PERL5200DELTA(1pm) Perl Programmers Reference Guide PERL5200DELTA(1pm)
NAME
perl5200delta - what is new for perl v5.20.0
DESCRIPTION
This document describes differences between the 5.18.0 release and the
5.20.0 release.
If you are upgrading from an earlier release such as 5.16.0, first read
perl5180delta, which describes differences between 5.16.0 and 5.18.0.
Core Enhancements
Experimental Subroutine signatures
Declarative syntax to unwrap argument list into lexical variables.
"sub foo ($a,$b) {...}" checks the number of arguments and puts the
arguments into lexical variables. Signatures are not equivalent to the
existing idiom of "sub foo { my($a,$b) = @_; ... }". Signatures are
only available by enabling a non-default feature, and generate warnings
about being experimental. The syntactic clash with prototypes is
managed by disabling the short prototype syntax when signatures are
enabled.
See "Signatures" in perlsub for details.
"sub"s now take a "prototype" attribute
When declaring or defining a "sub", the prototype can now be specified
inside of a "prototype" attribute instead of in parens following the
name.
For example, "sub foo($$){}" could be rewritten as "sub foo :
prototype($$){}".
More consistent prototype parsing
Multiple semicolons in subroutine prototypes have long been tolerated
and treated as a single semicolon. There was one case where this did
not happen. A subroutine whose prototype begins with "*" or ";*" can
affect whether a bareword is considered a method name or sub call.
This now applies also to ";;;*".
Whitespace has long been allowed inside subroutine prototypes, so "sub(
$ $ )" is equivalent to "sub($$)", but until now it was stripped when
the subroutine was parsed. Hence, whitespace was not allowed in
prototypes set by "Scalar::Util::set_prototype". Now it is permitted,
and the parser no longer strips whitespace. This means "prototype
&mysub" returns the original prototype, whitespace and all.
"rand" now uses a consistent random number generator
Previously perl would use a platform specific random number generator,
varying between the libc rand(), random() or drand48().
This meant that the quality of perl's random numbers would vary from
platform to platform, from the 15 bits of rand() on Windows to 48-bits
on POSIX platforms such as Linux with drand48().
Perl now uses its own internal drand48() implementation on all
platforms. This does not make perl's "rand" cryptographically secure.
[perl #115928]
New slice syntax
The new %hash{...} and %array[...] syntax returns a list of key/value
(or index/value) pairs. See "Key/Value Hash Slices" in perldata.
Experimental Postfix Dereferencing
When the "postderef" feature is in effect, the following syntactical
equivalencies are set up:
$sref->$*; # same as ${ $sref } # interpolates
$aref->@*; # same as @{ $aref } # interpolates
$href->%*; # same as %{ $href }
$cref->&*; # same as &{ $cref }
$gref->**; # same as *{ $gref }
$aref->$#*; # same as $#{ $aref }
$gref->*{ $slot }; # same as *{ $gref }{ $slot }
$aref->@[ ... ]; # same as @$aref[ ... ] # interpolates
$href->@{ ... }; # same as @$href{ ... } # interpolates
$aref->%[ ... ]; # same as %$aref[ ... ]
$href->%{ ... }; # same as %$href{ ... }
Those marked as interpolating only interpolate if the associated
"postderef_qq" feature is also enabled. This feature is experimental
and will trigger "experimental::postderef"-category warnings when used,
unless they are suppressed.
For more information, consult the Postfix Dereference Syntax section of
perlref.
Unicode 6.3 now supported
Perl now supports and is shipped with Unicode 6.3 (though Perl may be
recompiled with any previous Unicode release as well). A detailed list
of Unicode 6.3 changes is at
<http://www.unicode.org/versions/Unicode6.3.0/>.
New "\p{Unicode}" regular expression pattern property
This is a synonym for "\p{Any}" and matches the set of Unicode-defined
code points 0 - 0x10FFFF.
Better 64-bit support
On 64-bit platforms, the internal array functions now use 64-bit
offsets, allowing Perl arrays to hold more than 2**31 elements, if you
have the memory available.
The regular expression engine now supports strings longer than 2**31
characters. [perl #112790, #116907]
The functions PerlIO_get_bufsiz, PerlIO_get_cnt, PerlIO_set_cnt and
PerlIO_set_ptrcnt now have SSize_t, rather than int, return values and
parameters.
"use locale" now works on UTF-8 locales
Until this release, only single-byte locales, such as the ISO 8859
series were supported. Now, the increasingly common multi-byte UTF-8
locales are also supported. A UTF-8 locale is one in which the
character set is Unicode and the encoding is UTF-8. The POSIX
"LC_CTYPE" category operations (case changing (like "lc()", "\U"), and
character classification ("\w", "\D", "qr/[[:punct:]]/")) under such a
locale work just as if not under locale, but instead as if under
"use feature 'unicode_strings'", except taint rules are followed.
Sorting remains by code point order in this release. [perl #56820].
"use locale" now compiles on systems without locale ability
Previously doing this caused the program to not compile. Within its
scope the program behaves as if in the "C" locale. Thus programs
written for platforms that support locales can run on locale-less
platforms without change. Attempts to change the locale away from the
"C" locale will, of course, fail.
More locale initialization fallback options
If there was an error with locales during Perl start-up, it immediately
gave up and tried to use the "C" locale. Now it first tries using
other locales given by the environment variables, as detailed in
"ENVIRONMENT" in perllocale. For example, if "LC_ALL" and "LANG" are
both set, and using the "LC_ALL" locale fails, Perl will now try the
"LANG" locale, and only if that fails, will it fall back to "C". On
Windows machines, Perl will try, ahead of using "C", the system default
locale if all the locales given by environment variables fail.
"-DL" runtime option now added for tracing locale setting
This is designed for Perl core developers to aid in field debugging
bugs regarding locales.
-F now implies -a and -a implies -n
Previously -F without -a was a no-op, and -a without -n or -p was a no-
op, with this change, if you supply -F then both -a and -n are implied
and if you supply -a then -n is implied.
You can still use -p for its extra behaviour. [perl #116190]
$a and $b warnings exemption
The special variables $a and $b, used in "sort", are now exempt from
"used once" warnings, even where "sort" is not used. This makes it
easier for CPAN modules to provide functions using $a and $b for
similar purposes. [perl #120462]
Security
Avoid possible read of free()d memory during parsing
It was possible that free()d memory could be read during parsing in the
unusual circumstance of the Perl program ending with a heredoc and the
last line of the file on disk having no terminating newline character.
This has now been fixed.
Incompatible Changes
"do" can no longer be used to call subroutines
The "do SUBROUTINE(LIST)" form has resulted in a deprecation warning
since Perl v5.0.0, and is now a syntax error.
Quote-like escape changes
The character after "\c" in a double-quoted string ("..." or qq(...))
or regular expression must now be a printable character and may not be
"{".
A literal "{" after "\B" or "\b" is now fatal.
These were deprecated in perl v5.14.0.
Tainting happens under more circumstances; now conforms to documentation
This affects regular expression matching and changing the case of a
string ("lc", "\U", etc.) within the scope of "use locale". The result
is now tainted based on the operation, no matter what the contents of
the string were, as the documentation (perlsec, "SECURITY" in
perllocale) indicates it should. Previously, for the case change
operation, if the string contained no characters whose case change
could be affected by the locale, the result would not be tainted. For
example, the result of "uc()" on an empty string or one containing only
above-Latin1 code points is now tainted, and wasn't before. This leads
to more consistent tainting results. Regular expression patterns taint
their non-binary results (like $&, $2) if and only if the pattern
contains elements whose matching depends on the current (potentially
tainted) locale. Like the case changing functions, the actual contents
of the string being matched now do not matter, whereas formerly it did.
For example, if the pattern contains a "\w", the results will be
tainted even if the match did not have to use that portion of the
pattern to succeed or fail, because what a "\w" matches depends on
locale. However, for example, a "." in a pattern will not enable
tainting, because the dot matches any single character, and what the
current locale is doesn't change in any way what matches and what
doesn't.
"\p{}", "\P{}" matching has changed for non-Unicode code points.
"\p{}" and "\P{}" are defined by Unicode only on Unicode-defined code
points ("U+0000" through "U+10FFFF"). Their behavior on matching these
legal Unicode code points is unchanged, but there are changes for code
points 0x110000 and above. Previously, Perl treated the result of
matching "\p{}" and "\P{}" against these as "undef", which translates
into "false". For "\P{}", this was then complemented into "true". A
warning was supposed to be raised when this happened. However, various
optimizations could prevent the warning, and the results were often
counter-intuitive, with both a match and its seeming complement being
false. Now all non-Unicode code points are treated as typical
unassigned Unicode code points. This generally is more Do-What-I-Mean.
A warning is raised only if the results are arguably different from a
strict Unicode approach, and from what Perl used to do. Code that
needs to be strictly Unicode compliant can make this warning fatal, and
then Perl always raises the warning.
Details are in "Beyond Unicode code points" in perlunicode.
"\p{All}" has been expanded to match all possible code points
The Perl-defined regular expression pattern element "\p{All}", unused
on CPAN, used to match just the Unicode code points; now it matches all
possible code points; that is, it is equivalent to "qr/./s". Thus
"\p{All}" is no longer synonymous with "\p{Any}", which continues to
match just the Unicode code points, as Unicode says it should.
Data::Dumper's output may change
Depending on the data structures dumped and the settings set for
Data::Dumper, the dumped output may have changed from previous
versions.
If you have tests that depend on the exact output of Data::Dumper, they
may fail.
To avoid this problem in your code, test against the data structure
from evaluating the dumped structure, instead of the dump itself.
Locale decimal point character no longer leaks outside of "use locale"
scope
This is actually a bug fix, but some code has come to rely on the bug
being present, so this change is listed here. The current locale that
the program is running under is not supposed to be visible to Perl code
except within the scope of a "use locale". However, until now under
certain circumstances, the character used for a decimal point (often a
comma) leaked outside the scope. If your code is affected by this
change, simply add a "use locale".
Assignments of Windows sockets error codes to $! now prefer errno.h values
over WSAGetLastError() values
In previous versions of Perl, Windows sockets error codes as returned
by WSAGetLastError() were assigned to $!, and some constants such as
ECONNABORTED, not in errno.h in VC++ (or the various Windows ports of
gcc) were defined to corresponding WSAE* values to allow $! to be
tested against the E* constants exported by Errno and POSIX.
This worked well until VC++ 2010 and later, which introduced new E*
constants with values > 100 into errno.h, including some being
(re)defined by perl to WSAE* values. That caused problems when linking
XS code against other libraries which used the original definitions of
errno.h constants.
To avoid this incompatibility, perl now maps WSAE* error codes to E*
values where possible, and assigns those values to $!. The E*
constants exported by Errno and POSIX are updated to match so that
testing $! against them, wherever previously possible, will continue to
work as expected, and all E* constants found in errno.h are now
exported from those modules with their original errno.h values.
In order to avoid breakage in existing Perl code which assigns WSAE*
values to $!, perl now intercepts the assignment and performs the same
mapping to E* values as it uses internally when assigning to $! itself.
However, one backwards-incompatibility remains: existing Perl code
which compares $! against the numeric values of the WSAE* error codes
that were previously assigned to $! will now be broken in those cases
where a corresponding E* value has been assigned instead. This is only
an issue for those E* values < 100, which were always exported from
Errno and POSIX with their original errno.h values, and therefore could
not be used for WSAE* error code tests (e.g. WSAEINVAL is 10022, but
the corresponding EINVAL is 22). (E* values > 100, if present, were
redefined to WSAE* values anyway, so compatibility can be achieved by
using the E* constants, which will work both before and after this
change, albeit using different numeric values under the hood.)
Functions "PerlIO_vsprintf" and "PerlIO_sprintf" have been removed
These two functions, undocumented, unused in CPAN, and problematic,
have been removed.
Deprecations
The "/\C/" character class
The "/\C/" regular expression character class is deprecated. From perl
5.22 onwards it will generate a warning, and from perl 5.24 onwards it
will be a regular expression compiler error. If you need to examine the
individual bytes that make up a UTF8-encoded character, then use
"utf8::encode()" on the string (or a copy) first.
