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@(#)setjmp.3 5.1 (Berkeley) 05/15/85

C 4 setjmp, longjmp - non-local goto

 #include <setjmp.h> 

 setjmp(env)  jmp_buf env; 

 longjmp(env, val)  jmp_buf env; 

 _setjmp(env)  jmp_buf env; 

 _longjmp(env, val)  jmp_buf env; 

These routines 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. It returns value 0.

Longjmp restores the environment saved by the last call of setjmp . It then returns in such a way that execution continues as if the call of setjmp had just returned the value val to the function that invoked setjmp, which must not itself have returned in the interim. All accessible data have values as of the time longjmp was called.

Setjmp and longjmp save and restore the signal mask sigmask (2), while _setjmp and _longjmp manipulate only the C stack and registers.

sigvec(2), sigstack(2), signal(3) Setjmp does not save current notion of whether the process is executing on the signal stack. The result is that a longjmp to some place on the signal stack leaves the signal stack state incorrect.