kernel32: Don't use HIWORD to check for swapped args in GetCurrentDirectoryA.

dlls/kernel32/path.c

@@ -1400,13 +1400,13 @@ UINT WINAPI GetCurrentDirectoryA( UINT buflen, LPSTR buf )
     WCHAR bufferW[MAX_PATH];
     DWORD ret;
 
-    if (buflen && buf && !HIWORD(buf))
+    if (buflen && buf && ((ULONG_PTR)buf >> 16) == 0)
     {
         /* Win9x catches access violations here, returning zero.
          * This behaviour resulted in some people not noticing
          * that they got the argument order wrong. So let's be
          * nice and fail gracefully if buf is invalid and looks
-         * more like a buflen (which is probably MAX_PATH). */
+         * more like a buflen. */
         SetLastError(ERROR_INVALID_PARAMETER);
         return 0;
     }

dlls/kernel32/tests/path.c

@@ -467,6 +467,16 @@ static void test_CurrentDirectoryA(CHAR *origdir, CHAR *newdir)
   if (len) ok( !strcmp( buffer, origdir ), "wrong result %s\n", buffer );
   HeapFree( GetProcessHeap(), 0, buffer );
 
+/* Check for crash prevention on swapped args. Crashes all but Win9x.
+*/
+  if (0)
+  {
+    SetLastError( 0xdeadbeef );
+    len = GetCurrentDirectoryA( 42, (LPSTR)(MAX_PATH + 42) );
+    ok( len == 0 && GetLastError() == ERROR_INVALID_PARAMETER,
+        "GetCurrentDirectoryA failed to fail %u err %u\n", len, GetLastError() );
+  }
+
 /* SetCurrentDirectoryA shouldn't care whether the string has a
    trailing '\\' or not
 */