On Wed, May 24, 2017 at 5:46 AM, Kinney, Michael D <michael.d.kin...@intel.com> wrote: > 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.
I've sent another patch for MdePkg with a similar change but there might be more. > > 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? For my projects, using these 2 changes have been sufficient . > > 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
