MdePkg: 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: Laszlo Ersek <lersek@redhat.com>

1 files changed, 5 insertions, 7 deletions

diff --git a/MdePkg/Library/BasePeCoffLib/BasePeCoff.c b/MdePkg/Library/BasePeCoffLib/BasePeCoff.c
index 33cad23a01..8d1daba4bb 100644
--- a/MdePkg/Library/BasePeCoffLib/BasePeCoff.c
+++ b/MdePkg/Library/BasePeCoffLib/BasePeCoff.c
@@ -15,7 +15,7 @@
   PeCoffLoaderGetPeHeader() routine will do basic check for PE/COFF header.

   PeCoffLoaderGetImageInfo() routine will do basic check for whole PE/COFF image.

 

-  Copyright (c) 2006 - 2014, Intel Corporation. All rights reserved.<BR>

+  Copyright (c) 2006 - 2017, Intel Corporation. All rights reserved.<BR>

   Portions copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>

   This program and the accompanying materials

   are licensed and made available under the terms and conditions of the BSD License

@@ -703,12 +703,10 @@ PeCoffLoaderGetImageInfo (
       //

       DebugDirectoryEntryFileOffset = 0;

 

-      SectionHeaderOffset = (UINTN)(

-                               ImageContext->PeCoffHeaderOffset +

-                               sizeof (UINT32) +

-                               sizeof (EFI_IMAGE_FILE_HEADER) +

-                               Hdr.Pe32->FileHeader.SizeOfOptionalHeader

-                               );

+      SectionHeaderOffset = ImageContext->PeCoffHeaderOffset +

+                            sizeof (UINT32) +

+                            sizeof (EFI_IMAGE_FILE_HEADER) +

+                            Hdr.Pe32->FileHeader.SizeOfOptionalHeader;

 

       for (Index = 0; Index < Hdr.Pe32->FileHeader.NumberOfSections; Index++) {

         //