Integrate change #12820 from macperl to maint and blead;

[p5sagit/p5-mst-13.2.git] / README.tru64

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=head1 NAME

README.tru64 - Perl version 5 on Tru64 (formerly known as Digital UNIX formerly known as DEC OSF/1) systems

=head1 DESCRIPTION

This document describes various features of Compaq's (formerly Digital's)
Unix operating system (Tru64) that will affect how Perl version 5
is compiled and/or runs.

=head2 Compiling Perl 5 on Tru64

The recommended compiler to use in Tru64 is the native C compiler.
The native compiler produces much faster code (the speed difference
is noticeable: several dozen percentages) and also more correct code:
if you are considering using the GNU C compiler you should use the
gcc 2.95.3 since all older gcc releases are known to produce broken
code when compiling Perl.  One manifestation of this brokenness is
the lib/sdbm test dumping core; another is the op/regexp dumping core
(depending on the GCC release).

=head2 Using Large Files with Perl on Tru64

In Tru64 Perl is automatically able to use large files, that is, files
larger than 2 gigabytes, there is no need to use the Configure
-Duselargefiles option as described in INSTALL.

=head2 Threaded Perl on Tru64

To compile Perl to use the old Perl 5.005 threads model, run Configure
with the -Dusethreads -Duse5005threads options as described in INSTALL.
This will probably only work in Tru64 4.0 and newer releases, older
operating releases like 3.2 aren't probably going to work properly
with threads.

Beware: the Perl 5.005 threads model is known to have bugs, for
example the regular expressions are not thread-safe.  The bugs are
very hard to fix are and therefore the 5.005 threads model is still
classified as an experimental feature.

=head2 Long Doubles on Tru64

You cannot Configure Perl to use long doubles unless you have at least
Tru64 V5.0, the long double support simply wasn't functional before
that.

=head2 64-bit Perl on Tru64

In Tru64 Perl's integers are automatically 64-bit wide, there is
no need to use the Configure -Duse64bitint option as described
in INSTALL.  Similarly, there is no need for -Duse64bitall.

=head2 Warnings about floating-point overflow when compiling Perl on Tru64

When compiling Perl in Tru64 you may (depending on the compiler
release) see two warnings like this

    cc: Warning: numeric.c, line 104: In this statement, floating-point overflow occurs in evaluating the expression "1.8e308". (floatoverfl)
        return HUGE_VAL;
    -----------^

    cc: Warning: POSIX.xs, line 1304: In this statement, floating-point overflow occurs in evaluating the expression "1.8e308". (floatoverfl)
                return HUGE_VAL;
    -------------------^

The exact line numbers may vary between Perl releases.
The warnings are benign and can be ignored.

When the file F<pp_sys.c> is being compiled you may (depending on the
operating system release) see an additional compiler flag being used:
C<-DNO_EFF_ONLY_OK>.  This is normal and refers to a feature that is
relevant only if you use the C<filetest> pragma.  In older releases of
the operating system the feature was broken and the NO_EFF_ONLY_OK
instructs Perl not to use the feature.

=head1 Testing Perl on Tru64

During "make test" the C<comp/cpp> will be skipped because on Tru64 it
cannot be tested before Perl has been installed.  The test refers to
the use of the C<-P> option of Perl.

=head1 AUTHOR

Jarkko Hietaniemi <jhi@iki.fi>

=cut