Literal control characters in variable names
This deprecation affects things like $\cT, where \cT is a literal
control (such as a "NAK" or "NEGATIVE ACKNOWLEDGE" character) in the
source code. Surprisingly, it appears that originally this was
intended as the canonical way of accessing variables like $^T, with the
caret form only being added as an alternative.
The literal control form is being deprecated for two main reasons. It
has what are likely unfixable bugs, such as $\cI not working as an
alias for $^I, and their usage not being portable to non-ASCII
platforms: While $^T will work everywhere, \cT is whitespace in EBCDIC.
[perl #119123]
References to non-integers and non-positive integers in $/
Setting $/ to a reference to zero or a reference to a negative integer
is now deprecated, and will behave exactly as though it was set to
"undef". If you want slurp behavior set $/ to "undef" explicitly.
Setting $/ to a reference to a non integer is now forbidden and will
throw an error. Perl has never documented what would happen in this
context and while it used to behave the same as setting $/ to the
address of the references in future it may behave differently, so we
have forbidden this usage.
Character matching routines in POSIX
Use of any of these functions in the "POSIX" module is now deprecated:
"isalnum", "isalpha", "iscntrl", "isdigit", "isgraph", "islower",
"isprint", "ispunct", "isspace", "isupper", and "isxdigit". The
functions are buggy and don't work on UTF-8 encoded strings. See their
entries in POSIX for more information.
A warning is raised on the first call to any of them from each place in
the code that they are called. (Hence a repeated statement in a loop
will raise just the one warning.)
Interpreter-based threads are now discouraged
The "interpreter-based threads" provided by Perl are not the fast,
lightweight system for multitasking that one might expect or hope for.
Threads are implemented in a way that make them easy to misuse. Few
people know how to use them correctly or will be able to provide help.
The use of interpreter-based threads in perl is officially discouraged.
Module removals
The following modules will be removed from the core distribution in a
future release, and will at that time need to be installed from CPAN.
Distributions on CPAN which require these modules will need to list
them as prerequisites.
The core versions of these modules will now issue "deprecated"-category
warnings to alert you to this fact. To silence these deprecation
warnings, install the modules in question from CPAN.
Note that the planned removal of these modules from core does not
reflect a judgement about the quality of the code and should not be
taken as a suggestion that their use be halted. Their disinclusion
from core primarily hinges on their necessity to bootstrapping a fully
functional, CPAN-capable Perl installation, not on concerns over their
design.
CGI and its associated CGI:: packages
inc::latest
Package::Constants
Module::Build and its associated Module::Build:: packages
Utility removals
The following utilities will be removed from the core distribution in a
future release, and will at that time need to be installed from CPAN.
find2perl
s2p
a2p
Performance Enhancements
o Perl has a new copy-on-write mechanism that avoids the need to copy
the internal string buffer when assigning from one scalar to
another. This makes copying large strings appear much faster.
Modifying one of the two (or more) strings after an assignment will
force a copy internally. This makes it unnecessary to pass strings
by reference for efficiency.
This feature was already available in 5.18.0, but wasn't enabled by
default. It is the default now, and so you no longer need build
perl with the Configure argument:
-Accflags=-DPERL_NEW_COPY_ON_WRITE
It can be disabled (for now) in a perl build with:
-Accflags=-DPERL_NO_COW
On some operating systems Perl can be compiled in such a way that
any attempt to modify string buffers shared by multiple SVs will
crash. This way XS authors can test that their modules handle
copy-on-write scalars correctly. See "Copy on Write" in perlguts
for detail.
o Perl has an optimizer for regular expression patterns. It analyzes
the pattern to find things such as the minimum length a string has
to be to match, etc. It now better handles code points that are
above the Latin1 range.
o Executing a regex that contains the "^" anchor (or its variant
under the "/m" flag) has been made much faster in several
situations.
o Precomputed hash values are now used in more places during method
lookup.
o Constant hash key lookups ($hash{key} as opposed to $hash{$key})
have long had the internal hash value computed at compile time, to
speed up lookup. This optimisation has only now been applied to
hash slices as well.
o Combined "and" and "or" operators in void context, like those
generated for "unless ($a && $b)" and "if ($a || b)" now short
circuit directly to the end of the statement. [perl #120128]
o In certain situations, when "return" is the last statement in a
subroutine's main scope, it will be optimized out. This means code
like:
sub baz { return $cat; }
will now behave like:
sub baz { $cat; }
which is notably faster.
[perl #120765]
o Code like:
my $x; # or @x, %x
my $y;
is now optimized to:
my ($x, $y);
In combination with the padrange optimization introduced in
v5.18.0, this means longer uninitialized my variable statements are
also optimized, so:
my $x; my @y; my %z;
becomes:
my ($x, @y, %z);
[perl #121077]
o The creation of certain sorts of lists, including array and hash
slices, is now faster.
o The optimisation for arrays indexed with a small constant integer
is now applied for integers in the range -128..127, rather than
0..255. This should speed up Perl code using expressions like
$x[-1], at the expense of (presumably much rarer) code using
expressions like $x[200].
o The first iteration over a large hash (using "keys" or "each") is
now faster. This is achieved by preallocating the hash's internal
iterator state, rather than lazily creating it when the hash is
first iterated. (For small hashes, the iterator is still created
only when first needed. The assumption is that small hashes are
more likely to be used as objects, and therefore never allocated.
For large hashes, that's less likely to be true, and the cost of
allocating the iterator is swamped by the cost of allocating space
for the hash itself.)
o When doing a global regex match on a string that came from the
"readline" or "<>" operator, the data is no longer copied
unnecessarily. [perl #121259]
o Dereferencing (as in "$obj->[0]" or "$obj->{k}") is now faster when
$obj is an instance of a class that has overloaded methods, but
doesn't overload any of the dereferencing methods "@{}", "%{}", and
so on.
o Perl's optimiser no longer skips optimising code that follows
certain "eval {}" expressions (including those with an apparent
infinite loop).
o The implementation now does a better job of avoiding meaningless
work at runtime. Internal effect-free "null" operations (created as
a side-effect of parsing Perl programs) are normally deleted during
compilation. That deletion is now applied in some situations that
weren't previously handled.
o Perl now does less disk I/O when dealing with Unicode properties
that cover up to three ranges of consecutive code points.
Modules and Pragmata
New Modules and Pragmata
o experimental 0.007 has been added to the Perl core.
o IO::Socket::IP 0.29 has been added to the Perl core.
Updated Modules and Pragmata
o Archive::Tar has been upgraded from version 1.90 to 1.96.
o arybase has been upgraded from version 0.06 to 0.07.
o Attribute::Handlers has been upgraded from version 0.94 to 0.96.
o attributes has been upgraded from version 0.21 to 0.22.
o autodie has been upgraded from version 2.13 to 2.23.
o AutoLoader has been upgraded from version 5.73 to 5.74.
o autouse has been upgraded from version 1.07 to 1.08.
o B has been upgraded from version 1.42 to 1.48.
o B::Concise has been upgraded from version 0.95 to 0.992.
o B::Debug has been upgraded from version 1.18 to 1.19.
o B::Deparse has been upgraded from version 1.20 to 1.26.
o base has been upgraded from version 2.18 to 2.22.
o Benchmark has been upgraded from version 1.15 to 1.18.
o bignum has been upgraded from version 0.33 to 0.37.
o Carp has been upgraded from version 1.29 to 1.3301.
o CGI has been upgraded from version 3.63 to 3.65. NOTE: CGI is
deprecated and may be removed from a future version of Perl.
o charnames has been upgraded from version 1.36 to 1.40.
o Class::Struct has been upgraded from version 0.64 to 0.65.
o Compress::Raw::Bzip2 has been upgraded from version 2.060 to 2.064.
o Compress::Raw::Zlib has been upgraded from version 2.060 to 2.065.
o Config::Perl::V has been upgraded from version 0.17 to 0.20.
o constant has been upgraded from version 1.27 to 1.31.
o CPAN has been upgraded from version 2.00 to 2.05.
o CPAN::Meta has been upgraded from version 2.120921 to 2.140640.
o CPAN::Meta::Requirements has been upgraded from version 2.122 to
2.125.
o CPAN::Meta::YAML has been upgraded from version 0.008 to 0.012.
o Data::Dumper has been upgraded from version 2.145 to 2.151.
o DB has been upgraded from version 1.04 to 1.07.
o DB_File has been upgraded from version 1.827 to 1.831.
o DBM_Filter has been upgraded from version 0.05 to 0.06.
o deprecate has been upgraded from version 0.02 to 0.03.
o Devel::Peek has been upgraded from version 1.11 to 1.16.
o Devel::PPPort has been upgraded from version 3.20 to 3.21.
o diagnostics has been upgraded from version 1.31 to 1.34.
o Digest::MD5 has been upgraded from version 2.52 to 2.53.
o Digest::SHA has been upgraded from version 5.84 to 5.88.
o DynaLoader has been upgraded from version 1.18 to 1.25.
o Encode has been upgraded from version 2.49 to 2.60.
o encoding has been upgraded from version 2.6_01 to 2.12.
o English has been upgraded from version 1.06 to 1.09.
$OLD_PERL_VERSION was added as an alias of $].
o Errno has been upgraded from version 1.18 to 1.20_03.
o Exporter has been upgraded from version 5.68 to 5.70.
o ExtUtils::CBuilder has been upgraded from version 0.280210 to
0.280216.
o ExtUtils::Command has been upgraded from version 1.17 to 1.18.
o ExtUtils::Embed has been upgraded from version 1.30 to 1.32.
o ExtUtils::Install has been upgraded from version 1.59 to 1.67.
o ExtUtils::MakeMaker has been upgraded from version 6.66 to 6.98.
o ExtUtils::Miniperl has been upgraded from version to 1.01.
o ExtUtils::ParseXS has been upgraded from version 3.18 to 3.24.
o ExtUtils::Typemaps has been upgraded from version 3.19 to 3.24.
o ExtUtils::XSSymSet has been upgraded from version 1.2 to 1.3.
o feature has been upgraded from version 1.32 to 1.36.
o fields has been upgraded from version 2.16 to 2.17.
o File::Basename has been upgraded from version 2.84 to 2.85.
o File::Copy has been upgraded from version 2.26 to 2.29.
o File::DosGlob has been upgraded from version 1.10 to 1.12.
o File::Fetch has been upgraded from version 0.38 to 0.48.
o File::Find has been upgraded from version 1.23 to 1.27.
o File::Glob has been upgraded from version 1.20 to 1.23.
o File::Spec has been upgraded from version 3.40 to 3.47.
o File::Temp has been upgraded from version 0.23 to 0.2304.
o FileCache has been upgraded from version 1.08 to 1.09.
o Filter::Simple has been upgraded from version 0.89 to 0.91.
o Filter::Util::Call has been upgraded from version 1.45 to 1.49.
o Getopt::Long has been upgraded from version 2.39 to 2.42.
o Getopt::Std has been upgraded from version 1.07 to 1.10.
o Hash::Util::FieldHash has been upgraded from version 1.10 to 1.15.
o HTTP::Tiny has been upgraded from version 0.025 to 0.043.
o I18N::Langinfo has been upgraded from version 0.10 to 0.11.
o I18N::LangTags has been upgraded from version 0.39 to 0.40.
o if has been upgraded from version 0.0602 to 0.0603.
o inc::latest has been upgraded from version 0.4003 to 0.4205. NOTE:
inc::latest is deprecated and may be removed from a future version
of Perl.
o integer has been upgraded from version 1.00 to 1.01.
o IO has been upgraded from version 1.28 to 1.31.
o IO::Compress::Gzip and friends have been upgraded from version
2.060 to 2.064.
o IPC::Cmd has been upgraded from version 0.80 to 0.92.
o IPC::Open3 has been upgraded from version 1.13 to 1.16.
o IPC::SysV has been upgraded from version 2.03 to 2.04.
o JSON::PP has been upgraded from version 2.27202 to 2.27203.
o List::Util has been upgraded from version 1.27 to 1.38.
o locale has been upgraded from version 1.02 to 1.03.
o Locale::Codes has been upgraded from version 3.25 to 3.30.
o Locale::Maketext has been upgraded from version 1.23 to 1.25.
o Math::BigInt has been upgraded from version 1.9991 to 1.9993.
o Math::BigInt::FastCalc has been upgraded from version 0.30 to 0.31.
o Math::BigRat has been upgraded from version 0.2604 to 0.2606.
o MIME::Base64 has been upgraded from version 3.13 to 3.14.
o Module::Build has been upgraded from version 0.4003 to 0.4205.
