NAME
perl593delta - what is new for perl v5.9.3
DESCRIPTION
This document describes differences between the 5.9.2 and the 5.9.3 development releases. See perl590delta, perl591delta and perl592delta for the differences between 5.8.0 and 5.9.2.
Incompatible Changes
Parsing of \f(CW\-f _\fP
The identifier
_is now forced to be a bareword after a filetest operator. This solves a number of misparsing issues when a global
_subroutine is defined.
\f(CWmkdir()\fP
mkdir()without arguments now defaults to
$_.
Magic goto and eval
The construct
eval { goto &foo }is now disallowed. (Note that the similar construct, but with
eval("")instead, was already forbidden.)
\f(CW$#\fP has been removed
The deprecated
$#variable (output format for numbers) has been removed. A new warning,
$# is no longer supported, has been added.
\f(CW:unique\fP
The
:uniqueattribute has been made a no-op, since its current implementation was fundamentally flawed and not threadsafe.
Scoping of the \f(CWsort\fP pragma
The
sortpragma is now lexically scoped. Its effect used to be global.
Core Enhancements
The \f(CWfeature\fP pragma
The
featurepragma is used to enable new syntax that would break Perls backwards-compatibility with older releases of the language. Its a lexical pragma, like
strictor
warnings.
Currently the following new features are available:
switch(adds a switch statement),
~~(adds a Perl 6-like smart match operator),
say(adds a
saybuilt-in function), and
err(adds an
errkeyword). Those features are described below.
Note that
errlow-precedence defined-or operator used to be enabled by default (although as a weak keyword, meaning that any function would override it). Its now only recognized when explicitly turned on (and is then a regular keyword).
Those features, and the
featurepragma itself, have been contributed by Robin Houston.
Switch and Smart Match operator
Perl 5 now has a switch statement. Its available when
use feature switchis in effect. This feature introduces three new keywords,
given,
when, and
default:
given ($foo) {
when (/^abc/) { $abc = 1; }
when (/^def/) { $def = 1; }
when (/^xyz/) { $xyz = 1; }
default { $nothing = 1; }
}
A more complete description of how Perl matches the switch variable against the
whenconditions is given in Switch statements in perlsyn.
This kind of match is called smart match, and its also possible to use it outside of switch statements, via the new
~~operator (enabled via the
use feature ~~directive). See Smart matching in detail in perlsyn.
\f(CWsay()\fP
say() is a new built-in, only available when
use feature sayis in effect, that is similar to print(), but that implicitly appends a newline to the printed string. See say in perlfunc.
\f(CWCLONE_SKIP()\fP
Perl has now support for the
CLONE_SKIPspecial subroutine. Like
CLONE,
CLONE_SKIPis called once per package; however, it is called just before cloning starts, and in the context of the parent thread. If it returns a true value, then no objects of that class will be cloned. See perlmod for details. (Contributed by Dave Mitchell.)
\f(CW${^CHILD_ERROR_NATIVE}\fP
A new internal variable,
${^CHILD_ERROR_NATIVE}, gives the native status returned by the last pipe close, backtick command, successful call to wait() or waitpid(), or from the system() operator. See perlrun for details. (Contributed by Gisle Aas.)
Assertions
The support for assertions, introduced in perl 5.9.0, has been improved. The syntax for the
-Acommand-line switch has changed; it now accepts an optional module name, defaulting to
assertions::activate. See assertions and perlrun. (Contributed by Salvador Fandinõ Garciá.)
Unicode Character Database 4.1.0
The copy of the Unicode Character Database included in Perl 5.9 has been updated to 4.1.0.
\f(CWno VERSION\fP
You can now use
nofollowed by a version number to specify that you want to use a version of perl older than the specified one.
Recursive sort subs
You can now use recursive subroutines with sort(), thanks to Robin Houston.
Effect of pragmas in eval
The compile-time value of the
%^Hhint variable can now propagate into eval("")uated code. This makes it more useful to implement lexical pragmas.
As a side-effect of this, the overloaded-ness of constants now propagates into eval("").
New \fB\-E\fP command-line switch
-E is equivalent to -e, but it implicitly enables all optional features (like
use feature ":5.10").
\f(CWchdir\fP, \f(CWchmod\fP and \f(CWchown\fP on filehandles
chdir,
chmodand
chowncan now work on filehandles as well as filenames, if the system supports respectively
fchdir,
fchmodand
fchown, thanks to a patch provided by Gisle Aas.
\s-1OS\s0 groups
$(and
$)now return groups in the order where the OS returns them, thanks to Gisle Aas. This wasnt previously the case.
