NAME¶
perl5110delta - what is new for perl v5.11.0
DESCRIPTION¶
This document describes differences between the 5.10.0 release and the 5.11.0
development release.
Incompatible Changes¶
Unicode interpretation of \w, \d, \s, and the POSIX character
classes redefined.¶
Previous versions of Perl tried to map POSIX style character class definitions
onto Unicode property names so that patterns would "dwim" when
matches were made against latin-1 or unicode strings. This proved to be a
mistake, breaking character class negation, causing forward compatibility
problems (as Unicode keeps updating their property definitions and adding new
characters), and other problems.
Therefore we have now defined a new set of artificial "unicode"
property names which will be used to do unicode matching of patterns using
POSIX style character classes and perl short-form escape character classes
like \w and \d.
The key change here is that \d will no longer match every digit in the unicode
standard (there are thousands) nor will \w match every word character in the
standard, instead they will match precisely their POSIX or Perl definition.
Those needing to match based on Unicode properties can continue to do so by
using the \p{} syntax to match whichever property they like, including the new
artificial definitions.
NOTE: This is a backwards incompatible no-warning change in behaviour. If
you are upgrading and you process large volumes of text look for POSIX and
Perl style character classes and change them to the relevant property name (by
removing the word 'Posix' from the current name).
The following table maps the POSIX character class names, the escapes and the
old and new Unicode property mappings:
POSIX Esc Class New-Property ! Old-Property
----------------------------------------------+-------------
alnum [0-9A-Za-z] IsPosixAlnum ! IsAlnum
alpha [A-Za-z] IsPosixAlpha ! IsAlpha
ascii [\000-\177] IsASCII = IsASCII
blank [\011 ] IsPosixBlank !
cntrl [\0-\37\177] IsPosixCntrl ! IsCntrl
digit \d [0-9] IsPosixDigit ! IsDigit
graph [!-~] IsPosixGraph ! IsGraph
lower [a-z] IsPosixLower ! IsLower
print [ -~] IsPosixPrint ! IsPrint
punct [!-/:-@[-`{-~] IsPosixPunct ! IsPunct
space [\11-\15 ] IsPosixSpace ! IsSpace
\s [\11\12\14\15 ] IsPerlSpace ! IsSpacePerl
upper [A-Z] IsPosixUpper ! IsUpper
word \w [0-9A-Z_a-z] IsPerlWord ! IsWord
xdigit [0-9A-Fa-f] IsXDigit = IsXDigit
If you wish to build perl with the old mapping you may do so by setting
#define PERL_LEGACY_UNICODE_CHARCLASS_MAPPINGS 1
in regcomp.h, and then setting
PERL_TEST_LEGACY_POSIX_CC
to true your environment when testing.
@INC reorganization¶
In @INC, ARCHLIB and PRIVLIB now occur after after the current version's
site_perl and vendor_perl.
Switch statement changes¶
The handling of complex expressions by the "given"/"when"
switch statement has been enhanced. These enhancements are also available in
5.10.1 and subsequent 5.10 releases. There are two new cases where
"when" now interprets its argument as a boolean, instead of an
expression to be used in a smart match:
- flip-flop operators
- The ".." and "..." flip-flop operators
are now evaluated in boolean context, following their usual semantics; see
"Range Operators" in perlop.
Note that, as in perl 5.10.0, "when (1..10)" will not work to test
whether a given value is an integer between 1 and 10; you should use
"when ([1..10])" instead (note the array reference).
However, contrary to 5.10.0, evaluating the flip-flop operators in boolean
context ensures it can now be useful in a "when()", notably for
implementing bistable conditions, like in:
when (/^=begin/ .. /^=end/) {
# do something
}
- defined-or operator
- A compound expression involving the defined-or operator, as
in "when (expr1 // expr2)", will be treated as boolean if the
first expression is boolean. (This just extends the existing rule that
applies to the regular or operator, as in "when (expr1 ||
expr2)".)
The next section details more changes brought to the semantics to the smart
match operator, that naturally also modify the behaviour of the switch
statements where smart matching is implicitly used. These changers were also
made for the 5.10.1 release, and will remain in subsequent 5.10 releases.
Smart match changes¶
Changes to type-based dispatch
The smart match operator "~~" is no longer commutative. The behaviour
of a smart match now depends primarily on the type of its right hand argument.
Moreover, its semantics have been adjusted for greater consistency or
usefulness in several cases. While the general backwards compatibility is
maintained, several changes must be noted:
- •
- Code references with an empty prototype are no longer
treated specially. They are passed an argument like the other code
references (even if they choose to ignore it).
- •
- "%hash ~~ sub {}" and "@array ~~ sub
{}" now test that the subroutine returns a true value for each key of
the hash (or element of the array), instead of passing the whole hash or
array as a reference to the subroutine.
- •
- Due to the commutativity breakage, code references are no
longer treated specially when appearing on the left of the "~~"
operator, but like any vulgar scalar.
- •
- "undef ~~ %hash" is always false (since
"undef" can't be a key in a hash). No implicit conversion to
"" is done (as was the case in perl 5.10.0).
- •
- "$scalar ~~ @array" now always distributes the
smart match across the elements of the array. It's true if one element in
@array verifies "$scalar ~~ $element". This is a generalization
of the old behaviour that tested whether the array contained the
scalar.
