Re: Threaded Perl
Brendan O'Dea <bod@debian.org> writes:
> On Sat, Mar 09, 2002 at 03:52:42PM -0800, Ryan White wrote:
> >I posted to debian-user but no one seems to know or want to respond. So I
> >was wondering what the status of perl-thread is?
> I'm loathe to enable threading support in the standard perl package
> given that the documentation lists a bunch of warnings and notes that
> "it is not recommended for production machines".
...
>
> In addition, enabling thread support would break binary compatibility
> with the 100+ current binary perl modules.
>
> Providing a separate perl-thread (and libperl5.6-thread) package still
> has the binary compatibility issues, meaning that any binary module
> package which is to be used by perl-thread needs to be built twice:
> once for the perl package and once for perl-thread.
>
> To further complicate matters, there are two different threading models:
> 5.005 threads and ithreads. The former allows user-level threads to be
> created, the latter does not but is useful for interfacing with threaded
> libraries.
>
> So conceivably there would be three perl interpreters (perl, perl-thread
> and perl-ithread) and in cases three versions binary modules
> (libfoo-perl, libfoo-perl-thread, libfoo-perl-ithread).
>
> If/when threading support stabilises I will consider making the standard
> perl thread-enabled (which would require rebuilding a bunch of packages
> transitionally, but would be simpler in the long term).
>
> I will re-investigate the situation when 5.8.0 is released but for now
> I'm afraid that building your own perl is required if you need threads.
The 5.005 threads are deprecated. 5.8.0 uses ithreads. 5.8.0 has
user-level interface for ithreads. 5.8.0 has safe signals and safe
threading.
It will probably still be experimental, but it looks much more
promising.
I don't know whare on the net you can find the perldelta. I'll attach
it here.., from the 5.7.3 distro:
PERLDELTA(1) Perl Programmers Reference Guide PERLDELTA(1)
NAME
perldelta - what is new for perl v5.8.0
DESCRIPTION
This document describes differences between the 5.6.0
release and the 5.8.0 release.
Many of the bug fixes in 5.8.0 were already seen in the
5.6.1 maintenance release since the two releases were kept
closely coordinated.
If you are upgrading from Perl 5.005_03, you might also
want to read perl56delta.
Highlights In 5.8.0
· Better Unicode support
· New Thread Implementation
· Many New Modules
· Better Numeric Accuracy
· Safe Signals
· More Extensive Regression Testing
Incompatible Changes
64-bit platforms and malloc
If your pointers are 64 bits wide, the Perl malloc is no
longer being used because it does not work well with
8-byte pointers. Also, usually the system mallocs on such
platforms are much better optimized for such large memory
models than the Perl malloc. Some memory-hungry Perl
applications like the PDL don't work well with Perl's mal
loc. Finally, other applications than Perl (like modperl)
tend to prefer the system malloc. Such platforms include
Alpha and 64-bit HPPA, MIPS, PPC, and Sparc.
AIX Dynaloading
The AIX dynaloading now uses in AIX releases 4.3 and newer
the native dlopen interface of AIX instead of the old emu
lated interface. This change will probably break backward
compatibility with compiled modules. The change was made
to make Perl more compliant with other applications like
modperl which are using the AIX native interface.
Attributes for "my" variables now handled at run-time.
The "my EXPR : ATTRS" syntax now applies variable
attributes at run-time. (Subroutine and "our" variables
still get attributes applied at compile-time.) See
attributes for additional details. In particular, how
ever, this allows variable attributes to be useful for
"tie" interfaces, which was a deficiency of earlier
releases. Note that the new semantics doesn't work with
the Attribute::Handlers module (as of version 0.76).
Socket Extension Dynamic in VMS
The Socket extension is now dynamically loaded instead of
being statically built in. This may or may not be a prob
lem with ancient TCP/IP stacks of VMS: we do not know
since we weren't able to test Perl in such configurations.
IEEE-format Floating Point Default on OpenVMS Alpha
Perl now uses IEEE format (T_FLOAT) as the default inter
nal floating point format on OpenVMS Alpha, potentially
breaking binary compatibility with external libraries or
existing data. G_FLOAT is still available as a configura
tion option. The default on VAX (D_FLOAT) has not
changed.
New Unicode Properties
Unicode scripts are now supported. Scripts are similar to
(and superior to) Unicode blocks. The difference between
scripts and blocks is that scripts are the glyphs used by
a language or a group of languages, while the blocks are
more artificial groupings of (mostly) 256 characters based
on the Unicode numbering.
In general, scripts are more inclusive, but not univer
sally so. For example, while the script "Latin" includes
all the Latin characters and their various diacritic-
adorned versions, it does not include the various punctua
tion or digits (since they are not solely "Latin").
A number of other properties are now supported, including
"\p{L&}", "\p{Any}" "\p{Assigned}", "\p{Unassigned}",
"\p{Blank}" and "\p{SpacePerl}" (along with their
"\P{...}" versions, of course). See perlunicode for
details, and more additions.
The "In" or "Is" prefix to names used with the "\p{...}"
and "\P{...}" are now almost always optional. The only
exception is that a "In" prefix is required to signify a
Unicode block when a block name conflicts with a script
name. For example, "\p{Tibetan}" refers to the script,
while "\p{InTibetan}" refers to the block. When there is
no name conflict, you can omit the "In" from the block
name (e.g. "\p{BraillePatterns}"), but to be safe, it's
probably best to always use the "In").
Perl Parser Stress Tested
The Perl parser has been stress tested using both random
input and Markov chain input and the few found crashes and
lockups have been fixed.
REF(...) Instead Of SCALAR(...)
A reference to a reference now stringifies as
"REF(0x81485ec)" instead of "SCALAR(0x81485ec)" in order
to be more consistent with the return value of ref().
pack/unpack D/F recycled
The undocumented pack/unpack template letters D/F have
been recycled for better use: now they stand for long dou
ble (if supported by the platform) and NV (Perl internal
floating point type). (They used to be aliases for f/d,
but you never knew that.)
Deprecations
· The semantics of bless(REF, REF) were unclear and
until someone proves it to make some sense, it is for
bidden.
· The obsolete chat2 library that should never have been
allowed to escape the laboratory has been decommis
sioned.
· The builtin dump() function has probably outlived most
of its usefulness. The core-dumping functionality
will remain in future available as an explicit call to
"CORE::dump()", but in future releases the behaviour
of an unqualified "dump()" call may change.
· The very dusty examples in the eg/ directory have been
removed. Suggestions for new shiny examples welcome
but the main issue is that the examples need to be
documented, tested and (most importantly) maintained.
· The (bogus) escape sequences \8 and \9 now give an
optional warning ("Unrecognized escape passed
through"). There is no need to \-escape any "\w"
character.
· The list of filenames from glob() (or <...>) is now by
default sorted alphabetically to be csh-compliant
(which is what happened before in most UNIX plat
forms). (bsd_glob() does still sort platform
natively, ASCII or EBCDIC, unless GLOB_ALPHASORT is
specified.)
· Spurious syntax errors generated in certain situa
tions, when glob() caused File::Glob to be loaded for
the first time, have been fixed.
· Although "you shouldn't do that", it was possible to
write code that depends on Perl's hashed key order
(Data::Dumper does this). The new algorithm
"One-at-a-Time" produces a different hashed key order.
More details are in "Performance Enhancements".
· lstat(FILEHANDLE) now gives a warning because the
operation makes no sense. In future releases this may
become a fatal error.
· The "package;" syntax ("package" without an argument)
has been deprecated. Its semantics were never that
clear and its implementation even less so. If you
have used that feature to disallow all but fully qual
ified variables, "use strict;" instead.
· The unimplemented POSIX regex features [[.cc.]] and
[[=c=]] are still recognised but now cause fatal
errors. The previous behaviour of ignoring them by
default and warning if requested was unacceptable
since it, in a way, falsely promised that the features
could be used.
· The current user-visible implementation of pseudo-
hashes (the weird use of the first array element) is
deprecated starting from Perl 5.8.0 and will be
removed in Perl 5.10.0, and the feature will be imple
mented differently. Not only is the current interface
rather ugly, but the current implementation slows down
normal array and hash use quite noticeably. The
"fields" pragma interface will remain available.
· The syntaxes "@a->[...]" and "%h->{...}" have now
been deprecated.
· After years of trying the suidperl is considered to be
too complex to ever be considered truly secure. The
suidperl functionality is likely to be removed in a
future release.
· The long deprecated uppercase aliases for the string
comparison operators (EQ, NE, LT, LE, GE, GT) have now
been removed.
· The tr///C and tr///U features have been removed and
will not return; the interface was a mistake. Sorry
about that. For similar functionality, see pack('U0',
...) and pack('C0', ...).
· Earlier Perls treated "sub foo (@bar)" as equivalent
to "sub foo (@)". The prototypes are now checked at
compile-time for invalid characters. An optional
warning is generated ("Illegal character in proto
type...") but this may be upgraded to a fatal error
in a future release.
