/usr/ucb/cc [flag . . . ] file . . .
int sigstack (struct sigstack *ss, struct sigstack *oss);
A signal stack is specified by a sigstack structure, which includes the following members:
char *ss_sp; /* signal stack pointer */ int ss_onstack; /* current status */
ss_sp is the initial value to be assigned to the stack pointer when the system switches the process to the signal stack. Note that, on machines where the stack grows downwards in memory, this is not the address of the beginning of the signal stack area. ss_onstack field is zero or non-zero depending on whether the process is currently executing on the signal stack or not.
If ss is not a NULL pointer, sigstack sets the signal stack state to the value in the sigstack structure pointed to by ss. Note: if ss_onstack is non-zero, the system will think that the process is executing on the signal stack. If ss is a NULL pointer, the signal stack state will be unchanged. If oss is not a NULL pointer, the current signal stack state is stored in the sigstack structure pointed to by oss.
sigstack will fail and the signal stack context will remain unchanged if one of the following occurs.