The full dispatch table for the smart match operator is given in "Smart
matching in detail" in perlsyn.
Smart match and overloading
According to the rule of dispatch based on the rightmost argument type, when an
object overloading "~~" appears on the right side of the operator,
the overload routine will always be called (with a 3rd argument set to a true
value, see overload.) However, when the object will appear on the left, the
overload routine will be called only when the rightmost argument is a simple
scalar. This way distributivity of smart match across arrays is not broken, as
well as the other behaviours with complex types (coderefs, hashes, regexes).
Thus, writers of overloading routines for smart match mostly need to worry
only with comparing against a scalar, and possibly with stringification
overloading; the other common cases will be automatically handled
consistently.
"~~" will now refuse to work on objects that do not overload it (in
order to avoid relying on the object's underlying structure). (However, if the
object overloads the stringification or the numification operators, and if
overload fallback is active, it will be used instead, as usual.)
Labels can't be keywords¶
Labels used as targets for the "goto", "last",
"next" or "redo" statements cannot be keywords anymore.
This restriction will prevent potential confusion between the "goto
LABEL" and "goto EXPR" syntaxes: for example, a statement like
"goto print" would jump to a label whose name would be the return
value of "print()", (usually 1), instead of a label named
"print". Moreover, the other control flow statements would just
ignore any keyword passed to them as a label name. Since such labels cannot be
defined anymore, this kind of error will be avoided.
Other incompatible changes¶
- •
- The semantics of "use feature :5.10*" have
changed slightly. See "Modules and Pragmata" for more
information.
- •
- It is now a run-time error to use the smart match operator
"~~" with an object that has no overload defined for it. (This
way "~~" will not break encapsulation by matching against the
object's internal representation as a reference.)
- •
- The version control system used for the development of the
perl interpreter has been switched from Perforce to git. This is mainly an
internal issue that only affects people actively working on the perl core;
but it may have minor external visibility, for example in some of details
of the output of "perl -V". See perlrepository for more
information.
- •
- The internal structure of the "ext/" directory in
the perl source has been reorganised. In general, a module
"Foo::Bar" whose source was stored under ext/Foo/Bar/ is
now located under ext/Foo-Bar/. Also, nearly all dual-life modules
have been moved from lib/ to ext/. This is purely a source
tarball change, and should make no difference to the compilation or
installation of perl, unless you have a very customised build process that
explicitly relies on this structure, or which hard-codes the
"nonxs_ext" Configure parameter. Specifically, this
change does not by default alter the location of any files in the final
installation.
- •
- As part of the "Test::Harness" 2.x to 3.x
upgrade, the experimental "Test::Harness::Straps" module has
been removed. See "Updated Modules" for more details.
- •
- As part of the "ExtUtils::MakeMaker" upgrade, the
"ExtUtils::MakeMaker::bytes" and
"ExtUtils::MakeMaker::vmsish" modules have been removed from
this distribution.
- •
- "Module::CoreList" no longer contains the
%:patchlevel hash.
- •
- This one is actually a change introduced in 5.10.0, but it
was missed from that release's perldelta, so it is mentioned here instead.
A bugfix related to the handling of the "/m" modifier and
"qr" resulted in a change of behaviour between 5.8.x and 5.10.0:
# matches in 5.8.x, doesn't match in 5.10.0
$re = qr/^bar/; "foo\nbar" =~ /$re/m;
- •
- "length undef" now returns undef.
- •
- Unsupported private C API functions are now declared
"static" to prevent leakage to Perl's public API.
- •
- To support the bootstrapping process, miniperl no
longer builds with UTF-8 support in the regexp engine.
This allows a build to complete with PERL_UNICODE set and a UTF-8 locale.
Without this there's a bootstrapping problem, as miniperl can't load the
UTF-8 components of the regexp engine, because they're not yet built.
- •
- miniperl's @INC is now restricted to just -I..., the
split of $ENV{PERL5LIB}, and "."
- •
- A space or a newline is now required after a "#line
XXX" directive.
- •
- Tied filehandles now have an additional method EOF which
provides the EOF type
- •
- To better match all other flow control statements,
"foreach" may no longer be used as an attribute.
Core Enhancements¶
Unicode Character Database 5.1.0¶
The copy of the Unicode Character Database included in Perl 5.11.0 has been
updated to 5.1.0 from 5.0.0. See
<
http://www.unicode.org/versions/Unicode5.1.0/#Notable_Changes> for the
notable changes.
A proper interface for pluggable Method Resolution Orders¶
As of Perl 5.11.0 there is a new interface for plugging and using method
resolution orders other than the default (linear depth first search). The C3
method resolution order added in 5.10.0 has been re-implemented as a plugin,
without changing its Perl-space interface. See perlmroapi for more
information.