Core Enhancements
PerlIO is Now The Default
· IO is now by default done via PerlIO rather than sys
tem's "stdio". PerlIO allows "layers" to be "pushed"
onto a file handle to alter the handle's behaviour.
Layers can be specified at open time via 3-arg form of
open:
open($fh,'>:crlf :utf8', $path) || ...
or on already opened handles via extended "binmode":
binmode($fh,':encoding(iso-8859-7)');
The built-in layers are: unix (low level read/write),
stdio (as in previous Perls), perlio (re-implementa
tion of stdio buffering in a portable manner), crlf
(does CRLF <=> "\n" translation as on Win32, but
available on any platform). A mmap layer may be
available if platform supports it (mostly UNIXes).
Layers to be applied by default may be specified via
the 'open' pragma.
See "Installation and Configuration Improvements" for
the effects of PerlIO on your architecture name.
· File handles can be marked as accepting Perl's inter
nal encoding of Unicode (UTF-8 or UTF-EBCDIC depending
on platform) by a pseudo layer ":utf8" :
open($fh,">:utf8","Uni.txt");
Note for EBCDIC users: the pseudo layer ":utf8" is
erroneously named for you since it's not UTF-8 what
you will be getting but instead UTF-EBCDIC. See per
lunicode, utf8, and http://www.unicode.org/uni;
code/reports/tr16/ for more information. In future
releases this naming may change.
· File handles can translate character encodings from/to
Perl's internal Unicode form on read/write via the
":encoding()" layer.
· File handles can be opened to "in memory" files held
in Perl scalars via:
open($fh,'>', \$variable) || ...
· Anonymous temporary files are available without need
to 'use FileHandle' or other module via
open($fh,"+>", undef) || ...
That is a literal undef, not an undefined value.
· The list form of "open" is now implemented for pipes
(at least on UNIX):
open($fh,"-|", 'cat', '/etc/motd')
creates a pipe, and runs the equivalent of exec('cat',
'/etc/motd') in the child process.
Safe Signals
Perl used to be fragile in that signals arriving at inop
portune moments could corrupt Perl's internal state. Now
Perl postpones handling of signals until it's safe
(between opcodes).
This change may have surprising side effects because sig
nals no longer interrupt Perl instantly. Perl will now
first finish whatever it was doing, like finishing an
internal operation (like sort()) or an external operation
(like an I/O operation), and only then look at any arrived
signals (and before starting the next operation). No more
corrupt internal state since the current operation is
always finished first, but the signal may take more time
to get heard.
Unicode Overhaul
Unicode in general should be now much more usable than in
Perl 5.6.0 (or even in 5.6.1). Unicode can be used in
hash keys, Unicode in regular expressions should work now,
Unicode in tr/// should work now, Unicode in I/O should
work now.
· The Unicode Character Database coming with Perl has
been upgraded to Unicode 3.1.1. For more information,
see http://www.unicode.org/.
· For developers interested in enhancing Perl's Unicode
capabilities: almost all the UCD files are included
with the Perl distribution in the lib/unicore subdi
rectory. The most notable omission, for space consid
erations, is the Unihan database.
· The properties \p{Blank} and \p{SpacePerl} have been
added. "Blank" is like C isblank(), that is, it con
tains only "horizontal whitespace" (the space charac
ter is, the newline isn't), and the "SpacePerl" is the
Unicode equivalent of "\s" (\p{Space} isn't, since
that includes the vertical tabulator character,
whereas "\s" doesn't.)
See "New Unicode Properties" earlier in this document
for additional information on changes with Unicode
properties.
Understanding of Numbers
In general a lot of fixing has happened in the area of
Perl's understanding of numbers, both integer and floating
point. Since in many systems the standard number parsing
functions like "strtoul()" and "atof()" seem to have bugs,
Perl tries to work around their deficiencies. This
results hopefully in more accurate numbers.
Perl now tries internally to use integer values in numeric
conversions and basic arithmetics (+ - * /) if the argu
ments are integers, and tries also to keep the results
stored internally as integers. This change leads to often
slightly faster and always less lossy arithmetics. (Previ
ously Perl always preferred floating point numbers in its
math.)
Miscellaneous Changes
· AUTOLOAD is now lvaluable, meaning that you can add
the :lvalue attribute to AUTOLOAD subroutines and you
can assign to the AUTOLOAD return value.
· "perl -d:Module=arg,arg,arg" now works (previously one
couldn't pass in multiple arguments.)
· The builtin dump() now gives an optional warning
"dump() better written as CORE::dump()", meaning that
by default "dump(...)" is resolved as the builtin
dump() which dumps core and aborts, not as (possibly)
user-defined "sub dump". To call the latter, qualify
the call as "&dump(...)". (The whole dump() feature
is to considered deprecated, and possibly
removed/changed in future releases.)
· chomp() and chop() have been demoted back to not being
overridable because they cannot really be overridden--
the problem is that their prototype cannot be
expressed and therefore one really cannot write
replacements to override these builtins.
· END blocks are now run even if you exit/die in a BEGIN
block. Internally, the execution of END blocks is now
controlled by PL_exit_flags & PERL_EXIT_DESTRUCT_END.
This enables the new behaviour for Perl embedders.
This will default in 5.10. See perlembed.
· Formats now support zero-padded decimal fields.
· Lvalue subroutines can now return "undef" in list con
text. However, the lvalue subroutine feature still
remains experimental.
· A lost warning "Can't declare ... dereference in my"
has been restored (Perl had it earlier but it became
lost in later releases.)
· A new special regular expression variable has been
introduced: $^N, which contains the most-recently
closed group (submatch).
· "no Module;" now works even if there is no "sub unim
port" in the Module.
· The numerical comparison operators return "undef" if
either operand is a NaN. Previously the behaviour was
unspecified.
· The following builtin functions are now overridable:
each(), keys(), pop(), push(), shift(), splice(),
unshift().
· "pack() / unpack()" now can group template letters
with "()" and then apply repetition/count modifiers on
the groups.
· "pack() / unpack()" can now process the Perl internal
numeric types: IVs, UVs, NVs-- and also long doubles,
if supported by the platform. The template letters
are "j", "J", "F", and "D".
· "pack('U0a*', ...)" can now be used to force a string
to UTF8.
· my __PACKAGE__ $obj now works.
· The printf() and sprintf() now support parameter
reordering using the "%\d+\$" and "*\d+\$" syntaxes.
For example
print "%2\$s %1\$s\n", "foo", "bar";
will print "bar foo\n". This feature helps in writing
internationalised software, and in general when the
order of the parameters can vary.
· prototype(\&) is now available.
· prototype(\[$@%&]) is now available to implicitly cre
ate references (useful for example if you want to emu
late the tie() interface).
· A new command-line option, "-t" is available. It is
the little brother of "-T": instead of dieing on taint
violations, lexical warnings are given. This is only
meant as a temporary debugging aid while securing the
code of old legacy applications. This is not a sub
stitute for -T.
· In other taint news, the "exec LIST" and "system LIST"
have now been considered too risky (think "exec
@ARGV": it can start any program with any arguments),
and now the said forms cause a warning. You should
carefully launder the arguments to guarantee their
validity. In future releases of Perl the forms will
become fatal errors so consider starting laundering
now.
· If tr/// is just counting characters, it doesn't
attempt to modify its target.
· untie() will now call an UNTIE() hook if it exists.
See perltie for details.
· utime now supports "utime undef, undef, @files" to
change the file timestamps to the current time.
· The rules for allowing underscores (underbars) in
numeric constants have been relaxed and simplified:
now you can have an underscore simply between digits.
· Rather than relying on C's argv[0] (which may not con
tain a full pathname) where possible $^X is now set by
asking the operating system. (eg by reading
/proc/self/exe on Linux, /proc/curproc/file on
FreeBSD)
Modules and Pragmata
New Modules and Pragmata
· "Attribute::Handlers" allows a class to define
attribute handlers.
package MyPack;
use Attribute::Handlers;
sub Wolf :ATTR(SCALAR) { print "howl!\n" }
# later, in some package using or inheriting from MyPack...
my MyPack $Fluffy : Wolf; # the attribute handler Wolf will be called
Both variables and routines can have attribute han
dlers. Handlers can be specific to type (SCALAR,
ARRAY, HASH, or CODE), or specific to the exact compi
lation phase (BEGIN, CHECK, INIT, or END).
· B::Concise is a new compiler backend for walking the
Perl syntax tree, printing concise info about ops,
from Stephen McCamant. The output is highly customis
able. See B::Concise.
· "Class::ISA" for reporting the search path for a
class's ISA tree, by Sean Burke, has been added. See
Class::ISA.
· "Cwd" has now a split personality: if possible, an XS
extension is used, (this will hopefully be faster,
more secure, and more robust) but if not possible, the
familiar Perl implementation is used.
· "Devel::PPPort", originally from Kenneth Albanowski
and now maintained by Paul Marquess, has been added.
