Reportedly Mercury does not work on Solaris 2.5.1 if it is compiled with
gcc 2.7.x.  It should however work fine on Solaris 2.5.1 if you compile
it with gcc 2.8, or if you use gcc 2.7.x with an earlier version of Solaris.

The binary distribution for Solaris that we distribute was compiled
with gcc 2.7.2, so if you have Solaris 2.5.1, you may need to compile
Mercury yourself from our source distribution.

("Solaris 2.x" is also known as "SunOS 5.x".)