[asan] Close all loaded libs in stress_dtls.c test.

[alekseyshl]

Summary

.

test/asan/TestCases/Linux/stress_dtls.c

int main(int argc, char *argv[]) {
   int num_threads = 1;
   int num_libs = 1;
   if (argc >= 2)
     num_threads = atoi(argv[1]);
   if (argc >= 3)
     num_libs = atoi(argv[2]);
   assert(num_libs <= MAX_N_FUNCTIONS);
 
+  void* handles[MAX_N_FUNCTIONS];
   int lib;
   for (lib = 0; lib < num_libs; lib++) {
     char buf[4096];
     snprintf(buf, sizeof(buf), "%s-f%d.so", argv[0], lib);
-    void *handle = dlopen(buf, RTLD_LAZY);
-    if (!handle) {
+    handles[lib] = dlopen(buf, RTLD_LAZY);
+    if (!handles[lib]) {
       fprintf(stderr, "%s\n", dlerror());
       exit(1);
     }
     snprintf(buf, sizeof(buf), "f%d", lib);
-    Functions[lib] = (f_t)dlsym(handle, buf);
+    Functions[lib] = (f_t)dlsym(handles[lib], buf);
     if (!Functions[lib]) {
       fprintf(stderr, "%s\n", dlerror());
       exit(1);
     }
     fprintf(stderr, "LIB[%03d] %s: %p\n", lib, buf, Functions[lib]);
     PrintStuff(0);
 
     int i;
     for (i = 0; i < num_threads; i++) {
       pthread_t t;
       fprintf(stderr, "Creating thread %d\n", i);
       pthread_create(&t, 0, PrintStuff, 0);
       pthread_join(t, 0);
     }
   }
+
+  // Close all loaded libs to prevent the possible TLS leak described in
+  // https://sourceware.org/bugzilla/show_bug.cgi?id=12650.
+  for (lib = 0; lib < num_libs; lib++)
+    dlclose(handles[lib]);
+
   return 0;
 }
 #else  // SO_NAME
 #ifndef DTLS_SIZE
 # define DTLS_SIZE (1 << 17)
 #endif
 __thread void *huge_thread_local_array[DTLS_SIZE];
 void **SO_NAME() {
   return &huge_thread_local_array[0];
 }
 #endif