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author | Hao Wu <hao.a.wu@intel.com> | 2017-01-18 16:22:15 +0800 |
---|---|---|
committer | Hao Wu <hao.a.wu@intel.com> | 2017-03-06 14:18:45 +0800 |
commit | 95ba3d92dca2616715e2af89d2bbeca9577a3e2c (patch) | |
tree | e5fe1574dce77976ffe2b9dd96282f93f067bf64 /MdePkg/Library/BaseLib/String.c | |
parent | 810c635d6f40e85040033819f971d03d0f707c1a (diff) | |
download | edk2-95ba3d92dca2616715e2af89d2bbeca9577a3e2c.tar.gz edk2-95ba3d92dca2616715e2af89d2bbeca9577a3e2c.tar.bz2 edk2-95ba3d92dca2616715e2af89d2bbeca9577a3e2c.zip |
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>
Diffstat (limited to 'MdePkg/Library/BaseLib/String.c')
-rw-r--r-- | MdePkg/Library/BaseLib/String.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/MdePkg/Library/BaseLib/String.c b/MdePkg/Library/BaseLib/String.c index e84bf50d7f..4151e0e7ac 100644 --- a/MdePkg/Library/BaseLib/String.c +++ b/MdePkg/Library/BaseLib/String.c @@ -586,7 +586,7 @@ InternalHexCharToUintn ( return Char - L'0';
}
- return (UINTN) (10 + InternalCharToUpper (Char) - L'A');
+ return (10 + InternalCharToUpper (Char) - L'A');
}
/**
@@ -1211,7 +1211,7 @@ InternalAsciiHexCharToUintn ( return Char - '0';
}
- return (UINTN) (10 + InternalBaseLibAsciiToUpper (Char) - 'A');
+ return (10 + InternalBaseLibAsciiToUpper (Char) - 'A');
}
|