NAME¶
perl581delta - what is new for perl v5.8.1
DESCRIPTION¶
This document describes differences between the 5.8.0 release and the 5.8.1
release.
If you are upgrading from an earlier release such as 5.6.1, first read the
perl58delta, which describes differences between 5.6.0 and 5.8.0.
In case you are wondering about 5.6.1, it was bug-fix-wise rather identical to
the development release 5.7.1. Confused? This timeline hopefully helps a bit:
it lists the new major releases, their maintenance releases, and the
development releases.
New Maintenance Development
5.6.0 2000-Mar-22
5.7.0 2000-Sep-02
5.6.1 2001-Apr-08
5.7.1 2001-Apr-09
5.7.2 2001-Jul-13
5.7.3 2002-Mar-05
5.8.0 2002-Jul-18
5.8.1 2003-Sep-25
Incompatible Changes¶
Hash Randomisation¶
Mainly due to security reasons, the "random ordering" of hashes has
been made even more random. Previously while the order of hash elements from
keys(),
values(), and
each() was essentially random, it
was still repeatable. Now, however, the order varies between different runs of
Perl.
Perl has never guaranteed any ordering of the hash keys, and the ordering
has already changed several times during the lifetime of Perl 5. Also, the
ordering of hash keys has always been, and continues to be, affected by the
insertion order.
The added randomness may affect applications.
One possible scenario is when output of an application has included hash data.
For example, if you have used the Data::Dumper module to dump data into
different files, and then compared the files to see whether the data has
changed, now you will have false positives since the order in which hashes are
dumped will vary. In general the cure is to sort the keys (or the values); in
particular for Data::Dumper to use the "Sortkeys" option. If some
particular order is really important, use tied hashes: for example the
Tie::IxHash module which by default preserves the order in which the hash
elements were added.
More subtle problem is reliance on the order of "global destruction".
That is what happens at the end of execution: Perl destroys all data
structures, including user data. If your destructors (the DESTROY subroutines)
have assumed any particular ordering to the global destruction, there might be
problems ahead. For example, in a destructor of one object you cannot assume
that objects of any other class are still available, unless you hold a
reference to them. If the environment variable PERL_DESTRUCT_LEVEL is set to a
non-zero value, or if Perl is exiting a spawned thread, it will also destruct
the ordinary references and the symbol tables that are no longer in use. You
can't call a class method or an ordinary function on a class that has been
collected that way.
The hash randomisation is certain to reveal hidden assumptions about some
particular ordering of hash elements, and outright bugs: it revealed a few
bugs in the Perl core and core modules.
To disable the hash randomisation in runtime, set the environment variable
PERL_HASH_SEED to 0 (zero) before running Perl (for more information see
"PERL_HASH_SEED" in perlrun), or to disable the feature completely
in compile time, compile with "-DNO_HASH_SEED" (see
INSTALL).
See "Algorithmic Complexity Attacks" in perlsec for the original
rationale behind this change.
UTF-8 On Filehandles No Longer Activated By Locale¶
In Perl 5.8.0 all filehandles, including the standard filehandles, were
implicitly set to be in Unicode UTF-8 if the locale settings indicated the use
of UTF-8. This feature caused too many problems, so the feature was turned off
and redesigned: see "Core Enhancements".
Single-number v-strings are no longer v-strings before
"=>"¶
The version strings or v-strings (see "Version Strings" in perldata)
feature introduced in Perl 5.6.0 has been a source of some confusion--
especially when the user did not want to use it, but Perl thought it knew
better. Especially troublesome has been the feature that before a
"=>" a version string (a "v" followed by digits) has
been interpreted as a v-string instead of a string literal. In other words:
%h = ( v65 => 42 );
has meant since Perl 5.6.0
%h = ( 'A' => 42 );
(at least in platforms of ASCII progeny) Perl 5.8.1 restores the more natural
interpretation
%h = ( 'v65' => 42 );
The multi-number v-strings like v65.66 and 65.66.67 still continue to be
v-strings in Perl 5.8.