The "overloading" pragma¶
This pragma allows you to lexically disable or enable overloading for some or
all operations. (Yuval Kogman)
"\N" regex escape¶
A new regex escape has been added, "\N". It will match any character
that is not a newline, independently from the presence or absence of the
single line match modifier "/s". (If "\N" is followed by
an opening brace and by a letter, perl will still assume that a Unicode
character name is coming, so compatibility is preserved.) (Rafael
Garcia-Suarez)
Implicit strictures¶
Using the "use VERSION" syntax with a version number greater or equal
to 5.11.0 will also lexically enable strictures just like "use
strict" would do (in addition to enabling features.) So, the following:
use 5.11.0;
will now imply:
use strict;
use feature ':5.11';
Parallel tests¶
The core distribution can now run its regression tests in parallel on Unix-like
platforms. Instead of running "make test", set "TEST_JOBS"
in your environment to the number of tests to run in parallel, and run
"make test_harness". On a Bourne-like shell, this can be done as
TEST_JOBS=3 make test_harness # Run 3 tests in parallel
An environment variable is used, rather than parallel make itself, because
TAP::Harness needs to be able to schedule individual non-conflicting test
scripts itself, and there is no standard interface to "make"
utilities to interact with their job schedulers.
Note that currently some test scripts may fail when run in parallel (most
notably "ext/IO/t/io_dir.t"). If necessary run just the failing
scripts again sequentially and see if the failures go away.
The "..." operator¶
A new operator, "...", nicknamed the Yada Yada operator, has been
added. It is intended to mark placeholder code, that is not yet implemented.
See "Yada Yada Operator" in perlop. (chromatic)
DTrace support¶
Some support for DTrace has been added. See "DTrace support" in
INSTALL.
Both "CPAN" and "CPANPLUS" now support the
"configure_requires" keyword in the
META.yml metadata file
included in most recent CPAN distributions. This allows distribution authors
to specify configuration prerequisites that must be installed before running
Makefile.PL or
Build.PL.
See the documentation for "ExtUtils::MakeMaker" or
"Module::Build" for more on how to specify
"configure_requires" when creating a distribution for CPAN.
"each" is now more flexible¶
The "each" function can now operate on arrays.
Y2038 compliance¶
Perl's core time-related functions are now Y2038 compliant. (With 29 years to
spare!)
$, flexibility¶
The variable $, may now be tied.
// in where clauses¶
// now behaves like || in when clauses
Enabling warnings from your shell environment¶
You can now set "-W" from the "PERL5OPT" environment
variable
"delete local"¶
"delete local" now allows you to locally delete a hash entry.
New support for Abstract namespace sockets¶
Abstract namespace sockets are Linux-specific socket type that live in AF_UNIX
family, slightly abusing it to be able to use arbitrary character arrays as
addresses: They start with nul byte and are not terminated by nul byte, but
with the length passed to the
socket() system call.
Modules and Pragmata¶
Dual-lifed modules moved¶
Dual-lifed modules maintained primarily in the Perl core now live in dist/.
Dual-lifed modules maintained primarily on CPAN now live in cpan/
In previous releases of Perl, it was customary to enumerate all module changes
in this section of the "perldelta" file. From 5.11.0 forward only
notable updates (such as new or deprecated modules ) will be listed in this
section. For a complete reference to the versions of modules shipped in a
given release of perl, please see Module::CoreList.
New Modules and Pragmata¶
- "autodie"
- This is a new lexically-scoped alternative for the
"Fatal" module. The bundled version is 2.06_01. Note that in
this release, using a string eval when "autodie" is in effect
can cause the autodie behaviour to leak into the surrounding scope. See
"BUGS" in autodie for more details.
- "Compress::Raw::Bzip2"
- This has been added to the core (version 2.020).
- "parent"
- This pragma establishes an ISA relationship with base
classes at compile time. It provides the key feature of "base"
without the feature creep.
- "Parse::CPAN::Meta"
- This has been added to the core (version 1.39).
Pragmata Changes¶
- "overloading"
- See "The "overloading" pragma"
above.
- "attrs"
- The "attrs" pragma has been removed. It had been
marked as deprecated since 5.6.0.
- "charnames"
- The Unicode NameAliases.txt database file has been
added. This has the effect of adding some extra "\N" character
names that formerly wouldn't have been recognised; for example,
"\N{LATIN CAPITAL LETTER GHA}".
- "feature"
- The meaning of the ":5.10" and
":5.10.X" feature bundles has changed slightly. The last
component, if any (i.e. "X") is simply ignored. This is
predicated on the assumption that new features will not, in general, be
added to maintenance releases. So ":5.10" and
":5.10.X" have identical effect. This is a change to the
behaviour documented for 5.10.0.
- "mro"
- Upgraded from version 1.00 to 1.01. Performance for single
inheritance is 40% faster - see "Performance Enhancements"
below.
"mro" is now implemented as an XS extension. The documented
interface has not changed. Code relying on the implementation detail that
some "mro::" methods happened to be available at all times gets
to "keep both pieces".
Updated Modules¶
- "ExtUtils::MakeMaker"
- Upgraded from version 6.42 to 6.55_02.
Note that "ExtUtils::MakeMaker::bytes" and
"ExtUtils::MakeMaker::vmsish" have been removed from this
distribution.
- "Test::Harness"
- Upgraded from version 2.64 to 3.17.
Note that one side-effect of the 2.x to 3.x upgrade is that the experimental
"Test::Harness::Straps" module (and its supporting
"Assert", "Iterator", "Point" and
"Results" modules) have been removed. If you still need this,
then they are available in the (unmaintained)
"Test-Harness-Straps" distribution on CPAN.
- "UNIVERSAL"
- Upgraded from version 1.04 to 1.05.
"UNIVERSAL->import()" is now deprecated.
