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, 2 insertions, 2 deletions

diff --git a/MdePkg/Library/BaseS3PciLib/S3PciLib.c b/MdePkg/Library/BaseS3PciLib/S3PciLib.c
index e29f7fe63e..27342b0eca 100644
--- a/MdePkg/Library/BaseS3PciLib/S3PciLib.c
+++ b/MdePkg/Library/BaseS3PciLib/S3PciLib.c
@@ -3,7 +3,7 @@
   the PCI operations to be replayed during an S3 resume. This library class

   maps directly on top of the PciLib class. 

 

-  Copyright (c) 2006 - 2012, Intel Corporation. All rights reserved.<BR>

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

 

   This program and the accompanying materials

   are licensed and made available under the terms and conditions

@@ -25,7 +25,7 @@
 #include <Library/S3PciLib.h>

 

 #define PCILIB_TO_COMMON_ADDRESS(Address) \

-        ((UINT64) ((((UINTN) ((Address>>20) & 0xff)) << 24) + (((UINTN) ((Address>>15) & 0x1f)) << 16) + (((UINTN) ((Address>>12) & 0x07)) << 8) + ((UINTN) (Address & 0xfff ))))

+        ((((UINTN) ((Address>>20) & 0xff)) << 24) + (((UINTN) ((Address>>15) & 0x1f)) << 16) + (((UINTN) ((Address>>12) & 0x07)) << 8) + ((UINTN) (Address & 0xfff )))

 

 /**

   Saves a PCI configuration value to the boot script.