(Win32) The -C Switch Has Been Repurposed¶
The -C switch has changed in an incompatible way. The old semantics of this
switch only made sense in Win32 and only in the "use utf8" universe
in 5.6.x releases, and do not make sense for the Unicode implementation in
5.8.0. Since this switch could not have been used by anyone, it has been
repurposed. The behavior that this switch enabled in 5.6.x releases may be
supported in a transparent, data-dependent fashion in a future release.
For the new life of this switch, see "UTF-8 no longer default under UTF-8
locales", and "-C" in perlrun.
(Win32) The /d Switch Of cmd.exe¶
Perl 5.8.1 uses the /d switch when running the cmd.exe shell internally for
system(), backticks, and when opening pipes to external programs. The
extra switch disables the execution of AutoRun commands from the registry,
which is generally considered undesirable when running external programs. If
you wish to retain compatibility with the older behavior, set PERL5SHELL in
your environment to "cmd /x/c".
Core Enhancements¶
UTF-8 no longer default under UTF-8 locales¶
In Perl 5.8.0 many Unicode features were introduced. One of them was found to be
of more nuisance than benefit: the automagic (and silent)
"UTF-8-ification" of filehandles, including the standard
filehandles, if the user's locale settings indicated use of UTF-8.
For example, if you had "en_US.UTF-8" as your locale, your STDIN and
STDOUT were automatically "UTF-8", in other words an implicit
binmode(..., ":utf8") was made. This meant that trying to print,
say,
chr(0xff), ended up printing the bytes 0xc3 0xbf. Hardly what you
had in mind unless you were aware of this feature of Perl 5.8.0. The problem
is that the vast majority of people weren't: for example in RedHat releases 8
and 9 the
default locale setting is UTF-8, so all RedHat users got
UTF-8 filehandles, whether they wanted it or not. The pain was intensified by
the Unicode implementation of Perl 5.8.0 (still) having nasty bugs, especially
related to the use of s/// and tr///. (Bugs that have been fixed in 5.8.1)
Therefore a decision was made to backtrack the feature and change it from
implicit silent default to explicit conscious option. The new Perl command
line option "-C" and its counterpart environment variable
PERL_UNICODE can now be used to control how Perl and Unicode interact at
interfaces like I/O and for example the command line arguments. See
"-C" in perlrun and "PERL_UNICODE" in perlrun for more
information.
Unsafe signals again available¶
In Perl 5.8.0 the so-called "safe signals" were introduced. This means
that Perl no longer handles signals immediately but instead "between
opcodes", when it is safe to do so. The earlier immediate handling easily
could corrupt the internal state of Perl, resulting in mysterious crashes.
However, the new safer model has its problems too. Because now an opcode, a
basic unit of Perl execution, is never interrupted but instead let to run to
completion, certain operations that can take a long time now really do take a
long time. For example, certain network operations have their own blocking and
timeout mechanisms, and being able to interrupt them immediately would be
nice.
Therefore perl 5.8.1 introduces a "backdoor" to restore the pre-5.8.0
(pre-5.7.3, really) signal behaviour. Just set the environment variable
PERL_SIGNALS to "unsafe", and the old immediate (and unsafe) signal
handling behaviour returns. See "PERL_SIGNALS" in perlrun and
"Deferred Signals (Safe Signals)" in perlipc.
In completely unrelated news, you can now use safe signals with
POSIX::SigAction. See "POSIX::SigAction" in POSIX.
Tied Arrays with Negative Array Indices¶
Formerly, the indices passed to "FETCH", "STORE",
"EXISTS", and "DELETE" methods in tied array class were
always non-negative. If the actual argument was negative, Perl would call
FETCHSIZE implicitly and add the result to the index before passing the result
to the tied array method. This behaviour is now optional. If the tied array
class contains a package variable named $NEGATIVE_INDICES which is set to a
true value, negative values will be passed to "FETCH",
"STORE", "EXISTS", and "DELETE" unchanged.
local ${$x}¶
The syntaxes
local ${$x}
local @{$x}
local %{$x}
now do localise variables, given that the $x is a valid variable name.
Unicode Character Database 4.0.0¶
The copy of the Unicode Character Database included in Perl 5.8 has been updated
to 4.0.0 from 3.2.0. This means for example that the Unicode character
properties are as in Unicode 4.0.0.
Deprecation Warnings¶
There is one new feature deprecation. Perl 5.8.0 forgot to add some deprecation
warnings, these warnings have now been added. Finally, a reminder of an
impending feature removal.