NOTE: Module::Build is deprecated and may be removed from a future
version of Perl.
o Module::CoreList has been upgraded from version 2.89 to 3.10.
o Module::Load has been upgraded from version 0.24 to 0.32.
o Module::Load::Conditional has been upgraded from version 0.54 to
0.62.
o Module::Metadata has been upgraded from version 1.000011 to
1.000019.
o mro has been upgraded from version 1.11 to 1.16.
o Net::Ping has been upgraded from version 2.41 to 2.43.
o Opcode has been upgraded from version 1.25 to 1.27.
o Package::Constants has been upgraded from version 0.02 to 0.04.
NOTE: Package::Constants is deprecated and may be removed from a
future version of Perl.
o Params::Check has been upgraded from version 0.36 to 0.38.
o parent has been upgraded from version 0.225 to 0.228.
o Parse::CPAN::Meta has been upgraded from version 1.4404 to 1.4414.
o Perl::OSType has been upgraded from version 1.003 to 1.007.
o perlfaq has been upgraded from version 5.0150042 to 5.0150044.
o PerlIO has been upgraded from version 1.07 to 1.09.
o PerlIO::encoding has been upgraded from version 0.16 to 0.18.
o PerlIO::scalar has been upgraded from version 0.16 to 0.18.
o PerlIO::via has been upgraded from version 0.12 to 0.14.
o Pod::Escapes has been upgraded from version 1.04 to 1.06.
o Pod::Functions has been upgraded from version 1.06 to 1.08.
o Pod::Html has been upgraded from version 1.18 to 1.21.
o Pod::Parser has been upgraded from version 1.60 to 1.62.
o Pod::Perldoc has been upgraded from version 3.19 to 3.23.
o Pod::Usage has been upgraded from version 1.61 to 1.63.
o POSIX has been upgraded from version 1.32 to 1.38_03.
o re has been upgraded from version 0.23 to 0.26.
o Safe has been upgraded from version 2.35 to 2.37.
o Scalar::Util has been upgraded from version 1.27 to 1.38.
o SDBM_File has been upgraded from version 1.09 to 1.11.
o Socket has been upgraded from version 2.009 to 2.013.
o Storable has been upgraded from version 2.41 to 2.49.
o strict has been upgraded from version 1.07 to 1.08.
o subs has been upgraded from version 1.01 to 1.02.
o Sys::Hostname has been upgraded from version 1.17 to 1.18.
o Sys::Syslog has been upgraded from version 0.32 to 0.33.
o Term::Cap has been upgraded from version 1.13 to 1.15.
o Term::ReadLine has been upgraded from version 1.12 to 1.14.
o Test::Harness has been upgraded from version 3.26 to 3.30.
o Test::Simple has been upgraded from version 0.98 to 1.001002.
o Text::ParseWords has been upgraded from version 3.28 to 3.29.
o Text::Tabs has been upgraded from version 2012.0818 to 2013.0523.
o Text::Wrap has been upgraded from version 2012.0818 to 2013.0523.
o Thread has been upgraded from version 3.02 to 3.04.
o Thread::Queue has been upgraded from version 3.02 to 3.05.
o threads has been upgraded from version 1.86 to 1.93.
o threads::shared has been upgraded from version 1.43 to 1.46.
o Tie::Array has been upgraded from version 1.05 to 1.06.
o Tie::File has been upgraded from version 0.99 to 1.00.
o Tie::Hash has been upgraded from version 1.04 to 1.05.
o Tie::Scalar has been upgraded from version 1.02 to 1.03.
o Tie::StdHandle has been upgraded from version 4.3 to 4.4.
o Time::HiRes has been upgraded from version 1.9725 to 1.9726.
o Time::Piece has been upgraded from version 1.20_01 to 1.27.
o Unicode::Collate has been upgraded from version 0.97 to 1.04.
o Unicode::Normalize has been upgraded from version 1.16 to 1.17.
o Unicode::UCD has been upgraded from version 0.51 to 0.57.
o utf8 has been upgraded from version 1.10 to 1.13.
o version has been upgraded from version 0.9902 to 0.9908.
o vmsish has been upgraded from version 1.03 to 1.04.
o warnings has been upgraded from version 1.18 to 1.23.
o Win32 has been upgraded from version 0.47 to 0.49.
o XS::Typemap has been upgraded from version 0.10 to 0.13.
o XSLoader has been upgraded from version 0.16 to 0.17.
Documentation
New Documentation
perlrepository
This document was removed (actually, renamed perlgit and given a major
overhaul) in Perl v5.14, causing Perl documentation websites to show
the now out of date version in Perl v5.12 as the latest version. It
has now been restored in stub form, directing readers to current
information.
Changes to Existing Documentation
perldata
o New sections have been added to document the new index/value array
slice and key/value hash slice syntax.
perldebguts
o The "DB::goto" and "DB::lsub" debugger subroutines are now
documented. [perl #77680]
perlexperiment
o "\s" matching "\cK" is marked experimental.
o ithreads were accepted in v5.8.0 (but are discouraged as of
v5.20.0).
o Long doubles are not considered experimental.
o Code in regular expressions, regular expression backtracking verbs,
and lvalue subroutines are no longer listed as experimental. (This
also affects perlre and perlsub.)
perlfunc
o "chop" and "chomp" now note that they can reset the hash iterator.
o "exec"'s handling of arguments is now more clearly documented.
o "eval EXPR" now has caveats about expanding floating point numbers
in some locales.
o "goto EXPR" is now documented to handle an expression that evalutes
to a code reference as if it was "goto &$coderef". This behavior
is at least ten years old.
o Since Perl v5.10, it has been possible for subroutines in @INC to
return a reference to a scalar holding initial source code to
prepend to the file. This is now documented.
o The documentation of "ref" has been updated to recommend the use of
"blessed", "isa" and "reftype" when dealing with references to
blessed objects.
perlguts
o Numerous minor changes have been made to reflect changes made to
the perl internals in this release.
o New sections on Read-Only Values and Copy on Write have been added.
perlhack
o The Super Quick Patch Guide section has been updated.
perlhacktips
o The documentation has been updated to include some more examples of
"gdb" usage.
perllexwarn
o The perllexwarn documentation used to describe the hierarchy of
warning categories understood by the warnings pragma. That
description has now been moved to the warnings documentation
itself, leaving perllexwarn as a stub that points to it. This
change consolidates all documentation for lexical warnings in a
single place.
perllocale
o The documentation now mentions fc() and "\F", and includes many
clarifications and corrections in general.
perlop
o The language design of Perl has always called for monomorphic
operators. This is now mentioned explicitly.
perlopentut
o The "open" tutorial has been completely rewritten by Tom
Christiansen, and now focuses on covering only the basics, rather
than providing a comprehensive reference to all things openable.
This rewrite came as the result of a vigorous discussion on
perl5-porters kicked off by a set of improvements written by
Alexander Hartmaier to the existing perlopentut. A "more than you
ever wanted to know about "open"" document may follow in subsequent
versions of perl.
perlre
o The fact that the regexp engine makes no effort to call (?{}) and
(??{}) constructs any specified number of times (although it will
basically DWIM in case of a successful match) has been documented.
o The "/r" modifier (for non-destructive substitution) is now
documented. [perl #119151]
o The documentation for "/x" and "(?# comment)" has been expanded and
clarified.
perlreguts
o The documentation has been updated in the light of recent changes
to regcomp.c.
perlsub
o The need to predeclare recursive functions with prototypes in order
for the prototype to be honoured in the recursive call is now
documented. [perl #2726]
o A list of subroutine names used by the perl implementation is now
included. [perl #77680]
perltrap
o There is now a JavaScript section.
perlunicode
o The documentation has been updated to reflect "Bidi_Class" changes
in Unicode 6.3.
perlvar
o A new section explaining the performance issues of $`, $& and $',
including workarounds and changes in different versions of Perl,
has been added.
o Three English variable names which have long been documented but do
not actually exist have been removed from the documentation. These
were $OLD_PERL_VERSION, $OFMT, and $ARRAY_BASE.
(Actually, "OLD_PERL_VERSION" does exist, starting with this
revision, but remained undocumented until perl 5.22.0.)
perlxs
o Several problems in the "MY_CXT" example have been fixed.
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
o delete argument is index/value array slice, use array slice
(F) You used index/value array slice syntax (%array[...]) as the
argument to "delete". You probably meant @array[...] with an @
symbol instead.
o delete argument is key/value hash slice, use hash slice
(F) You used key/value hash slice syntax (%hash{...}) as the
argument to "delete". You probably meant @hash{...} with an @
symbol instead.
o Magical list constants are not supported
(F) You assigned a magical array to a stash element, and then tried
to use the subroutine from the same slot. You are asking Perl to
do something it cannot do, details subject to change between Perl
versions.
o Added Setting $/ to a %s reference is forbidden
New Warnings
o %s on reference is experimental:
The "auto-deref" feature is experimental.
Starting in v5.14.0, it was possible to use push, pop, keys, and
other built-in functions not only on aggregate types, but on
references to them. The feature was not deployed to its original
intended specification, and now may become redundant to postfix
dereferencing. It has always been categorized as an experimental
feature, and in v5.20.0 is carries a warning as such.
Warnings will now be issued at compile time when these operations
are detected.
no if $] >= 5.01908, warnings => "experimental::autoderef";
Consider, though, replacing the use of these features, as they may
change behavior again before becoming stable.
o A sequence of multiple spaces in a charnames alias definition is
deprecated
Trailing white-space in a charnames alias definition is deprecated
These two deprecation warnings involving "\N{...}" were incorrectly
implemented. They did not warn by default (now they do) and could
not be made fatal via "use warnings FATAL => 'deprecated'" (now
they can).
o Attribute prototype(%s) discards earlier prototype attribute in
same sub
(W misc) A sub was declared as "sub foo : prototype(A) :
prototype(B) {}", for example. Since each sub can only have one
prototype, the earlier declaration(s) are discarded while the last
one is applied.
o Invalid \0 character in %s for %s: %s\0%s
(W syscalls) Embedded \0 characters in pathnames or other system
call arguments produce a warning as of 5.20. The parts after the
\0 were formerly ignored by system calls.
o Matched non-Unicode code point 0x%X against Unicode property; may
not be portable.
This replaces the message "Code point 0x%X is not Unicode, all \p{}
matches fail; all \P{} matches succeed".
o Missing ']' in prototype for %s : %s
(W illegalproto) A grouping was started with "[" but never closed
with "]".
o Possible precedence issue with control flow operator
(W syntax) There is a possible problem with the mixing of a control
flow operator (e.g. "return") and a low-precedence operator like
"or". Consider:
sub { return $a or $b; }
This is parsed as:
sub { (return $a) or $b; }
Which is effectively just:
sub { return $a; }
Either use parentheses or the high-precedence variant of the
operator.
Note this may be also triggered for constructs like:
sub { 1 if die; }
o Postfix dereference is experimental
(S experimental::postderef) This warning is emitted if you use the
experimental postfix dereference syntax. Simply suppress the
warning if you want to use the feature, but know that in doing so
you are taking the risk of using an experimental feature which may
change or be removed in a future Perl version:
no warnings "experimental::postderef";
use feature "postderef", "postderef_qq";
$ref->$*;
$aref->@*;
$aref->@[@indices];
... etc ...
o Prototype '%s' overridden by attribute 'prototype(%s)' in %s
(W prototype) A prototype was declared in both the parentheses
after the sub name and via the prototype attribute. The prototype
in parentheses is useless, since it will be replaced by the
prototype from the attribute before it's ever used.
o Scalar value @%s[%s] better written as $%s[%s]
(W syntax) In scalar context, you've used an array index/value
slice (indicated by %) to select a single element of an array.
