Multilib allows you to have both 32-bit and 64-bit versions of libmunge
installed at the same time, capable of communicating with either a 32-bit
or 64-bit version of munged.

On Linux, at least, 32-bit libraries usually reside in /usr/lib, and
64-bit libraries usually reside in /usr/lib64.  But on ia64, for example,
64-bit libraries reside in /usr/lib since everything is 64-bit there.

If you are building from source, you can pass a command-line option to
the configure script:

  $ ./configure --enable-arch=32

  $ ./configure --enable-arch=64

If you are building RPMs, you can pass a command-line option to rpmbuild:

  $ rpmbuild -ta --clean --with arch32 munge-x.y.z.tar.bz2

  $ rpmbuild -ta --clean --with arch64 munge-x.y.z.tar.bz2

You might also have to specify the --target command-line option:

  $ rpmbuild -ta --clean --with arch32 --target i386 munge-x.y.z.tar.bz2

  $ rpmbuild -ta --clean --with arch64 --target x86_64 munge-x.y.z.tar.bz2

For each platform, you will have one source RPM and three binary RPMs
(munge, munge-devel, and munge-libs).

If you wanted to install both 32-bit and 64-bit MUNGE libraries on an
RPM-based x86_64 system, for example, you would need to install either
the 32-bit or 64-bit version of the main munge RPM (containing munged),
and both 32-bit and 64-bit versions of the munge-devel and munge-libs RPMs:

  $ rpm -ivh RPMS/x86_64/munge-0.5-1.x86_64.rpm \
             RPMS/x86_64/munge-devel-0.5-1.x86_64.rpm \
             RPMS/x86_64/munge-libs-0.5-1.x86_64.rpm \
             RPMS/i386/munge-devel-0.5-1.i386.rpm \
             RPMS/i386/munge-libs-0.5-1.i386.rpm

You can then link your application against either the 32-bit or 64-bit library:

  $ gcc -o foo foo.c -m32 -lmunge

  $ gcc -o foo foo.c -m64 -lmunge


AIX uses RPM 3.x which does not recognize the "--with" command-line option.
The 'arch 32_64' define builds a single multiarch library where both 32-bit
and 64-bit objects reside in libmunge.a.  Note that the 'arch 32_64' string
must be quoted to appear as a single command-line argument.  Export the
OBJECT_MODE variable to the environment.

The OS detection in RPM 3.x appends the OS version and release to the name
(eg, "aix5.3").  Since I didn't want to pin the spec file to a particular
set of AIX versions, I used the generic OS string "aix".  Consequently,
you must specify "--target ppc-aix" when building the RPM, and "--ignoreos"
when installing the RPM.

  $ export OBJECT_MODE=32
  $ rpm -ta --clean --define 'arch 32' --target ppc-aix munge-x.y.z.tar.bz2

  $ export OBJECT_MODE=64
  $ rpm -ta --clean --define 'arch 64' --target ppc-aix munge-x.y.z.tar.bz2

  $ export OBJECT_MODE=32
  $ rpm -ta --clean --define 'arch 32_64' --target ppc-aix munge-x.y.z.tar.bz2

You can then link your application against either the 32-bit or 64-bit library:

  $ export OBJECT_MODE=32
  $ gcc -o foo foo.c -lmunge

  $ export OBJECT_MODE=64
  $ gcc -o foo foo.c -lmunge