(Reminder) Pseudo-hashes are deprecated (really)
Pseudo-hashes were deprecated in Perl 5.8.0 and will be removed in Perl 5.10.0,
see perl58delta for details. Each attempt to access pseudo-hashes will trigger
the warning "Pseudo-hashes are deprecated". If you really want to
continue using pseudo-hashes but not to see the deprecation warnings, use:
no warnings 'deprecated';
Or you can continue to use the fields pragma, but please don't expect the data
structures to be pseudohashes any more.
(Reminder) 5.005-style threads are deprecated (really)
5.005-style threads (activated by "use Thread;") were deprecated in
Perl 5.8.0 and will be removed after Perl 5.8, see perl58delta for details.
Each 5.005-style thread creation will trigger the warning "5.005 threads
are deprecated". If you really want to continue using the 5.005 threads
but not to see the deprecation warnings, use:
no warnings 'deprecated';
(Reminder) The $* variable is deprecated (really)
The $* variable controlling multi-line matching has been deprecated and will be
removed after 5.8. The variable has been deprecated for a long time, and a
deprecation warning "Use of $* is deprecated" is given, now the
variable will just finally be removed. The functionality has been supplanted
by the "/s" and "/m" modifiers on pattern matching. If you
really want to continue using the $*-variable but not to see the deprecation
warnings, use:
no warnings 'deprecated';
Miscellaneous Enhancements¶
"map" in void context is no longer expensive. "map" is now
context aware, and will not construct a list if called in void context.
If a socket gets closed by the server while printing to it, the client now gets
a SIGPIPE. While this new feature was not planned, it fell naturally out of
PerlIO changes, and is to be considered an accidental feature.
PerlIO::get_layers(FH) returns the names of the PerlIO layers active on a
filehandle.
PerlIO::via layers can now have an optional UTF8 method to indicate whether the
layer wants to "auto-:utf8" the stream.
utf8::is_utf8() has been added as a quick way to test whether a scalar is
encoded internally in UTF-8 (Unicode).
Modules and Pragmata¶
Updated Modules And Pragmata¶
The following modules and pragmata have been updated since Perl 5.8.0:
- base
- B::Bytecode
- In much better shape than it used to be. Still far from
perfect, but maybe worth a try.
- B::Concise
- B::Deparse
- Benchmark
- An optional feature, ":hireswallclock", now
allows for high resolution wall clock times (uses Time::HiRes).
- ByteLoader
- See B::Bytecode.
- bytes
- Now has bytes::substr.
- CGI
- charnames
- One can now have custom character name aliases.
- CPAN
- There is now a simple command line frontend to the CPAN.pm
module called cpan.
- Data::Dumper
- A new option, Pair, allows choosing the separator between
hash keys and values.
- DB_File
- Devel::PPPort
- Digest::MD5
- Encode
- Significant updates on the encoding pragma functionality
(tr/// and the DATA filehandle, formats).
If a filehandle has been marked as to have an encoding, unmappable
characters are detected already during input, not later (when the
corrupted data is being used).
The ISO 8859-6 conversion table has been corrected (the 0x30..0x39
erroneously mapped to U+0660..U+0669, instead of U+0030..U+0039). The GSM
03.38 conversion did not handle escape sequences correctly. The UTF-7
encoding has been added (making Encode feature-complete with
Unicode::String).
- fields
- libnet
- Math::BigInt
- A lot of bugs have been fixed since v1.60, the version
included in Perl v5.8.0. Especially noteworthy are the bug in Calc that
caused div and mod to fail for some large values, and the fixes to the
handling of bad inputs.
Some new features were added, e.g. the broot() method, you can now
pass parameters to config() to change some settings at runtime, and
it is now possible to trap the creation of NaN and infinity.
As usual, some optimizations took place and made the math overall a tad
faster. In some cases, quite a lot faster, actually. Especially
alternative libraries like Math::BigInt::GMP benefit from this. In
addition, a lot of the quite clunky routines like fsqrt() and
flog() are now much much faster.
- MIME::Base64
- NEXT
- Diamond inheritance now works.
