# 4.9.9. Linker “rpath” and “runpath” functionality

Open MPI and OpenSHMEM v5.0.6 are both composed of multiple libraries that depend on each other.

When built from official distribution tarballs (from the official Open MPI download site), Open MPI and OpenSHMEM are built with the following versions of the GNU Autotools:

- Autoconf 2.69.0

- Automake 1.13.4

- Libtool 2.4.2

This set of GNU Autotools invokes the `libtool` executable to build Open MPI’s libraries and executables with the -rpath CLI option.

The behavior of `libtool -rpath ...` is, unfortunately, highly system-dependent. In conjunction with compiler-, linker-, and other system-level settings, the end result may be to effect “rpath” behavior, “runpath” behavior, or possibly even neither behavior.

Although the specific behavior of `libtool -rpath ..` is outside the scope of this documentation, you can run commands such as `readelf -d ...` to find out with which behavior your Open MPI was built.

For example:

    shell$ ./configure --prefix=/opt/openmpi/ ...
    ...
    shell$ make -j 32 all && make install
    ...
    shell$ readelf -d /opt/openmpi/lib/libmpi.so | egrep -i 'rpath|runpath'
     0x000000000000001d (RUNPATH)            Library runpath: [/opt/openmpi/lib]

The above output indicates that `libmpi.so` was built with “runpath” support, whereas output like this:

    shell$ readelf -d /opt/openmpi/lib/libmpi.so | egrep -i 'rpath|runpath'
     0x000000000000000f (RPATH)              Library rpath: [/opt/openmpi/lib]

indicates that `libmpi.so` was built with “rpath” support.

Note

If you want to utilize additional compiler or linker flags (such as runpath flags) when building Open MPI/OpenSHMEM, you can specify these flags on the configure command line.

For example, if invoking `libtool -rpath ...` on your system actually effects “rpath” behavior, and you wish to effect “runpath” behavior, you could set `LDFLAGS` when invoking `configure`, like this:

    shell$ ./configure LDFLAGS=-Wl,--enable-new-dtags ...