correctness in localized global variable between setjmp and longjmp

I noticed that c code below failed with -O3 :

#include <setjmp.h>

#include <stdio.h>

static int cnt;

int main(){

int var;

jmp_buf buffer;

cnt = 0;

if ((var = setjmp(buffer)) == 0) {

printf(" if true, var: %d, .count:%d , increase count !\n",var, cnt);


longjmp(buffer, 2);

} else {

if (cnt == 1)

printf(" Pass var: %d, .count:%d \n",var, cnt);


printf(" Fail !!! var: %d, .count:%d \n",var, cnt);


return 0;


The documentation of setjmp/longjmp says that the values of objects of automatic storage duration which are local to the function containing the invocation of the corresponding setjmp() which do not have volatile-qualified type and which are changed between the setjmp() invocation and longjmp() call are indeterminate.

Even though “cnt” is a global variable, above c code failed because the globalopt pass localizes the global value (cnt) in main(), causing that the value of the global variable becomes indeterminate between setjmp() and longjmp. I believe the globalopt pass need to check this case before localizing global variables. Is there any better solution about it?



No, looks like it has to check it.

This is a very specific optimization, but it looks like it is still
important in old benchmarks.


Perhaps you should file a bug report here: