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 unpre-
       dictable. 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)