24.2. What's New in Perl 5.6.0-5.8.0
As mentioned earlier, Perl 5.6.0 is
the minimum requirement for mod_perl
2.0. However, certain new features work only with Perl 5.8.0 and
higher.
The following are the important changes in the recent Perl versions
that had an impact on mod_perl. For a complete list of changes, see
the appropriate perldelta manpage. The 5.6
generation of Perl introduced the following features:
-
The beginnings of support for running multiple interpreters
concurrently in different threads. In conjunction with the
perl_clone( ) API call, which can be used to
selectively duplicate the state of any given interpreter, it is
possible to compile a piece of code once in an interpreter, clone
that interpreter one or more times, and run all the resulting
interpreters in distinct threads. See the
perlembed and perl561delta
manpages.
-
The core support for declaring subroutine attributes, which is used
by mod_perl 2.0's method handlers (with the
: method attribute). See the
attributes manpage.
-
The warnings pragma, which allows programmers to
force the code to be super clean, via the setting:
use warnings FATAL => 'all';
which will abort any code that generates warnings. This pragma also
allows fine control over what warnings should be reported. See the
perllexwarn manpage.
-
Certain CORE:: functions can now be overridden via
the CORE::GLOBAL:: namespace. For example,
mod_perl now can override exit( ) globally by
defining CORE::GLOBAL::exit. So when
exit( ) is called, CORE::GLOBAL::exit(
) gets invoked. Note that you can still use
CORE::exit( ) to get the original behavior. See
the perlsub manpage.
-
The XSLoader extension as a simpler alternative to
DynaLoader. See the XSLoader
manpage.
-
Large-file support. If you have filesystems that support files larger
than 2 GB), you may now also be able to create and access them from
Perl. See the perl561delta manpage.
-
Multiple performance enhancements. See the
perl561delta manpage.
-
Numerous memory leaks were fixed. See the
perl561delta manpage.
-
Improved security features: more potentially unsafe operations taint
their results for improved security. See the
perlsec and perl561delta
manpages.
-
Perl is now available on new platforms: GNU/Hurd, Rhapsody/Darwin,
and EPOC.
Overall, multiple bugs and problems were fixed in Perl 5.6.1, so if
you plan on running the 5.6 generation, you should run at least
5.6.1. It is possible that when this book is released 5.6.2 will be
out, which will then incorporate the bug fixes from Perl 5.8.0.
Perl 5.8.0 has introduced the following features:
-
The experimental PerlIO layer, introduced in 5.6.0, has been
stabilized and become the default I/O layer in 5.8.0. Now the I/O
stream can be filtered through multiple I/O layers. See the
perlapio and perliol
manpages.
For example, this allows mod_perl to interoperate with the APR I/O
layer and even use the APR I/O layer in Perl code. See the
APR::PerlIO manpage.
Another example of using this new feature is the extension of the
open( ) functionality to create anonymous
temporary files via:
open my $fh, "+>", undef or die $!;
That is a literal undef( ), not an undefined
value. See the open( ) entry in the
perlfunc manpage.
-
More keywords are now overridable via
CORE::GLOBAL::. See the
perlsub manpage.
-
The signal handling in Perl has been notoriously unsafe because
signals have been able to arrive at inopportune moments, leaving Perl
in an inconsistent state. Now Perl delays signal handling until it is
safe.
-
File::Temp was added to allow creation of
temporary files and directories in an easy, portable, and secure way.
See the File::Temp manpage.
-
A new command-line option, -t, is available. It
is the little brother of -T: instead of dying on
taint violations, lexical warnings are given. This is meant only as a
temporary debugging aid while securing the code of old legacy
applications. It is not a substitute for
-T. See the perlrun
manpage.
-
A new special variable, ${^TAINT}, was introduced.
It indicates whether taint mode is enabled. See the
perlvar manpage.
-
Thread implementation is much improved since 5.6.0. The Perl
interpreter should now be completely thread-safe, and 5.8.0 marks the
arrival of the threads module, which allows Perl
programs to work with threads (creating them, sharing variables,
etc.).
-
Much better support for Unicode has been added.
-
Numerous bugs and memory leaks have been fixed. For example, now you
can localize the tied Apache::DBI database handles
without leaking memory.
-
Perl is now available on new platforms: AtheOS, Mac OS Classic,
MinGW, NCR MP-RAS, NonStop-UX, NetWare, and UTS. Also, the following
platforms are again supported: BeOS, DYNIX/ptx, POSIX-BC, VM/ESA, and
z/OS (OS/390).
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