tyler.durden/audk
1
0
Fork 0
mirror of https://github.com/acidanthera/audk.git synced 2025-04-08 17:05:09 +02:00
Code Issues Packages Projects Releases Wiki Activity

FatPkg: Refine casting expression result to bigger size

Browse Source 
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>
This commit is contained in:
Hao Wu 2017-01-22 10:17:52 +08:00
parent 16f6922709
commit 64b25f5db1
2 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
FatPkg/EnhancedFatDxe/ReadWrite.c
View File

@ -1,7 +1,7 @@
/** @file
Functions that perform file read/write.
Copyright (c) 2005 - 2015, Intel Corporation. All rights reserved.<BR>
Copyright (c) 2005 - 2017, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials are licensed and made available
under the terms and conditions of the BSD License which accompanies this
distribution. The full text of the license may be found at
@ -173,7 +173,7 @@ Done:
// Update IFile->Position, if everything is all right
//
CurrentPos = ODir->CurrentPos;
IFile->Position = (UINT64) (CurrentPos * sizeof (FAT_DIRECTORY_ENTRY));
IFile->Position = CurrentPos * sizeof (FAT_DIRECTORY_ENTRY);
}
return Status;

4
FatPkg/FatPei/FatLiteAccess.c
View File

@ -1,7 +1,7 @@
/** @file
FAT file system access routines for FAT recovery PEIM
Copyright (c) 2006 - 2013, 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 of the BSD License which accompanies this
@ -393,7 +393,7 @@ FatReadFile (
} else {
if ((File->Attributes & FAT_ATTR_DIRECTORY) == 0) {
Size = Size < (File->FileSize - File->CurrentPos) ? Size : (UINTN) (File->FileSize - File->CurrentPos);
Size = Size < (File->FileSize - File->CurrentPos) ? Size : (File->FileSize - File->CurrentPos);
}
//
// This is a normal cluster based file