VMS Help CC, Run-time functions, sigstack  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Defines an alternate stack on which to process signals.  This
  allows the processing of signals in a separate environment from
  that of the current process.  This function is nonreentrant.

  Syntax:

       #include <signal.h>

       int sigstack(struct sigstack *ss, struct sigstack *oss);