Utility Changes¶
- h2ph
- Now looks in "include-fixed" too, which is a
recent addition to gcc's search path.
- h2xs
- No longer incorrectly treats enum values like macros
(Daniel Burr).
Now handles C++ style constants ("//") properly in enums. (A patch
from Rainer Weikusat was used; Daniel Burr also proposed a similar
fix).
- perl5db.pl
- "LVALUE" subroutines now work under the debugger.
The debugger now correctly handles proxy constant subroutines, and
subroutine stubs.
- perlbug
- perlbug now uses %Module::CoreList::bug_tracker to
print out upstream bug tracker URLs.
Where the user names a module that their bug report is about, and we know
the URL for its upstream bug tracker, provide a message to the user
explaining that the core copies the CPAN version directly, and provide the
URL for reporting the bug directly to upstream.
- perlthanks
- Perl 5.11.0 added a new utility perlthanks, which is
a variant of perlbug, but for sending non-bug-reports to the
authors and maintainers of Perl. Getting nothing but bug reports can
become a bit demoralising: we'll see if this changes things.
New Documentation¶
- perlhaiku
- This contains instructions on how to build perl for the
Haiku platform.
- perlmroapi
- This describes the new interface for pluggable Method
Resolution Orders.
- perlperf
- This document, by Richard Foley, provides an introduction
to the use of performance and optimization techniques which can be used
with particular reference to perl programs.
- perlrepository
- This describes how to access the perl source using the
git version control system.
Changes to Existing Documentation¶
The various large
Changes* files (which listed every change made to perl
over the last 18 years) have been removed, and replaced by a small file, also
called
Changes, which just explains how that same information may be
extracted from the git version control system.
The file
Porting/patching.pod has been deleted, as it mainly described
interacting with the old Perforce-based repository, which is now obsolete.
Information still relevant has been moved to perlrepository.
perlapi, perlintern, perlmodlib and perltoc are now all generated at build time,
rather than being shipped as part of the release.
- •
- Documented -X overloading.
- •
- Documented that "when()" treats specially most of
the filetest operators
- •
- Documented when as a syntax modifier
- •
- Eliminated "Old Perl threads tutorial", which
describes 5005 threads.
pod/perlthrtut.pod is the same material reworked for ithreads.
- •
- Correct previous documentation: v-strings are not
deprecated
With version objects, we need them to use MODULE VERSION syntax. This patch
removes the deprecation note.
- •
- Added security contact information to perlsec
- •
- A new internal cache means that "isa()" will
often be faster.
- •
- The implementation of "C3" Method Resolution
Order has been optimised - linearisation for classes with single
inheritance is 40% faster. Performance for multiple inheritance is
unchanged.
- •
- Under "use locale", the locale-relevant
information is now cached on read-only values, such as the list returned
by "keys %hash". This makes operations such as "sort keys
%hash" in the scope of "use locale" much faster.
- •
- Empty "DESTROY" methods are no longer
called.
- •
- Faster "Perl_sv_utf8_upgrade()"
- •
- Speed up "keys" on empty hash
Installation and Configuration Improvements¶
ext/ reorganisation¶
The layout of directories in
ext has been revised. Specifically, all
extensions are now flat, and at the top level, with "/" in pathnames
replaced by "-", so that
ext/Data/Dumper/ is now
ext/Data-Dumper/, etc. The names of the extensions as specified to
Configure, and as reported by %Config::Config under the keys
"dynamic_ext", "known_extensions", "nonxs_ext"
and "static_ext" have not changed, and still use "/".
Hence this change will not have any affect once perl is installed.
"Safe" has been split out from being part of "Opcode", and
"mro" is now an extension in its own right.
Nearly all dual-life modules have been moved from
lib to
ext, and
will now appear as known "nonxs_ext". This will made no difference
to the structure of an installed perl, nor will the modules installed differ,
unless you run
Configure with options to specify an exact list of
extensions to build. In this case, you will rapidly become aware that you need
to add to your list, because various modules needed to complete the build,
such as "ExtUtils::ParseXS", have now become extensions, and without
them the build will fail well before it attempts to run the regression tests.
Configuration improvements¶
If "vendorlib" and "vendorarch" are the same, then they are
only added to @INC once.
$Config{usedevel} and the C-level "PERL_USE_DEVEL" are now defined if
perl is built with "-Dusedevel".
Configure will enable use of "-fstack-protector", to provide
protection against stack-smashing attacks, if the compiler supports it.
Configure will now determine the correct prototypes for re-entrant
functions, and for "gconvert", if you are using a C++ compiler
rather than a C compiler.
On Unix, if you build from a tree containing a git repository, the configuration
process will note the commit hash you have checked out, for display in the
output of "perl -v" and "perl -V". Unpushed local commits
are automatically added to the list of local patches displayed by "perl
-V".
Compilation improvements¶
As part of the flattening of
ext, all extensions on all platforms are
built by
make_ext.pl. This replaces the Unix-specific
ext/util/make_ext, VMS-specific
make_ext.com and Win32-specific
win32/buildext.pl.
- AIX
- Removed libbsd for AIX 5L and 6.1. Only
"flock()" was used from libbsd.
Removed libgdbm for AIX 5L and 6.1. The libgdbm is delivered
as an optional package with the AIX Toolbox. Unfortunately the 64 bit
version is broken.
