setjmp(3C)                                             setjmp(3C)



NAME
     setjmp, longjmp - provide non-local goto

SYNOPSIS
     #include <setjmp.h>

     int setjmp(env)
     jmp_buf env;

     void longjmp(env, val)
     jmp_buf env;
     int val;

DESCRIPTION
     These functions are useful for dealing with errors and
     interrupts encountered in a low-level subroutine of a
     program.

     setjmp saves its stack environment in env for later use by
     longjmp.  The environment type jmp_buf is defined in the
     <setjmp.h> header file.

STATUS MESSAGES AND VALUES
     When setjmp has been called by the calling process, it
     returns 0.

     The longjmp program restores the environment saved by the
     last call of setjmp with the corresponding env argument.
     After longjmp is completed, program execution continues as
     if the corresponding call of setjmp (which must not itself
     have returned in the interim) had just returned the value
     val.  longjmp cannot cause setjmp to return the value 0.  If
     longjmp is invoked with a second argument of 0, setjmp will
     return 1.  All accessible data have values as of the time
     longjmp was called.

WARNINGS
     longjmp fails if it is called when env was never primed by a
     call to setjmp or when the last such call is in a function
     that has since returned.

SEE ALSO
     signal(3)












January 1992                                                    1