perl594delta
(1)
名称
perl594delta - what is new for perl v5.9.4
用法概要
Please see following description for synopsis
描述
Perl Programmers Reference Guide PERL594DELTA(1)
NAME
perl594delta - what is new for perl v5.9.4
DESCRIPTION
This document describes differences between the 5.9.3 and
the 5.9.4 development releases. See perl590delta,
perl591delta, perl592delta and perl593delta for the
differences between 5.8.0 and 5.9.3.
Incompatible Changes
chdir FOO
A bareword argument to chdir() is now recognized as a file
handle. Earlier releases interpreted the bareword as a
directory name. (Gisle Aas)
Handling of pmc files
An old feature of perl was that before "require" or "use"
look for a file with a .pm extension, they will first look
for a similar filename with a .pmc extension. If this file
is found, it will be loaded in place of any potentially
existing file ending in a .pm extension.
Previously, .pmc files were loaded only if more recent than
the matching .pm file. Starting with 5.9.4, they'll be
always loaded if they exist. (This trick is used by Pugs.)
@- and @+ in patterns
The special arrays "@-" and "@+" are no longer interpolated
in regular expressions. (Sadahiro Tomoyuki)
$AUTOLOAD can now be tainted
If you call a subroutine by a tainted name, and if it defers
to an AUTOLOAD function, then $AUTOLOAD will be (correctly)
tainted. (Rick Delaney)
Core Enhancements
state() variables
A new class of variables has been introduced. State
variables are similar to "my" variables, but are declared
with the "state" keyword in place of "my". They're visible
only in their lexical scope, but their value is persistent:
unlike "my" variables, they're not undefined at scope entry,
but retain their previous value. (Rafael Garcia-Suarez)
To use state variables, one needs to enable them by using
use feature "state";
or by using the "-E" command-line switch in one-liners.
See "Persistent variables via state()" in perlsub.
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UNIVERSAL::DOES()
The "UNIVERSAL" class has a new method, "DOES()". It has
been added to solve semantic problems with the "isa()"
method. "isa()" checks for inheritance, while "DOES()" has
been designed to be overridden when module authors use other
types of relations between classes (in addition to
inheritance). (chromatic)
See "$obj->DOES( ROLE )" in UNIVERSAL.
Exceptions in constant folding
The constant folding routine is now wrapped in an exception
handler, and if folding throws an exception (such as
attempting to evaluate 0/0), perl now retains the current
optree, rather than aborting the whole program. (Nicholas
Clark, Dave Mitchell)
Source filters in @INC
It's possible to enhance the mechanism of subroutine hooks
in @INC by adding a source filter on top of the filehandle
opened and returned by the hook. This feature was planned a
long time ago, but wasn't quite working until now. See
"require" in perlfunc for details. (Nicholas Clark)
MAD
MAD, which stands for Misc Attribute Decoration, is a still-
in-development work leading to a Perl 5 to Perl 6 converter.
To enable it, it's necessary to pass the argument "-Dmad" to
Configure. The obtained perl isn't binary compatible with a
regular perl 5.9.4, and has space and speed penalties;
moreover not all regression tests still pass with it. (Larry
Wall, Nicholas Clark)
Modules and Pragmas
o "encoding::warnings" is now a lexical pragma. (Although
on older perls, which don't have support for lexical
pragmas, it keeps its global behaviour.) (Audrey Tang)
o "threads" is now a dual-life module, also available on
CPAN. It has been expanded in many ways. A kill() method
is available for thread signalling. One can get thread
status, or the list of running or joinable threads.
A new "threads->exit()" method is used to exit from the
application (this is the default for the main thread) or
from the current thread only (this is the default for
all other threads). On the other hand, the exit() built-
in now always causes the whole application to terminate.
(Jerry D. Hedden)
New Core Modules
o "Hash::Util::FieldHash", by Anno Siegel, has been added.
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This module provides support for field hashes: hashes
that maintain an association of a reference with a
value, in a thread-safe garbage-collected way. Such
hashes are useful to implement inside-out objects.
o "Module::Build", by Ken Williams, has been added. It's
an alternative to "ExtUtils::MakeMaker" to build and
install perl modules.
o "Module::Load", by Jos Boumans, has been added. It
provides a single interface to load Perl modules and .pl
files.
o "Module::Loaded", by Jos Boumans, has been added. It's
used to mark modules as loaded or unloaded.
o "Package::Constants", by Jos Boumans, has been added.
It's a simple helper to list all constants declared in a
given package.
o "Win32API::File", by Tye McQueen, has been added (for
Windows builds). This module provides low-level access
to Win32 system API calls for files/dirs.
Utility Changes
config_data
"config_data" is a new utility that comes with
"Module::Build". It provides a command-line interface to the
configuration of Perl modules that use Module::Build's
framework of configurability (that is, *::ConfigData modules
that contain local configuration information for their
parent modules.)
Documentation
New manpage, perlpragma
The perlpragma manpage documents how to write one's own
lexical pragmas in pure Perl (something that is possible
starting with 5.9.4).
New manpage, perlreguts
The perlreguts manpage, courtesy of Yves Orton, describes
internals of the Perl regular expression engine.
New manpage, perlunitut
The perlunitut manpage is an tutorial for programming with
Unicode and string encodings in Perl, courtesy of Juerd
Waalboer.