Generally it's better to ask for a scalar value (indicated by $).
The difference is that $foo[&bar] always behaves like a scalar,
both in the value it returns and when evaluating its argument,
while %foo[&bar] provides a list context to its subscript, which
can do weird things if you're expecting only one subscript. When
called in list context, it also returns the index (what &bar
returns) in addition to the value.
o Scalar value @%s{%s} better written as $%s{%s}
(W syntax) In scalar context, you've used a hash key/value slice
(indicated by %) to select a single element of a hash. Generally
it's better to ask for a scalar value (indicated by $). The
difference is that $foo{&bar} always behaves like a scalar, both in
the value it returns and when evaluating its argument, while
@foo{&bar} and provides a list context to its subscript, which can
do weird things if you're expecting only one subscript. When
called in list context, it also returns the key in addition to the
value.
o Setting $/ to a reference to %s as a form of slurp is deprecated,
treating as undef
o Unexpected exit %u
(S) exit() was called or the script otherwise finished gracefully
when "PERL_EXIT_WARN" was set in "PL_exit_flags".
o Unexpected exit failure %d
(S) An uncaught die() was called when "PERL_EXIT_WARN" was set in
"PL_exit_flags".
o Use of literal control characters in variable names is deprecated
(D deprecated) Using literal control characters in the source to
refer to the ^FOO variables, like $^X and ${^GLOBAL_PHASE} is now
deprecated. This only affects code like $\cT, where \cT is a
control (like a "SOH") in the source code: ${"\cT"} and $^T remain
valid.
o Useless use of greediness modifier
This fixes [Perl #42957].
Changes to Existing Diagnostics
o Warnings and errors from the regexp engine are now UTF-8 clean.
o The "Unknown switch condition" error message has some slight
changes. This error triggers when there is an unknown condition in
a "(?(foo))" conditional. The error message used to read:
Unknown switch condition (?(%s in regex;
But what %s could be was mostly up to luck. For "(?(foobar))", you
might have seen "fo" or "f". For Unicode characters, you would
generally get a corrupted string. The message has been changed to
read:
Unknown switch condition (?(...)) in regex;
Additionally, the '<-- HERE' marker in the error will now point to
the correct spot in the regex.
o The "%s "\x%X" does not map to Unicode" warning is now correctly
listed as a severe warning rather than as a fatal error.
o Under rare circumstances, one could get a "Can't coerce readonly
REF to string" instead of the customary "Modification of a read-
only value". This alternate error message has been removed.
o "Ambiguous use of * resolved as operator *": This and similar
warnings about "%" and "&" used to occur in some circumstances
where there was no operator of the type cited, so the warning was
completely wrong. This has been fixed [perl #117535, #76910].
o Warnings about malformed subroutine prototypes are now more
consistent in how the prototypes are rendered. Some of these
warnings would truncate prototypes containing nulls. In other
cases one warning would suppress another. The warning about
illegal characters in prototypes no longer says "after '_'" if the
bad character came before the underscore.
o Perl folding rules are not up-to-date for 0x%X; please use the
perlbug utility to report; in regex; marked by <-- HERE in m/%s/
This message is now only in the regexp category, and not in the
deprecated category. It is still a default (i.e., severe) warning
[perl #89648].
o %%s[%s] in scalar context better written as $%s[%s]
This warning now occurs for any %array[$index] or %hash{key} known
to be in scalar context at compile time. Previously it was worded
"Scalar value %%s[%s] better written as $%s[%s]".
o Switch condition not recognized in regex; marked by <-- HERE in
m/%s/:
The description for this diagnostic has been extended to cover all
cases where the warning may occur. Issues with the positioning of
the arrow indicator have also been resolved.
o The error messages for "my($a?$b$c)" and "my(do{})" now mention
"conditional expression" and "do block", respectively, instead of
reading 'Can't declare null operation in "my"'.
o When "use re "debug"" executes a regex containing a backreference,
the debugging output now shows what string is being matched.
o The now fatal error message "Character following "\c" must be
ASCII" has been reworded as "Character following "\c" must be
printable ASCII" to emphasize that in "\cX", X must be a printable
(non-control) ASCII character.
Utility Changes
a2p
o A possible crash from an off-by-one error when trying to access
before the beginning of a buffer has been fixed. [perl #120244]
bisect.pl
The git bisection tool Porting/bisect.pl has had many enhancements.
It is provided as part of the source distribution but not installed
because it is not self-contained as it relies on being run from within
a git checkout. Note also that it makes no attempt to fix tests,
correct runtime bugs or make something useful to install - its purpose
is to make minimal changes to get any historical revision of interest
to build and run as close as possible to "as-was", and thereby make
"git bisect" easy to use.
o Can optionally run the test case with a timeout.
o Can now run in-place in a clean git checkout.
o Can run the test case under "valgrind".
o Can apply user supplied patches and fixes to the source checkout
before building.
o Now has fixups to enable building several more historical ranges of
bleadperl, which can be useful for pinpointing the origins of bugs
or behaviour changes.
find2perl
o find2perl now handles "?" wildcards correctly. [perl #113054]
perlbug
o perlbug now has a "-p" option for attaching patches with a bug
report.
o perlbug has been modified to supply the report template with CRLF
line endings on Windows. [GH #13612]
<https://github.com/Perl/perl5/issues/13612>
o perlbug now makes as few assumptions as possible about the encoding
of the report. This will likely change in the future to assume
UTF-8 by default but allow a user override.
Configuration and Compilation
o The Makefile.PL for SDBM_File now generates a better Makefile,
which avoids a race condition during parallel makes, which could
cause the build to fail. This is the last known parallel make
problem (on *nix platforms), and therefore we believe that a
parallel make should now always be error free.
o installperl and installman's option handling has been refactored to
use Getopt::Long. Both are used by the Makefile "install" targets,
and are not installed, so these changes are only likely to affect
custom installation scripts.
o Single letter options now also have long names.
o Invalid options are now rejected.
o Command line arguments that are not options are now rejected.
o Each now has a "--help" option to display the usage message.
The behaviour for all valid documented invocations is unchanged.
o Where possible, the build now avoids recursive invocations of make
when building pure-Perl extensions, without removing any
parallelism from the build. Currently around 80 extensions can be
processed directly by the make_ext.pl tool, meaning that 80
invocations of make and 160 invocations of miniperl are no longer
made.
o The build system now works correctly when compiling under GCC or
Clang with link-time optimization enabled (the "-flto" option).
[perl #113022]
o Distinct library basenames with "d_libname_unique".
When compiling perl with this option, the library files for XS
modules are named something "unique" -- for example,
Hash/Util/Util.so becomes Hash/Util/PL_Hash__Util.so. This
behavior is similar to what currently happens on VMS, and serves as
groundwork for the Android port.
o "sysroot" option to indicate the logical root directory under gcc
and clang.
When building with this option set, both Configure and the
compilers search for all headers and libraries under this new
sysroot, instead of /.
This is a huge time saver if cross-compiling, but can also help on
native builds if your toolchain's files have non-standard
locations.
o The cross-compilation model has been renovated. There's several
new options, and some backwards-incompatible changes:
We now build binaries for miniperl and generate_uudmap to be used
on the host, rather than running every miniperl call on the target;
this means that, short of 'make test', we no longer need access to
the target system once Configure is done. You can provide already-
built binaries through the "hostperl" and "hostgenerate" options to
Configure.
Additionally, if targeting an EBCDIC platform from an ASCII host,
or viceversa, you'll need to run Configure with "-Uhostgenerate",
to indicate that generate_uudmap should be run on the target.
Finally, there's also a way of having Configure end early, right
after building the host binaries, by cross-compiling without
specifying a "targethost".
The incompatible changes include no longer using xconfig.h, xlib,
or Cross.pm, so canned config files and Makefiles will have to be
updated.
o Related to the above, there is now a way of specifying the location
of sh (or equivalent) on the target system: "targetsh".
For example, Android has its sh in /system/bin/sh, so if cross-
compiling from a more normal Unixy system with sh in /bin/sh,
"targetsh" would end up as /system/bin/sh, and "sh" as /bin/sh.
o By default, gcc 4.9 does some optimizations that break perl. The
-fwrapv option disables those optimizations (and probably others),
so for gcc 4.3 and later (since the there might be similar problems
lurking on older versions too, but -fwrapv was broken before 4.3,
and the optimizations probably won't go away), Configure now adds
-fwrapv unless the user requests -fno-wrapv, which disables
-fwrapv, or -fsanitize=undefined, which turns the overflows -fwrapv
ignores into runtime errors. [GH #13690]
<https://github.com/Perl/perl5/issues/13690>
Testing
o The "test.valgrind" make target now allows tests to be run in
parallel. This target allows Perl's test suite to be run under
Valgrind, which detects certain sorts of C programming errors,
though at significant cost in running time. On suitable hardware,
allowing parallel execution claws back a lot of that additional
cost. [perl #121431]
o Various tests in t/porting/ are no longer skipped when the perl
.git directory is outside the perl tree and pointed to by $GIT_DIR.
[perl #120505]
o The test suite no longer fails when the user's interactive shell
maintains a $PWD environment variable, but the /bin/sh used for
running tests doesn't.
Platform Support
New Platforms
Android
Perl can now be built for Android, either natively or through
cross-compilation, for all three currently available architectures
(ARM, MIPS, and x86), on a wide range of versions.
Bitrig
Compile support has been added for Bitrig, a fork of OpenBSD.
FreeMiNT
Support has been added for FreeMiNT, a free open-source OS for the
Atari ST system and its successors, based on the original MiNT that
was officially adopted by Atari.
Synology
Synology ships its NAS boxes with a lean Linux distribution (DSM)
on relative cheap CPU's (like the Marvell Kirkwood mv6282 -
ARMv5tel or Freescale QorIQ P1022 ppc - e500v2) not meant for
workstations or development. These boxes should build now. The
basic problems are the non-standard location for tools.
Discontinued Platforms
"sfio"
Code related to supporting the "sfio" I/O system has been removed.
Perl 5.004 added support to use the native API of "sfio", AT&T's
Safe/Fast I/O library. This code still built with v5.8.0, albeit
with many regression tests failing, but was inadvertently broken
before the v5.8.1 release, meaning that it has not worked on any
version of Perl released since then. In over a decade we have
received no bug reports about this, hence it is clear that no-one
is using this functionality on any version of Perl that is still
supported to any degree.
AT&T 3b1
Configure support for the 3b1, also known as the AT&T Unix PC (and
the similar AT&T 7300), has been removed.
DG/UX
DG/UX was a Unix sold by Data General. The last release was in
April 2001. It only runs on Data General's own hardware.
EBCDIC
In the absence of a regular source of smoke reports, code intended
to support native EBCDIC platforms will be removed from perl before
5.22.0.
Platform-Specific Notes
Cygwin
o recv() on a connected handle would populate the returned sender
address with whatever happened to be in the working buffer.
recv() now uses a workaround similar to the Win32 recv()
wrapper and returns an empty string when recvfrom(2) doesn't
modify the supplied address length. [perl #118843]
o Fixed a build error in cygwin.c on Cygwin 1.7.28.
Tests now handle the errors that occur when "cygserver" isn't
running.
GNU/Hurd
The BSD compatibility library "libbsd" is no longer required for
builds.
Linux
The hints file now looks for "libgdbm_compat" only if "libgdbm"
itself is also wanted. The former is never useful without the
latter, and in some circumstances, including it could actually
prevent building.
Mac OS
The build system now honors an "ld" setting supplied by the user
running Configure.
MidnightBSD
"objformat" was removed from version 0.4-RELEASE of MidnightBSD and
had been deprecated on earlier versions. This caused the build
environment to be erroneously configured for "a.out" rather than
"elf". This has been now been corrected.
