Sergey, We also need to do a full search for use of variadic parameters to make sure we have a solution for all of them and update the EDK II C coding standard to make sure the rules for use of variadic parameters for maximum compiler compatibility are captured correctly.
Did you try Andrew Fish's suggestion to add -Wno-varargs to the components that have this issue to see if that is a temporary workaround for your specific build failures? Thanks, Mike > -----Original Message----- > From: edk2-devel [mailto:edk2-devel-boun...@lists.01.org] On Behalf Of Gao, > Liming > Sent: Tuesday, May 23, 2017 7:14 PM > To: 'Laszlo Ersek' <ler...@redhat.com>; Sergei Temerkhanov > <s.temerkha...@gmail.com> > Cc: edk2-devel@lists.01.org > Subject: Re: [edk2] [PATCH] MdePkg: Fix undefined behavior on variadic > parameters > > Sergey: > This patch updates API interface. I still need to verify its functionality > on other > tool chain. I will give you feedback after I am done. > > Thanks > Liming > >-----Original Message----- > >From: Laszlo Ersek [mailto:ler...@redhat.com] > >Sent: Friday, May 19, 2017 4:16 PM > >To: Sergei Temerkhanov <s.temerkha...@gmail.com> > >Cc: Gao, Liming <liming....@intel.com>; edk2-devel@lists.01.org > >Subject: Re: [edk2] [PATCH] MdePkg: Fix undefined behavior on variadic > >parameters > > > >On 05/19/17 04:45, Sergei Temerkhanov wrote: > >> On Thu, May 18, 2017 at 1:19 PM, Laszlo Ersek <ler...@redhat.com> wrote: > >>> On 05/16/17 14:10, Sergei Temerkhanov wrote: > >>>> On Tue, May 16, 2017 at 8:10 AM, Gao, Liming <liming....@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 > >>> > >>> Side topic: > >>> > >>> It is promoted, but not to "unsigned int". > >>> > >>> The standard says, in "6.3.1.1 Boolean, characters, and integers", > >>> paragraph 2, > >>> > >>> The following may be used in an expression wherever an /int/ or > >>> /unsigned int/ may be used: > >>> > >>> — An object or expression with an integer type whose integer > >>> conversion rank is less than or equal to the rank of /int/ and > >>> /unsigned int/. > >>> — A bit-field of type /_Bool/, /int/, /signed int/, or > >>> /unsigned int/. > >>> > >>> If an /int/ can represent all values of the original type, the value > >>> is converted to an /int/; otherwise, it is converted to an > >>> /unsigned int/. These are called the /integer promotions/. [...] > >>> > >>> On all supported edk2 platforms, "unsigned char"'s range is 0..255 > >>> inclusive, which can be represented by "int" (again on all supported > >>> edk2 platforms). So the promotion occurs to "int", not "unsigned int" > >>> > >>> > >>> Furthermore, in place of the suggested UINTN type (which is fine), the > >>> following further types would be correct: INT32, UINT32, INT64, UINT64, > >>> INTN. > >> > >> On 32-bit architectures, using 64-bit types here may change the ABI. Which > >might > >> affect some corner cases like linking precompiled object files to the > >> library in question. > > > >True. > > > >I missed the fact that in edk2 you can have binary-only library > >instances. I should have remembered, after all I had filed > ><https://bugzilla.tianocore.org/show_bug.cgi?id=463> :) > > > >So yes, UINTN is the best choice; it keeps binary compat beyond > >everything else. > > > >Thanks! > >Laszlo > > > >> > >>> The reason is that all of these map to standard C types, on all > >>> edk2 platforms, whose integer conversion ranks are not less than that of > >>> "int" and "unsigned int". Hence they are all unaffected by the integer > >>> promotions. > >>> > >>> (This digression does not affect your main point, which remains correct; > >>> I just wanted to be precise here, since we're quoting the standard.) > >>> > >>> Thanks > >>> Laszlo > >>> > >>>> 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-boun...@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.temerkha...@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 > >>>>>> > >>>>>> _______________________________________________ > >>>>>> edk2-devel mailing list > >>>>>> edk2-devel@lists.01.org > >>>>>> https://lists.01.org/mailman/listinfo/edk2-devel > >>>> _______________________________________________ > >>>> edk2-devel mailing list > >>>> edk2-devel@lists.01.org > >>>> https://lists.01.org/mailman/listinfo/edk2-devel > >>>> > >>> > > _______________________________________________ > edk2-devel mailing list > edk2-devel@lists.01.org > https://lists.01.org/mailman/listinfo/edk2-devel _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
