Atomics demo

atomics.c

@@ -0,0 +1,43 @@
+#include <stdatomic.h>
+#include <stdio.h>
+#include <threads.h>
+
+atomic_int x; // _Atomic int
+
+int thread1(void *arg) {
+    (void)arg;
+
+    printf("Thread 1: Sleeping for 1.5 seconds\n");
+    thrd_sleep(&(struct timespec){.tv_sec = 1, .tv_nsec = 500000000}, NULL);
+
+    printf("Thread 1: Setting x to 3490\n");
+    x = 3490;
+
+    printf("Thread 1: Exiting\n");
+    return 0;
+}
+
+int thread2(void *arg) {
+    (void)arg;
+
+    printf("Thread 2: Waiting for 3490\n");
+    while (x != 3490); // spin here
+
+    printf("Thread 2: Got 3490--exiting!\n");
+    return 0;
+}
+
+int main(void) {
+    x = 0;
+
+    thrd_t t1, t2;
+
+    thrd_create(&t1, thread1, NULL);
+    thrd_create(&t2, thread2, NULL);
+
+    thrd_join(t1, NULL);
+    thrd_join(t2, NULL);
+
+    printf("Main    : Threads are done, so x better be 3490\n");
+    printf("Main    : And indeed, x == %d\n", x);
+}