use local variable instead of global

thread_setup_unix.c

@@ -9,9 +9,6 @@ static pthread_mutex_t *mutex_buf = NULL;
 
 static pthread_key_t destructor_key;
 
-/* An unused value whose address is passed to pthread_setspecific. It only needs to have a valid size. See https://github.com/golang-fips/openssl/pull/162. */
-static char stub;
-
 /* Used by unit tests. */
 volatile unsigned int go_openssl_threads_cleaned_up = 0;
 
@@ -31,7 +28,10 @@ static void thread_id(GO_CRYPTO_THREADID_PTR tid)
     // per-thread error state, so this function is guaranteed to be executed at
     // least once on any thread with associated error state. The thread-local
     // variable needs to be set to a non-NULL value so that the destructor will
-    // be called when the thread exits. The actual value does not matter.
+    // be called when the thread exits.
+    // The actual value does not matter, but should be a pointer with a valid size.
+    // See https://github.com/golang-fips/openssl/pull/162
+    static char stub;
     (void) pthread_setspecific(destructor_key, &stub);
 }