Modules and Pragmata
New Core Modules
o |
A new pragma, feature, has been added; see above in Core Enhancements. |
o |
assertions::compat, also available on CPAN, allows the use of assertions on perl versions prior to 5.9.0 (that is the first one to natively support them). |
o |
Math::BigInt::FastCalcis an XS-enabled, and thus faster, version of Math::BigInt::Calc. |
o |
Compress::Zlibis an interface to the zlib compression library. It comes with a bundled version of zlib, so having a working zlib is not a prerequisite to install it. Its used by Archive::Tar(see below). |
o |
IO::Zlibis an IO::-style interface to Compress::Zlib. |
o |
Archive::Taris a module to manipulate tararchives. |
o |
Digest::SHAis a module used to calculate many types of SHA digests, has been included for SHA support in the CPAN module. |
o |
ExtUtils::CBuilderand ExtUtils::ParseXShave been added. |
Utility Changes
\f(CWptar\fP
ptaris a pure perl implementation of
tar, that comes with
Archive::Tar.
\f(CWptardiff\fP
ptardiffis a small script used to generate a diff between the contents of a tar archive and a directory tree. Like
ptar, it comes with
Archive::Tar.
\f(CWshasum\fP
This command-line utility, used to print or to check SHA digests, comes with the new
Digest::SHAmodule.
\f(CWh2xs\fP enhancements
h2xsimplements a new option
--use-xsloaderto force use of
XSLoadereven in backwards compatible modules.
The handling of authors names that had apostrophes has been fixed.
Any enums with negative values are now skipped.
\f(CWperlivp\fP enhancements
perlivpno longer checks for *.ph files by default. Use the new
-aoption to run all tests.
Documentation
Perl Glossary
The perlglossary manpage is a glossary of terms used in the Perl documentation, technical and otherwise, kindly provided by OReilly Media, Inc.
perltodo now lists a rough roadmap to Perl 5.10.
Performance Enhancements
XS-assisted \s-1SWASHGET\s0
Some pure-perl code that perl was using to retrieve Unicode properties and transliteration mappings has been reimplemented in XS.
Constant subroutines
The interpreter internals now support a far more memory efficient form of inlineable constants. Storing a reference to a constant value in a symbol table is equivalent to a full typeglob referencing a constant subroutine, but using about 400 bytes less memory. This proxy constant subroutine is automatically upgraded to a real typeglob with subroutine if necessary. The approach taken is analogous to the existing space optimisation for subroutine stub declarations, which are stored as plain scalars in place of the full typeglob.
Several of the core modules have been converted to use this feature for their system dependent constants - as a result
use POSIX;now takes about 200K less memory.
\f(CWPERL_DONT_CREATE_GVSV\fP
The new compilation flag
PERL_DONT_CREATE_GVSV, introduced as an option in perl 5.8.8, is turned on by default in perl 5.9.3. It prevents perl from creating an empty scalar with every new typeglob. See perl588delta for details.
Weak references are cheaper
Weak reference creation is now O(1) rather than O(n), courtesy of Nicholas Clark. Weak reference deletion remains O(n), but if deletion only happens at program exit, it may be skipped completely.
\fIsort()\fP enhancements
Salvador Fandinõ provided improvements to reduce the memory usage of
sortand to speed up some cases.
Installation and Configuration Improvements
Compilation improvements
Parallel makes should work properly now, although there may still be problems if
make testis instructed to run in parallel.
Building with Borlands compilers on Win32 should work more smoothly. In particular Steve Hay has worked to side step many warnings emitted by their compilers and at least one C compiler internal error.
Perl extensions on Windows now can be statically built into the Perl DLL, thanks to a work by Vadim Konovalov.
New Or Improved Platforms
Perl is being ported to Symbian OS. See perlsymbian for more information.
The VMS port has been improved. See perlvms.
DynaLoader::dl_unload_file() now works on Windows.
Portability of Perl on various recent compilers on Windows has been improved (Borland C++, Visual C++ 7.0).
New probes
Configurewill now detect
clearenvand
unsetenv, thanks to a patch from Alan Burlison. It will also probe for
futimes(and use it internally if available), and whether
sprintfcorrectly returns the length of the formatted string.
Module auxiliary files
README files and changelogs for CPAN modules bundled with perl are no longer installed.
Selected Bug Fixes
\f(CWdefined $$x\fP
use strict "refs"was ignoring taking a hard reference in an argument to defined(), as in :
use strict "refs";
my $x = "foo";
if (defined $$x) {...}
This now correctly produces the run-time error
Cant use string as a SCALAR ref while "strict refs" in use. (However,
defined @$fooand
defined %$fooare still allowed. Those constructs are discouraged anyway.)
Calling \fICORE::require()\fP
CORE::require() and CORE::do() were always parsed as require() and do() when they were overridden. This is now fixed.
Subscripts of slices
You can now use a non-arrowed form for chained subscripts after a list slice, like in:
({foo => "bar"})[0]{foo}
This used to be a syntax error; a
->was required.
Remove over-optimisation
Perl 5.9.2 introduced a change so that assignments of
undefto a scalar, or of an empty list to an array or a hash, were optimised out. As this could cause problems when
gotojumps were involved, this change was backed out.
