test/Xm/textf/test8.c does not compile with the MipsPro 7.3 C compiler for IRIX. That compiler rejects performing arithmetic with void pointers. The attached patch inserts some casts to char* to solve the problem and removes the commented out printf statement since casts would have to be added there as well to make the argument types agree with the format string.
The patch was computed against version 1.5 of test/Xm/textf/test8.c and can be applied from the top
level of the Lesstif source tree with
patch -Np1 <patch_file