- Net::Ping
- PerlIO::scalar
- Reading from non-string scalars (like the special
variables, see perlvar) now works.
- podlators
- Pod::LaTeX
- PodParsers
- Pod::Perldoc
- Complete rewrite. As a side-effect, no longer refuses to
startup when run by root.
- Scalar::Util
- New utilities: refaddr, isvstring, looks_like_number,
set_prototype.
- Storable
- Can now store code references (via B::Deparse, so not
foolproof).
- strict
- Earlier versions of the strict pragma did not check the
parameters implicitly passed to its "import" (use) and
"unimport" (no) routine. This caused the false idiom such as:
use strict qw(@ISA);
@ISA = qw(Foo);
This however (probably) raised the false expectation that the strict refs,
vars and subs were being enforced (and that @ISA was somehow
"declared"). But the strict refs, vars, and subs are not
enforced when using this false idiom.
Starting from Perl 5.8.1, the above will cause an error to be raised.
This may cause programs which used to execute seemingly correctly without
warnings and errors to fail when run under 5.8.1. This happens because
use strict qw(@ISA);
will now fail with the error:
Unknown 'strict' tag(s) '@ISA'
The remedy to this problem is to replace this code with the correct idiom:
use strict;
use vars qw(@ISA);
@ISA = qw(Foo);
- Term::ANSIcolor
- Test::Harness
- Now much more picky about extra or missing output from test
scripts.
- Test::More
- Test::Simple
- Text::Balanced
- Time::HiRes
- Use of nanosleep(), if available, allows mixing
subsecond sleeps with alarms.
- threads
- Several fixes, for example for join() problems and
memory leaks. In some platforms (like Linux) that use glibc the minimum
memory footprint of one ithread has been reduced by several hundred
kilobytes.
- threads::shared
- Many memory leaks have been fixed.
- Unicode::Collate
- Unicode::Normalize
- Win32::GetFolderPath
- Win32::GetOSVersion
- Now returns extra information.
Utility Changes¶
The "h2xs" utility now produces a more modern layout:
Foo-Bar/lib/Foo/Bar.pm instead of
Foo/Bar/Bar.pm. Also, the
boilerplate test is now called
t/Foo-Bar.t instead of
t/1.t.
The Perl debugger (
lib/perl5db.pl) has now been extensively documented
and bugs found while documenting have been fixed.
"perldoc" has been rewritten from scratch to be more robust and
feature rich.
"perlcc -B" works now at least somewhat better, while "perlcc
-c" is rather more broken. (The Perl compiler suite as a whole continues
to be experimental.)
New Documentation¶
perl573delta has been added to list the differences between the (now quite
obsolete) development releases 5.7.2 and 5.7.3.
perl58delta has been added: it is the perldelta of 5.8.0, detailing the
differences between 5.6.0 and 5.8.0.
perlartistic has been added: it is the Artistic License in pod format, making it
easier for modules to refer to it.
perlcheat has been added: it is a Perl cheat sheet.
perlgpl has been added: it is the GNU General Public License in pod format,
making it easier for modules to refer to it.
perlmacosx has been added to tell about the installation and use of Perl in Mac
OS X.
perlos400 has been added to tell about the installation and use of Perl in
OS/400 PASE.
perlreref has been added: it is a regular expressions quick reference.
Installation and Configuration Improvements¶
The Unix standard Perl location,
/usr/bin/perl, is no longer overwritten
by default if it exists. This change was very prudent because so many Unix
vendors already provide a
/usr/bin/perl, but simultaneously many system
utilities may depend on that exact version of Perl, so better not to overwrite
it.
One can now specify installation directories for site and vendor man and HTML
pages, and site and vendor scripts. See
INSTALL.
One can now specify a destination directory for Perl installation by specifying
the DESTDIR variable for "make install". (This feature is slightly
different from the previous "Configure -Dinstallprefix=...".) See
INSTALL.
gcc versions 3.x introduced a new warning that caused a lot of noise during Perl
compilation: "gcc -Ialreadyknowndirectory (warning: changing search
order)". This warning has now been avoided by Configure weeding out such
directories before the compilation.
One can now build subsets of Perl core modules by using the Configure flags
"-Dnoextensions=..." and "-Donlyextensions=...", see
INSTALL.
