call_once - initialization function
#include <threads.h> once_flag flag = ONCE_FLAG_INIT;
void call_once(once_flag *flag, void (*func)(void));
The object pointed to by flag must be initialized with the value ONCE_FLAG_INIT before any call to the call_once() function using that object and it must not be modified again before the last call to call_once() using that object.
The constant ONCE_FLAG_INIT is defined in the <threads.h> header.
No value is returned by the call_once() function.
See attributes(7) for descriptions of the following attributes: