We have so far failed to find a good way to determine the stack base.

It is highly recommended that GC_stackbottom be set explicitly on program

startup. The supplied value sometimes causes failure under AIX 4.1, though

it appears to work under 3.X. HEURISTIC2 seems to work under 4.1, but

involves a substantial performance penalty, and will fail if there is

no limit on stack size.

There is no multi-threading support. (I assume recent versions of AIX provide

pthreads? I no longer have access to a machine ...)