From 809e2bbf41241f35140dd7f294ddf2489836eef9 Mon Sep 17 00:00:00 2001 From: Hao Wu Date: Mon, 23 Jan 2017 11:56:05 +0800 Subject: MdeModulePkg: Refine type cast for pointer subtraction For pointer subtraction, the result is of type "ptrdiff_t". According to the C11 standard (Committee Draft - April 12, 2011): "When two pointers are subtracted, both shall point to elements of the same array object, or one past the last element of the array object; the result is the difference of the subscripts of the two array elements. The size of the result is implementation-defined, and its type (a signed integer type) is ptrdiff_t defined in the header. If the result is not representable in an object of that type, the behavior is undefined." In our codes, there are cases that the pointer subtraction is not performed by pointers to elements of the same array object. This might lead to potential issues, since the behavior is undefined according to C11 standard. Also, since the size of type "ptrdiff_t" is implementation-defined. Some static code checkers may warn that the pointer subtraction might underflow first and then being cast to a bigger size. For example: UINT8 *Ptr1, *Ptr2; UINTN PtrDiff; ... PtrDiff = (UINTN) (Ptr1 - Ptr2); The commit will refine the pointer subtraction expressions by casting each pointer to UINTN first and then perform the subtraction: PtrDiff = (UINTN) Ptr1 - (UINTN) Ptr2; Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Hao Wu Acked-by: Laszlo Ersek Reviewed-by: Feng Tian --- MdeModulePkg/Universal/DebugPortDxe/DebugPort.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'MdeModulePkg/Universal/DebugPortDxe/DebugPort.c') diff --git a/MdeModulePkg/Universal/DebugPortDxe/DebugPort.c b/MdeModulePkg/Universal/DebugPortDxe/DebugPort.c index 298b6b2da3..dcb623cfeb 100644 --- a/MdeModulePkg/Universal/DebugPortDxe/DebugPort.c +++ b/MdeModulePkg/Universal/DebugPortDxe/DebugPort.c @@ -4,7 +4,7 @@ ALL CODE IN THE SERIALIO STACK MUST BE RE-ENTRANT AND CALLABLE FROM INTERRUPT CONTEXT -Copyright (c) 2006 - 2014, Intel Corporation. All rights reserved.
+Copyright (c) 2006 - 2017, Intel Corporation. All rights reserved.
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 @@ -569,7 +569,7 @@ DebugPortRead ( LocalBufferSize = *BufferSize - (BufferPtr - (UINT8 *) Buffer); } while (LocalBufferSize != 0 && Timeout > 0); - *BufferSize = (UINTN) (BufferPtr - (UINT8 *) Buffer); + *BufferSize = (UINTN) BufferPtr - (UINTN) Buffer; return Status; } -- cgit v1.2.3