d3d8: Sign-compare warnings fix (try 2)

[Andrew Talbot]

Changelog:
    d3d8: Sign-compare warnings fix.

diff --git a/dlls/d3d8/surface.c b/dlls/d3d8/surface.c
index 6ecd7af..521ba56 100644
--- a/dlls/d3d8/surface.c
+++ b/dlls/d3d8/surface.c
@@ -18,6 +18,9 @@
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  */
 
+#include <assert.h>
+#include <limits.h>
+
 #include "config.h"
 #include "d3d8_private.h"
 
@@ -179,14 +182,19 @@ static HRESULT WINAPI IDirect3DSurface8Impl_LockRect(LPDIRECT3DSURFACE8 iface, D
     EnterCriticalSection(&d3d8_cs);
     if (pRect) {
         D3DSURFACE_DESC desc;
-        IDirect3DSurface8_GetDesc(iface, &desc);
+        INT desc_width;
+        INT desc_height;
 
+        IDirect3DSurface8_GetDesc(iface, &desc);
+        assert(desc.Width <= INT_MAX && desc.Height <= INT_MAX);
+        desc_width = desc.Width;
+        desc_height = desc.Height;
         if ((pRect->left < 0)
                 || (pRect->top < 0)
                 || (pRect->left >= pRect->right)
                 || (pRect->top >= pRect->bottom)
-                || (pRect->right > desc.Width)
-                || (pRect->bottom > desc.Height)) {
+                || (pRect->right > desc_width)
+                || (pRect->bottom > desc_height)) {
             WARN("Trying to lock an invalid rectangle, returning D3DERR_INVALIDCALL\n");
             LeaveCriticalSection(&d3d8_cs);
             return D3DERR_INVALIDCALL;