Mixed-endian platforms
The code supporting "pack" and "unpack" operations on mixed endian
platforms has been removed. We believe that Perl has long been
unable to build on mixed endian architectures (such as PDP-11s), so
we don't think that this change will affect any platforms which
were able to build v5.18.0.
VMS
o The "PERL_ENV_TABLES" feature to control the population of %ENV
at perl start-up was broken in Perl 5.16.0 but has now been
fixed.
o Skip access checks on remotes in opendir(). [perl #121002]
o A check for glob metacharacters in a path returned by the
"glob()" operator has been replaced with a check for VMS
wildcard characters. This saves a significant number of
unnecessary "lstat()" calls such that some simple glob
operations become 60-80% faster.
Win32
o "rename" and "link" on Win32 now set $! to ENOSPC and EDQUOT
when appropriate. [perl #119857]
o The BUILD_STATIC and ALL_STATIC makefile options for linking
some or (nearly) all extensions statically (into perl520.dll,
and into a separate perl-static.exe too) were broken for MinGW
builds. This has now been fixed.
The ALL_STATIC option has also been improved to include the
Encode and Win32 extensions (for both VC++ and MinGW builds).
o Support for building with Visual C++ 2013 has been added.
There are currently two possible test failures (see "Testing
Perl on Windows" in perlwin32) which will hopefully be resolved
soon.
o Experimental support for building with Intel C++ Compiler has
been added. The nmake makefile (win32/Makefile) and the dmake
makefile (win32/makefile.mk) can be used. A "nmake test" will
not pass at this time due to cpan/CGI/t/url.t.
o Killing a process tree with "kill" in perlfunc and a negative
signal, was broken starting in 5.18.0. In this bug, "kill"
always returned 0 for a negative signal even for valid PIDs,
and no processes were terminated. This has been fixed [perl
#121230].
o The time taken to build perl on Windows has been reduced quite
significantly (time savings in the region of 30-40% are
typically seen) by reducing the number of, usually failing, I/O
calls for each "require()" (for miniperl.exe only). [GH
#13566] <https://github.com/Perl/perl5/issues/13566>
o About 15 minutes of idle sleeping was removed from running
"make test" due to a bug in which the timeout monitor used for
tests could not be cancelled once the test completes, and the
full timeout period elapsed before running the next test file.
[GH #13647] <https://github.com/Perl/perl5/issues/13647>
o On a perl built without pseudo-fork (pseudo-fork builds were
not affected by this bug), killing a process tree with "kill()"
and a negative signal resulted in "kill()" inverting the
returned value. For example, if "kill()" killed 1 process tree
PID then it returned 0 instead of 1, and if "kill()" was passed
2 invalid PIDs then it returned 2 instead of 0. This has
probably been the case since the process tree kill feature was
implemented on Win32. It has now been corrected to follow the
documented behaviour. [GH #13595]
<https://github.com/Perl/perl5/issues/13595>
o When building a 64-bit perl, an uninitialized memory read in
miniperl.exe, used during the build process, could lead to a
4GB wperl.exe being created. This has now been fixed. (Note
that perl.exe itself was unaffected, but obviously wperl.exe
would have been completely broken.) [GH #13677]
<https://github.com/Perl/perl5/issues/13677>
o Perl can now be built with gcc version 4.8.1 from
<http://www.mingw.org>. This was previously broken due to an
incorrect definition of DllMain() in one of perl's source
files. Earlier gcc versions were also affected when using
version 4 of the w32api package. Versions of gcc available
from <http://mingw-w64.sourceforge.net/> were not affected.
[GH #13733] <https://github.com/Perl/perl5/issues/13733>
o The test harness now has no failures when perl is built on a
FAT drive with the Windows OS on an NTFS drive. [GH #6348]
<https://github.com/Perl/perl5/issues/6348>
o When cloning the context stack in fork() emulation,
Perl_cx_dup() would crash accessing parameter information for
context stack entries that included no parameters, as with
"&foo;". [GH #13763]
<https://github.com/Perl/perl5/issues/13763>
o Introduced by [GH #12161]
<https://github.com/Perl/perl5/issues/12161>, a memory leak on
every call to "system" and backticks (" `` "), on most Win32
Perls starting from 5.18.0 has been fixed. The memory leak
only occurred if you enabled pseudo-fork in your build of Win32
Perl, and were running that build on Server 2003 R2 or newer
OS. The leak does not appear on WinXP SP3. [GH #13741]
<https://github.com/Perl/perl5/issues/13741>
WinCE
o The building of XS modules has largely been restored. Several
still cannot (yet) be built but it is now possible to build
Perl on WinCE with only a couple of further patches (to Socket
and ExtUtils::MakeMaker), hopefully to be incorporated soon.
o Perl can now be built in one shot with no user intervention on
WinCE by running "nmake -f Makefile.ce all".
Support for building with EVC (Embedded Visual C++) 4 has been
restored. Perl can also be built using Smart Devices for
Visual C++ 2005 or 2008.
Internal Changes
o The internal representation has changed for the match variables $1,
$2 etc., $`, $&, $', ${^PREMATCH}, ${^MATCH} and ${^POSTMATCH}. It
uses slightly less memory, avoids string comparisons and numeric
conversions during lookup, and uses 23 fewer lines of C. This
change should not affect any external code.
o Arrays now use NULL internally to represent unused slots, instead
of &PL_sv_undef. &PL_sv_undef is no longer treated as a special
value, so av_store(av, 0, &PL_sv_undef) will cause element 0 of
that array to hold a read-only undefined scalar. "$array[0] =
anything" will croak and "\$array[0]" will compare equal to
"\undef".
o The SV returned by HeSVKEY_force() now correctly reflects the
UTF8ness of the underlying hash key when that key is not stored as
a SV. [perl #79074]
o Certain rarely used functions and macros available to XS code are
now deprecated. These are: "utf8_to_uvuni_buf" (use
"utf8_to_uvchr_buf" instead), "valid_utf8_to_uvuni" (use
"utf8_to_uvchr_buf" instead), "NATIVE_TO_NEED" (this did not work
properly anyway), and "ASCII_TO_NEED" (this did not work properly
anyway).
Starting in this release, almost never does application code need
to distinguish between the platform's character set and Latin1, on
which the lowest 256 characters of Unicode are based. New code
should not use "utf8n_to_uvuni" (use "utf8_to_uvchr_buf" instead),
nor "uvuni_to_utf8" (use "uvchr_to_utf8" instead),
o The Makefile shortcut targets for many rarely (or never) used
testing and profiling targets have been removed, or merged into the
only other Makefile target that uses them. Specifically, these
targets are gone, along with documentation that referenced them or
explained how to use them:
check.third check.utf16 check.utf8 coretest minitest.prep
minitest.utf16 perl.config.dashg perl.config.dashpg
perl.config.gcov perl.gcov perl.gprof perl.gprof.config
perl.pixie perl.pixie.atom perl.pixie.config perl.pixie.irix
perl.third perl.third.config perl.valgrind.config purecovperl
pureperl quantperl test.deparse test.taintwarn test.third
test.torture test.utf16 test.utf8 test_notty.deparse
test_notty.third test_notty.valgrind test_prep.third
test_prep.valgrind torturetest ucheck ucheck.third ucheck.utf16
ucheck.valgrind utest utest.third utest.utf16 utest.valgrind
It's still possible to run the relevant commands by "hand" - no
underlying functionality has been removed.
o It is now possible to keep Perl from initializing locale handling.
For the most part, Perl doesn't pay attention to locale. (See
perllocale.) Nonetheless, until now, on startup, it has always
initialized locale handling to the system default, just in case the
program being executed ends up using locales. (This is one of the
first things a locale-aware program should do, long before Perl
knows if it will actually be needed or not.) This works well
except when Perl is embedded in another application which wants a
locale that isn't the system default. Now, if the environment
variable "PERL_SKIP_LOCALE_INIT" is set at the time Perl is
started, this initialization step is skipped. Prior to this, on
Windows platforms, the only workaround for this deficiency was to
use a hacked-up copy of internal Perl code. Applications that need
to use older Perls can discover if the embedded Perl they are using
needs the workaround by testing that the C preprocessor symbol
"HAS_SKIP_LOCALE_INIT" is not defined. [RT #38193]
o "BmRARE" and "BmPREVIOUS" have been removed. They were not used
anywhere and are not part of the API. For XS modules, they are now
#defined as 0.
o "sv_force_normal", which usually croaks on read-only values, used
to allow read-only values to be modified at compile time. This has
been changed to croak on read-only values regardless. This change
uncovered several core bugs.
o Perl's new copy-on-write mechanism (which is now enabled by
default), allows any "SvPOK" scalar to be automatically upgraded to
a copy-on-write scalar when copied. A reference count on the string
buffer is stored in the string buffer itself.
For example:
$ perl -MDevel::Peek -e'$a="abc"; $b = $a; Dump $a; Dump $b'
SV = PV(0x260cd80) at 0x2620ad8
REFCNT = 1
FLAGS = (POK,IsCOW,pPOK)
PV = 0x2619bc0 "abc"\0
CUR = 3
LEN = 16
COW_REFCNT = 1
SV = PV(0x260ce30) at 0x2620b20
REFCNT = 1
FLAGS = (POK,IsCOW,pPOK)
PV = 0x2619bc0 "abc"\0
CUR = 3
LEN = 16
COW_REFCNT = 1
Note that both scalars share the same PV buffer and have a
COW_REFCNT greater than zero.
This means that XS code which wishes to modify the "SvPVX()" buffer
of an SV should call "SvPV_force()" or similar first, to ensure a
valid (and unshared) buffer, and to call "SvSETMAGIC()" afterwards.
This in fact has always been the case (for example hash keys were
already copy-on-write); this change just spreads the COW behaviour
to a wider variety of SVs.
One important difference is that before 5.18.0, shared hash-key
scalars used to have the "SvREADONLY" flag set; this is no longer
the case.
This new behaviour can still be disabled by running Configure with
-Accflags=-DPERL_NO_COW. This option will probably be removed in
Perl 5.22.
o "PL_sawampersand" is now a constant. The switch this variable
provided (to enable/disable the pre-match copy depending on whether
$& had been seen) has been removed and replaced with copy-on-write,
eliminating a few bugs.
The previous behaviour can still be enabled by running Configure
with -Accflags=-DPERL_SAWAMPERSAND.
o The functions "my_swap", "my_htonl" and "my_ntohl" have been
removed. It is unclear why these functions were ever marked as A,
part of the API. XS code can't call them directly, as it can't rely
on them being compiled. Unsurprisingly, no code on CPAN references
them.
o The signature of the "Perl_re_intuit_start()" regex function has
changed; the function pointer "intuit" in the regex engine plugin
structure has also changed accordingly. A new parameter, "strbeg"
has been added; this has the same meaning as the same-named
parameter in "Perl_regexec_flags". Previously intuit would try to
guess the start of the string from the passed SV (if any), and
would sometimes get it wrong (e.g. with an overloaded SV).
o The signature of the "Perl_regexec_flags()" regex function has
changed; the function pointer "exec" in the regex engine plugin
structure has also changed to match. The "minend" parameter now
has type "SSize_t" to better support 64-bit systems.
o XS code may use various macros to change the case of a character or
code point (for example "toLOWER_utf8()"). Only a couple of these
were documented until now; and now they should be used in
preference to calling the underlying functions. See "Character
case changing" in perlapi.
o The code dealt rather inconsistently with uids and gids. Some
places assumed that they could be safely stored in UVs, others in
IVs, others in ints. Four new macros are introduced: SvUID(),
sv_setuid(), SvGID(), and sv_setgid()
o "sv_pos_b2u_flags" has been added to the API. It is similar to
"sv_pos_b2u", but supports long strings on 64-bit platforms.
o "PL_exit_flags" can now be used by perl embedders or other XS code
to have perl "warn" or "abort" on an attempted exit. [perl #52000]
o Compiling with "-Accflags=-PERL_BOOL_AS_CHAR" now allows C99 and
C++ compilers to emulate the aliasing of "bool" to "char" that perl
does for C89 compilers. [perl #120314]
o The "sv" argument in "sv_2pv_flags" in perlapi, "sv_2iv_flags" in
perlapi, "sv_2uv_flags" in perlapi, and "sv_2nv_flags" in perlapi
and their older wrappers sv_2pv, sv_2iv, sv_2uv, sv_2nv, is now
non-NULL. Passing NULL now will crash. When the non-NULL marker
was introduced en masse in 5.9.3 the functions were marked non-
NULL, but since the creation of the SV API in 5.0 alpha 2, if NULL
was passed, the functions returned 0 or false-type values. The code
that supports "sv" argument being non-NULL dates to 5.0 alpha 2
directly, and indirectly to Perl 1.0 (pre 5.0 api). The lack of
documentation that the functions accepted a NULL "sv" was corrected
in 5.11.0 and between 5.11.0 and 5.19.5 the functions were marked
NULLOK. As an optimization the NULLOK code has now been removed,
and the functions became non-NULL marked again, because core
getter-type macros never pass NULL to these functions and would
crash before ever passing NULL.