In Cygwin Perl can now be built with threads ("Configure
-Duseithreads"). This works with both Cygwin 1.3.22 and Cygwin 1.5.3.
In newer FreeBSD releases Perl 5.8.0 compilation failed because of trying to use
malloc.h, which in FreeBSD is just a dummy file, and a fatal error to
even try to use. Now
malloc.h is not used.
Perl is now known to build also in Hitachi HI-UXMPP.
Perl is now known to build again in LynxOS.
Mac OS X now installs with Perl version number embedded in installation
directory names for easier upgrading of user-compiled Perl, and the
installation directories in general are more standard. In other words, the
default installation no longer breaks the Apple-provided Perl. On the other
hand, with "Configure -Dprefix=/usr" you can now really replace the
Apple-supplied Perl (
please be careful).
Mac OS X now builds Perl statically by default. This change was done mainly for
faster startup times. The Apple-provided Perl is still dynamically linked and
shared, and you can enable the sharedness for your own Perl builds by
"Configure -Duseshrplib".
Perl has been ported to IBM's OS/400 PASE environment. The best way to build a
Perl for PASE is to use an AIX host as a cross-compilation environment. See
README.os400.
Yet another cross-compilation option has been added: now Perl builds on
OpenZaurus, an Linux distribution based on Mandrake + Embedix for the Sharp
Zaurus PDA. See the Cross/README file.
Tru64 when using gcc 3 drops the optimisation for
toke.c to
"-O2" because of gigantic memory use with the default
"-O3".
Tru64 can now build Perl with the newer Berkeley DBs.
Building Perl on WinCE has been much enhanced, see
README.ce and
README.perlce.
Selected Bug Fixes¶
Closures, eval and lexicals¶
There have been many fixes in the area of anonymous subs, lexicals and closures.
Although this means that Perl is now more "correct", it is possible
that some existing code will break that happens to rely on the faulty
behaviour. In practice this is unlikely unless your code contains a very
complex nesting of anonymous subs, evals and lexicals.
Generic fixes¶
If an input filehandle is marked ":utf8" and Perl sees illegal UTF-8
coming in when doing "<FH>", if warnings are enabled a warning
is immediately given - instead of being silent about it and Perl being unhappy
about the broken data later. (The ":encoding(utf8)" layer also works
the same way.)
binmode(SOCKET, ":utf8") only worked on the input side, not on the
output side of the socket. Now it works both ways.
For threaded Perls certain system database functions like
getpwent() and
getgrent() now grow their result buffer dynamically, instead of
failing. This means that at sites with lots of users and groups the functions
no longer fail by returning only partial results.
Perl 5.8.0 had accidentally broken the capability for users to define their own
uppercase<->lowercase Unicode mappings (as advertised by the Camel).
This feature has been fixed and is also documented better.
In 5.8.0 this
$some_unicode .= <FH>;
didn't work correctly but instead corrupted the data. This has now been fixed.
Tied methods like FETCH etc. may now safely access tied values, i.e. resulting
in a recursive call to FETCH etc. Remember to break the recursion, though.
At startup Perl blocks the SIGFPE signal away since there isn't much Perl can do
about it. Previously this blocking was in effect also for programs executed
from within Perl. Now Perl restores the original SIGFPE handling routine,
whatever it was, before running external programs.
Linenumbers in Perl scripts may now be greater than 65536, or 2**16. (Perl
scripts have always been able to be larger than that, it's just that the
linenumber for reported errors and warnings have "wrapped around".)
While scripts that large usually indicate a need to rethink your code a bit,
such Perl scripts do exist, for example as results from generated code. Now
linenumbers can go all the way to 4294967296, or 2**32.
Linux
- •
- Setting $0 works again (with certain limitations that Perl
cannot do much about: see "$0" in perlvar)
HP-UX
- •
- Setting $0 now works.
VMS
- •
- Configuration now tests for the presence of
"poll()", and IO::Poll now uses the vendor-supplied function if
detected.
- •
- A rare access violation at Perl start-up could occur if the
Perl image was installed with privileges or if there was an identifier
with the subsystem attribute set in the process's rightslist. Either of
these circumstances triggered tainting code that contained a pointer bug.
The faulty pointer arithmetic has been fixed.
