From 99576ee3fde9228dd5cfedd268f6bc82a0c9f732 Mon Sep 17 00:00:00 2001
From: Hao Wu <hao.a.wu@intel.com>
Date: Tue, 13 Feb 2018 10:23:51 +0800
Subject: [PATCH] MdeModulePkg/BmpSupportLib: Refine type cast for pointer
 subtraction

Since the pointer subtraction here is not performed by pointers to
elements of the same array object. This might lead to potential issues,
such behavior is undefined according to C11 standard.

Refine the pointer subtraction expressions by casting each pointer to
UINTN first and then perform the subtraction.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>
---
 MdeModulePkg/Library/BaseBmpSupportLib/BmpSupportLib.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/MdeModulePkg/Library/BaseBmpSupportLib/BmpSupportLib.c b/MdeModulePkg/Library/BaseBmpSupportLib/BmpSupportLib.c
index 2c95e91ecc..467cd6a58d 100644
--- a/MdeModulePkg/Library/BaseBmpSupportLib/BmpSupportLib.c
+++ b/MdeModulePkg/Library/BaseBmpSupportLib/BmpSupportLib.c
@@ -426,7 +426,7 @@ TranslateBmpToGopBlt (
 
     }
 
-    ImageIndex = (UINTN)(Image - ImageHeader);
+    ImageIndex = (UINTN)Image - (UINTN)ImageHeader;
     if ((ImageIndex % 4) != 0) {
       //
       // Bmp Image starts each row on a 32-bit boundary!