Hints changes mean that AIX 4.2 should work again.
- Cygwin
- On Cygwin we now strip the last number from the DLL. This
has been the behaviour in the cygwin.com build for years. The hints files
have been updated.
- DomainOS
- Support for Apollo DomainOS was removed in Perl 5.11.0
- FreeBSD
- The hints files now identify the correct threading
libraries on FreeBSD 7 and later.
- Irix
- We now work around a bizarre preprocessor bug in the Irix
6.5 compiler: "cc -E -" unfortunately goes into K&R mode,
but "cc -E file.c" doesn't.
- Haiku
- Patches from the Haiku maintainers have been merged in.
Perl should now build on Haiku.
- MachTen
- Support for Tenon Intersystems MachTen Unix layer for MacOS
Classic was removed in Perl 5.11.0
- MiNT
- Support for Atari MiNT was removed in Perl 5.11.0.
- MirOS BSD
- Perl should now build on MirOS BSD.
- NetBSD
- Hints now supports versions 5.*.
- Stratus VOS
- Various changes from Stratus have been merged in.
- Symbian
- There is now support for Symbian S60 3.2 SDK and S60 5.0
SDK.
- Win32
- Improved message window handling means that
"alarm" and "kill" messages will no longer be dropped
under race conditions.
- VMS
- Reads from the in-memory temporary files of
"PerlIO::scalar" used to fail if $/ was set to a numeric
reference (to indicate record-style reads). This is now fixed.
VMS now supports "getgrgid".
Many improvements and cleanups have been made to the VMS file name handling
and conversion code.
Enabling the "PERL_VMS_POSIX_EXIT" logical name now encodes a
POSIX exit status in a VMS condition value for better interaction with
GNV's bash shell and other utilities that depend on POSIX exit values. See
"$?" in perlvms for details.
"File::Copy" now detects Unix compatibility mode on VMS.
Selected Bug Fixes¶
- •
- "-I" on shebang line now adds directories in
front of @INC as documented, and as does "-I" when specified on
the command-line.
- •
- "kill" is now fatal when called on non-numeric
process identifiers. Previously, an 'undef' process identifier would be
interpreted as a request to kill process "0", which would
terminate the current process group on POSIX systems. Since process
identifiers are always integers, killing a non-numeric process is now
fatal.
- •
- 5.10.0 inadvertently disabled an optimisation, which caused
a measurable performance drop in list assignment, such as is often used to
assign function parameters from @_. The optimisation has been re-instated,
and the performance regression fixed.
- •
- Fixed memory leak on "while (1) { map 1, 1 }" [RT
#53038].
- •
- Some potential coredumps in PerlIO fixed [RT
#57322,54828].
- •
- The debugger now works with lvalue subroutines.
- •
- The debugger's "m" command was broken on modules
that defined constants [RT #61222].
- •
- "crypt" and string complement could return
tainted values for untainted arguments [RT #59998].
- •
- The "-i".suffix command-line switch now
recreates the file using restricted permissions, before changing its mode
to match the original file. This eliminates a potential race condition [RT
#60904].
- •
- On some Unix systems, the value in $? would not have the
top bit set ("$? & 128") even if the child core dumped.
- •
- Under some circumstances, $^R could incorrectly become
undefined [RT #57042].
- •
- In the XS API, various hash functions, when passed a
pre-computed hash where the key is UTF-8, might result in an incorrect
lookup.
- •
- XS code including XSUB.h before perl.h gave a
compile-time error [RT #57176].
- •
- "$object->isa('Foo')" would report false if
the package "Foo" didn't exist, even if the object's @ISA
contained "Foo".
- •
- Various bugs in the new-to 5.10.0 mro code, triggered by
manipulating @ISA, have been found and fixed.
- •
- Bitwise operations on references could crash the
interpreter, e.g. "$x=\$y; $x |= "foo"" [RT
#54956].
- •
- Patterns including alternation might be sensitive to the
internal UTF-8 representation, e.g.
my $byte = chr(192);
my $utf8 = chr(192); utf8::upgrade($utf8);
$utf8 =~ /$byte|X}/i; # failed in 5.10.0
- •
- Within UTF8-encoded Perl source files (i.e. where "use
utf8" is in effect), double-quoted literal strings could be corrupted
where a "\xNN", "\0NNN" or "\N{}" is
followed by a literal character with ordinal value greater than 255 [RT
#59908].
- •
- "B::Deparse" failed to correctly deparse various
constructs: "readpipe STRING" [RT #62428],
"CORE::require(STRING)" [RT #62488], "sub foo(_)" [RT
#62484].
- •
- Using "setpgrp" with no arguments could corrupt
the perl stack.
- •
- The block form of "eval" is now specifically
trappable by "Safe" and "ops". Previously it was
erroneously treated like string "eval".
- •
- In 5.10.0, the two characters "[~" were sometimes
parsed as the smart match operator ("~~") [RT #63854].
- •
- In 5.10.0, the "*" quantifier in patterns was
sometimes treated as "{0,32767}" [RT #60034, #60464]. For
example, this match would fail:
("ab" x 32768) =~ /^(ab)*$/
- •
- "shmget" was limited to a 32 bit segment size on
a 64 bit OS [RT #63924].
