1 files changed, 28 insertions, 3 deletions
diff --git a/misc.c b/misc.c
index e79819d..ec5f9fa 100644
--- a/misc.c
+++ b/misc.c
@@ -143,12 +143,37 @@ pthread_self (void)
       */
 {
   pthread_t self = NULL;
+  DWORD lastErr;
+
   /*
-   * need to ensure there always is a self
+   * Need to ensure there always is a self.
+   *
+   * The following call to pthread_getspecific uses TlsGetValue.
+   * Win32 functions that return indications of failure call SetLastError when
+   * they fail. They generally do not call SetLastError when they succeed. The
+   * TlsGetValue function is an exception to this general rule. The TlsGetValue
+   * function calls SetLastError to clear a thread's last error when it
+   * succeeds.
+   *
+   * We restore the last error if TlsGetValue succeeds.
    */
+  lastErr = GetLastError();
+  self = (pthread_t) pthread_getspecific (ptw32_selfThreadKey);
+  if (GetLastError() == NO_ERROR)
+    {
+      SetLastError(lastErr);
+    }
+  else
+    {
+      /*
+       * What else can we do? GetLastError will tell the
+       * the caller more but this is not supposed to
+       * happen.
+       */
+      return(NULL);
+    }
 
-  if ((self = (pthread_t) pthread_getspecific (ptw32_selfThreadKey)) 
-      == NULL)
+  if (self == NULL)
     {
       /*
        * Need to create an implicit 'self' for the currently