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author | Hao Wu <hao.a.wu@intel.com> | 2017-01-22 10:17:52 +0800 |
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committer | Hao Wu <hao.a.wu@intel.com> | 2017-03-06 14:33:21 +0800 |
commit | 64b25f5db17c3b16d2a898095a4a205404126b49 (patch) | |
tree | 0474682709cb94e92dda407f08dbb9d7614e1997 /IntelFrameworkModulePkg | |
parent | 16f6922709952c7ad468dcdee6ef94b3e5a3cd90 (diff) | |
download | edk2-64b25f5db17c3b16d2a898095a4a205404126b49.tar.gz edk2-64b25f5db17c3b16d2a898095a4a205404126b49.tar.bz2 edk2-64b25f5db17c3b16d2a898095a4a205404126b49.zip |
FatPkg: 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: Ruiyu Ni <ruiyu.ni@intel.com>
Diffstat (limited to 'IntelFrameworkModulePkg')
0 files changed, 0 insertions, 0 deletions