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=head1 NAME

perlbs2000 - building and installing Perl for BS2000.

=head1 SYNOPSIS

This document will help you Configure, build, test and install Perl
on BS2000 in the POSIX subsystem.

=head1 DESCRIPTION

This is a ported perl for the POSIX subsystem in BS2000 VERSION OSD
V3.1A or later.  It may work on other versions, but we started porting
and testing it with 3.1A and are currently using Version V4.0A.

You may need the following GNU programs in order to install perl:

=head2 gzip on BS2000

We used version 1.2.4, which could be installed out of the box with
one failure during 'make check'.

=head2 bison on BS2000

The yacc coming with BS2000 POSIX didn't work for us.  So we had to
use bison.  We had to make a few changes to perl in order to use the
pure (reentrant) parser of bison.  We used version 1.25, but we had to
add a few changes due to EBCDIC.  See below for more details
concerning yacc.

=head2 Unpacking Perl Distribution on BS2000

To extract an ASCII tar archive on BS2000 POSIX you need an ASCII
filesystem (we used the mountpoint /usr/local/ascii for this).  Now
you extract the archive in the ASCII filesystem without
I/O-conversion:

cd /usr/local/ascii
export IO_CONVERSION=NO
gunzip < /usr/local/src/perl.tar.gz | pax -r

You may ignore the error message for the first element of the archive
(this doesn't look like a tar archive / skipping to next file...),
it's only the directory which will be created automatically anyway.

After extracting the archive you copy the whole directory tree to your
EBCDIC filesystem.  B<This time you use I/O-conversion>:

cd /usr/local/src
IO_CONVERSION=YES
cp -r /usr/local/ascii/perl5.005_02 ./

=head2 Compiling Perl on BS2000

There is a "hints" file for BS2000 called hints.posix-bc (because
posix-bc is the OS name given by `uname`) that specifies the correct
values for most things.  The major problem is (of course) the EBCDIC
character set.  We have german EBCDIC version.

Because of our problems with the native yacc we used GNU bison to
generate a pure (=reentrant) parser for perly.y.  So our yacc is
really the following script:

-----8<-----/usr/local/bin/yacc-----8<-----
#! /usr/bin/sh

# Bison as a reentrant yacc:

# save parameters:
params=""
while [[ $# -gt 1 ]]; do
    params="$params $1"
    shift
done

# add flag %pure_parser:

tmpfile=/tmp/bison.$$.y
echo %pure_parser > $tmpfile
cat $1 >> $tmpfile

# call bison:

echo "/usr/local/bin/bison --yacc $params $1\t\t\t(Pure Parser)"
/usr/local/bin/bison --yacc $params $tmpfile

# cleanup:

rm -f $tmpfile
-----8<----------8<-----

We still use the normal yacc for a2p.y though!!!  We made a softlink
called byacc to distinguish between the two versions:

ln -s /usr/bin/yacc /usr/local/bin/byacc

We build perl using GNU make.  We tried the native make once and it
worked too.

=head2 Testing Perl on BS2000

We still got a few errors during C<make test>.  Some of them are the
result of using bison.  Bison prints I<parser error> instead of I<syntax
error>, so we may ignore them.  The following list shows
our errors, your results may differ:

op/numconvert.......FAILED tests 1409-1440
op/regexp...........FAILED tests 483, 496
op/regexp_noamp.....FAILED tests 483, 496
pragma/overload.....FAILED tests 152-153, 170-171
pragma/warnings.....FAILED tests 14, 82, 129, 155, 192, 205, 207
lib/bigfloat........FAILED tests 351-352, 355
lib/bigfltpm........FAILED tests 354-355, 358
lib/complex.........FAILED tests 267, 487
lib/dumper..........FAILED tests 43, 45
Failed 11/231 test scripts, 95.24% okay. 57/10595 subtests failed, 99.46% okay.

