Defined in header <setjmp.h>
#define setjmp(env) /* implementation-defined */

Saves the current execution context into a variable env of type jmp_buf. This variable can later be used to restore the current execution context by longjmp function. That is, when a call to longjmp function is made, the execution continues at the particular call site that constructed the jmp_buf variable passed to longjmp. In that case setjmp returns the value passed to longjmp.

The invocation of setjmp must appear only in one of the following contexts:

switch(setjmp(env)) { ..
  • one operand of a relational or equality operator with the other operand an integer constant expression, with the resulting expression being the entire controlling expression of if, switch, while, do-while, for
if(setjmp(env) > 10) { ...
  • the operand of a unary ! operator with the resulting expression being the entire controlling expression of if, switch, while, do-while, for
while(!setjmp(env)) { ...

If setjmp appears in any other context, the behavior is undefined.

Upon return to the scope of setjmp, all accessible objects, floating-point status flags, and other components of the abstract machine have the same values as they had when longjmp was executed, except for the non-volatile local variables in setjmp's scope, whose values are indeterminate if they have been changed since the setjmp invocation.


env - variable to save the execution state of the program to.

Return value

​0​ if the macro was called by the original code and the execution context was saved to env.

Non-zero value if a non-local jump was just performed. The return value is the same as passed to longjmp.


#include <stdio.h>
#include <setjmp.h>
#include <stdnoreturn.h>
jmp_buf jump_buffer;
noreturn void a(int count) 
    printf("a(%d) called\n", count);
    longjmp(jump_buffer, count+1); // will return count+1 out of setjmp
int main(void)
    volatile int count = 0; // modified local vars in setjmp scope must be volatile
    if (setjmp(jump_buffer) != 9) // compare against constant in an if


a(1) called
a(2) called
a(3) called
a(4) called
a(5) called
a(6) called
a(7) called
a(8) called


  • C11 standard (ISO/IEC 9899:2011):
    • The setjmp macro (p: 262-263)
  • C99 standard (ISO/IEC 9899:1999):
    • The setjmp macro (p: 243-244)
  • C89/C90 standard (ISO/IEC 9899:1990):
    • 4.6.1 The setjmp macro

See also

jumps to specified location

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