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PERL581DELTA(1)
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 featureful.
"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.
Platform-specific enhancements
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.
Platform-specific fixes
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 uptodate 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.)
Platform Specific Problems
EBCDIC Platforms
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.
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