It is primarily used by "h2xs" to enhance portability
of XS modules between different versions of Perl.
· "Digest", frontend module for calculating digests
(checksums), from Gisle Aas, has been added. See
Digest.
· "Digest::MD5" for calculating MD5 digests (checksums)
as defined in RFC 1321, from Gisle Aas, has been
added. See Digest::MD5.
use Digest::MD5 'md5_hex';
$digest = md5_hex("Thirsty Camel");
print $digest, "\n"; # 01d19d9d2045e005c3f1b80e8b164de1
NOTE: the "MD5" backward compatibility module is
deliberately not included since its further use is
discouraged.
· "Encode", by Nick Ing-Simmons, provides a mechanism to
translate between different character encodings. Sup
port for Unicode, ISO-8859-*, ASCII, CP*, KOI8-R, and
three variants of EBCDIC are compiled in to the mod
ule. Several other encodings (like Japanese, Chinese,
and MacIntosh encodings) are included and will be
loaded at runtime. See Encode.
Any encoding supported by Encode module is also avail
able to the ":encoding()" layer if PerlIO is used.
· "I18N::Langinfo" can be use to query locale informa
tion. See I18N::Langinfo.
· "I18N::LangTags" has functions for dealing with
RFC3066-style language tags, by Sean Burke. See
I18N::LangTags.
· "ExtUtils::Constant" is a new tool for extension writ
ers for generating XS code to import C header con
stants, by Nicholas Clark. See ExtUtils::Constant.
· "Filter::Simple" is an easy-to-use frontend to Fil
ter::Util::Call, from Damian Conway. See Filter::Sim
ple.
# in MyFilter.pm:
package MyFilter;
use Filter::Simple sub {
while (my ($from, $to) = splice @_, 0, 2) {
s/$from/$to/g;
}
};
1;
# in user's code:
use MyFilter qr/red/ => 'green';
print "red\n"; # this code is filtered, will print "green\n"
print "bored\n"; # this code is filtered, will print "bogreen\n"
no MyFilter;
print "red\n"; # this code is not filtered, will print "red\n"
· "File::Temp" allows one to create temporary files and
directories in an easy, portable, and secure way, by
Tim Jenness. See File::Temp.
· "Filter::Util::Call" provides you with the framework
to write Source Filters in Perl, from Paul Marquess.
For most uses the frontend Filter::Simple is to be
preferred. See Filter::Util::Call.
· "if" is a new pragma for conditional inclusion of mod
ules, from Ilya Zakharevich.
· libnet is a collection of perl5 modules related to
network programming, from Graham Barr. See Net::FTP,
Net::NNTP, Net::Ping, Net::POP3, Net::SMTP, and
Net::Time.
Perl installation leaves libnet unconfigured, use lib
netcfg to configure.
· "List::Util" is a selection of general-utility list
subroutines, like sum(), min(), first(), and shuf
fle(), by Graham Barr. See List::Util.
· "Locale::Constants", "Locale::Country", "Locale::Cur
rency", and "Locale::Language", from Neil Bowers, have
been added. They provide the codes for various locale
standards, such as "fr" for France, "usd" for US Dol
lar, and "jp" for Japanese.
use Locale::Country;
$country = code2country('jp'); # $country gets 'Japan'
$code = country2code('Norway'); # $code gets 'no'
See Locale::Constants, Locale::Country, Locale::Cur
rency, and Locale::Language.
· "Locale::Maketext" is localization framework from Sean
Burke. See Locale::Maketext, and Locale::Make
text::TPJ13. The latter is an article about software
localization, originally published in The Perl Journal
#13, republished here with kind permission.
· "Memoize" can make your functions faster by trading
space for time, from Mark-Jason Dominus. See Memoize.
· "MIME::Base64" allows you to encode data in base64,
from Gisle Aas, as defined in RFC 2045 - MIME (Multi
purpose Internet Mail Extensions).
use MIME::Base64;
$encoded = encode_base64('Aladdin:open sesame');
$decoded = decode_base64($encoded);
print $encoded, "\n"; # "QWxhZGRpbjpvcGVuIHNlc2FtZQ=="
See MIME::Base64.
· "MIME::QuotedPrint" allows you to encode data in
quoted-printable encoding, as defined in RFC 2045 -
MIME (Multipurpose Internet Mail Extensions), from
Gisle Aas.
use MIME::QuotedPrint;
$encoded = encode_qp("Smiley in Unicode: \x{263a}");
$decoded = decode_qp($encoded);
print $encoded, "\n"; # "Smiley in Unicode: =263A"
MIME::QuotedPrint has been enhanced to provide the
basic methods necessary to use it with PerlIO::Via as
in :
use MIME::QuotedPrint;
open($fh,">Via(MIME::QuotedPrint)",$path);
See MIME::QuotedPrint.
· "NEXT" is pseudo-class for method redispatch, from
Damian Conway. See NEXT.
· "open" is a new pragma for setting the default I/O
disciplines for open().
· "PerlIO::Scalar" provides the implementation of IO to
"in memory" Perl scalars as discussed above, from Nick
Ing-Simmons. It also serves as an example of a load
able PerlIO layer. Other future possibilities include
PerlIO::Array and PerlIO::Code. See PerlIO::Scalar.
· "PerlIO::Via" acts as a PerlIO layer and wraps PerlIO
layer functionality provided by a class (typically
implemented in perl code), from Nick Ing-Simmons.
use MIME::QuotedPrint;
open($fh,">Via(MIME::QuotedPrint)",$path);
This will automatically convert everything output to
$fh to Quoted-Printable. See PerlIO::Via.
· "Pod::ParseLink", by Russ Allbery, has been added, to
parse L<> links in pods as described in the new
perlpodspec.
· "Pod::Text::Overstrike", by Joe Smith, has been added.
It converts POD data to formatted overstrike text.
See Pod::Text::Overstrike.
· "Scalar::Util" is a selection of general-utility
scalar subroutines, like blessed(), reftype(), and
tainted(). See Scalar::Util.
· "sort" is a new pragma for controlling the behaviour
of sort().
· "Storable" gives persistence to Perl data structures
by allowing the storage and retrieval of Perl data to
and from files in a fast and compact binary format,
from Raphael Manfredi. See Storable.
· "Switch", from Damian Conway, has been added. Just by
saying
use Switch;
you have "switch" and "case" available in Perl.
use Switch;
switch ($val) {
case 1 { print "number 1" }
case "a" { print "string a" }
case [1..10,42] { print "number in list" }
case (@array) { print "number in list" }
case /\w+/ { print "pattern" }
case qr/\w+/ { print "pattern" }
case (%hash) { print "entry in hash" }
case (\%hash) { print "entry in hash" }
case (\&sub) { print "arg to subroutine" }
else { print "previous case not true" }
}
See Switch.
· "Test::More" is yet another framework for writing test
scripts, more extensive than Test::Simple, by Michael
Schwern. See Test::More.
· "Test::Simple" has basic utilities for writing tests,
by Michael Schwern. See Test::Simple.
· "Text::Balanced" has been added, for extracting delim
ited text sequences from strings, from Damian Conway.
use Text::Balanced 'extract_delimited';
($a, $b) = extract_delimited("'never say never', he never said", "'", '');
$a will be "'never say never'", $b will be ', he never
said'.
In addition to extract_delimited() there are also
extract_bracketed(), extract_quotelike(),
extract_codeblock(), extract_variable(),
extract_tagged(), extract_multiple(), gen_delim
ited_pat(), and gen_extract_tagged(). With these you
can implement rather advanced parsing algorithms. See
Text::Balanced.
· "threads" is an interface to interpreter threads, by
Arthur Bergman. Interpreter threads (ithreads) is the
new thread model introduced in Perl 5.6 but only
available as an internal interface for extension writ
ers (and for Win32 Perl for "fork()" emulation). See
threads.
· "threads::shared" allows data sharing for interpreter
threads, from Arthur Bergman. In the ithreads model
any data sharing between threads must be explicit, as
opposed to the old 5.005 thread model where data shar
ing was implicit. See threads::shared.
· "Tie::File", by Mark-Jason Dominus, associates a Perl
array with the lines of a file.
· "Tie::Memoize", by Ilya Zakharevich, provides on-
demand loaded hashes.
· "Tie::RefHash::Nestable", by Edward Avis, allows stor
ing hash references (unlike the standard Tie::RefHash)
The module is contained within Tie::RefHash, see
Tie::RefHash.
· "Time::HiRes" provides high resolution timing (ualarm,
usleep, and gettimeofday), from Douglas E. Wegscheid.
See Time::HiRes.
· "Unicode::UCD" offers a querying interface to the Uni
code Character Database. See Unicode::UCD.
· "Unicode::Collate" implements the UCA (Unicode Colla
tion Algorithm) for sorting Unicode strings, by
SADAHIRO Tomoyuki. See Unicode::Collate.
