Most languages allow the main program to have any name. The
N_MAIN stab type tells the debugger the name that is used in this
program. Only the string field is significant; it is the name of
a function which is the main program. Most C compilers do not use this
stab (they expect the debugger to assume that the name is main),
but some C compilers emit an N_MAIN stab for the main
function. I'm not sure how XCOFF handles this.