Performance Enhancements
Memory optimisations
Several internal data structures (typeglobs, GVs, CVs,
formats) have been restructured to use less memory.
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(Nicholas Clark)
UTF-8 cache optimisation
The UTF-8 caching code is now more efficient, and used more
often. (Nicholas Clark)
Regular expressions
Engine de-recursivised
The regular expression engine is no longer recursive,
meaning that patterns that used to overflow the stack
will either die with useful explanations, or run to
completion, which, since they were able to blow the
stack before, will likely take a very long time to
happen. If you were experiencing the occasional stack
overflow (or segfault) and upgrade to discover that now
perl apparently hangs instead, look for a degenerate
regex. (Dave Mitchell)
Single char char-classes treated as literals
Classes of a single character are now treated the same
as if the character had been used as a literal, meaning
that code that uses char-classes as an escaping
mechanism will see a speedup. (Yves Orton)
Trie optimisation of literal string alternations
Alternations, where possible, are optimised into more
efficient matching structures. String literal
alternations are merged into a trie and are matched
simultaneously. This means that instead of O(N) time
for matching N alternations at a given point the new
code performs in O(1) time. (Yves Orton)
Note: Much code exists that works around perl's historic
poor performance on alternations. Often the tricks used
to do so will disable the new optimisations. Hopefully
the utility modules used for this purpose will be
educated about these new optimisations by the time 5.10
is released.
Aho-Corasick start-point optimisation
When a pattern starts with a trie-able alternation and
there aren't better optimisations available the regex
engine will use Aho-Corasick matching to find the start
point. (Yves Orton)
Sloppy stat on Windows
On Windows, perl's stat() function normally opens the file
to determine the link count and update attributes that may
have been changed through hard links. Setting
${^WIN32_SLOPPY_STAT} to a true value speeds up stat() by
not performing this operation. (Jan Dubois)
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Installation and Configuration Improvements
Relocatable installations
There is now Configure support for creating a relocatable
perl tree. If you Configure with "-Duserelocatableinc", then
the paths in @INC (and everything else in %Config) can be
optionally located via the path of the perl executable.
That means that, if the string ".../" is found at the start
of any path, it's substituted with the directory of $^X. So,
the relocation can be configured on a per-directory basis,
although the default with "-Duserelocatableinc" is that
everything is relocated. The initial install is done to the
original configured prefix.
Ports
Many improvements have been made towards making Perl work
correctly on z/OS.
Perl has been reported to work on DragonFlyBSD.
Compilation improvements
All ppport.h files in the XS modules bundled with perl are
now autogenerated at build time. (Marcus Holland-Moritz)
New probes
The configuration process now detects whether strlcat() and
strlcpy() are available. When they are not available,
perl's own version is used (from Russ Allbery's public
domain implementation). Various places in the perl
interpreter now use them. (Steve Peters)
Windows build improvements
Building XS extensions
Support for building XS extension modules with the free
MinGW compiler has been improved in the case where perl
itself was built with the Microsoft VC++ compiler.
(ActiveState)
Support for 64-bit compiler
Support for building perl with Microsoft's 64-bit
compiler has been improved. (ActiveState)
Selected Bug Fixes
PERL5SHELL and tainting
On Windows, the PERL5SHELL environment variable is now
checked for taintedness. (Rafael Garcia-Suarez)
Using *FILE{IO}
"stat()" and "-X" filetests now treat *FILE{IO} filehandles
like *FILE filehandles. (Steve Peters)
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Overloading and reblessing
Overloading now works when references are reblessed into
another class. Internally, this has been implemented by
moving the flag for "overloading" from the reference to the
referent, which logically is where it should always have
been. (Nicholas Clark)
Overloading and UTF-8
A few bugs related to UTF-8 handling with objects that have
stringification overloaded have been fixed. (Nicholas Clark)
eval memory leaks fixed
Traditionally, "eval 'syntax error'" has leaked badly. Many
(but not all) of these leaks have now been eliminated or
reduced. (Dave Mitchell)
Random device on Windows
In previous versions, perl would read the file /dev/urandom
if it existed when seeding its random number generator.
That file is unlikely to exist on Windows, and if it did
would probably not contain appropriate data, so perl no
longer tries to read it on Windows. (Alex Davies)
New or Changed Diagnostics
State variable %s will be reinitialized
One can assign initial values to state variables, but
not when they're declared as a sub-part of a list
assignment. See perldiag.
Changed Internals
A new file, mathoms.c, contains functions that aren't used
anymore in the perl core, but remain around because modules
out there might still use them. They come from a
factorization effort: for example, many PP functions are now
shared for several ops.
The implementation of the special variables $^H and %^H has
changed, to allow implementing lexical pragmas in pure perl.
Known Problems
One warning test (number 263 in lib/warnings.t) fails under
UTF-8 locales.
Bytecode tests fail under several platforms. We are
considering removing support for byteloader and compiler
before the 5.10.0 release.
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/rt3/ . There may also be information at
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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.
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
+---------------+------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+------------------+
|Availability | runtime/perl-512 |
+---------------+------------------+
|Stability | Uncommitted |
+---------------+------------------+
SEE ALSO
The Changes file for 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.
NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from
http://www.cpan.org/src/5.0/perl-5.12.5.tar.bz2
Further information about this software can be found on the
open source community website at http://www.perl.org/.
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