The only way a NULL "sv" can be passed to sv_2*v* functions is if
XS code directly calls sv_2*v*. This is unlikely as XS code uses
Sv*V* macros to get the underlying value out of the SV. One
possible situation which leads to a NULL "sv" being passed to
sv_2*v* functions, is if XS code defines its own getter type Sv*V*
macros, which check for NULL before dereferencing and checking the
SV's flags through public API Sv*OK* macros or directly using
private API "SvFLAGS", and if "sv" is NULL, then calling the sv_2*v
functions with a NULL literal or passing the "sv" containing a NULL
value.
o newATTRSUB is now a macro
The public API newATTRSUB was previously a macro to the private
function Perl_newATTRSUB. Function Perl_newATTRSUB has been
removed. newATTRSUB is now macro to a different internal function.
o Changes in warnings raised by "utf8n_to_uvchr()"
This bottom level function decodes the first character of a UTF-8
string into a code point. It is accessible to "XS" level code, but
it's discouraged from using it directly. There are higher level
functions that call this that should be used instead, such as
"utf8_to_uvchr_buf" in perlapi. For completeness though, this
documents some changes to it. Now, tests for malformations are
done before any tests for other potential issues. One of those
issues involves code points so large that they have never appeared
in any official standard (the current standard has scaled back the
highest acceptable code point from earlier versions). It is
possible (though not done in CPAN) to warn and/or forbid these code
points, while accepting smaller code points that are still above
the legal Unicode maximum. The warning message for this now
includes the code point if representable on the machine.
Previously it always displayed raw bytes, which is what it still
does for non-representable code points.
o Regexp engine changes that affect the pluggable regex engine
interface
Many flags that used to be exposed via regexp.h and used to
populate the extflags member of struct regexp have been removed.
These fields were technically private to Perl's own regexp engine
and should not have been exposed there in the first place.
The affected flags are:
RXf_NOSCAN
RXf_CANY_SEEN
RXf_GPOS_SEEN
RXf_GPOS_FLOAT
RXf_ANCH_BOL
RXf_ANCH_MBOL
RXf_ANCH_SBOL
RXf_ANCH_GPOS
As well as the follow flag masks:
RXf_ANCH_SINGLE
RXf_ANCH
All have been renamed to PREGf_ equivalents and moved to regcomp.h.
The behavior previously achieved by setting one or more of the
RXf_ANCH_ flags (via the RXf_ANCH mask) have now been replaced by a
*single* flag bit in extflags:
RXf_IS_ANCHORED
pluggable regex engines which previously used to set these flags
should now set this flag ALONE.
o The Perl core now consistently uses "av_tindex()" ("the top index
of an array") as a more clearly-named synonym for "av_len()".
o The obscure interpreter variable "PL_timesbuf" is expected to be
removed early in the 5.21.x development series, so that Perl 5.22.0
will not provide it to XS authors. While the variable still exists
in 5.20.0, we hope that this advance warning of the deprecation
will help anyone who is using that variable.
Selected Bug Fixes
Regular Expressions
o Fixed a small number of regexp constructions that could either fail
to match or crash perl when the string being matched against was
allocated above the 2GB line on 32-bit systems. [RT #118175]
o Various memory leaks involving the parsing of the "(?[...])"
regular expression construct have been fixed.
o "(?[...])" now allows interpolation of precompiled patterns
consisting of "(?[...])" with bracketed character classes inside
("$pat = qr/(?[ [a] ])/; /(?[ $pat ])/"). Formerly, the brackets
would confuse the regular expression parser.
o The "Quantifier unexpected on zero-length expression" warning
message could appear twice starting in Perl v5.10 for a regular
expression also containing alternations (e.g., "a|b") triggering
the trie optimisation.
o Perl v5.18 inadvertently introduced a bug whereby interpolating
mixed up- and down-graded UTF-8 strings in a regex could result in
malformed UTF-8 in the pattern: specifically if a downgraded
character in the range "\x80..\xff" followed a UTF-8 string, e.g.
utf8::upgrade( my $u = "\x{e5}");
utf8::downgrade(my $d = "\x{e5}");
/$u$d/
[RT #118297]
o In regular expressions containing multiple code blocks, the values
of $1, $2, etc., set by nested regular expression calls would leak
from one block to the next. Now these variables always refer to
the outer regular expression at the start of an embedded block
[perl #117917].
o "/$qr/p" was broken in Perl 5.18.0; the "/p" flag was ignored.
This has been fixed. [perl #118213]
o Starting in Perl 5.18.0, a construct like "/[#](?{})/x" would have
its "#" incorrectly interpreted as a comment. The code block would
be skipped, unparsed. This has been corrected.
o Starting in Perl 5.001, a regular expression like "/[#$a]/x" or
"/[#]$a/x" would have its "#" incorrectly interpreted as a comment,
so the variable would not interpolate. This has been corrected.
[perl #45667]
o Perl 5.18.0 inadvertently made dereferenced regular expressions
("${ qr// }") false as booleans. This has been fixed.
o The use of "\G" in regular expressions, where it's not at the start
of the pattern, is now slightly less buggy (although it is still
somewhat problematic).
o Where a regular expression included code blocks ("/(?{...})/"), and
where the use of constant overloading triggered a re-compilation of
the code block, the second compilation didn't see its outer lexical
scope. This was a regression in Perl 5.18.0.
o The string position set by "pos" could shift if the string changed
representation internally to or from utf8. This could happen,
e.g., with references to objects with string overloading.
o Taking references to the return values of two "pos" calls with the
same argument, and then assigning a reference to one and "undef" to
the other, could result in assertion failures or memory leaks.
o Elements of @- and @+ now update correctly when they refer to non-
existent captures. Previously, a referenced element ("$ref =
\$-[1]") could refer to the wrong match after subsequent matches.
o The code that parses regex backrefs (or ambiguous backref/octals)
such as \123 did a simple atoi(), which could wrap round to
negative values on long digit strings and cause segmentation
faults. This has now been fixed. [perl #119505]
o Assigning another typeglob to "*^R" no longer makes the regular
expression engine crash.
o The "\N" regular expression escape, when used without the curly
braces (to mean "[^\n]"), was ignoring a following "*" if followed
by whitespace under /x. It had been this way since "\N" to mean
"[^\n]" was introduced in 5.12.0.
o "s///", "tr///" and "y///" now work when a wide character is used
as the delimiter. [perl #120463]
o Some cases of unterminated (?...) sequences in regular expressions
(e.g., "/(?</") have been fixed to produce the proper error message
instead of "panic: memory wrap". Other cases (e.g., "/(?(/") have
yet to be fixed.
o When a reference to a reference to an overloaded object was
returned from a regular expression "(??{...})" code block, an
incorrect implicit dereference could take place if the inner
reference had been returned by a code block previously.
o A tied variable returned from "(??{...})" sees the inner values of
match variables (i.e., the $1 etc. from any matches inside the
block) in its FETCH method. This was not the case if a reference
to an overloaded object was the last thing assigned to the tied
variable. Instead, the match variables referred to the outer
pattern during the FETCH call.
o Fix unexpected tainting via regexp using locale. Previously, under
certain conditions, the use of character classes could cause
tainting when it shouldn't. Some character classes are locale-
dependent, but before this patch, sometimes tainting was happening
even for character classes that don't depend on the locale. [perl
#120675]
o Under certain conditions, Perl would throw an error if in a
lookbehind assertion in a regexp, the assertion referred to a named
subpattern, complaining the lookbehind was variable when it wasn't.
This has been fixed. [perl #120600], [perl #120618]. The current
fix may be improved on in the future.
o $^R wasn't available outside of the regular expression that
initialized it. [perl #121070]
o A large set of fixes and refactoring for re_intuit_start() was
merged, the highlights are:
o Fixed a panic when compiling the regular expression
"/\x{100}[xy]\x{100}{2}/".
o Fixed a performance regression when performing a global pattern
match against a UTF-8 string. [perl #120692]
o Fixed another performance issue where matching a regular
expression like "/ab.{1,2}x/" against a long UTF-8 string would
unnecessarily calculate byte offsets for a large portion of the
string. [perl #120692]
o Fixed an alignment error when compiling regular expressions when
built with GCC on HP-UX 64-bit.
o On 64-bit platforms "pos" can now be set to a value higher than
2**31-1. [perl #72766]
Perl 5 Debugger and -d
o The debugger's "man" command been fixed. It was broken in the
v5.18.0 release. The "man" command is aliased to the names "doc"
and "perldoc" - all now work again.
o @_ is now correctly visible in the debugger, fixing a regression
introduced in v5.18.0's debugger. [RT #118169]
o Under copy-on-write builds (the default as of 5.20.0)
"${'_<-e'}[0]" no longer gets mangled. This is the first line of
input saved for the debugger's use for one-liners [perl #118627].
o On non-threaded builds, setting "${"_<filename"}" to a reference or
typeglob no longer causes "__FILE__" and some error messages to
produce a corrupt string, and no longer prevents "#line" directives
in string evals from providing the source lines to the debugger.
Threaded builds were unaffected.
o Starting with Perl 5.12, line numbers were off by one if the -d
switch was used on the #! line. Now they are correct.
o "*DB::DB = sub {} if 0" no longer stops Perl's debugging mode from
finding "DB::DB" subs declared thereafter.
o "%{'_<...'}" hashes now set breakpoints on the corresponding
"@{'_<...'}" rather than whichever array @DB::dbline is aliased to.
[perl #119799]
o Call set-magic when setting $DB::sub. [perl #121255]
o The debugger's "n" command now respects lvalue subroutines and
steps over them [perl #118839].
Lexical Subroutines
o Lexical constants ("my sub a() { 42 }") no longer crash when
inlined.
o Parameter prototypes attached to lexical subroutines are now
respected when compiling sub calls without parentheses.
Previously, the prototypes were honoured only for calls with
parentheses. [RT #116735]
o Syntax errors in lexical subroutines in combination with calls to
the same subroutines no longer cause crashes at compile time.
o Deep recursion warnings no longer crash lexical subroutines. [RT
#118521]
o The dtrace sub-entry probe now works with lexical subs, instead of
crashing [perl #118305].
o Undefining an inlinable lexical subroutine ("my sub foo() { 42 }
undef &foo") would result in a crash if warnings were turned on.
o An undefined lexical sub used as an inherited method no longer
crashes.
o The presence of a lexical sub named "CORE" no longer stops the
CORE:: prefix from working.