- •
- Using "next" or "last" to exit a
"given" block no longer produces a spurious warning like the
following:
Exiting given via last at foo.pl line 123
- •
- On Windows, '.\foo' and '..\foo' were treated differently
than './foo' and '../foo' by "do" and "require" [RT
#63492].
- •
- Assigning a format to a glob could corrupt the format;
e.g.:
*bar=*foo{FORMAT}; # foo format now bad
- •
- Attempting to coerce a typeglob to a string or number could
cause an assertion failure. The correct error message is now generated,
"Can't coerce GLOB to $type".
- •
- Under "use filetest 'access'", "-x" was
using the wrong access mode. This has been fixed [RT #49003].
- •
- "length" on a tied scalar that returned a Unicode
value would not be correct the first time. This has been fixed.
- •
- Using an array "tie" inside in array
"tie" could SEGV. This has been fixed. [RT #51636]
- •
- A race condition inside "PerlIOStdio_close()" has
been identified and fixed. This used to cause various threading issues,
including SEGVs.
- •
- In "unpack", the use of "()" groups in
scalar context was internally placing a list on the interpreter's stack,
which manifested in various ways, including SEGVs. This is now fixed [RT
#50256].
- •
- Magic was called twice in "substr",
"\&$x", "tie $x, $m" and "chop". These
have all been fixed.
- •
- A 5.10.0 optimisation to clear the temporary stack within
the implicit loop of "s///ge" has been reverted, as it turned
out to be the cause of obscure bugs in seemingly unrelated parts of the
interpreter [commit ef0d4e17921ee3de].
- •
- The line numbers for warnings inside "elsif" are
now correct.
- •
- The ".." operator now works correctly with ranges
whose ends are at or close to the values of the smallest and largest
integers.
- •
- "binmode STDIN, ':raw'" could lead to
segmentation faults on some platforms. This has been fixed [RT
#54828].
- •
- An off-by-one error meant that "index $str, ..."
was effectively being executed as "index "$str\0",
...". This has been fixed [RT #53746].
- •
- Various leaks associated with named captures in regexes
have been fixed [RT #57024].
- •
- A weak reference to a hash would leak. This was affecting
"DBI" [RT #56908].
- •
- Using (?|) in a regex could cause a segfault [RT
#59734].
- •
- Use of a UTF-8 "tr//" within a closure could
cause a segfault [RT #61520].
- •
- Calling "Perl_sv_chop()" or otherwise upgrading
an SV could result in an unaligned 64-bit access on the SPARC architecture
[RT #60574].
- •
- In the 5.10.0 release, "inc_version_list" would
incorrectly list "5.10.*" after "5.8.*"; this affected
the @INC search order [RT #67628].
- •
- In 5.10.0, "pack "a*", $tainted_value"
returned a non-tainted value [RT #52552].
- •
- In 5.10.0, "printf" and "sprintf" could
produce the fatal error "panic: utf8_mg_pos_cache_update" when
printing UTF-8 strings [RT #62666].
- •
- In the 5.10.0 release, a dynamically created
"AUTOLOAD" method might be missed (method cache issue) [RT
#60220,60232].
- •
- In the 5.10.0 release, a combination of "use
feature" and "//ee" could cause a memory leak [RT
#63110].
- •
- "-C" on the shebang ("#!") line is once
more permitted if it is also specified on the command line. "-C"
on the shebang line used to be a silent no-op if it was not also on
the command line, so perl 5.10.0 disallowed it, which broke some scripts.
Now perl checks whether it is also on the command line and only dies if it
is not [RT #67880].
- •
- In 5.10.0, certain types of re-entrant regular expression
could crash, or cause the following assertion failure [RT #60508]:
Assertion rx->sublen >= (s - rx->subbeg) + i failed
- •
- Previously missing files from Unicode 5.1 Character
Database are now included.
- •
- "TMPDIR" is now honored when opening an anonymous
temporary file
New or Changed Diagnostics¶
- "panic: sv_chop %s"
- This new fatal error occurs when the C routine
"Perl_sv_chop()" was passed a position that is not within the
scalar's string buffer. This could be caused by buggy XS code, and at this
point recovery is not possible.
- "Can't locate package %s for the parents of
%s"
- This warning has been removed. In general, it only got
produced in conjunction with other warnings, and removing it allowed an
ISA lookup optimisation to be added.
- "v-string in use/require is non-portable"
- This warning has been removed.
- "Deep recursion on subroutine
"%s""
- It is now possible to change the depth threshold for this
warning from the default of 100, by recompiling the perl binary,
setting the C pre-processor macro "PERL_SUB_DEPTH_WARN" to the
desired value.
Changed Internals¶
- •
- TODO: "SVt_RV" is gone. RVs are now stored in
IVs
- •
- TODO: REGEXPs are first class
- •
- TODO: OOK is reworked, such that an OOKed scalar is PV not
PVIV
- •
- The J.R.R. Tolkien quotes at the head of C source file have
been checked and proper citations added, thanks to a patch from Tom
Christiansen.
- •
- "Perl_vcroak()" now accepts a null first
argument. In addition, a full audit was made of the "not NULL"
compiler annotations, and those for several other internal functions were
corrected.