=head2 Installing Perl on BS2000

We have no nroff on BS2000 POSIX (yet), so we ignored any errors while
installing the documentation.

=head2 Using Perl in the Posix-Shell of BS2000

BS2000 POSIX doesn't support the shebang notation
(C<#!/usr/local/bin/perl>), so you have to use the following lines
instead:

: # use perl
    eval 'exec /usr/local/bin/perl -S $0 ${1+"$@"}'
        if $running_under_some_shell;

=head2 Using Perl in "native" BS2000

We don't have much experience with this yet, but try the following:

Copy your Perl executable to a BS2000 LLM using bs2cp:

C<bs2cp /usr/local/bin/perl 'bs2:perl(perl,l)'>

Now you can start it with the following (SDF) command:

C</START-PROG FROM-FILE=*MODULE(PERL,PERL),PROG-MODE=*ANY,RUN-MODE=*ADV>

First you get the BS2000 commandline prompt ('*').  Here you may enter
your parameters, e.g. C<-e 'print "Hello World!\\n";'> (note the
double backslash!) or C<-w> and the name of your Perl script.
Filenames starting with C</> are searched in the Posix filesystem,
others are searched in the BS2000 filesystem.  You may even use
wildcards if you put a C<%> in front of your filename (e.g. C<-w
checkfiles.pl %*.c>).  Read your C/C++ manual for additional
possibilities of the commandline prompt (look for
PARAMETER-PROMPTING).

=head2 Floating point anomalies on BS2000

There appears to be a bug in the floating point implementation on BS2000 POSIX
systems such that calling int() on the product of a number and a small
magnitude number is not the same as calling int() on the quotient of
that number and a large magnitude number.  For example, in the following
Perl code:

my $x = 100000.0;
    my $y = int($x * 1e-5) * 1e5; # '0'
    my $z = int($x / 1e+5) * 1e5;  # '100000'
    print "\$y is $y and \$z is $z\n"; # $y is 0 and $z is 100000

Although one would expect the quantities $y and $z to be the same and equal
to 100000 they will differ and instead will be 0 and 100000 respectively.

=head2 Using PerlIO and different encodings on ASCII and EBCDIC partitions

Since version 5.8 Perl uses the new PerlIO on BS2000.  This enables
you using different encodings per IO channel.  For example you may use

use Encode;
    open($f, ">:encoding(ascii)", "test.ascii");
    print $f "Hello World!\n";
    open($f, ">:encoding(posix-bc)", "test.ebcdic");
    print $f "Hello World!\n";
    open($f, ">:encoding(latin1)", "test.latin1");
    print $f "Hello World!\n";
    open($f, ">:encoding(utf8)", "test.utf8");
    print $f "Hello World!\n";

to get two files containing "Hello World!\n" in ASCII, EBCDIC, ISO
Latin-1 (in this example identical to ASCII) respective UTF-EBCDIC (in
this example identical to normal EBCDIC).  See the documentation of
Encode::PerlIO for details.

As the PerlIO layer uses raw IO internally, all this totally ignores
the type of your filesystem (ASCII or EBCDIC) and the IO_CONVERSION
environment variable.  If you want to get the old behavior, that the
BS2000 IO functions determine conversion depending on the filesystem
PerlIO still is your friend.  You use IO_CONVERSION as usual and tell
Perl, that it should use the native IO layer:

export IO_CONVERSION=YES
    export PERLIO=stdio

Now your IO would be ASCII on ASCII partitions and EBCDIC on EBCDIC
partitions.  See the documentation of PerlIO (without C<Encode::>!)
for further possibilities.

=head1 AUTHORS

Thomas Dorner

=head1 SEE ALSO

L<INSTALL>, L<perlport>.

=head2 Mailing list

If you are interested in the VM/ESA, z/OS (formerly known as OS/390)
and POSIX-BC (BS2000) ports of Perl then see the perl-mvs mailing list.
To subscribe, send an empty message to perl-mvs-subscribe@perl.org.