1 files changed, 40 insertions, 3 deletions
diff --git a/src/mapi/u_current.c b/src/mapi/u_current.c
index eb77cc7772f..c1a486bd0e1 100644
--- a/src/mapi/u_current.c
+++ b/src/mapi/u_current.c
@@ -146,6 +146,43 @@ u_current_init_tsd(void)
  */
 static mtx_t ThreadCheckMutex = _MTX_INITIALIZER_NP;
 
+
+#ifdef _WIN32
+typedef DWORD thread_id;
+#else
+typedef thrd_t thread_id;
+#endif
+
+
+static inline thread_id
+get_thread_id(void)
+{
+   /*
+    * XXX: Callers of of this function assume it is a lightweight function.
+    * But unfortunately C11's thrd_current() gives no such guarantees.  In
+    * fact, it's pretty hard to have a compliant implementation of
+    * thrd_current() on Windows with such characteristics.  So for now, we
+    * side-step this mess and use Windows thread primitives directly here.
+    */
+#ifdef _WIN32
+   return GetCurrentThreadId();
+#else
+   return thrd_current();
+#endif
+}
+
+
+static inline int
+thread_id_equal(thread_id t1, thread_id t2)
+{
+#ifdef _WIN32
+   return t1 == t2;
+#else
+   return thrd_equal(t1, t2);
+#endif
+}
+
+
 /**
  * We should call this periodically from a function such as glXMakeCurrent
  * in order to test if multiple threads are being used.
@@ -153,7 +190,7 @@ static mtx_t ThreadCheckMutex = _MTX_INITIALIZER_NP;
 void
 u_current_init(void)
 {
-   static unsigned long knownID;
+   static thread_id knownID;
    static int firstCall = 1;
 
    if (ThreadSafe)
@@ -163,10 +200,10 @@ u_current_init(void)
    if (firstCall) {
       u_current_init_tsd();
 
-      knownID = u_thread_self();
+      knownID = get_thread_id();
       firstCall = 0;
    }
-   else if (knownID != u_thread_self()) {
+   else if (!thread_id_equal(knownID, get_thread_id())) {
       ThreadSafe = 1;
       u_current_set_table(NULL);
       u_current_set_context(NULL);