- •
- New macros "dSAVEDERRNO",
"dSAVE_ERRNO", "SAVE_ERRNO", "RESTORE_ERRNO"
have been added to formalise the temporary saving of the "errno"
variable.
- •
- The function "Perl_sv_insert_flags" has been
added to augment "Perl_sv_insert".
- •
- The function "Perl_newSV_type(type)" has been
added, equivalent to "Perl_newSV()" followed by
"Perl_sv_upgrade(type)".
- •
- The function "Perl_newSVpvn_flags()" has been
added, equivalent to "Perl_newSVpvn()" and then performing the
action relevant to the flag.
Two flag bits are currently supported.
- "SVf_UTF8"
- This will call "SvUTF8_on()" for you. (Note that
this does not convert an sequence of ISO 8859-1 characters to UTF-8). A
wrapper, "newSVpvn_utf8()" is available for this.
- "SVs_TEMP"
- Call "Perl_sv_2mortal()" on the new SV.
There is also a wrapper that takes constant strings,
"newSVpvs_flags()".
- •
- The function "Perl_croak_xs_usage" has been added
as a wrapper to "Perl_croak".
- •
- The functions "PerlIO_find_layer" and
"PerlIO_list_alloc" are now exported.
- •
- "PL_na" has been exterminated from the core code,
replaced by local STRLEN temporaries, or "*_nolen()" calls.
Either approach is faster than "PL_na", which is a pointer
deference into the interpreter structure under ithreads, and a global
variable otherwise.
- •
- "Perl_mg_free()" used to leave freed memory
accessible via "SvMAGIC()" on the scalar. It now updates the
linked list to remove each piece of magic as it is freed.
- •
- Under ithreads, the regex in "PL_reg_curpm" is
now reference counted. This eliminates a lot of hackish workarounds to
cope with it not being reference counted.
- •
- "Perl_mg_magical()" would sometimes incorrectly
turn on "SvRMAGICAL()". This has been fixed.
- •
- The public IV and NV flags are now not set if the
string value has trailing "garbage". This behaviour is
consistent with not setting the public IV or NV flags if the value is out
of range for the type.
- •
- SV allocation tracing has been added to the diagnostics
enabled by "-Dm". The tracing can alternatively output via the
"PERL_MEM_LOG" mechanism, if that was enabled when the
perl binary was compiled.
- •
- Smartmatch resolution tracing has been added as a new
diagnostic. Use "-DM" to enable it.
- •
- A new debugging flag "-DB" now dumps subroutine
definitions, leaving "-Dx" for its original purpose of dumping
syntax trees.
- •
- Uses of "Nullav", "Nullcv",
"Nullhv", "Nullop", "Nullsv" etc have been
replaced by "NULL" in the core code, and non-dual-life modules,
as "NULL" is clearer to those unfamiliar with the core
code.
- •
- A macro MUTABLE_PTR(p) has been added, which on
(non-pedantic) gcc will not cast away "const", returning a
"void *". Macros "MUTABLE_SV(av)",
"MUTABLE_SV(cv)" etc build on this, casting to "AV *"
etc without casting away "const". This allows proper
compile-time auditing of "const" correctness in the core, and
helped picked up some errors (now fixed).
- •
- Macros "mPUSHs()" and "mXPUSHs()" have
been added, for pushing SVs on the stack and mortalizing them.
- •
- Use of the private structure "mro_meta" has
changed slightly. Nothing outside the core should be accessing this
directly anyway.
- •
- A new tool, Porting/expand-macro.pl has been added,
that allows you to view how a C preprocessor macro would be expanded when
compiled. This is handy when trying to decode the macro hell that is the
perl guts.
New Tests¶
Many modules updated from CPAN incorporate new tests.
Several tests that have the potential to hang forever if they fail now
incorporate a "watchdog" functionality that will kill them after a
timeout, which helps ensure that "make test" and "make
test_harness" run to completion automatically. (Jerry Hedden).
Some core-specific tests have been added:
- t/comp/retainedlines.t
- Check that the debugger can retain source lines from
"eval".
- t/io/perlio_fail.t
- Check that bad layers fail.
- t/io/perlio_leaks.t
- Check that PerlIO layers are not leaking.
- t/io/perlio_open.t
- Check that certain special forms of open work.
- t/io/perlio.t
- General PerlIO tests.
- t/io/pvbm.t
- Check that there is no unexpected interaction between the
internal types "PVBM" and "PVGV".
- t/mro/package_aliases.t
- Check that mro works properly in the presence of aliased
packages.
- t/op/dbm.t
- Tests for "dbmopen" and
"dbmclose".
- t/op/index_thr.t
- Tests for the interaction of "index" and
threads.
- t/op/pat_thr.t
- Tests for the interaction of esoteric patterns and
threads.
- t/op/qr_gc.t
- Test that "qr" doesn't leak.
- t/op/reg_email_thr.t
- Tests for the interaction of regex recursion and
threads.
- t/op/regexp_qr_embed_thr.t
- Tests for the interaction of patterns with embedded
"qr//" and threads.
- t/op/regexp_unicode_prop.t
- Tests for Unicode properties in regular expressions.
- t/op/regexp_unicode_prop_thr.t
- Tests for the interaction of Unicode properties and
threads.
- t/op/reg_nc_tie.t
- Test the tied methods of
"Tie::Hash::NamedCapture".
