Extract semaphore-posix example from ProcDump-for-Linux

tests/regression/03-practical/47-semaphore-posix.c

@@ -0,0 +1,40 @@
+// POSIX semaphore used as a mutex.
+// Extracted from concrat/ProcDump-for-Linux.
+#include <stdlib.h>
+#include <pthread.h>
+#include <semaphore.h>
+#include <goblint.h>
+extern int __VERIFIER_nondet_int();
+
+int data = 0;
+sem_t data_sem;
+
+void *thread(void *arg) {
+  sem_wait(&data_sem);
+  data = __VERIFIER_nondet_int(); // NORACE
+  sem_post(&data_sem);
+  return NULL;
+}
+
+int main() {
+  sem_init(&data_sem, 0, 1);
+
+  int threads_total = __VERIFIER_nondet_int();
+  __goblint_assume(threads_total >= 0);
+
+  pthread_t *tids = malloc(threads_total * sizeof(pthread_t));
+
+  // create threads
+  for (int i = 0; i < threads_total; i++) {
+    pthread_create(&tids[i], NULL, &thread, NULL); // may fail but doesn't matter
+  }
+
+  // join threads
+  for (int i = 0; i < threads_total; i++) {
+    pthread_join(tids[i], NULL);
+  }
+
+  free(tids);
+
+  return 0;
+}