c - Initializing an atomic flag in a malloc'd structure -

i'm trying use atomics in c on freebsd 10.1 release clang 3.6.1, when try compile program using atomic_flag_init on atomic_flag variable in struct error: expected expression.

here program trying compile.

#include <stdio.h> #include <stdatomic.h>  struct map {      atomic_flag flag;  };  int main(void) {     struct map *m = malloc(sizeof(struct map));      m->flag = atomic_flag_init;      free(m);      return 0; } 

i can use atomic_flag outside of structs in example below not in structs, how use atomic variables in c structs?

#include <stdio.h> #include <stdatomic.h>  int main(void) {     atomic_flag flag = atomic_flag_init;      return 0; } 

atomic_flag doesn't have value can assign or read from, internal state.

the way interact atomic_flag 2 functions (or 4 if count _explicit versions) defined it. case when got object through malloc flag in "indeterminate state" (7.17.8 p4 of c11). can put known state applying 1 of 2 functions, use atomic_flag_clear set "clear" state, or use atomic_flag_test_and_set set "set" state.

using atomic_flag_clear right after allocation malloc equivalent initialization of variable atomic_flag_init.