Re: [PATCH] MdePkg: Fix undefined behavior on variadic parameters

["Gao, Liming" <liming.gao@intel.com>]

Sergey:
  Now, VS and GCC don't report such issue. How do you find them? And, this change modifies the function API, does it impact the consumer code?

Thanks
Liming
> -----Original Message-----
> From: Sergei Temerkhanov [mailto:s.temerkhanov@gmail.com]
> Sent: Tuesday, May 16, 2017 8:11 PM
> To: Gao, Liming <liming.gao@intel.com>
> Cc: edk2-devel@lists.01.org
> Subject: Re: [edk2] [PATCH] MdePkg: Fix undefined behavior on variadic parameters
> 
> On Tue, May 16, 2017 at 8:10 AM, Gao, Liming <liming.gao@intel.com> wrote:
> > Sergey:
> >   Could you give more detail on the undefined behavior on variadic parameters?
> >
> >   I see https://bugzilla.tianocore.org/show_bug.cgi?id=410 describe this issues found in the latest CLANG tool chain. Do you find
> other tool chain reports it?
> 
> Yes, this is exactly the bug this patch fixes.
> 
> As per the C99 standard:
> "The parameter parmN is the identifier of the rightmost parameter in
> the variable parameter list in the function definition (the one just
> before the , ...). If the parameter parmN is declared with the
> register storage class, with a function or array type, or with a type
> that is not compatible with the type that results after application of
> the default argument promotions, the behavior is undefined."
> 
> That's exactly the case here since BOOLEAN is a typedef for unsigned
> char. It undergoes a promotion to an unsigned int which is not a
> compatible type for unsigned char. Correct me if I'm wrong.
> 
> Regards,
> Sergey
> 
> >
> > Thanks
> > Liming
> >> -----Original Message-----
> >> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Sergey Temerkhanov
> >> Sent: Tuesday, May 16, 2017 10:57 AM
> >> To: edk2-devel@lists.01.org
> >> Subject: [edk2] [PATCH] MdePkg: Fix undefined behavior on variadic parameters
> >>
> >> Fix undefined behavior by avoiding parameter type promotion
> >>
> >> Signed-off-by: Sergey Temerkhanov <s.temerkhanov@gmail.com>
> >> ---
> >>  MdePkg/Include/Library/UefiLib.h | 2 +-
> >>  MdePkg/Library/UefiLib/UefiLib.c | 2 +-
> >>  2 files changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/MdePkg/Include/Library/UefiLib.h b/MdePkg/Include/Library/UefiLib.h
> >> index 0b14792..4e4697c 100644
> >> --- a/MdePkg/Include/Library/UefiLib.h
> >> +++ b/MdePkg/Include/Library/UefiLib.h
> >> @@ -818,7 +818,7 @@ CHAR8 *
> >>  EFIAPI
> >>  GetBestLanguage (
> >>    IN CONST CHAR8  *SupportedLanguages,
> >> -  IN BOOLEAN      Iso639Language,
> >> +  IN UINTN      Iso639Language,
> >>    ...
> >>    );
> >>
> >> diff --git a/MdePkg/Library/UefiLib/UefiLib.c b/MdePkg/Library/UefiLib/UefiLib.c
> >> index a7eee01..74528ec 100644
> >> --- a/MdePkg/Library/UefiLib/UefiLib.c
> >> +++ b/MdePkg/Library/UefiLib/UefiLib.c
> >> @@ -1514,7 +1514,7 @@ CHAR8 *
> >>  EFIAPI
> >>  GetBestLanguage (
> >>    IN CONST CHAR8  *SupportedLanguages,
> >> -  IN BOOLEAN      Iso639Language,
> >> +  IN UINTN      Iso639Language,
> >>    ...
> >>    )
> >>  {
> >> --
> >> 2.7.4
> >>
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