· "Unicode::Normalize" implements the various Unicode
normalization forms, by SADAHIRO Tomoyuki. See Uni
code::Normalize.
· "XS::Typemap", by Tim Jenness, is a test extension
that exercises XS typemaps. Nothing gets installed
but for extension writers the code is worth studying.
Updated And Improved Modules and Pragmata
· The following independently supported modules have
been updated to the newest versions from CPAN: CGI,
CPAN, DB_File, File::Spec, File::Temp, Getopt::Long,
Math::BigFloat, Math::BigInt, the podlators bundle
(Pod::Man, Pod::Text), Pod::LaTeX, Pod::Parser,
Storable, Term::ANSIColor, Test, Text-Tabs+Wrap.
· The attributes::reftype() now works on tied arguments.
· AutoLoader can now be disabled with "no AutoLoader;".
· B::Deparse has been significantly enhanced. It now
can deparse almost all of the standard test suite (so
that the tests still succeed). There is a make target
"test.deparse" for trying this out.
· Class::Struct can now define the classes in compile
time.
· Class::Struct now assigns the array/hash element if
the accessor is called with an array/hash element as
the sole argument.
· Data::Dumper has now an option to sort hashes.
· Data::Dumper has now an option to dump code references
using B::Deparse.
· DB_File now supports newer Berkeley DB versions, among
other improvements.
· The English module can now be used without the infa
mous performance hit by saying
use English '-no_match_vars';
(Assuming, of course, that one doesn't need the trou
blesome variables $`, $&, or $'.) Also, introduced
@LAST_MATCH_START and @LAST_MATCH_END English aliases
for "@-" and "@+".
· Fcntl, Socket, and Sys::Syslog have been rewritten to
use the new-style constant dispatch section (see ExtU
tils::Constant). This means that they will be more
robust and hopefully faster.
· File::Find now chdir()s correctly when chasing
symbolic links.
· File::Find now has pre- and post-processing callbacks.
It also correctly changes directories when chasing
symbolic links. Callbacks (naughtily) exiting with
"next;" instead of "return;" now work.
· File::Find is now (again) reentrant. It also has been
made more portable.
· File::Glob::glob() renamed to File::Glob::bsd_glob()
to avoid prototype mismatch with CORE::glob().
· File::Glob now supports "GLOB_LIMIT" constant to limit
the size of the returned list of filenames.
· Devel::Peek now has an interface for the Perl memory
statistics (this works only if you are using perl's
malloc, and if you have compiled with debugging).
· IPC::Open3 now allows the use of numeric file descrip
tors.
· IO::Socket has now atmark() method, which returns true
if the socket is positioned at the out-of-band mark.
The method is also exportable as a sockatmark() func
tion.
· IO::Socket::INET has support for ReusePort option (if
your platform supports it). The Reuse option now has
an alias, ReuseAddr. For clarity you may want to pre
fer ReuseAddr.
· IO::Socket::INET now supports "LocalPort" of zero
(usually meaning that the operating system will make
one up.)
· use lib now works identically to @INC. Removing
directories with 'no lib' now works.
· ExtUtils::MakeMaker now uses File::Spec internally,
which hopefully leads into better portability.
· Math::BigFloat and Math::BigInt have undergone a full
rewrite. They are now magnitudes faster, and they
support various bignum libraries such as GMP and PARI
as their backends.
· Math::Complex handles inf, NaN etc., better.
· Net::Ping has been muchly enhanced. Multihoming is
now supported. There is now "external" protocol which
uses Net::Ping::External module which runs external
ping(1) and parses the output. A version of
Net::Ping::External is available in CPAN.
· POSIX::sigaction() is now much more flexible and
robust. You can now install coderef handlers,
'DEFAULT', and 'IGNORE' handlers, installing new han
dlers was not atomic.
· In Safe the %INC now localised in a Safe compartment
so that use/require work.
· In SDBM_File on dosish platforms, some keys went miss
ing because of lack of support for files with "holes".
A workaround for the problem has been added.
· In Search::Dict one can now have a pre-processing hook
for the lines being searched.
· The Shell module now has an OO interface.
· The Test module has been significantly enhanced.
· The vars pragma now supports declaring fully qualified
variables. (Something that "our()" does not and will
not support.)
· The "utf8::" name space (as in the pragma) provides
various Perl-callable functions to provide low level
access to Perl's internal Unicode representation. At
the moment only length() has been implemented.
Utility Changes
· Emacs perl mode (emacs/cperl-mode.el) has been updated
to version 4.31.
· emacs/e2ctags.pl is now much faster.
· "h2ph" now supports C trigraphs.
· "h2xs" now produces a template README.
· "h2xs" now uses "Devel::PPort" for better portability
between different versions of Perl.
· "h2xs" uses the new ExtUtils::Constant module which
will affect newly created extensions that define con
stants. Since the new code is more correct (if you
have two constants where the first one is a prefix of
the second one, the first constant never gets
defined), less lossy (it uses integers for integer
constant, as opposed to the old code that used float
ing point numbers even for integer constants), and
slightly faster, you might want to consider regenerat
ing your extension code (the new scheme makes regener
ating easy). h2xs now also supports C trigraphs.
· "libnetcfg" has been added to configure the libnet.
· "perlbug" is now much more robust. It also sends the
bug report to perl.org, not perl.com.
· "perlcc" has been rewritten and its user interface
(that is, command line) is much more like that of the
UNIX C compiler, cc. (The perlbc tools has been
removed. Use "perlcc -B" instead.)
· "perlivp" is a new Installation Verification Procedure
utility for running any time after installing Perl.
· "pod2html" now allows specifying a cache directory.
· "s2p" has been completely rewritten in Perl. (It is
in fact a full implementation of sed in Perl: you can
use the sed functionality by using the "psed" util
ity.)
· "xsubpp" now understands POD documentation embedded in
the *.xs files.
· "xsubpp" now supports OUT keyword.
New Documentation
· perl56delta details the changes between the 5.005
release and the 5.6.0 release.
· perlclib documents the internal replacements for stan
dard C library functions. (Interesting only for
extension writers and Perl core hackers.)
· perldebtut is a Perl debugging tutorial.
· perlebcdic contains considerations for running Perl on
EBCDIC platforms.
· perlintro is a gentle introduction to Perl.
· perliol documents the internals of PerlIO with layers.
· perlmodstyle is a style guide for writing modules.
· perlnewmod tells about writing and submitting a new
module.
· perlpacktut is a pack() tutorial.
· perlpod has been rewritten to be clearer and to record
the best practices gathered over the years.
· perlpodspec is a more formal specification of the pod
format, mainly of interest for writers of pod applica
tions, not to people writing in pod.
· perlretut is a regular expression tutorial.
· perlrequick is a regular expressions quick-start
guide. Yes, much quicker than perlretut.
· perltodo has been updated.
· perltootc has been renamed as perltooc (to not to con
flict with perltoot in filesystems restricted to "8.3"
names)
· perluniintro is an introduction to using Unicode in
Perl. (perlunicode is more of a detailed reference
and background information)
· perlutil explains the command line utilities packaged
with the Perl distribution.
The following platform-specific documents are available
before the installation as README.platform, and after the
installation as perlplatform:
perlaix perlamiga perlapollo perlbeos perlbs2000
perlce perlcygwin perldgux perldos perlepoc perlhpux
perlhurd perlmachten perlmacos perlmint perlmpeix
perlnetware perlos2 perlos390 perlplan9 perlqnx perlsolaris
perltru64 perluts perlvmesa perlvms perlvos perlwin32
· The documentation for the POSIX-BC platform is called
"BS2000", to avoid confusion with the Perl POSIX mod
ule.
· The documentation for the WinCE platform is called
"CE", to avoid confusion with the perlwin32 documenta
tion on 8.3-restricted filesystems.
Performance Enhancements
· map() could get pathologically slow when the result
list it generates is larger than the source list. The
performance has been improved for common scenarios.
· sort() has been changed to use primarily mergesort
internally as opposed to the earlier quicksort. For
very small lists this may result in slightly slower
sorting times, but in general the speedup should be at
least 20%. Additional bonuses are that the worst case
behaviour of sort() is now better (in computer science
terms it now runs in time O(N log N), as opposed to
quicksort's Theta(N**2) worst-case run time
behaviour), and that sort() is now stable (meaning
that elements with identical keys will stay ordered as
they were before the sort). See the "sort" pragma for
information.
The story in more detail: suppose you want to serve
yourself a little slice of Pi.
@digits = ( 3,1,4,1,5,9 );
A numerical sort of the digits will yield
(1,1,3,4,5,9), as expected. Which 1 comes first is
hard to know, since one 1 looks pretty much like any
other. You can regard this as totally trivial, or
somewhat profound. However, if you just want to sort
the even digits ahead of the odd ones, then what will
sort { ($a % 2) <=> ($b % 2) } @digits;
yield? The only even digit, 4, will come first. But
how about the odd numbers, which all compare equal?