- •
- The length limit on values (not keys) in the %ENV hash has
been raised from 255 bytes to 32640 bytes (except when the PERL_ENV_TABLES
setting overrides the default use of logical names for %ENV). If it is
necessary to access these long values from outside Perl, be aware that
they are implemented using search list logical names that store the value
in pieces, each 255-byte piece (up to 128 of them) being an element in the
search list. When doing a lookup in %ENV from within Perl, the elements
are combined into a single value. The existing VMS-specific ability to
access individual elements of a search list logical name via the
$ENV{'foo;N'} syntax (where N is the search list index) is
unimpaired.
- •
- The piping implementation now uses local rather than global
DCL symbols for inter-process communication.
- •
- File::Find could become confused when navigating to a
relative directory whose name collided with a logical name. This problem
has been corrected by adding directory syntax to relative path names, thus
preventing logical name translation.
Win32
- •
- A memory leak in the fork() emulation has been
fixed.
- •
- The return value of the ioctl() built-in function
was accidentally broken in 5.8.0. This has been corrected.
- •
- The internal message loop executed by perl during blocking
operations sometimes interfered with messages that were external to Perl.
This often resulted in blocking operations terminating prematurely or
returning incorrect results, when Perl was executing under environments
that could generate Windows messages. This has been corrected.
- •
- Pipes and sockets are now automatically in binary
mode.
- •
- The four-argument form of select() did not preserve
$! (errno) properly when there were errors in the underlying call. This is
now fixed.
- •
- The "CR CR LF" problem of has been fixed,
binmode(FH, ":crlf") is now effectively a no-op.
New or Changed Diagnostics¶
All the warnings related to
pack() and
unpack() were made more
informative and consistent.
Changed "A thread exited while %d threads were
running"¶
The old version
A thread exited while %d other threads were still running
was misleading because the "other" included also the thread giving the
warning.
Removed "Attempt to clear a restricted hash"¶
It is not illegal to clear a restricted hash, so the warning was removed.
New "Illegal declaration of anonymous subroutine"¶
You must specify the block of code for "sub".
Changed "Invalid range "%s" in transliteration
operator"¶
The old version
Invalid [] range "%s" in transliteration operator
was simply wrong because there are no "[] ranges" in tr///.
New "Missing control char name in \c"¶
Self-explanatory.
New "Newline in left-justified string for %s"¶
The padding spaces would appear after the newline, which is probably not what
you had in mind.
New "Possible precedence problem on bitwise %c
operator"¶
If you think this
$x & $y == 0
tests whether the bitwise AND of $x and $y is zero, you will like this warning.
New "Pseudo-hashes are deprecated"¶
This warning should have been already in 5.8.0, since they are.
New "read() on %s filehandle %s"¶
You cannot
read() (or
sysread()) from a closed or unopened
filehandle.
New "5.005 threads are deprecated"¶
This warning should have been already in 5.8.0, since they are.
New "Tied variable freed while still in use"¶
Something pulled the plug on a live tied variable, Perl plays safe by bailing
out.
New "To%s: illegal mapping '%s'"¶
An illegal user-defined Unicode casemapping was specified.
New "Use of freed value in iteration"¶
Something modified the values being iterated over. This is not good.
Changed Internals¶
These news matter to you only if you either write XS code or like to know about
or hack Perl internals (using Devel::Peek or any of the "B::"
modules counts), or like to run Perl with the "-D" option.
The embedding examples of perlembed have been reviewed to be up to date and
consistent: for example, the correct use of
PERL_SYS_INIT3() and
PERL_SYS_TERM().
Extensive reworking of the pad code (the code responsible for lexical variables)
has been conducted by Dave Mitchell.
Extensive work on the v-strings by John Peacock.
UTF-8 length and position cache: to speed up the handling of Unicode (UTF-8)
scalars, a cache was introduced. Potential problems exist if an extension
bypasses the official APIs and directly modifies the PV of an SV: the UTF-8
cache does not get cleared as it should.
APIs obsoleted in Perl 5.8.0, like sv_2pv, sv_catpvn, sv_catsv, sv_setsv, are
again available.
