From ce5c3273c30b76cb002034387df13a4e6bc98e96 Mon Sep 17 00:00:00 2001
From: Hao Wu <hao.a.wu@intel.com>
Date: Thu, 16 Feb 2017 14:58:03 +0800
Subject: NetworkPkg: Refine casting expression result to bigger size

There are cases that the operands of an expression are all with rank less
than UINT64/INT64 and the result of the expression is explicitly cast to
UINT64/INT64 to fit the target size.

An example will be:
UINT32 a,b;
// a and b can be any unsigned int type with rank less than UINT64, like
// UINT8, UINT16, etc.
UINT64 c;
c = (UINT64) (a + b);

Some static code checkers may warn that the expression result might
overflow within the rank of "int" (integer promotions) and the result is
then cast to a bigger size.

The commit refines codes by the following rules:
1). When the expression is possible to overflow the range of unsigned int/
int:
c = (UINT64)a + b;

2). When the expression will not overflow within the rank of "int", remove
the explicit type casts:
c = a + b;

3). When the expression will be cast to pointer of possible greater size:
UINT32 a,b;
VOID *c;
c = (VOID *)(UINTN)(a + b); --> c = (VOID *)((UINTN)a + b);

4). When one side of a comparison expression contains only operands with
rank less than UINT32:
UINT8 a;
UINT16 b;
UINTN c;
if ((UINTN)(a + b) > c) {...} --> if (((UINT32)a + b) > c) {...}

For rule 4), if we remove the 'UINTN' type cast like:
if (a + b > c) {...}
The VS compiler will complain with warning C4018 (signed/unsigned
mismatch, level 3 warning) due to promoting 'a + b' to type 'int'.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Reviewed-by: Wu Jiaxin <jiaxin.wu@intel.com>
---
 NetworkPkg/IpSecDxe/Ikev2/Payload.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'NetworkPkg/IpSecDxe/Ikev2')

diff --git a/NetworkPkg/IpSecDxe/Ikev2/Payload.c b/NetworkPkg/IpSecDxe/Ikev2/Payload.c
index f32b3a8394..237743b1b1 100644
--- a/NetworkPkg/IpSecDxe/Ikev2/Payload.c
+++ b/NetworkPkg/IpSecDxe/Ikev2/Payload.c
@@ -2,7 +2,7 @@
   The implementation of Payloads Creation.
 
   (C) Copyright 2015 Hewlett-Packard Development Company, L.P.<BR>
-  Copyright (c) 2010 - 2016, Intel Corporation. All rights reserved.<BR>
+  Copyright (c) 2010 - 2017, Intel Corporation. All rights reserved.<BR>
 
   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD License
@@ -1748,7 +1748,7 @@ Ikev2EncodeSa (
       Transform->Header.NextPayload   = IKE_TRANSFORM_NEXT_PAYLOAD_MORE;
       Transform->Header.PayloadLength = HTONS ((UINT16)TransformSize);
 
-      if (TransformIndex == (UINTN)(ProposalData->NumTransforms - 1)) {
+      if (TransformIndex == ((UINT32)ProposalData->NumTransforms - 1)) {
         Transform->Header.NextPayload = IKE_TRANSFORM_NEXT_PAYLOAD_NONE;
       }
 
-- 
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