- t/op/reg_posixcc.t
- Check that POSIX character classes behave
consistently.
- t/op/re.t
- Check that exportable "re" functions in
universal.c work.
- t/op/setpgrpstack.t
- Check that "setpgrp" works.
- t/op/substr_thr.t
- Tests for the interaction of "substr" and
threads.
- t/op/upgrade.t
- Check that upgrading and assigning scalars works.
- t/uni/lex_utf8.t
- Check that Unicode in the lexer works.
- t/uni/tie.t
- Check that Unicode and "tie" work.
Known Problems¶
This is a list of some significant unfixed bugs, which are regressions from
either 5.10.0 or 5.8.x.
- •
- "List::Util::first" misbehaves in the presence of
a lexical $_ (typically introduced by "my $_" or implicitly by
"given"). The variable which gets set for each iteration is the
package variable $_, not the lexical $_ [RT #67694].
A similar issue may occur in other modules that provide functions which take
a block as their first argument, like
foo { ... $_ ...} list
- •
- The "charnames" pragma may generate a run-time
error when a regex is interpolated [RT #56444]:
use charnames ':full';
my $r1 = qr/\N{THAI CHARACTER SARA I}/;
"foo" =~ $r1; # okay
"foo" =~ /$r1+/; # runtime error
A workaround is to generate the character outside of the regex:
my $a = "\N{THAI CHARACTER SARA I}";
my $r1 = qr/$a/;
- •
- Some regexes may run much more slowly when run in a child
thread compared with the thread the pattern was compiled into [RT
#55600].
Deprecations¶
The following items are now deprecated.
- •
- "Switch" is buggy and should be avoided. From
perl 5.11.0 onwards, it is intended that any use of the core version of
this module will emit a warning, and that the module will eventually be
removed from the core (probably in perl 5.14.0). See "Switch
statements" in perlsyn for its replacement.
- •
- The following modules will be removed from the core
distribution in a future release, and should be installed from CPAN
instead. Distributions on CPAN which require these should add them to
their prerequisites. The core versions of these modules warnings will
issue a deprecation warning.
- •
- "Class::ISA"
- •
- "Pod::Plainer"
- •
- "Shell"
Currently support to install from CPAN without a
force is
"TODO" in CPAN and CPANPLUS. This will be addressed before 5.12.0
ships.
- •
- "suidperl" has been removed. It used to provide a
mechanism to emulate setuid permission bits on systems that don't support
it properly.
- •
- Deprecate assignment to $[
- •
- Remove attrs, which has been deprecated since
1999/10/02.
- •
- Deprecate use of the attribute :locked on subroutines.
- •
- Deprecate using "locked" with the attributes
pragma.
- •
- Deprecate using "unique" with the attributes
pragma.
- •
- warn if ++ or -- are unable to change the value because
it's beyond the limit of representation
This uses a new warnings category: "imprecision".
- •
- Make lc/uc/lcfirst/ucfirst warn when passed undef.
- •
- Show constant in "Useless use of a constant in void
context"
- •
- Make the new warning report undef constants as undef
- •
- Add a new warning, "Prototype after '%s'"
- •
- Tweak the "Illegal character in prototype"
warning so it's more precise when reporting illegal characters after
_
- •
- Unintended interpolation of $\ in regex
- •
- Make overflow warnings in gmtime/localtime only occur when
warnings are on
- •
- Improve mro merging error messages.
They are now very similar to those produced by Algorithm::C3.
- •
- Amelioration of the error message "Unrecognized
character %s in column %d"
Changes the error message to "Unrecognized character %s; marked by
<-- HERE after %s<-- HERE near column %d". This should make it
a little simpler to spot and correct the suspicious character.
- •
- Explicitly point to $. when it causes an uninitialized
warning for ranges in scalar context
- •
- Deprecated numerous Perl 4-era libraries:
termcap.pl, tainted.pl, stat.pl, shellwords.pl,
pwd.pl, open3.pl, open2.pl, newgetopt.pl,
look.pl, find.pl, finddepth.pl, importenv.pl,
hostname.pl, getopts.pl, getopt.pl, getcwd.pl,
flush.pl, fastcwd.pl, exceptions.pl, ctime.pl,
complete.pl, cacheout.pl, bigrat.pl,
bigint.pl, bigfloat.pl, assert.pl, abbrev.pl,
dotsh.pl, and timelocal.pl are all now deprecated. Using
them will incur a warning.
Acknowledgements¶
Some of the work in this release was funded by a TPF grant funded by Dijkmat BV,
The Netherlands.
Steffen Mueller and David Golden in particular helped getting CPAN modules
polished and synchronised with their in-core equivalents.
Craig Berry was tireless in getting maint to run under VMS, no matter how many
times we broke it for him.
The other core committers contributed most of the changes, and applied most of
the patches sent in by the hundreds of contributors listed in
AUTHORS.
Much of the work of categorizing changes in this perldelta file was contributed
by the following porters using changelogger.bestpractical.com:
Nicholas Clark, leon, shawn, alexm, rjbs, rafl, Pedro Melo, brunorc, anonymous,
X, Tom Hukins, anonymous, Jesse, dagolden, Moritz Onken, Mark Fowler, chorny,
anonymous, tmtm
Finally, thanks to Larry Wall, without whom none of this would be necessary.
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 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.