Certain Perl core C APIs like cxinc and regatom are no longer available at all
to code outside the Perl core of the Perl core extensions. This is
intentional. They never should have been available with the shorter names, and
if you application depends on them, you should (be ashamed and) contact
perl5-porters to discuss what are the proper APIs.
Certain Perl core C APIs like "Perl_list" are no longer available
without their "Perl_" prefix. If your XS module stops working
because some functions cannot be found, in many cases a simple fix is to add
the "Perl_" prefix to the function and the thread context
"aTHX_" as the first argument of the function call. This is also how
it should always have been done: letting the Perl_-less forms to leak from the
core was an accident. For cleaner embedding you can also force this for all
APIs by defining at compile time the cpp define PERL_NO_SHORT_NAMES.
Perl_save_bool() has been added.
Regexp objects (those created with "qr") now have S-magic rather than
R-magic. This fixed regexps of the form /...(??{...;$x})/ to no longer ignore
changes made to $x. The S-magic avoids dropping the caching optimization and
making (??{...}) constructs obscenely slow (and consequently useless). See
also "Magic Variables" in perlguts. Regexp::Copy was affected by
this change.
The Perl internal debugging macros
DEBUG() and
DEB() have been
renamed to
PERL_DEBUG() and
PERL_DEB() to avoid namespace
conflicts.
"-DL" removed (the leaktest had been broken and unsupported for years,
use alternative debugging mallocs or tools like valgrind and Purify).
Verbose modifier "v" added for "-DXv" and "-Dsv",
see perlrun.
New Tests¶
In Perl 5.8.0 there were about 69000 separate tests in about 700 test files, in
Perl 5.8.1 there are about 77000 separate tests in about 780 test files. The
exact numbers depend on the Perl configuration and on the operating system
platform.
Known Problems¶
The hash randomisation mentioned in "Incompatible Changes" is
definitely problematic: it will wake dormant bugs and shake out bad
assumptions.
If you want to use mod_perl 2.x with Perl 5.8.1, you will need mod_perl-1.99_10
or higher. Earlier versions of mod_perl 2.x do not work with the randomised
hashes. (mod_perl 1.x works fine.) You will also need Apache::Test 1.04 or
higher.
Many of the rarer platforms that worked 100% or pretty close to it with perl
5.8.0 have been left a little bit untended since their maintainers have been
otherwise busy lately, and therefore there will be more failures on those
platforms. Such platforms include Mac OS Classic, IBM z/OS (and other EBCDIC
platforms), and NetWare. The most common Perl platforms (Unix and Unix-like,
Microsoft platforms, and VMS) have large enough testing and expert population
that they are doing well.
Tied hashes in scalar context¶
Tied hashes do not currently return anything useful in scalar context, for
example when used as boolean tests:
if (%tied_hash) { ... }
The current nonsensical behaviour is always to return false, regardless of
whether the hash is empty or has elements.
The root cause is that there is no interface for the implementors of tied hashes
to implement the behaviour of a hash in scalar context.
Net::Ping 450_service and 510_ping_udp failures¶
The subtests 9 and 18 of lib/Net/Ping/t/450_service.t, and the subtest 2 of
lib/Net/Ping/t/510_ping_udp.t might fail if you have an unusual networking
setup. For example in the latter case the test is trying to send a UDP ping to
the IP address 127.0.0.1.
B::C¶
The C-generating compiler backend B::C (the frontend being "perlcc
-c") is even more broken than it used to be because of the extensive
lexical variable changes. (The good news is that B::Bytecode and ByteLoader
are better than they used to be.)
IBM z/OS and other EBCDIC platforms continue to be problematic regarding Unicode
support. Many Unicode tests are skipped when they really should be fixed.
Cygwin 1.5 problems¶
In Cygwin 1.5 the
io/tell and
op/sysio tests have failures for
some yet unknown reason. In 1.5.5 the threads tests stress_cv, stress_re, and
stress_string are failing unless the environment variable PERLIO is set to
"perlio" (which makes also the io/tell failure go away).
Perl 5.8.1 does build and work well with Cygwin 1.3: with (uname -a)
"CYGWIN_NT-5.0 ... 1.3.22(0.78/3/2) 2003-03-18 09:20 i686 ..." a
100% "make test" was achieved with "Configure -des
-Duseithreads".
