Add smtprc-tid unsound case

tests/regression/03-practical/50-smtprc-tid.c

@@ -0,0 +1,38 @@
+#include <pthread.h>
+#include <stdlib.h>
+
+int threads_total = 4;
+pthread_t *tids;
+
+void *cleaner(void *arg) {
+  while (1) {
+    for (int i = 0; i < threads_total; i++) {
+      if (tids[i]) { // RACE!
+        if (!pthread_join(tids[i], NULL)) // RACE!
+          tids[i] = 0; // RACE!
+      }
+    }
+  }
+  return NULL;
+}
+
+void *thread(int i) { // wrong argument type is important
+  tids[i] = pthread_self(); // RACE!
+  return NULL;
+}
+
+int main() {
+  pthread_t tid;
+  tids = malloc(threads_total * sizeof(pthread_t));
+
+  for(int i = 0; i < threads_total; i++)
+    tids[i] = 0;
+
+  pthread_create(&tid, NULL, cleaner, NULL);
+
+  for(int i = 0; i < threads_total; i++) {
+    pthread_create(&tid, NULL, thread, (int *)i); // cast is important
+  }
+
+  return 0;
+}