opendarwin man page for sigreturn

SIGRETURN(2)						      BSD System Calls Manual						      SIGRETURN(2)

NAME
     sigreturn -- return from signal

SYNOPSIS
     #include <signal.h>

     struct sigcontext {
	     int sc_onstack;
	     int sc_mask;
	     int sc_sp;
	     int sc_fp;
	     int sc_ap;
	     int sc_pc;
	     int sc_ps;
     };

     int
     sigreturn(struct sigcontext *scp);

DESCRIPTION
     Sigreturn() allows users to atomically unmask, switch stacks, and return from a signal context.  The processes signal mask and stack status
     are restored from the context.  The system call does not return; the users stack pointer, frame pointer, argument pointer, and processor sta-
     tus longword are restored from the context.  Execution resumes at the specified pc.  This system call is used by the trampoline code and
     longjmp(3) when returning from a signal to the previously executing program.

NOTES
     This system call is not available in 4.2 BSD hence it should not be used if backward compatibility is needed.

RETURN VALUES
     If successful, the system call does not return.  Otherwise, a value of -1 is returned and errno is set to indicate the error.

ERRORS
     Sigreturn() will fail and the process context will remain unchanged if one of the following occurs.

     [EFAULT]		Scp points to memory that is not a valid part of the process address space.

     [EINVAL]		The process status longword is invalid or would improperly raise the privilege level of the process.

SEE ALSO
     sigaction(2), setjmp(3)

HISTORY
     The sigreturn() function call appeared in 4.3BSD.

4.3 Berkeley Distribution					   June 4, 1993 					 4.3 Berkeley Distribution