With the quicksort algorithm used to implement Perl
5.6 and earlier, the order of ties is left up to the
sort. So, as you add more and more digits of Pi, the
order in which the sorted even and odd digits appear
will change. and, for sufficiently large slices of
Pi, the quicksort algorithm in Perl 5.8 won't return
the same results even if reinvoked with the same
input. The justification for this rests with quick
sort's worst case behavior. If you run
sort { $a <=> $b } ( 1 .. $N , 1 .. $N );
(something you might approximate if you wanted to
merge two sorted arrays using sort), doubling $N
doesn't just double the quicksort time, it quadruples
it. Quicksort has a worst case run time that can grow
like N**2, so-called quadratic behaviour, and it can
happen on patterns that may well arise in normal use.
You won't notice this for small arrays, but you will
notice it with larger arrays, and you may not live
long enough for the sort to complete on arrays of a
million elements. So the 5.8 quicksort scrambles
large arrays before sorting them, as a statistical
defence against quadratic behaviour. But that means
if you sort the same large array twice, ties may be
broken in different ways.
Because of the unpredictability of tie-breaking order,
and the quadratic worst-case behaviour, quicksort was
almost replaced completely with a stable mergesort.
Stable means that ties are broken to preserve the
original order of appearance in the input array. So
sort { ($a % 2) <=> ($b % 2) } (3,1,4,1,5,9);
will yield (4,3,1,1,5,9), guaranteed. The even and
odd numbers appear in the output in the same order
they appeared in the input. Mergesort has worst case
O(NlogN) behaviour, the best value attainable. And,
ironically, this mergesort does particularly well
where quicksort goes quadratic: mergesort sorts
(1..$N, 1..$N) in O(N) time. But quicksort was res
cued at the last moment because it is faster than
mergesort on certain inputs and platforms. For exam
ple, if you really don't care about the order of even
and odd digits, quicksort will run in O(N) time; it's
very good at sorting many repetitions of a small num
ber of distinct elements. The quicksort divide and
conquer strategy works well on platforms with rela
tively small, very fast, caches. Eventually, the
problem gets whittled down to one that fits in the
cache, from which point it benefits from the increased
memory speed.
Quicksort was rescued by implementing a sort pragma to
control aspects of the sort. The stable subpragma
forces stable behaviour, regardless of algorithm. The
_quicksort and _mergesort subpragmas are heavy-handed
ways to select the underlying implementation. The
leading "_" is a reminder that these subpragmas may
not survive beyond 5.8. More appropriate mechanisms
for selecting the implementation exist, but they
wouldn't have arrived in time to save quicksort.
· Hashes now use Bob Jenkins "One-at-a-Time" hashing key
algorithm (http://burtlebur;
tle.net/bob/hash/doobs.html). This algorithm is rea
sonably fast while producing a much better spread of
values than the old hashing algorithm (originally by
Chris Torek, later tweaked by Ilya Zakharevich). Hash
values output from the algorithm on a hash of all
3-char printable ASCII keys comes much closer to pass
ing the DIEHARD random number generation tests.
According to perlbench, this change has not affected
the overall speed of Perl.
· unshift() should now be noticeably faster.
Installation and Configuration Improvements
Generic Improvements
· INSTALL now explains how you can configure Perl to use
64-bit integers even on non-64-bit platforms.
· Policy.sh policy change: if you are reusing a Pol
icy.sh file (see INSTALL) and you use Configure -Dpre
fix=/foo/bar and in the old Policy $prefix eq
$siteprefix and $prefix eq $vendorprefix, all of them
will now be changed to the new prefix, /foo/bar.
(Previously only $prefix changed.) If you do not like
this new behaviour, specify prefix, siteprefix, and
vendorprefix explicitly.
· A new optional location for Perl libraries,
otherlibdirs, is available. It can be used for exam
ple for vendor add-ons without disturbing Perl's own
library directories.
· In many platforms the vendor-supplied 'cc' is too
stripped-down to build Perl (basically, 'cc' doesn't
do ANSI C). If this seems to be the case and 'cc'
does not seem to be the GNU C compiler 'gcc', an auto
matic attempt is made to find and use 'gcc' instead.
· gcc needs to closely track the operating system
release to avoid build problems. If Configure finds
that gcc was built for a different operating system
release than is running, it now gives a clearly visi
ble warning that there may be trouble ahead.
· If binary compatibility with the 5.005 release is not
wanted, Configure no longer suggests including the
5.005 modules in @INC.
· Configure "-S" can now run non-interactively.
· Configure support for pdp11-style memory models has
been removed due to obsolescence.
· configure.gnu now works with options with whitespace
in them.
· installperl now outputs everything to STDERR.
· $Config{byteorder} is now computed dynamically (this
is more robust with "fat binaries" where an executable
image contains binaries for more than one binary plat
form.)
· Because PerlIO is now the default on most platforms,
"-perlio" doesn't get appended to the $Config{arch
name} (also known as $^O) anymore. Instead, if you
explicitly choose not to use perlio (Configure command
line option -Uuseperlio), you will get "-stdio"
appended.
· Another change related to the architecture name is
that "-64all" (-Duse64bitall, or "maximally 64-bit")
is appended only if your pointers are 64 bits wide.
(To be exact, the use64bitall is ignored.)
· In AFS installations one can configure the root of the
AFS to be somewhere else than the default /afs by
using the Configure parameter "-Dafs
root=/some/where/else".
· APPLLIB_EXP, a less-know configuration-time defini
tion, has been documented. It can be used to prepend
site-specific directories to Perl's default search
path (@INC), see INSTALL for information.
· The version of Berkeley DB used when the Perl (and,
presumably, the DB_File extension) was built is now
available as @Config{qw(db_version_major db_ver
sion_minor db_version_patch)} from Perl and as
"DB_VERSION_MAJOR_CFG DB_VERSION_MINOR_CFG DB_VER
SION_PATCH_CFG" from C.
· Building Berkeley DB3 for compatibility modes for DB,
NDBM, and ODBM has been documented in INSTALL.
· If you have CPAN access (either network or a local
copy such as a CD-ROM) you can during specify extra
modules to Configure to build and install with Perl
using the -Dextras=... option. See INSTALL for more
details.
· In addition to config.over a new override file, con
fig.arch, is available. That is supposed to be used
by hints file writers for architecture-wide changes
(as opposed to config.over which is for site-wide
changes).
· If your file system supports symbolic links you can
build Perl outside of the source directory by
mkdir /tmp/perl/build/directory
cd /tmp/perl/build/directory
sh /path/to/perl/source/Configure -Dmksymlinks ...
This will create in /tmp/perl/build/directory a tree
of symbolic links pointing to files in
/path/to/perl/source. The original files are left
unaffected. After Configure has finished you can just
say
make all test
and Perl will be built and tested, all in
/tmp/perl/build/directory.
· For Perl developers several new make targets for pro
filing and debugging have been added, see perlhack.
· Use of the gprof tool to profile Perl has been
documented in perlhack. There is a make tar
get called "perl.gprof" for generating a gpro
filed Perl executable.
· If you have GCC 3, there is a make target
called "perl.gcov" for creating a gcoved Perl
executable for coverage analysis. See perl
hack.
· If you are on IRIX or Tru64 platforms, new
profiling/debugging options have been added,
see perlhack for more information about pixie
and Third Degree.
· Guidelines of how to construct minimal Perl installa
tions have been added to INSTALL.
· The Thread extension is now not built at all under
ithreads ("Configure -Duseithreads") because it
wouldn't work anyway (the Thread extension requires
being Configured with "-Duse5005threads").
But note that the Thread.pm interface is now shared by
both thread models.
New Or Improved Platforms
For the list of platforms known to support Perl, see "Sup
ported Platforms" in perlport.
· AIX dynamic loading should be now better supported.
· AIX should now work better with gcc, threads, and
64-bitness. Also the long doubles support in AIX
should be better now. See perlaix.
· After a long pause, AmigaOS has been verified to be
happy with Perl.
· AtheOS (http://www.atheos.cx/) is a new platform.
· BeOS has been reclaimed.
· DG/UX platform now supports the 5.005-style threads.
See perldgux.
· DYNIX/ptx platform (a.k.a. dynixptx) is supported at
or near osvers 4.5.2.
· EBCDIC platforms (z/OS, also known as OS/390,
POSIX-BC, and VM/ESA) have been regained. Many test
suite tests still fail and the co-existence of Unicode
and EBCDIC isn't quite settled, but the situation is
much better than with Perl 5.6. See perlos390,
perlbs2000 (for POSIX-BC), and perlvmesa for more
information.
· Building perl with -Duseithreads or -Duse5005threads
now works under HP-UX 10.20 (previously it only worked
under 10.30 or later). You will need a thread library
package installed. See README.hpux.
· MacOS Classic (MacPerl has of course been available
since perl 5.004 but now the source code bases of
standard Perl and MacPerl have been synchronised)
· MacOS X (or Darwin) should now be able to build Perl
even on HFS+ filesystems. (The case-insensitivity
confused the Perl build process.)
