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* [PATCH v2 0/6] Refine type cast for pointer subtraction
@ 2017-01-25  5:28 Hao Wu
  2017-01-25  5:28 ` [PATCH v2 1/6] MdeModulePkg: " Hao Wu
  2017-01-25  5:36 ` [PATCH v2 0/6] " Laszlo Ersek
  0 siblings, 2 replies; 3+ messages in thread
From: Hao Wu @ 2017-01-25  5:28 UTC (permalink / raw)
  To: edk2-devel; +Cc: Hao Wu, Laszlo Ersek

Please note that this patch is maily for feedback collection and only the
MdeModulePkg part of the series is sent out firstly.


V2 refines the commit messages:
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 <stddef.h> 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;


V1:
For pointer subtraction, the result is of type "ptrdiff_t". According to
the C11 spec, ptrdiff_t is a signed integer type but its size is
implementation-defined.

There are cases that the result of pointer subtraction is type casted to
UINTN, like:

UINT8  *Ptr1, *Ptr2;
UINTN  PtrDiff;
...
PtrDiff = (UINTN) (Ptr1 - Ptr2);

Some static code checkers may warn that the pointer subtraction might
overflow first and then the result is being cast to a bigger size.

The series will cast each pointer to UINTN first and then perform the
subtraction:

PtrDiff = (UINTN) Ptr1 - (UINTN) Ptr2;


Cc: Laszlo Ersek <lersek@redhat.com>

Hao Wu (6):
  MdeModulePkg: Refine type cast for pointer subtraction
  CryptoPkg: Refine type cast for pointer subtraction
  IntelFrameworkModulePkg: Refine type cast for pointer subtraction
  NetworkPkg: Refine type cast for pointer subtraction
  SecurityPkg: Refine type cast for pointer subtraction
  ShellPkg: Refine type cast for pointer subtraction

 CryptoPkg/Library/BaseCryptLib/SysCall/RuntimeMemAllocation.c                |  6 +++---
 IntelFrameworkModulePkg/Csm/LegacyBiosDxe/LegacyPci.c                        |  4 ++--
 IntelFrameworkModulePkg/Library/GenericBdsLib/BdsBoot.c                      |  4 ++--
 IntelFrameworkModulePkg/Library/GenericBdsLib/BdsConsole.c                   |  4 ++--
 IntelFrameworkModulePkg/Library/GenericBdsLib/BdsMisc.c                      |  4 ++--
 IntelFrameworkModulePkg/Library/LegacyBootManagerLib/LegacyBm.c              |  4 ++--
 IntelFrameworkModulePkg/Universal/BdsDxe/BootMaint/BootOption.c              |  6 +++---
 MdeModulePkg/Bus/Pci/PciBusDxe/PciOptionRomSupport.c                         |  4 ++--
 MdeModulePkg/Include/Library/NetLib.h                                        |  6 +++---
 MdeModulePkg/Library/DxeCapsuleLibFmp/DxeCapsuleLib.c                        |  4 ++--
 MdeModulePkg/Library/DxePrintLibPrint2Protocol/PrintLib.c                    |  2 +-
 MdeModulePkg/Library/FileExplorerLib/FileExplorer.c                          |  6 +++---
 MdeModulePkg/Library/PiDxeS3BootScriptLib/BootScriptSave.c                   |  4 ++--
 MdeModulePkg/Library/UefiBootManagerLib/BmLoadOption.c                       |  4 ++--
 MdeModulePkg/Universal/DebugPortDxe/DebugPort.c                              |  4 ++--
 MdeModulePkg/Universal/FaultTolerantWriteDxe/FaultTolerantWrite.c            |  4 ++--
 MdeModulePkg/Universal/HiiDatabaseDxe/Image.c                                |  4 ++--
 MdeModulePkg/Universal/Variable/RuntimeDxe/Variable.c                        | 10 +++++-----
 NetworkPkg/HttpDxe/HttpImpl.c                                                |  6 +++---
 SecurityPkg/Library/DxeImageVerificationLib/DxeImageVerificationLib.c        | 18 +++++++++---------
 SecurityPkg/Library/DxeTpmMeasureBootLib/DxeTpmMeasureBootLib.c              | 10 +++++-----
 SecurityPkg/Library/Tpm2CommandLib/Tpm2Help.c                                |  6 +++---
 SecurityPkg/Tcg/Tcg2Dxe/MeasureBootPeCoff.c                                  | 10 +++++-----
 SecurityPkg/Tcg/TrEEDxe/MeasureBootPeCoff.c                                  | 10 +++++-----
 SecurityPkg/VariableAuthenticated/SecureBootConfigDxe/SecureBootConfigImpl.c | 14 +++++++-------
 ShellPkg/Application/Shell/ShellParametersProtocol.c                         |  6 +++---
 ShellPkg/Library/UefiShellDebug1CommandsLib/DmpStore.c                       |  4 ++--
 ShellPkg/Library/UefiShellDebug1CommandsLib/SmbiosView/SmbiosView.c          |  4 ++--
 ShellPkg/Library/UefiShellDriver1CommandsLib/Dh.c                            |  4 ++--
 ShellPkg/Library/UefiShellLevel2CommandsLib/Cd.c                             |  6 +++---
 30 files changed, 91 insertions(+), 91 deletions(-)

-- 
1.9.5.msysgit.0



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2017-01-25  5:28 [PATCH v2 0/6] Refine type cast for pointer subtraction Hao Wu
2017-01-25  5:28 ` [PATCH v2 1/6] MdeModulePkg: " Hao Wu
2017-01-25  5:36 ` [PATCH v2 0/6] " Laszlo Ersek

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