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, 6 insertions, 8 deletions

diff --git a/MdeModulePkg/Core/Dxe/Image/Image.c b/MdeModulePkg/Core/Dxe/Image/Image.c
index 652da8bf10..80128e729b 100644
--- a/MdeModulePkg/Core/Dxe/Image/Image.c
+++ b/MdeModulePkg/Core/Dxe/Image/Image.c
@@ -313,8 +313,8 @@ CheckAndMarkFixLoadingMemoryUsageBitMap (
    //

    // Test if the memory is avalaible or not.

    // 

-   BaseOffsetPageNumber = (UINTN)EFI_SIZE_TO_PAGES((UINT32)(ImageBase - DxeCodeBase));

-   TopOffsetPageNumber  = (UINTN)EFI_SIZE_TO_PAGES((UINT32)(ImageBase + ImageSize - DxeCodeBase));

+   BaseOffsetPageNumber = EFI_SIZE_TO_PAGES((UINT32)(ImageBase - DxeCodeBase));

+   TopOffsetPageNumber  = EFI_SIZE_TO_PAGES((UINT32)(ImageBase + ImageSize - DxeCodeBase));

    for (Index = BaseOffsetPageNumber; Index < TopOffsetPageNumber; Index ++) {

      if ((mDxeCodeMemoryRangeUsageBitMap[Index / 64] & LShiftU64(1, (Index % 64))) != 0) {

        //

@@ -366,12 +366,10 @@ GetPeCoffImageFixLoadingAssignedAddress(
    //

    Handle = (IMAGE_FILE_HANDLE*)ImageContext->Handle;

    ImgHdr = (EFI_IMAGE_OPTIONAL_HEADER_UNION *)((CHAR8* )Handle->Source + ImageContext->PeCoffHeaderOffset);

-   SectionHeaderOffset = (UINTN)(

-                                 ImageContext->PeCoffHeaderOffset +

-                                 sizeof (UINT32) +

-                                 sizeof (EFI_IMAGE_FILE_HEADER) +

-                                 ImgHdr->Pe32.FileHeader.SizeOfOptionalHeader

-                                 );

+   SectionHeaderOffset = ImageContext->PeCoffHeaderOffset +

+                         sizeof (UINT32) +

+                         sizeof (EFI_IMAGE_FILE_HEADER) +

+                         ImgHdr->Pe32.FileHeader.SizeOfOptionalHeader;

    NumberOfSections = ImgHdr->Pe32.FileHeader.NumberOfSections;

 

    //