· NCR MP-RAS is now supported.
· All the NetBSD specific patches (except for the
installation specific ones) have been merged back to
the main distribution.
· NetWare from Novell is now supported. See perlnet
ware.
· NonStop-UX is now supported.
· NEC SUPER-UX is now supported.
· All the OpenBSD specific patches (except for the
installation specific ones) have been merged back to
the main distribution.
· Perl has been tested with the GNU pth userlevel thread
package ( http://www.gnu.org/software/pth/pth.html ) .
All but one thread test worked, and that one failure
was because of test results arriving in unexpected
order.
· Amdahl UTS UNIX mainframe platform is now supported.
· WinCE is now supported. See perlce.
· z/OS (formerly known as OS/390, formerly known as MVS
OE) has now support for dynamic loading. This is not
selected by default, however, you must specify -Dusedl
in the arguments of Configure.
Selected Bug Fixes
Numerous memory leaks and uninitialized memory accesses
have been hunted down. Most importantly anonymous subs
used to leak quite a bit.
· The autouse pragma didn't work for Multi::Part::Func
tion::Names.
· caller() could cause core dumps in certain situations.
Carp was sometimes affected by this problem.
· chop(@list) in list context returned the characters
chopped in reverse order. This has been reversed to
be in the right order.
· Configure no longer includes the DBM libraries (dbm,
gdbm, db, ndbm) when building the Perl binary. The
only exception to this is SunOS 4.x, which needs them.
· The behaviour of non-decimal but numeric string con
stants such as "0x23" was platform-dependent: in some
platforms that was seen as 35, in some as 0, in some
as a floating point number (don't ask). This was
caused by Perl using the operating system libraries in
a situation where the result of the string to number
conversion is undefined: now Perl consistently handles
such strings as zero in numeric contexts.
· The order of DESTROYs has been made more predictable.
· Several debugger fixes: exit code now reflects the
script exit code, condition "0" now treated correctly,
the "d" command now checks line number, the $. no
longer gets corrupted, all debugger output now goes
correctly to the socket if RemotePort is set.
· Perl 5.6.0 could emit spurious warnings about redefi
nition of dl_error() when statically building exten
sions into perl. This has been corrected.
· dprofpp -R didn't work.
· *foo{FORMAT} now works. =item *
Infinity is now recognized as a number.
· UNIVERSAL::isa no longer caches methods incorrectly.
(This broke the Tk extension with 5.6.0.)
· Lexicals I: lexicals outside an eval "" weren't
resolved correctly inside a subroutine definition
inside the eval "" if they were not already referenced
in the top level of the eval""ed code.
· Lexicals II: lexicals leaked at file scope into sub
routines that were declared before the lexicals.
· Lexical warnings now propagating correctly between
scopes and into "eval "..."".
· "use warnings qw(FATAL all)" did not work as intended.
This has been corrected.
· warnings::enabled() now reports the state of $^W cor
rectly if the caller isn't using lexical warnings.
· Line renumbering with eval and "#line" now works.
· Fixed numerous memory leaks, especially in eval "".
· mkdir() now ignores trailing slashes in the directory
name, as mandated by POSIX.
· Some versions of glibc have a broken modfl(). This
affects builds with "-Duselongdouble". This version
of Perl detects this brokenness and has a workaround
for it. The glibc release 2.2.2 is known to have
fixed the modfl() bug.
· Modulus of unsigned numbers now works (4063328477 %
65535 used to return 27406, instead of 27047).
· Some "not a number" warnings introduced in 5.6.0 elim
inated to be more compatible with 5.005. Infinity is
now recognised as a number.
· Numeric conversions did not recognize changes in the
string value properly in certain circumstances.
· Attributes (like :shared) didn't work with our().
· our() variables will not cause "will not stay shared"
warnings.
· "our" variables of the same name declared in two sib
ling blocks resulted in bogus warnings about "redecla
ration" of the variables. The problem has been cor
rected.
· pack "Z" now correctly terminates the string with
"\0".
· Fix password routines which in some shadow password
platforms (e.g. HP-UX) caused getpwent() to return
every other entry.
· The PERL5OPT environment variable (for passing command
line arguments to Perl) didn't work for more than a
single group of options.
· PERL5OPT with embedded spaces didn't work.
· printf() no longer resets the numeric locale to "C".
· "qw(a\\b)" now parses correctly as 'a\\b'.
· pos() did not return the correct value within s///ge
in earlier versions. This is now handled correctly.
· Printing quads (64-bit integers) with printf/sprintf
now works without the q L ll prefixes (assuming you
are on a quad-capable platform).
· Regular expressions on references and overloaded
scalars now work.
· Right-hand side magic (GMAGIC) could in many cases
such as string concatenation be invoked too many
times.
· scalar() now forces scalar context even when used in
void context.
· SOCKS support is now much more robust.
· sort() arguments are now compiled in the right wantar
ray context (they were accidentally using the context
of the sort() itself). The comparison block is now
run in scalar context, and the arguments to be sorted
are always provided list context.
· Changed the POSIX character class "[[:space:]]" to
include the (very rarely used) vertical tab character.
Added a new POSIX-ish character class "[[:blank:]]"
which stands for horizontal whitespace (currently, the
space and the tab).
· The tainting behaviour of sprintf() has been rational
ized. It does not taint the result of floating point
formats anymore, making the behaviour consistent with
that of string interpolation.
· Some cases of inconsistent taint propagation (such as
within hash values) have been fixed.
· The RE engine found in Perl 5.6.0 accidentally pes
simised certain kinds of simple pattern matches.
These are now handled better.
· Regular expression debug output (whether through "use
re 'debug'" or via "-Dr") now looks better.
· Multi-line matches like ""a\nxb\n" =~ /(?!\A)x/m" were
flawed. The bug has been fixed.
· Use of $& could trigger a core dump under some situa
tions. This is now avoided.
· The regular expression captured submatches ($1, $2,
...) are now more consistently unset if the match
fails, instead of leaving false data lying around in
them.
· readline() on files opened in "slurp" mode could
return an extra "" at the end in certain situations.
This has been corrected.
· Autovivification of symbolic references of special
variables described in perlvar (as in "${$num}") was
accidentally disabled. This works again now.
· Sys::Syslog ignored the "LOG_AUTH" constant.
· All but the first argument of the IO syswrite() method
are now optional.
· $AUTOLOAD, sort(), lock(), and spawning subprocesses
in multiple threads simultaneously are now
thread-safe.
· Tie::ARRAY SPLICE method was broken.
· Allow read-only string on left hand side of non-
modifying tr///.
· Several Unicode fixes.
· BOMs (byte order marks) in the beginning of
Perl files (scripts, modules) should now be
transparently skipped. UTF-16 (UCS-2) encoded
Perl files should now be read correctly.
· The character tables have been updated to Uni
code 3.1.1.
· Comparing with utf8 data does not magically
upgrade non-utf8 data into utf8. (This was a
problem for example if you were mixing data
from I/O and Unicode data: your output might
have got magically encoded as UTF-8.)
· Generating illegal Unicode code points like
U+FFFE, or the UTF-16 surrogates, now also
generates an optional warning.
· "IsAlnum", "IsAlpha", and "IsWord" now match
titlecase.
· Concatenation with the . operator or via vari
able interpolation, "eq", "substr", "reverse",
"quotemeta", the "x" operator, substitution
with "s///", single-quoted UTF8, should now
work.
· The "tr///" operator now works. Note that the
"tr///CU" functionality has been removed (but
see pack('U0', ...)).
· "eval "v200"" now works.
· Perl 5.6.0 parsed m/\x{ab}/ incorrectly, lead
ing to spurious warnings. This has been cor
rected.
· Zero entries were missing from the Unicode
classes like "IsDigit".
· Large unsigned numbers (those above 2**31) could some
times lose their unsignedness, causing bogus results
in arithmetic operations.
Platform Specific Changes and Fixes
· BSDI 4.*
Perl now works on post-4.0 BSD/OSes.
· All BSDs
Setting $0 now works (as much as possible; see perlvar
for details).
· Cygwin
Numerous updates; currently synchronised with Cygwin
1.1.4.
· Previously DYNIX/ptx had problems in its Configure
probe for non-blocking I/O.
· EPOC
EPOC update after Perl 5.6.0. See README.epoc.
· FreeBSD 3.*
Perl now works on post-3.0 FreeBSDs.
· HP-UX
README.hpux updated; "Configure -Duse64bitall" now
almost works.
· IRIX
Numerous compilation flag and hint enhancements; acci
dental mixing of 32-bit and 64-bit libraries (a doomed
attempt) made much harder.
· Linux
· Long doubles should now work (see INSTALL).
· Linux previously had problems related to sock
addrlen when using accept(), revcfrom() (in
Perl: recv()), getpeername(), and getsock
name().
