[PATCH 0/1] Refine casting expression result to bigger size

[Hao Wu <hao.a.wu@intel.com>]

Please note that this patch is maily for feedback collection and the patch
only covers MdePkg. We are working on patches for other packages.


There are cases that the operands of an expression are all with rank less
than UINT64/INT64 and the result of the expression is casted 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.

For the consideration of generated binaries size, the commit will keep the
size of the operands as the size of int, and explitly add a type cast
before converting the result to UINT64/INT64.

1). When there is no operand with type UINTN
(UINTN)  (a + b) -> (UINTN)(UINT32)  (a + b) or
(UINT64) (a + b) -> (UINT64)(UINT32) (a + b)

2). Otherwise
(UINT64) (a + b) -> (UINT64)(UINTN)  (a + b)

Hao Wu (1):
  MdePkg: Refine casting expression result to bigger size

 MdePkg/Library/BaseLib/String.c                              | 4 ++--
 MdePkg/Library/BasePeCoffLib/BasePeCoff.c                    | 4 ++--
 MdePkg/Library/BaseS3PciLib/S3PciLib.c                       | 4 ++--
 MdePkg/Library/SmmMemoryAllocationLib/MemoryAllocationLib.c  | 4 ++--
 MdePkg/Library/UefiMemoryAllocationLib/MemoryAllocationLib.c | 4 ++--
 5 files changed, 10 insertions(+), 10 deletions(-)

-- 
1.9.5.msysgit.0