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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 HP's (formerly Compaq's,
formerly Digital's) Unix operating system (Tru64) that will affect
how Perl version 5 (hereafter just Perl) is configured, 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 at the
very least the release of 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 many
of the op/regexp and op/pat, or ext/Storable tests dumping core
(the exact pattern of failures depending on the GCC release and
optimization flags).

gcc 3.2.1 is known to work okay with Perl 5.8.0.  However, when
optimizing the toke.c gcc likes to have a lot of memory, 256 megabytes
seems to be enough.  The default setting of the process data section
in Tru64 should be one gigabyte, but some sites/setups might have
lowered that.  The configuration process of Perl checks for too low
process limits, and lowers the optimization for the toke.c if
necessary, and also gives advice on how to raise the process limits.

=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 (though using the option
is harmless).

=head2 Threaded Perl on Tru64

If you want to use threads, you should primarily use the Perl
5.8.0 threads model by running Configure with -Duseithreads.

Perl threading is going to work only in Tru64 4.0 and newer releases,
older operating releases like 3.2 aren't probably going to work
properly with threads.

In Tru64 V5 (at least V5.1A, V5.1B) you cannot build threaded Perl with gcc
because the system header <pthread.h> explicitly checks for supported
C compilers, gcc (at least 3.2.2) not being one of them.  But the
system C compiler should work just fine.

=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 enough
before that.  Perl's Configure will override attempts to use the long
doubles (you can notice this by Configure finding out that the modfl()
function does not work as it should).

At the time of this writing (June 2002), there is a known bug in the
Tru64 libc printing of long doubles when not using "e" notation.
The values are correct and usable, but you only get a limited number
of digits displayed unless you force the issue by using C<printf
"%.33e",$num> or the like.  For Tru64 versions V5.0A through V5.1A, a
patch is expected sometime after perl 5.8.0 is released.  If your libc
has not yet been patched, you'll get a warning from Configure when
selecting long doubles.

=head2 DB_File tests failing on Tru64

The DB_File tests (db-btree.t, db-hash.t, db-recno.t) may fail you
have installed a newer version of Berkeley DB into the system and the
-I and -L compiler and linker flags introduce version conflicts with
the DB 1.85 headers and libraries that came with the Tru64.  For example, 
mixing a DB v2 library with the DB v1 headers is a bad idea.  Watch
out for Configure options -Dlocincpth and -Dloclibpth, and check your
/usr/local/include and /usr/local/lib since they are included by default.

The second option is to explicitly instruct Configure to detect the
newer Berkeley DB installation, by supplying the right directories with
C<-Dlocincpth=/some/include> and C<-Dloclibpth=/some/lib> B<and> before
running "make test" setting your LD_LIBRARY_PATH to F</some/lib>.

The third option is to work around the problem by disabling the
DB_File completely when build Perl by specifying -Ui_db to Configure,
and then using the BerkeleyDB module from CPAN instead of DB_File.
The BerkeleyDB works with Berkeley DB versions 2.* or greater.

The Berkeley DB 4.1.25 has been tested with Tru64 V5.1A and found
to work.  The latest Berkeley DB can be found from F<http://www.sleepycat.com>.

=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
since pointers are automatically 64-bit wide.

=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;
    -----------^

and when compiling the POSIX extension

    cc: Warning: const-c.inc, line 2007: 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: in later C compiler releases the warnings
should be gone.

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 ext/ODBM_File/odbm Test Failing With Static Builds

The ext/ODBM_File/odbm is known to fail with static builds
(Configure -Uusedl) due to a known bug in Tru64's static libdbm
library.  The good news is that you very probably don't need to ever
use the ODBM_File extension since more advanced NDBM_File works fine,
not to mention the even more advanced DB_File.

=head1 Perl Fails Because Of Unresolved Symbol sockatmark

If you get an error like

    Can't load '.../OSF1/lib/perl5/5.8.0/alpha-dec_osf/auto/IO/IO.so' for module IO: Unresolved symbol in .../lib/perl5/5.8.0/alpha-dec_osf/auto/IO/IO.so: sockatmark at .../lib/perl5/5.8.0/alpha-dec_osf/XSLoader.pm line 75.

you need to either recompile your Perl in Tru64 4.0D or upgrade your
Tru64 4.0D to at least 4.0F: the sockatmark() system call was
added in Tru64 4.0F, and the IO extension refers that symbol.

=head1 AUTHOR

Jarkko Hietaniemi <jhi@iki.fi>

=cut