Everything Else
o The OP allocation code now returns correctly aligned memory in all
cases for "struct pmop". Previously it could return memory only
aligned to a 4-byte boundary, which is not correct for an ithreads
build with 64 bit IVs on some 32 bit platforms. Notably, this
caused the build to fail completely on sparc GNU/Linux. [RT
#118055]
o Evaluating large hashes in scalar context is now much faster, as
the number of used chains in the hash is now cached for larger
hashes. Smaller hashes continue not to store it and calculate it
when needed, as this saves one IV. That would be 1 IV overhead for
every object built from a hash. [RT #114576]
o Perl v5.16 inadvertently introduced a bug whereby calls to XSUBs
that were not visible at compile time were treated as lvalues and
could be assigned to, even when the subroutine was not an lvalue
sub. This has been fixed. [RT #117947]
o In Perl v5.18.0 dualvars that had an empty string for the string
part but a non-zero number for the number part starting being
treated as true. In previous versions they were treated as false,
the string representation taking precedence. The old behaviour has
been restored. [RT #118159]
o Since Perl v5.12, inlining of constants that override built-in
keywords of the same name had countermanded "use subs", causing
subsequent mentions of the constant to use the built-in keyword
instead. This has been fixed.
o The warning produced by "-l $handle" now applies to IO refs and
globs, not just to glob refs. That warning is also now UTF8-clean.
[RT #117595]
o "delete local $ENV{nonexistent_env_var}" no longer leaks memory.
o "sort" and "require" followed by a keyword prefixed with "CORE::"
now treat it as a keyword, and not as a subroutine or module name.
[RT #24482]
o Through certain conundrums, it is possible to cause the current
package to be freed. Certain operators ("bless", "reset", "open",
"eval") could not cope and would crash. They have been made more
resilient. [RT #117941]
o Aliasing filehandles through glob-to-glob assignment would not
update internal method caches properly if a package of the same
name as the filehandle existed, resulting in filehandle method
calls going to the package instead. This has been fixed.
o "./Configure -de -Dusevendorprefix" didn't default. [RT #64126]
o The "Statement unlikely to be reached" warning was listed in
perldiag as an "exec"-category warning, but was enabled and
disabled by the "syntax" category. On the other hand, the "exec"
category controlled its fatal-ness. It is now entirely handled by
the "exec" category.
o The "Replacement list is longer that search list" warning for
"tr///" and "y///" no longer occurs in the presence of the "/c"
flag. [RT #118047]
o Stringification of NVs are not cached so that the lexical locale
controls stringification of the decimal point. [perl #108378] [perl
#115800]
o There have been several fixes related to Perl's handling of
locales. perl #38193 was described above in "Internal Changes".
Also fixed is #118197, where the radix (decimal point) character
had to be an ASCII character (which doesn't work for some non-
Western languages); and #115808, in which "POSIX::setlocale()" on
failure returned an "undef" which didn't warn about not being
defined even if those warnings were enabled.
o Compiling a "split" operator whose third argument is a named
constant evaluating to 0 no longer causes the constant's value to
change.
o A named constant used as the second argument to "index" no longer
gets coerced to a string if it is a reference, regular expression,
dualvar, etc.
o A named constant evaluating to the undefined value used as the
second argument to "index" no longer produces "uninitialized"
warnings at compile time. It will still produce them at run time.
o When a scalar was returned from a subroutine in @INC, the
referenced scalar was magically converted into an IO thingy,
possibly resulting in "Bizarre copy" errors if that scalar
continued to be used elsewhere. Now Perl uses an internal copy of
the scalar instead.
o Certain uses of the "sort" operator are optimised to modify an
array in place, such as "@a = sort @a". During the sorting, the
array is made read-only. If a sort block should happen to die,
then the array remained read-only even outside the "sort". This
has been fixed.
o $a and $b inside a sort block are aliased to the actual arguments
to "sort", so they can be modified through those two variables.
This did not always work, e.g., for lvalue subs and $#ary, and
probably many other operators. It works now.
o The arguments to "sort" are now all in list context. If the "sort"
itself were called in void or scalar context, then some, but not
all, of the arguments used to be in void or scalar context.
o Subroutine prototypes with Unicode characters above U+00FF were
getting mangled during closure cloning. This would happen with
subroutines closing over lexical variables declared outside, and
with lexical subs.
o "UNIVERSAL::can" now treats its first argument the same way that
method calls do: Typeglobs and glob references with non-empty IO
slots are treated as handles, and strings are treated as
filehandles, rather than packages, if a handle with that name
exists [perl #113932].
o Method calls on typeglobs (e.g., "*ARGV->getline") used to
stringify the typeglob and then look it up again. Combined with
changes in Perl 5.18.0, this allowed "*foo->bar" to call methods on
the "foo" package (like "foo->bar"). In some cases it could cause
the method to be called on the wrong handle. Now a typeglob
argument is treated as a handle (just like "(\*foo)->bar"), or, if
its IO slot is empty, an error is raised.
o Assigning a vstring to a tied variable or to a subroutine argument
aliased to a nonexistent hash or array element now works, without
flattening the vstring into a regular string.
o "pos", "tie", "tied" and "untie" did not work properly on
subroutine arguments aliased to nonexistent hash and array elements
[perl #77814, #27010].
o The "=>" fat arrow operator can now quote built-in keywords even if
it occurs on the next line, making it consistent with how it treats
other barewords.
o Autovivifying a subroutine stub via "\&$glob" started causing
crashes in Perl 5.18.0 if the $glob was merely a copy of a real
glob, i.e., a scalar that had had a glob assigned to it. This has
been fixed. [perl #119051]
o Perl used to leak an implementation detail when it came to
referencing the return values of certain operators. "for ($a+$b) {
warn \$_; warn \$_ }" used to display two different memory
addresses, because the "\" operator was copying the variable.
Under threaded builds, it would also happen for constants ("for(1)
{ ... }"). This has been fixed. [perl #21979, #78194, #89188,
#109746, #114838, #115388]
o The range operator ".." was returning the same modifiable scalars
with each call, unless it was the only thing in a "foreach" loop
header. This meant that changes to values within the list returned
would be visible the next time the operator was executed. [perl
#3105]
o Constant folding and subroutine inlining no longer cause operations
that would normally return new modifiable scalars to return read-
only values instead.
o Closures of the form "sub () { $some_variable }" are no longer
inlined, causing changes to the variable to be ignored by callers
of the subroutine. [perl #79908]
o Return values of certain operators such as "ref" would sometimes be
shared between recursive calls to the same subroutine, causing the
inner call to modify the value returned by "ref" in the outer call.
This has been fixed.
o "__PACKAGE__" and constants returning a package name or hash key
are now consistently read-only. In various previous Perl releases,
they have become mutable under certain circumstances.
o Enabling "used once" warnings no longer causes crashes on stash
circularities created at compile time ("*Foo::Bar::Foo:: =
*Foo::").
o Undef constants used in hash keys ("use constant u => undef;
$h{+u}") no longer produce "uninitialized" warnings at compile
time.
o Modifying a substitution target inside the substitution replacement
no longer causes crashes.
o The first statement inside a string eval used to use the wrong
pragma setting sometimes during constant folding. "eval 'uc chr
0xe0'" would randomly choose between Unicode, byte, and locale
semantics. This has been fixed.
o The handling of return values of @INC filters (subroutines returned
by subroutines in @INC) has been fixed in various ways. Previously
tied variables were mishandled, and setting $_ to a reference or
typeglob could result in crashes.
o The "SvPVbyte" XS function has been fixed to work with tied scalars
returning something other than a string. It used to return utf8 in
those cases where "SvPV" would.
o Perl 5.18.0 inadvertently made "--" and "++" crash on dereferenced
regular expressions, and stopped "++" from flattening vstrings.
o "bless" no longer dies with "Can't bless non-reference value" if
its first argument is a tied reference.
o "reset" with an argument no longer skips copy-on-write scalars,
regular expressions, typeglob copies, and vstrings. Also, when
encountering those or read-only values, it no longer skips any
array or hash with the same name.
o "reset" with an argument now skips scalars aliased to typeglobs
("for $z (*foo) { reset "z" }"). Previously it would corrupt
memory or crash.
o "ucfirst" and "lcfirst" were not respecting the bytes pragma. This
was a regression from Perl 5.12. [perl #117355]
o Changes to "UNIVERSAL::DESTROY" now update DESTROY caches in all
classes, instead of causing classes that have already had objects
destroyed to continue using the old sub. This was a regression in
Perl 5.18. [perl #114864]
o All known false-positive occurrences of the deprecation warning
"Useless use of '\'; doesn't escape metacharacter '%c'", added in
Perl 5.18.0, have been removed. [perl #119101]
o The value of $^E is now saved across signal handlers on Windows.
[perl #85104]
o A lexical filehandle (as in "open my $fh...") is usually given a
name based on the current package and the name of the variable,
e.g. "main::$fh". Under recursion, the filehandle was losing the
"$fh" part of the name. This has been fixed.
o Uninitialized values returned by XSUBs are no longer exempt from
uninitialized warnings. [perl #118693]
o "elsif ("")" no longer erroneously produces a warning about void
context. [perl #118753]
o Passing "undef" to a subroutine now causes @_ to contain the same
read-only undefined scalar that "undef" returns. Furthermore,
"exists $_[0]" will now return true if "undef" was the first
argument. [perl #7508, #109726]
o Passing a non-existent array element to a subroutine does not
usually autovivify it unless the subroutine modifies its argument.
This did not work correctly with negative indices and with non-
existent elements within the array. The element would be vivified
immediately. The delayed vivification has been extended to work
with those. [perl #118691]
o Assigning references or globs to the scalar returned by $#foo after
the @foo array has been freed no longer causes assertion failures
on debugging builds and memory leaks on regular builds.
o On 64-bit platforms, large ranges like 1..1000000000000 no longer
crash, but eat up all your memory instead. [perl #119161]
o "__DATA__" now puts the "DATA" handle in the right package, even if
the current package has been renamed through glob assignment.
o When "die", "last", "next", "redo", "goto" and "exit" unwind the
scope, it is possible for "DESTROY" recursively to call a
subroutine or format that is currently being exited. It that case,
sometimes the lexical variables inside the sub would start out
having values from the outer call, instead of being undefined as
they should. This has been fixed. [perl #119311]
o ${^MPEN} is no longer treated as a synonym for ${^MATCH}.
o Perl now tries a little harder to return the correct line number in
"(caller)[2]". [perl #115768]
o Line numbers inside multiline quote-like operators are now reported
correctly. [perl #3643]
o "#line" directives inside code embedded in quote-like operators are
now respected.
o Line numbers are now correct inside the second here-doc when two
here-doc markers occur on the same line.
o An optimization in Perl 5.18 made incorrect assumptions causing a
bad interaction with the Devel::CallParser CPAN module. If the
module was loaded then lexical variables declared in separate
statements following a "my(...)" list might fail to be cleared on
scope exit.
o &xsub and "goto &xsub" calls now allow the called subroutine to
autovivify elements of @_.
o &xsub and "goto &xsub" no longer crash if *_ has been undefined and
has no ARRAY entry (i.e. @_ does not exist).
o &xsub and "goto &xsub" now work with tied @_.
o Overlong identifiers no longer cause a buffer overflow (and a
crash). They started doing so in Perl 5.18.
o The warning "Scalar value @hash{foo} better written as $hash{foo}"
now produces far fewer false positives. In particular,
@hash{+function_returning_a_list} and @hash{ qw "foo bar baz" } no
longer warn. The same applies to array slices. [perl #28380,
#114024]
o "$! = EINVAL; waitpid(0, WNOHANG);" no longer goes into an internal
infinite loop. [perl #85228]
o A possible segmentation fault in filehandle duplication has been
fixed.
o A subroutine in @INC can return a reference to a scalar containing
the initial contents of the file. However, that scalar was freed
prematurely if not referenced elsewhere, giving random results.
o "last" no longer returns values that the same statement has
accumulated so far, fixing amongst other things the long-standing
bug that "push @a, last" would try to return the @a, copying it
like a scalar in the process and resulting in the error, "Bizarre
copy of ARRAY in last." [perl #3112]
o In some cases, closing file handles opened to pipe to or from a
process, which had been duplicated into a standard handle, would
call perl's internal waitpid wrapper with a pid of zero. With the
fix for [perl #85228] this zero pid was passed to "waitpid",
possibly blocking the process. This wait for process zero no
longer occurs. [perl #119893]
o "select" used to ignore magic on the fourth (timeout) argument,
leading to effects such as "select" blocking indefinitely rather
than the expected sleep time. This has now been fixed. [perl
#120102]
o The class name in "for my class $foo" is now parsed correctly. In
the case of the second character of the class name being followed
by a digit (e.g. 'a1b') this used to give the error "Missing $ on
loop variable". [perl #120112]
o Perl 5.18.0 accidentally disallowed "-bareword" under "use strict"
and "use integer". This has been fixed. [perl #120288]
o "-a" at the start of a line (or a hyphen with any single letter
that is not a filetest operator) no longer produces an erroneous
'Use of "-a" without parentheses is ambiguous' warning. [perl
#120288]
o Lvalue context is now properly propagated into bare blocks and "if"
and "else" blocks in lvalue subroutines. Previously, arrays and
hashes would sometimes incorrectly be flattened when returned in
lvalue list context, or "Bizarre copy" errors could occur. [perl
#119797]
o Lvalue context is now propagated to the branches of "||" and "&&"
(and their alphabetic equivalents, "or" and "and"). This means
"foreach (pos $x || pos $y) {...}" now allows "pos" to be modified
through $_.
o "stat" and "readline" remember the last handle used; the former for
the special "_" filehandle, the latter for "${^LAST_FH}". "eval
"*foo if 0"" where *foo was the last handle passed to "stat" or
"readline" could cause that handle to be forgotten if the handle
were not opened yet. This has been fixed.
o Various cases of "delete $::{a}", "delete $::{ENV}" etc. causing a
crash have been fixed. [perl #54044]
o Setting $! to EACCESS before calling "require" could affect
"require"'s behaviour. This has been fixed.
o The "Can't use \1 to mean $1 in expression" warning message now
only occurs on the right-hand (replacement) part of a substitution.