HP-UX: HP cc warnings about sendfile and sendpath¶
With certain HP C compiler releases (e.g. B.11.11.02) you will get many warnings
like this (lines wrapped for easier reading):
cc: "/usr/include/sys/socket.h", line 504: warning 562:
Redeclaration of "sendfile" with a different storage class specifier:
"sendfile" will have internal linkage.
cc: "/usr/include/sys/socket.h", line 505: warning 562:
Redeclaration of "sendpath" with a different storage class specifier:
"sendpath" will have internal linkage.
The warnings show up both during the build of Perl and during certain
lib/ExtUtils tests that invoke the C compiler. The warning, however, is not
serious and can be ignored.
IRIX: t/uni/tr_7jis.t falsely failing¶
The test t/uni/tr_7jis.t is known to report failure under 'make test' or the
test harness with certain releases of IRIX (at least IRIX 6.5 and MIPSpro
Compilers Version 7.3.1.1m), but if run manually the test fully passes.
Mac OS X: no usemymalloc¶
The Perl malloc ("-Dusemymalloc") does not work at all in Mac OS X.
This is not that serious, though, since the native malloc works just fine.
Tru64: No threaded builds with GNU cc (gcc)¶
In the latest Tru64 releases (e.g. v5.1B or later) gcc cannot be used to compile
a threaded Perl (-Duseithreads) because the system
"<pthread.h>" file doesn't know about gcc.
Win32: sysopen, sysread, syswrite¶
As of the 5.8.0 release,
sysopen()/
sysread()/
syswrite() do
not behave like they used to in 5.6.1 and earlier with respect to
"text" mode. These built-ins now always operate in
"binary" mode (even if
sysopen() was passed the O_TEXT flag,
or if
binmode() was used on the file handle). Note that this issue
should only make a difference for disk files, as sockets and pipes have always
been in "binary" mode in the Windows port. As this behavior is
currently considered a bug, compatible behavior may be re-introduced in a
future release. Until then, the use of
sysopen(),
sysread() and
syswrite() is not supported for "text" mode operations.
Future Directions¶
The following things
might happen in future. The first publicly available
releases having these characteristics will be the developer releases Perl
5.9.x, culminating in the Perl 5.10.0 release. These are our best guesses at
the moment: we reserve the right to rethink.
- •
- PerlIO will become The Default. Currently (in Perl 5.8.x)
the stdio library is still used if Perl thinks it can use certain tricks
to make stdio go really fast. For future releases our goal is to
make PerlIO go even faster.
- •
- A new feature called assertions will be available.
This means that one can have code called assertions sprinkled in the code:
usually they are optimised away, but they can be enabled with the
"-A" option.
- •
- A new operator "//" (defined-or) will be
available. This means that one will be able to say
$a // $b
instead of
defined $a ? $a : $b
and
$c //= $d;
instead of
$c = $d unless defined $c;
The operator will have the same precedence and associativity as
"||". A source code patch against the Perl 5.8.1 sources will be
available in CPAN as authors/id/H/HM/HMBRAND/dor-5.8.1.diff.
- •
- "unpack()" will default to unpacking the $_.
- •
- Various Copy-On-Write techniques will be investigated in
hopes of speeding up Perl.
- •
- CPANPLUS, Inline, and Module::Build will become core
modules.
- •
- The ability to write true lexically scoped pragmas will be
introduced.
- •
- Work will continue on the bytecompiler and byteloader.
- •
- v-strings as they currently exist are scheduled to be
deprecated. The v-less form (1.2.3) will become a "version
object" when used with "use", "require", and
$VERSION. $^V will also be a "version object" so the
printf("%vd",...) construct will no longer be needed. The v-ful
version (v1.2.3) will become obsolete. The equivalence of strings and
v-strings (e.g. that currently 5.8.0 is equal to "\5\8\0") will
go away. There may be no deprecation warning for v-strings,
though: it is quite hard to detect when v-strings are being used safely,
and when they are not.
- •
- 5.005 Threads Will Be Removed
- •
- The $* Variable Will Be Removed (it was deprecated a long
time ago)
- •
- Pseudohashes Will Be Removed
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.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. You can browse and search the Perl 5 bugs at
http://bugs.perl.org/
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.