Permit empth_self() before empth_init()

Next commit wants this.

include/empthread.h

@@ -30,7 +30,7 @@
  *     Sasha Mikheev
  *     Doug Hay, 1998
  *     Steve McClure, 1998
- *     Markus Armbruster, 2005-2009
+ *     Markus Armbruster, 2005-2012
  *     Ron Koenderink, 2005-2009
  */
 
@@ -125,7 +125,8 @@ empth_t *empth_create(void (*entry)(void *),
 		      int size, int flags, char *name, void *ud);
 
 /*
- * Return the current thread.
+ * Return the current thread, NULL before empth_init().
+ * This is the only function that may be called before empth_init().
  */
 empth_t *empth_self(void);
 

src/lib/empthread/ntthread.c

@@ -467,9 +467,7 @@ bad:
 empth_t *
 empth_self(void)
 {
-    empth_t *pThread = TlsGetValue(dwTLSIndex);
-
-    return pThread;
+    return ppvUserData ? TlsGetValue(dwTLSIndex) : NULL;
 }
 
 /************************

src/lib/empthread/pthread.c

@@ -29,7 +29,7 @@
  *  Known contributors to this file:
  *     Sasha Mikheev
  *     Steve McClure, 1998
- *     Markus Armbruster, 2005-2011
+ *     Markus Armbruster, 2005-2012
  *     Ron Koenderink, 2007-2009
  */
 
@@ -240,7 +240,7 @@ empth_restorectx(void)
 empth_t *
 empth_self(void)
 {
-    return pthread_getspecific(ctx_key);
+    return udata ? pthread_getspecific(ctx_key) : NULL;
 }
 
 char *