Formerly it could happen in code embedded in the left-hand side, or
in any other quote-like operator.
o Blessing into a reference ("bless $thisref, $thatref") has long
been disallowed, but magical scalars for the second like $/ and
those tied were exempt. They no longer are. [perl #119809]
o Blessing into a reference was accidentally allowed in 5.18 if the
class argument were a blessed reference with stale method caches
(i.e., whose class had had subs defined since the last method
call). They are disallowed once more, as in 5.16.
o "$x->{key}" where $x was declared as "my Class $x" no longer
crashes if a Class::FIELDS subroutine stub has been declared.
o @$obj{'key'} and "${$obj}{key}" used to be exempt from compile-time
field checking ("No such class field"; see fields) but no longer
are.
o A nonexistent array element with a large index passed to a
subroutine that ties the array and then tries to access the element
no longer results in a crash.
o Declaring a subroutine stub named NEGATIVE_INDICES no longer makes
negative array indices crash when the current package is a tied
array class.
o Declaring a "require", "glob", or "do" subroutine stub in the
CORE::GLOBAL:: package no longer makes compilation of calls to the
corresponding functions crash.
o Aliasing CORE::GLOBAL:: functions to constants stopped working in
Perl 5.10 but has now been fixed.
o When "`...`" or "qx/.../" calls a "readpipe" override, double-
quotish interpolation now happens, as is the case when there is no
override. Previously, the presence of an override would make these
quote-like operators act like "q{}", suppressing interpolation.
[perl #115330]
o "<<<`...`" here-docs (with backticks as the delimiters) now call
"readpipe" overrides. [perl #119827]
o "&CORE::exit()" and "&CORE::die()" now respect vmsish hints.
o Undefining a glob that triggers a DESTROY method that undefines the
same glob is now safe. It used to produce "Attempt to free
unreferenced glob pointer" warnings and leak memory.
o If subroutine redefinition ("eval 'sub foo{}'" or "newXS" for XS
code) triggers a DESTROY method on the sub that is being redefined,
and that method assigns a subroutine to the same slot ("*foo = sub
{}"), $_[0] is no longer left pointing to a freed scalar. Now
DESTROY is delayed until the new subroutine has been installed.
o On Windows, perl no longer calls CloseHandle() on a socket handle.
This makes debugging easier on Windows by removing certain
irrelevant bad handle exceptions. It also fixes a race condition
that made socket functions randomly fail in a Perl process with
multiple OS threads, and possible test failures in
dist/IO/t/cachepropagate-tcp.t. [perl #120091/118059]
o Formats involving UTF-8 encoded strings, or strange vars like ties,
overloads, or stringified refs (and in recent perls, pure NOK vars)
would generally do the wrong thing in formats when the var is
treated as a string and repeatedly chopped, as in "^<<<~~" and
similar. This has now been resolved. [perl
#33832/45325/113868/119847/119849/119851]
o "semctl(..., SETVAL, ...)" would set the semaphore to the top
32-bits of the supplied integer instead of the bottom 32-bits on
64-bit big-endian systems. [perl #120635]
o "readdir()" now only sets $! on error. $! is no longer set to
"EBADF" when then terminating "undef" is read from the directory
unless the system call sets $!. [perl #118651]
o &CORE::glob no longer causes an intermittent crash due to perl's
stack getting corrupted. [perl #119993]
o "open" with layers that load modules (e.g., "<:encoding(utf8)") no
longer runs the risk of crashing due to stack corruption.
o Perl 5.18 broke autoloading via "->SUPER::foo" method calls by
looking up AUTOLOAD from the current package rather than the
current package's superclass. This has been fixed. [perl #120694]
o A longstanding bug causing "do {} until CONSTANT", where the
constant holds a true value, to read unallocated memory has been
resolved. This would usually happen after a syntax error. In past
versions of Perl it has crashed intermittently. [perl #72406]
o Fix HP-UX $! failure. HP-UX strerror() returns an empty string for
an unknown error code. This caused an assertion to fail under
DEBUGGING builds. Now instead, the returned string for "$!"
contains text indicating the code is for an unknown error.
o Individually-tied elements of @INC (as in "tie $INC[0]...") are now
handled correctly. Formerly, whether a sub returned by such a tied
element would be treated as a sub depended on whether a FETCH had
occurred previously.
o "getc" on a byte-sized handle after the same "getc" operator had
been used on a utf8 handle used to treat the bytes as utf8,
resulting in erratic behavior (e.g., malformed UTF-8 warnings).
o An initial "{" at the beginning of a format argument line was
always interpreted as the beginning of a block prior to v5.18. In
Perl v5.18, it started being treated as an ambiguous token. The
parser would guess whether it was supposed to be an anonymous hash
constructor or a block based on the contents. Now the previous
behaviour has been restored. [perl #119973]
o In Perl v5.18 "undef *_; goto &sub" and "local *_; goto &sub"
started crashing. This has been fixed. [perl #119949]
o Backticks (" `` " or " qx// ") combined with multiple threads on
Win32 could result in output sent to stdout on one thread being
captured by backticks of an external command in another thread.
This could occur for pseudo-forked processes too, as Win32's
pseudo-fork is implemented in terms of threads. [perl #77672]
o "open $fh, ">+", undef" no longer leaks memory when TMPDIR is set
but points to a directory a temporary file cannot be created in.
[perl #120951]
o " for ( $h{k} || '' ) " no longer auto-vivifies $h{k}. [perl
#120374]
o On Windows machines, Perl now emulates the POSIX use of the
environment for locale initialization. Previously, the environment
was ignored. See "ENVIRONMENT" in perllocale.
o Fixed a crash when destroying a self-referencing GLOB. [perl
#121242]
Known Problems
o IO::Socket is known to fail tests on AIX 5.3. There is a patch
<https://github.com/Perl/perl5/issues/13484> in the request
tracker, #120835, which may be applied to future releases.
o The following modules are known to have test failures with this
version of Perl. Patches have been submitted, so there will
hopefully be new releases soon:
o Data::Structure::Util version 0.15
o HTML::StripScripts version 1.05
o List::Gather version 0.08.
Obituary
Diana Rosa, 27, of Rio de Janeiro, went to her long rest on May 10,
2014, along with the plush camel she kept hanging on her computer
screen all the time. She was a passionate Perl hacker who loved the
language and its community, and who never missed a Rio.pm event. She
was a true artist, an enthusiast about writing code, singing arias and
graffiting walls. We'll never forget you.
Greg McCarroll died on August 28, 2013.
Greg was well known for many good reasons. He was one of the organisers
of the first YAPC::Europe, which concluded with an unscheduled auction
where he frantically tried to raise extra money to avoid the conference
making a loss. It was Greg who mistakenly arrived for a london.pm
meeting a week late; some years later he was the one who sold the
choice of official meeting date at a YAPC::Europe auction, and
eventually as glorious leader of london.pm he got to inherit the
irreverent confusion that he had created.
Always helpful, friendly and cheerfully optimistic, you will be missed,
but never forgotten.
Acknowledgements
Perl 5.20.0 represents approximately 12 months of development since
Perl 5.18.0 and contains approximately 470,000 lines of changes across
2,900 files from 124 authors.
Excluding auto-generated files, documentation and release tools, there
were approximately 280,000 lines of changes to 1,800 .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 5.20.0:
Aaron Crane, Abhijit Menon-Sen, Abigail, Abir Viqar, Alan Haggai Alavi,
Alan Hourihane, Alexander Voronov, Alexandr Ciornii, Andy Dougherty,
Anno Siegel, Aristotle Pagaltzis, Arthur Axel 'fREW' Schmidt, Brad
Gilbert, Brendan Byrd, Brian Childs, Brian Fraser, Brian Gottreu, Chris
'BinGOs' Williams, Christian Millour, Colin Kuskie, Craig A. Berry,
Dabrien 'Dabe' Murphy, Dagfinn Ilmari Mannsaaker, Daniel Dragan, Darin
McBride, David Golden, David Leadbeater, David Mitchell, David Nicol,
David Steinbrunner, Dennis Kaarsemaker, Dominic Hargreaves, Ed Avis,
Eric Brine, Evan Zacks, Father Chrysostomos, Florian Ragwitz, Francois
Perrad, Gavin Shelley, Gideon Israel Dsouza, Gisle Aas, Graham Knop,
H.Merijn Brand, Hauke D, Heiko Eissfeldt, Hiroo Hayashi, Hojung Youn,
James E Keenan, Jarkko Hietaniemi, Jerry D. Hedden, Jess Robinson,
Jesse Luehrs, Johan Vromans, John Gardiner Myers, John Goodyear, John
P. Linderman, John Peacock, kafka, Kang-min Liu, Karen Etheridge, Karl
Williamson, Keedi Kim, Kent Fredric, kevin dawson, Kevin Falcone, Kevin
Ryde, Leon Timmermans, Lukas Mai, Marc Simpson, Marcel Gruenauer, Marco
Peereboom, Marcus Holland-Moritz, Mark Jason Dominus, Martin McGrath,
Matthew Horsfall, Max Maischein, Mike Doherty, Moritz Lenz, Nathan
Glenn, Nathan Trapuzzano, Neil Bowers, Neil Williams, Nicholas Clark,
Niels Thykier, Niko Tyni, Olivier Mengue, Owain G. Ainsworth, Paul
Green, Paul Johnson, Peter John Acklam, Peter Martini, Peter Rabbitson,
Petr PisaX, Philip Boulain, Philip Guenther, Piotr Roszatycki, Rafael
Garcia-Suarez, Reini Urban, Reuben Thomas, Ricardo Signes, Ruslan
Zakirov, Sergey Alekseev, Shirakata Kentaro, Shlomi Fish, Slaven Rezic,
Smylers, Steffen Mueller, Steve Hay, Sullivan Beck, Thomas Sibley,
Tobias Leich, Toby Inkster, Tokuhiro Matsuno, Tom Christiansen, Tom
Hukins, Tony Cook, Victor Efimov, Viktor Turskyi, Vladimir Timofeev,
YAMASHINA Hio, Yves Orton, Zefram, Zsban Ambrus, AEvar Arnfjoer`
Bjarmason.
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 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 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.
perl v5.34.0 2021-05-04 PERL5200DELTA(1pm)
perl 5.34.0 - Generated Thu Feb 24 19:09:31 CST 2022