· MacOS Classic
Compilation of the standard Perl distribution in MacOS
Classic should now work if you have the Metrowerks
development environment and the missing Mac-specific
toolkit bits. Contact the macperl mailing list for
details.
· MPE/iX
MPE/iX update after Perl 5.6.0. See README.mpeix.
· NetBSD/sparc
Perl now works on NetBSD/sparc.
· OS/2
Now works with usethreads (see INSTALL).
· Solaris
64-bitness using the Sun Workshop compiler now works.
· Tru64 (aka Digital UNIX, aka DEC OSF/1)
The operating system version letter now recorded in
$Config{osvers}. Allow compiling with gcc (previously
explicitly forbidden). Compiling with gcc still not
recommended because buggy code results, even with gcc
2.95.2.
· Unicos
Fixed various alignment problems that lead into core
dumps either during build or later; no longer dies on
math errors at runtime; now using full quad integers
(64 bits), previously was using only 46 bit integers
for speed.
· VMS
chdir() now works better despite a CRT bug; now works
with MULTIPLICITY (see INSTALL); now works with Perl's
malloc.
The tainting of %ENV elements via "keys" or "values"
was previously unimplemented. It now works as docu
mented.
The "waitpid" emulation has been improved. The worst
bug (now fixed) was that a pid of -1 would cause a
wildcard search of all processes on the system. The
most significant enhancement is that we can now usu
ally get the completion status of a terminated pro
cess.
POSIX-style signals are now emulated much better on
VMS versions prior to 7.0.
The "system" function and backticks operator have
improved functionality and better error handling.
File access tests now use current process privileges
rather than the user's default privileges, which could
sometimes result in a mismatch between reported access
and actual access.
· Windows
· accept() no longer leaks memory.
· Borland C++ v5.5 is now a supported compiler
that can build Perl. However, the generated
binaries continue to be incompatible with
those generated by the other supported compil
ers (GCC and Visual C++).
· Better chdir() return value for a non-existent
directory.
· Duping socket handles with open(F, ">&MYSOCK")
now works under Windows 9x.
· New %ENV entries now propagate to subpro
cesses.
· Current directory entries in %ENV are now cor
rectly propagated to child processes.
· $ENV{LIB} now used to search for libs under
Visual C.
· fork() emulation has been improved in various
ways, but still continues to be experimental.
See perlfork for known bugs and caveats.
· A failed (pseudo)fork now returns undef and
sets errno to EAGAIN.
· Win32::GetCwd() correctly returns C:\ instead
of C: when at the drive root. Other bugs in
chdir() and Cwd::cwd() have also been fixed.
· HTML files will be installed in c:\perl\html
instead of c:\perl\lib\pod\html
· The makefiles now provide a single switch to
bulk-enable all the features enabled in
ActiveState ActivePerl (a popular Win32 binary
distribution).
· Allow REG_EXPAND_SZ keys in the registry.
· Can now send() from all threads, not just the
first one.
· Fake signal handling reenabled, bugs and all.
· %SIG has been enabled under USE_ITHREADS, but
its use is completely unsupported under all
configurations.
· Less stack reserved per thread so that more
threads can run concurrently. (Still 16M per
thread.)
· "File::Spec->tmpdir()" now prefers C:/temp
over /tmp (works better when perl is running
as service).
· Better UNC path handling under ithreads.
· wait(), waitpid() and backticks now return the
correct exit status under Windows 9x.
· winsock handle leak fixed.
New or Changed Diagnostics
· The lexical warnings category "deprecated" is no
longer a sub-category of the "syntax" category. It is
now a top-level category in its own right.
· All regular expression compilation error messages are
now hopefully easier to understand both because the
error message now comes before the failed regex and
because the point of failure is now clearly marked by
a "<-- HERE" marker.
· The various "opened only for", "on closed", "never
opened" warnings drop the "main::" prefix for filehan
dles in the "main" package, for example "STDIN"
instead of "main::STDIN".
· The "Unrecognized escape" warning has been extended to
include "\8", "\9", and "\_". There is no need to
escape any of the "\w" characters.
· Two new debugging options have been added: if you have
compiled your Perl with debugging, you can use the -DT
and -DR options to trace tokenising and to add refer
ence counts to displaying variables, respectively.
· perl5db.pl has been modified to present a more consis
tent commands interface, via (CommandSet=580).
perl5db.t was also added to test the changes, and as a
placeholder for further tests.
See perldebug
· If an attempt to use a (non-blessed) reference as an
array index is made, a warning is given.
· "push @a;" and "unshift @a;" (with no values to push
or unshift) now give a warning. This may be a problem
for generated and evaled code.
· If you try to "pack" in perlfunc a number less than 0
or larger than 255 using the "C" format you will get
an optional warning. Similarly for the "c" format and
a number less than -128 or more than 127.
· Certain regex modifiers such as "(?o)" make sense only
if applied to the entire regex. You will an optional
warning if you try to do otherwise.
· Using arrays or hashes as references (e.g.
"%foo->{bar}" has been deprecated for a while. Now
you will get an optional warning.
Changed Internals
· perlapi.pod (a companion to perlguts) now attempts to
document the internal API.
· You can now build a really minimal perl called microp
erl. Building microperl does not require even running
Configure; "make -f Makefile.micro" should be enough.
Beware: microperl makes many assumptions, some of
which may be too bold; the resulting executable may
crash or otherwise misbehave in wondrous ways. For
careful hackers only.
· Added rsignal(), whichsig(), do_join(), op_clear,
op_null, ptr_table_clear(), ptr_table_free(),
sv_setref_uv(), and several UTF-8 interfaces to the
publicised API. For the full list of the available
APIs see perlapi.
· Made possible to propagate customised exceptions via
croak()ing.
· Now xsubs can have attributes just like subs. (Well,
at least the built-in attributes.)
· dTHR and djSP have been obsoleted; the former removed
(because it's a no-op) and the latter replaced with
dSP.
· PERL_OBJECT has been completely removed.
· The MAGIC constants (e.g. 'P') have been macrofied
(e.g. "PERL_MAGIC_TIED") for better source code read
ability and maintainability.
· The regex compiler now maintains a structure that
identifies nodes in the compiled bytecode with the
corresponding syntactic features of the original regex
expression. The information is attached to the new
"offsets" member of the "struct regexp". See perlde
bguts for more complete information.
· The C code has been made much more "gcc -Wall" clean.
Some warning messages still remain in some platforms,
so if you are compiling with gcc you may see some
warnings about dubious practices. The warnings are
being worked on.
· perly.c, sv.c, and sv.h have now been extensively com
mented.
· Documentation on how to use the Perl source repository
has been added to Porting/repository.pod.
· There are now several profiling make targets.
Security Vulnerability Closed
(This change was already made in 5.7.0 but bears repeating
here.)
A potential security vulnerability in the optional suid
perl component of Perl was identified in August 2000.
suidperl is neither built nor installed by default. As of
November 2001 the only known vulnerable platform is Linux,
most likely all Linux distributions. CERT and various
vendors and distributors have been alerted about the vul
nerability. See
http://www.cpan.org/src/5.0/sperl-2000-08-05/sperl-2000-08-05.txt
for more information.
The problem was caused by Perl trying to report a sus
pected security exploit attempt using an external program,
/bin/mail. On Linux platforms the /bin/mail program had
an undocumented feature which when combined with suidperl
gave access to a root shell, resulting in a serious com
promise instead of reporting the exploit attempt. If you
don't have /bin/mail, or if you have 'safe setuid
scripts', or if suidperl is not installed, you are safe.
The exploit attempt reporting feature has been completely
removed from Perl 5.8.0 (and the maintenance release
5.6.1, and it was removed also from all the Perl 5.7
releases), so that particular vulnerability isn't there
anymore. However, further security vulnerabilities are,
unfortunately, always possible. The suidperl functional
ity is most probably going to be removed in Perl 5.10. In
any case, suidperl should only be used by security experts
who know exactly what they are doing and why they are
using suidperl instead of some other solution such as sudo
(see http://www.courtesan.com/sudo/).
New Tests
Several new tests have been added, especially for the lib
subsection. There are now about 34 000 individual tests
(spread over about 530 test scripts), in the regression
suite (5.6.1 has about 11700 tests, in 258 test scripts)
Many of the new tests are introduced by the new modules,
but still in general Perl is now more thoroughly tested.
Because of the large number of tests, running the regres
sion suite will take considerably longer time than it used
to: expect the suite to take up to 4-5 times longer to run
than in perl 5.6. In a really fast machine you can hope
to finish the suite in about 5 minutes (wallclock time).
The tests are now reported in a different order than in
earlier Perls. (This happens because the test scripts
from under t/lib have been moved to be closer to the
library/extension they are testing.)
Known Problems
AIX
· In AIX 4.2 Perl extensions that use C++ functions that
use statics may have problems in that the statics are
not getting initialized. In newer AIX releases this
has been solved by linking Perl with the libC_r
library, but unfortunately in AIX 4.2 the said library
has an obscure bug where the various functions related
to time (such as time() and gettimeofday()) return
broken values, and therefore in AIX 4.2 Perl is not
linked against the libC_r.
