double checked locking alternative

gistfile1.c

enum { uninitialized, initializing, initialized };
static state = uninitialized;
static var = 0;
while (true) {
    switch(cmpxchg(state, initializing, uninitialized)) {
    case uninitialized:
        var = stmt;
        xchg(state, initialized);
        return;
    case initializing:
        continue;
    case initialized:
        return;
    }
}