\fIsprintf()\fP fixes
Using the sprintf() function with some formats could lead to a buffer overflow in some specific cases. This has been fixed, along with several other bugs, notably in bounds checking.
In related fixes, it was possible for badly written code that did not follow the documentation of
Sys::Syslogto have formatting vulnerabilities.
Sys::Sysloghas been changed to protect people from poor quality third party code.
no warnings 'category' works correctly with \-w
Previously when running with warnings enabled globally via
-w, selective disabling of specific warning categories would actually turn off all warnings. This is now fixed; now
no warnings io;will only turn off warnings in the
ioclass. Previously it would erroneously turn off all warnings.
Smaller fixes
o |
FindBinnow works better with directories where access rights are more restrictive than usual. |
o | Several memory leaks in ithreads were closed. Also, ithreads were made less memory-intensive. |
o |
Trailing spaces are now trimmed from $!and $^E. |
o |
Operations that require perl to read a process list of groups, such as reads
of $(and $), now dynamically allocate memory rather than using a fixed sized array. The fixed size array could cause C stack exhaustion on systems configured to use large numbers of groups. |
o |
PerlIO::scalarnow works better with non-default $/settings. |
o |
The xrepetition operator is now able to operate on qw//lists. This used to raise a syntax error. |
o | The debugger now traces correctly execution in eval("")uated code that contains #line directives. |
o |
The value of the openpragma is no longer ignored for three-argument opens. |
o |
Perl will now use the C library calls unsetenvand clearenvif present to delete keys from %ENVand delete %ENVentirely, thanks to a patch from Alan Burlison. |
More Unicode Fixes
o |
chr() on a negative value now gives \x{FFFD}, the Unicode replacement character, unless when the bytespragma is in effect, where the low eight bytes of the value are used. |
o | Some case insensitive matches between UTF-8 encoded data and 8 bit regexps, and vice versa, could give malformed character warnings. These have been fixed by Dave Mitchell and Yves Orton. |
o |
lcfirstand ucfirstcould corrupt the string for certain cases where the length UTF-8 encoding of the string in lower case, upper case or title case differed. This was fixed by Nicholas Clark. |
New or Changed Diagnostics
Attempt to set length of freed array
This is a new warning, produced in situations like the following one:
$r = do {my @a; \$#a};
$$r = 503;
Non-string passed as bitmask
This is a new warning, produced when number has been passed as a argument to select(), instead of a bitmask.
# Wrong, will now warn
$rin = fileno(STDIN);
($nfound,$timeleft) = select($rout=$rin, undef, undef, $timeout);
# Should be
$rin = ;
vec($rin,fileno(STDIN),1) = 1;
($nfound,$timeleft) = select($rout=$rin, undef, undef, $timeout);
Search pattern not terminated or ternary operator parsed as search pattern
This syntax error indicates that the lexer couldnt find the final delimiter of a
?PATTERN?construct. Mentioning the ternary operator in this error message makes syntax diagnostic easier.
``%s'' variable \f(CW%s\fP masks earlier declaration
This warning is now emitted in more consistent cases; in short, when one of the declarations involved is a
myvariable:
my $x; my $x; # warns
my $x; our $x; # warns
our $x; my $x; # warns
On the other hand, the following:
our $x; our $x;
now gives a
"our" variable %s redeclaredwarning.
\fIreaddir()\fP/\fIclosedir()\fP/etc. attempted on invalid dirhandle
These new warnings are now emitted when a dirhandle is used but is either closed or not really a dirhandle.
Changed Internals
In general, the source code of perl has been refactored, tied up, and optimized in many places. Also, memory management and allocation has been improved in a couple of points.
Andy Lester supplied many improvements to determine which function parameters and local variables could actually be declared
constto the C compiler. Steve Peters provided new
*_setmacros and reworked the core to use these rather than assigning to macros in LVALUE context.
Dave Mitchell improved the lexer debugging output under
-DT.
A new file, mathoms.c, has been added. It contains functions that are no longer used in the perl core, but that remain available for binary or source compatibility reasons. However, those functions will not be compiled in if you add
-DNO_MATHOMSin the compiler flags.
The
AvFLAGSmacro has been removed.
The
av_*()functions, used to manipulate arrays, no longer accept null
AV*parameters.
B:: modules inheritance changed
The inheritance hierarchy of
B::modules has changed;
B::NVnow inherits from
B::SV(it used to inherit from
B::IV).
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://bugs.perl.org/ . There may also be information at http://www.perl.org/ , the Perl Home Page.
If you believe you have an unreported bug, please run the perlbug program included with your release. Be sure to trim your bug down to a tiny but sufficient test case. Your bug report, along with the output of
perl -V, will be sent off to perlbug@perl.org to be analysed by the Perl porting team.
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.