MdeModulePkg: 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: Feng Tian <feng.tian@intel.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/MdeModulePkg/Library/DxeCapsuleLibFmp/DxeCapsuleLib.c b/MdeModulePkg/Library/DxeCapsuleLibFmp/DxeCapsuleLib.c
index d7abcc879b..7f500a96eb 100644
--- a/MdeModulePkg/Library/DxeCapsuleLibFmp/DxeCapsuleLib.c
+++ b/MdeModulePkg/Library/DxeCapsuleLibFmp/DxeCapsuleLib.c
@@ -585,7 +585,7 @@ DisplayCapsuleImage (
   EFI_GRAPHICS_OUTPUT_PROTOCOL  *GraphicsOutput;

 

   ImagePayload = (DISPLAY_DISPLAY_PAYLOAD *)(CapsuleHeader + 1);

-  PayloadSize = (UINTN)(CapsuleHeader->CapsuleImageSize - sizeof(EFI_CAPSULE_HEADER));

+  PayloadSize = CapsuleHeader->CapsuleImageSize - sizeof(EFI_CAPSULE_HEADER);

 

   if (ImagePayload->Version != 1) {

     return EFI_UNSUPPORTED;

@@ -733,7 +733,7 @@ DumpFmpCapsule (
   for (Index = 0; Index < FmpCapsuleHeader->EmbeddedDriverCount; Index++) {

     DEBUG((DEBUG_VERBOSE, "  ItemOffsetList[%d]      - 0x%lx\n", Index, ItemOffsetList[Index]));

   }

-  for (; Index < (UINTN)(FmpCapsuleHeader->EmbeddedDriverCount + FmpCapsuleHeader->PayloadItemCount); Index++) {

+  for (; Index < (UINT32)FmpCapsuleHeader->EmbeddedDriverCount + FmpCapsuleHeader->PayloadItemCount; Index++) {

     DEBUG((DEBUG_VERBOSE, "  ItemOffsetList[%d]      - 0x%lx\n", Index, ItemOffsetList[Index]));

     ImageHeader = (EFI_FIRMWARE_MANAGEMENT_CAPSULE_IMAGE_HEADER *)((UINT8 *)FmpCapsuleHeader + ItemOffsetList[Index]);