redhat man page for setcontext

GETCONTEXT(2)						     Linux Programmer's Manual						     GETCONTEXT(2)

NAME
       getcontext, setcontext - get or set the user context

SYNOPSIS
       #include <ucontext.h>

       int getcontext(ucontext_t *ucp);
       int setcontext(const ucontext_t *ucp);

       where:

       ucp    points to a structure defined in <ucontext.h> containing the signal mask, execution stack, and machine registers.

DESCRIPTION
       getcontext(2) gets the current context of the calling process, storing it in the ucontext struct pointed to by ucp.

       setcontext(2)  sets the context of the calling process to the state stored in the ucontext struct pointed to by ucp. The struct must either
       have been created by getcontext(2) or have been passed as the third parameter of the sigaction(2) signal handler.

       The ucontext struct created by getcontext(2) is defined in <ucontext.h> as follows:

	      typedef struct ucontext
		{
		    unsigned long int uc_flags;
		    struct ucontext *uc_link;
		    stack_t uc_stack;
		    mcontext_t uc_mcontext;
		    __sigset_t uc_sigmask;
		    struct _fpstate __fpregs_mem;
		  } ucontext_t;

RETURN VALUES
       getcontext(2) returns 0 on success and -1 on failure.  setcontext(2) does not return a value on success and returns -1 on failure.

STANDARDS
       These functions comform to: XPG4-UNIX.

NOTES
       When a signal handler executes, the current user context is saved and a new context is created by  the  kernel.	 If  the  calling  process
       leaves  the  signal  handler using longjmp(2), the original context cannot be restored, and the result of future calls to getcontext(2) are
       unpredictable. To avoid this problem, use siglongjmp(2) or setcontext(2) in signal handlers instead of longjmp(2).

SEE ALSO
       sigaction(2), sigaltstack(2), sigprocmask(2), sigsetjmp(3), setjmp(3).

Red Hat Linux 6.1						 20 September 1999						     GETCONTEXT(2)