· vac 5.0.0.0 May Produce Buggy Code For Perl
The AIX C compiler vac version 5.0.0.0 may produce
buggy code, resulting in few random tests failing, but
when the failing tests are run by hand, they succeed.
We suggest upgrading to at least vac version 5.0.1.0,
that has been known to compile Perl correctly. "lslpp
-L|grep vac.C" will tell you the vac version.
Amiga Perl Invoking Mystery
One cannot call Perl using the "volume:" syntax, that is,
"perl -v" works, but for example "bin:perl -v" doesn't.
The exact reason isn't known but the current suspect is
the ixemul library.
lib/ftmp-security tests warn 'system possibly insecure'
Don't panic. Read INSTALL 'make test' section instead.
Cygwin intermittent failures of lib/Memoize/t/expire_file
11 and 12
The subtests 11 and 12 sometimes fail and sometimes work.
FreeBSD 4.5 fails lib/File/Spec/t/rel2abs2rel.t
lib/File/Spec/t/rel2abs2rel.t tests that "`` works" by
running a a perl 1 liner in backticks, using "$^X" as the
path to perl. It is failing on FreeBSD 4.5, but only when
run as part of make test. This seems to be a kernel prob
lem rather than perl - reading the symlink /proc/cur
proc/file returns "unknown" rather than the path to perl,
and a kernel debugger reveals that variable "numfullpath
fail2" in /usr/src/sys/kern/vfs_cache.c is being incre
mented whenever /proc/curproc/file fails to return the
perl executable's path.
HP-UX lib/io_multihomed Fails When LP64-Configured
The lib/io_multihomed test may hang in HP-UX if Perl has
been configured to be 64-bit. Because other 64-bit plat
forms do not hang in this test, HP-UX is suspect. All
other tests pass in 64-bit HP-UX. The test attempts to
create and connect to "multihomed" sockets (sockets which
have multiple IP addresses).
HP-UX lib/posix Subtest 9 Fails When LP64-Configured
If perl is configured with -Duse64bitall, the successful
result of the subtest 10 of lib/posix may arrive before
the successful result of the subtest 9, which confuses the
test harness so much that it thinks the subtest 9 failed.
Linux With Sfio Fails op/misc Test 48
No known fix.
Mac OS X
The following tests are known to fail:
Failed Test Stat Wstat Total Fail Failed List of Failed
-------------------------------------------------------------------------
../ext/DB_File/t/db-btree.t 0 11 ?? ?? % ??
../ext/DB_File/t/db-recno.t 149 3 2.01% 61 63 65
../ext/POSIX/t/posix.t 31 1 3.23% 10
OS/390
OS/390 has rather many test failures but the situation is
actually better than it was in 5.6.0, it's just that so
many new modules and tests have been added.
Failed 10/611 test scripts, 98.36% okay. 72/53809 subtests
failed, 99.87% okay. Failed Test Stat
Wstat Total Fail Failed List of Failed
-------------------------------------------------------------------------------
../ext/B/t/deparse.t 17 1 5.88%
14 ../ext/IO/lib/IO/t/io_unix.t 5 4
80.00% 2-5 ../lib/utf8.t 94
13 13.83% 27 30-31 43 46 73
76
79 82 85 88 91
94
../lib/Benchmark.t 1 256 159 1 0.63%
75 ../lib/ExtUtils/t/Embed.t 9 9
100.00% 1-9 ../lib/ExtUtils/t/ExtUtils.t 27
19 70.37% 5-23 op/pat.t
858 9 1.05% 242-243 665 776 785
832-834
845 op/sprintf.t 224 3
1.34% 98 100 136 op/tr.t
97 5 5.15% 63 71-74 uni/fold.t
767 8 1.04% 25-26 62 169 196
648
697-698 57 tests and 377 subtests skipped.
op/sprintf tests 129 and 130
The op/sprintf tests 129 and 130 are known to fail on some
platforms. Examples include any platform using sfio, and
Compaq/Tandem's NonStop-UX. The failing platforms do not
comply with the ANSI C Standard, line 19ff on page 134 of
ANSI X3.159 1989 to be exact. (They produce something
other than "1" and "-1" when formatting 0.6 and -0.6 using
the printf format "%.0f", most often they produce "0" and
"-0".)
Failure of Thread tests
Note that support for 5.005-style threading remains exper
imental and practically unsupported.
The following tests are known to fail due to fundamental
problems in the 5.005 threading implementation. These are
not new failures--Perl 5.005_0x has the same bugs, but
didn't have these tests.
ext/List/Util/t/first 2
lib/autouse 4
ext/Thread/thr5005 19-20
These failures are unlikely to get fixed as the
5.005-style threads are considered fundamentally broken.
UNICOS
../ext/Socket/socketpair.t 1 256 45 1 2.22% 12
../lib/Math/Trig.t 26 1 3.85% 25
../lib/warnings.t 460 1 0.22% 425
io/fs.t 36 1 2.78% 31
op/numconvert.t 1440 13 0.90% 208 509-510
657-658 665-666 829-830 989-990 1149-1150
UNICOS and UNICOS/mk
The io/fs test #31 is failing because in UNICOS and UNI
COS/mk truncate() cannot be used to grow the size of file
handles, only to reduce the size. The workaround is to
truncate files instead of filehandles.
UTS
There are a few known test failures, see perluts.
VMS
There should be no reported test failures with a default
configuration, though there are a number of tests marked
TODO that point to areas needing further debugging and/or
porting work.
Win32
In multi-CPU boxes there are some problems with the I/O
buffering: some output may appear twice. The Win32 fol
lowing failures are known as of 5.7.3:
..\ext/Encode/t/JP.t 4 1024 22 4 18.18% 9 14 18 21
..\ext/threads/t/end.t 6 4 66.67% 3-6
..\lib/blib.t 3 768 7 3 42.86% 1 4-5
Localising a Tied Variable Leaks Memory
use Tie::Hash;
tie my %tie_hash => 'Tie::StdHash';
...
local($tie_hash{Foo}) = 1; # leaks
Code like the above is known to leak memory every time the
local() is executed.
Localising Tied Arrays and Hashes Is Broken
local %tied_array;
doesn't work as one would expect: the old value is
restored incorrectly.
Self-tying of Arrays and Hashes Is Forbidden
Self-tying of arrays and hashes is broken in rather deep
and hard-to-fix ways. As a stop-gap measure to avoid peo
ple from getting frustrated at the mysterious results
(core dumps, most often) it is for now forbidden (you will
get a fatal error even from an attempt).
Building Extensions Can Fail Because Of Largefiles
Some extensions like mod_perl are known to have issues
with `largefiles', a change brought by Perl 5.6.0 in which
file offsets default to 64 bits wide, where supported.
Modules may fail to compile at all or compile and work
incorrectly. Currently there is no good solution for the
problem, but Configure now provides appropriate non-large
file ccflags, ldflags, libswanted, and libs in the %Config
hash (e.g., $Config{ccflags_nolargefiles}) so the exten
sions that are having problems can try configuring them
selves without the largefileness. This is admittedly not
a clean solution, and the solution may not even work at
all. One potential failure is whether one can (or, if one
can, whether it's a good idea) link together at all bina
ries with different ideas about file offsets, all this is
platform-dependent.
Unicode Support on EBCDIC Still Spotty
Though mostly working, Unicode support still has problem
spots on EBCDIC platforms. One such known spot are the
"\p{}" and "\P{}" regular expression constructs for code
points less than 256: the pP are testing for Unicode code
points, not knowing about EBCDIC.
The Compiler Suite Is Still Experimental
The compiler suite is slowly getting better but it contin
ues to be highly experimental. Use in production environ
ments is discouraged.
The Long Double Support Is Still Experimental
The ability to configure Perl's numbers to use "long dou
bles", floating point numbers of hopefully better accu
racy, is still experimental. The implementations of long
doubles are not yet widespread and the existing implemen
tations are not quite mature or standardised, therefore
trying to support them is a rare and moving target. The
gain of more precision may also be offset by slowdown in
computations (more bits to move around, and the operations
are more likely to be executed by less optimised
libraries).
Seen In Perl 5.7 But Gone Now
"Time::Piece" (previously known as "Time::Object") was
removed because it was felt that it didn't have enough
value in it to be a core module. It is still a useful
module, though, and is available from the CPAN.
Reporting Bugs
If you find what you think is a bug, you might check the
articles recently posted to the comp.lang.perl.misc news
group and the perl bug database at http://bugs.perl.org.
There may also be information at http://www.perl.com/, 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.
HISTORY
Written by Jarkko Hietaniemi <jhi@iki.fi>.
perl v5.7.3 2002-03-05 PERLDELTA(1)
--
/ Jonas - http://jonas.liljegren.org/myself/en/index.html
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