulting in C<getcwd()> being 605x faster in Win32 miniperl.

=item *

Configure now takes C into account when calculating the C configuration variable. Previously the mis-calculated C could cause alignment errors on debugging builds. [ perl #127894

=back

=head1 Testing

=over 4

=item *

A new test (F<t/op/aassign.t>) has been added to test the list assignment operator C<OP_AASSIGN>.

=item *

Parallel building has been added to the dmake C<makefile.mk> makefile. All Win32 compilers are supported.

=back

=head1 Platform Support

=head2 Platform-Specific Notes

=over 4

=item AmigaOS

=over 4

=item *

The AmigaOS port has been reintegrated into the main tree, based off of Perl 5.22.1.

=back

=item Cygwin

=over 4

=item *

Tests are more robust against unusual cygdrive prefixes. Lperl #126834 ]|https://rt.perl.org/Ticket/Display.html?id=126834>

=back

=item EBCDIC

=over 4

=item UTF-EBCDIC extended

UTF-EBCDIC is like UTF-8, but for EBCDIC platforms. It now has been extended so that it can represent code points up to 2 ** 64 - 1 on platforms with 64-bit words. This brings it into parity with UTF-8. This enhancement requires an incompatible change to the representation of code points in the range 2 ** 30 to 2 ** 31 -1 (the latter was the previous maximum representable code point). This means that a file that contains one of these code points, written out with previous versions of perl cannot be read in, without conversion, by a perl containing this change. We do not believe any such files are in existence, but if you do have one, submit a ticket at L<perlbug@perl.org|mailto:perlbug@perl.org>, and we will write a conversion script for you.

=item EBCDIC C<cmp()> and C<sort()> fixed for UTF-EBCDIC strings

Comparing two strings that were both encoded in UTF-8 (or more precisely, UTF-EBCDIC) did not work properly until now. Since C<sort()> uses C<cmp()>, this fixes that as well.

=item EBCDIC C<tr///> and C<y///> fixed for C<\N{}>, and C<S<use utf8>> ranges

Perl v5.22 introduced the concept of portable ranges to regular expression patterns. A portable range matches the same set of characters no matter what platform is being run on. This concept is now extended to C<tr///>. See C<L<trE<sol>E<sol>E<sol>|perlop/trE<sol>SEARCHLISTE<sol>REPLACEMENTLISTE<sol>cdsr>>.

There were also some problems with these operations under S<C<use utf8>>, which are now fixed

=back

=item FreeBSD

=over 4

=item *

Use the C function from FreeBSD if it is available. Lperl #126847 ]|https://rt.perl.org/Ticket/Display.html?id=126847>

=back

=item IRIX

=over 4

=item *

Under some circumstances IRIX stdio C and C set the errno to C , which made no sense according to either IRIX or POSIX docs. Errno is now cleared in such cases. Lperl #123977 ]|https://rt.perl.org/Ticket/Display.html?id=123977>

=item *

Problems when multiplying long doubles by infinity have been fixed. Lperl #126396 ]|https://rt.perl.org/Ticket/Display.html?id=126396>

=back

=item MacOS X

=over 4

=item *

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 C<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.

=item *

Builds with both -DDEBUGGING and threading enabled would fail with a "panic: free from wrong pool" error when built or tested from Terminal on OS X. This was caused by perl's internal management of the environment conflicting with an atfork handler using the libc C<setenv()> function to update the environment.

Perl now uses C /C to update the environment on OS X. Lperl #126240 ]|https://rt.perl.org/Ticket/Display.html?id=126240>

=back

=item Solaris

=over 4

=item *

All Solaris variants now build a shared libperl

Solaris and variants like OpenIndiana now always build with the shared Perl library (Configure -Duseshrplib). This was required for the OpenIndiana builds, but this has also been the setting for Oracle/Sun Perl builds for several years.

=back

=item Tru64

=over 4

=item *

Workaround where Tru64 balks when prototypes are listed as C<< PERL_STATIC_INLINE >>, but where the test is build with C<< -DPERL_NO_INLINE_FUNCTIONS >>.

=back

=item VMS

=over 4

=item *

On VMS, the math function prototypes in C<math.h> are now visible under C++. Now building the POSIX extension with C++ will no longer crash.

=item *

VMS has had C<setenv>/C<unsetenv> since v7.0 (released in 1996), C<Perl_vmssetenv> now always uses C<setenv>/C<unsetenv>.

=item *

Perl now implements its own C<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 C<$pid>.

=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>.

=item *

The minimum supported version of VMS is now v7.3-2, released in 2003. As a side effect of this change, VAX is no longer supported as the terminal release of OpenVMS VAX was v7.3 in 2001.

=back

=item Win32

=over 4

=item *

A new build option C<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 L<perlwin32>. Internally, in C, the name of this option is C<WIN32_NO_REGISTRY>.

=item *

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

=item *

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

=item *

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

=item *

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

=item *

Visual C++ 2013 builds will now execute on XP and higher. Previously they would only execute on Vista and higher.

=item *

You can now build perl with GNU Make and GCC. [ perl #123440

=item *