PERL581DELTA(1) Perl Programmers Reference Guide 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 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.
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, a 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 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.)
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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