sock: use atomic_cas_ptr correctly

This bug was caused by incorrect documentation (already fixed).  It resulted
in us freeing the name on successful CAS and caching the freed pointer.

Signed-off-by: Josef 'Jeff' Sipek <[email protected]>

Author: jeffpc

sock.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016-2019 Josef 'Jeff' Sipek <[email protected]>
+ * Copyright (c) 2016-2020 Josef 'Jeff' Sipek <[email protected]>
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -60,7 +60,7 @@ const char *xgethostname(void)
 		goto unknown;
 	}
 
-	if (atomic_cas_ptr(&cached, NULL, name) != name)
+	if (atomic_cas_ptr(&cached, NULL, name) != NULL)
 		free(name);
 
 	return cached;