core::rt: 0 is a valid TLS key

src/libcore/rt/local_sched.rs

@@ -119,7 +119,7 @@ fn maybe_tls_key() -> Option<tls::Key> {
         // another thread. I think this is fine since the only action
         // they could take if it was initialized would be to check the
         // thread-local value and see that it's not set.
-        if key != 0 {
+        if key != -1 {
             return Some(key);
         } else {
             return None;

src/rt/rust_builtin.cpp

@@ -830,9 +830,9 @@ rust_get_rt_env() {
 }
 
 #ifndef _WIN32
-pthread_key_t sched_key;
+pthread_key_t sched_key = -1;
 #else
-DWORD sched_key;
+DWORD sched_key = -1;
 #endif
 
 extern "C" void*