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Shi, Steven via llvm-dev

2016-Jan-09 03:15 UTC

[llvm-dev] [cfe-dev] Is it a va_arg bug in clang?

Hi Richard,
Thank you for the info.  I build my code in Ubuntu-64bits with simply commands:
“clang X64.c”, then run “./a.out” to see the output. If I replace my va_list,
va_start, va_arg va_end with __builtin_ms_va_list, __builtin_ms_va_start,
__builtin_ms_va_arg, __builtin_ms_va_end, my code will build fail in Ubuntu with
below message. Do you suggest I should build it in windows and not in Linux? Or
did I miss any build option here? Appreciate if you could let me know the
correct build steps.



jshi19 at jshi19-Intel:/mnt/disk3$ clang X64.c
X64.c:12:2: error: unknown type name '__builtin_ms_va_list'; did you
mean
      '__builtin_va_list'?
        __builtin_ms_va_list   Marker;
        ^~~~~~~~~~~~~~~~~~~~
        __builtin_va_list
note: '__builtin_va_list' declared here
X64.c:15:2: error: use of unknown builtin '__builtin_ms_va_start'
      [-Wimplicit-function-declaration]
        __builtin_ms_va_start (Marker, Format);
        ^
X64.c:17:11: error: use of unknown builtin '__builtin_ms_va_arg'
      [-Wimplicit-function-declaration]
                Value = __builtin_ms_va_arg (Marker, int);
                        ^
X64.c:17:11: note: did you mean '__builtin_ms_va_start'?
X64.c:15:2: note: '__builtin_ms_va_start' declared here
        __builtin_ms_va_start (Marker, Format);
        ^
X64.c:17:40: error: expected expression
                Value = __builtin_ms_va_arg (Marker, int);
                                                     ^
X64.c:20:2: error: use of unknown builtin '__builtin_ms_va_end'
      [-Wimplicit-function-declaration]
        __builtin_ms_va_end  (Marker);
        ^
X64.c:20:2: note: did you mean '__builtin_ms_va_arg'?
X64.c:17:11: note: '__builtin_ms_va_arg' declared here
                Value = __builtin_ms_va_arg (Marker, int);
                        ^
5 errors generated.





Steven Shi
Intel\SSG\STO\UEFI Firmware

Tel: +86 021-61166522
iNet: 821-6522

From: metafoo at gmail.com [mailto:metafoo at gmail.com] On Behalf Of Richard
Smith
Sent: Saturday, January 09, 2016 3:26 AM
To: Shi, Steven
Cc: cfe-dev at lists.llvm.org; llvm-dev at lists.llvm.org
Subject: Re: [cfe-dev] Is it a va_arg bug in clang?

On Thu, Jan 7, 2016 at 11:15 PM, Shi, Steven via cfe-dev <cfe-dev at
lists.llvm.org<mailto:cfe-dev at lists.llvm.org>> wrote:
For the variadic function error with AMD64 abi and windows calling convention on
64bits x86, I find it has been tracked in Bug 20847
(https://llvm.org/bugs/show_bug.cgi?id=20847)
(http://reviews.llvm.org/D1622#inline-9345). Do we still plan to fix it?

You know, I meet exactly same va_arg mistake with llvm3.7 when I enable the Uefi
firmware (http://www.uefi.org/) build with clang. The ms_abi is the Uefi
firmware binary module standard interface. I really hope this bug fix can been
checked in as soon as possible. If we cannot fix it in short time, could we
offer a temporary fix patch based on llvm3.7?

This is already fixed in clang trunk. Your code is rejected as follows:

<stdin>:15:17: error: 'va_start' used in Win64 ABI function
                va_start (Marker, Format);
                ^

You need to use __builtin_ms_va_list, __builtin_ms_va_start, __builtin_ms_va_end
to use ms_abi varargs semantics. (In particular, note that __builtin_ms_va_list
is a different type from va_list, so this can't "just work" in the
way you expect it to.)

Steven Shi
Intel\SSG\STO\UEFI Firmware

Tel: +86 021-61166522<tel:%2B86%20021-61166522>
iNet: 821-6522

From: Shi, Steven
Sent: Thursday, January 07, 2016 11:07 PM
To: 'cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>'
Subject: Is it a va_arg bug in clang?

Hello,
I’m trying to use the clang3.7 to compile  64bits x86 code with Microsoft ABI in
Ubuntu 64bit, but I find the va_arg get the wrong variable argument from the
va_list. Below is my test code.

#include <stdio.h>
#include <stdarg.h>

void
__attribute__((ms_abi))
Foo_va_list (
    int                       VaNum,
    const char  *Format,
  ...
  )
{
                va_list  Marker;
                long long    Value;

                va_start (Marker, Format);
                for (int i = 0; i < VaNum; i++ ) {
                                Value = va_arg (Marker, int);
                                printf("Value = 0x%llx\n", Value);
                }
                va_end (Marker);
}


int main()
{
  Foo_va_list (16, "0123456789abcdef= %x%x%x%x%x%x%x%x%x%x%x%x%x%x%x%x
\n", 0,1,2,3,4,5,6,7,8,9,0xa,0xb,0xc,0xd,0xe,0xf);
  return 0;
}

The expected output are:
Value = 0x0
Value = 0x1
Value = 0x2
Value = 0x3
Value = 0x4
Value = 0x5
Value = 0x6
Value = 0x7
Value = 0x8
Value = 0x9
Value = 0xa
Value = 0xb
Value = 0xc
Value = 0xd
Value = 0xe
Value = 0xf

But the real output are:
Value = 0x0
Value = 0x1
Value = 0x2
Value = 0x3
Value = 0x4
Value = 0x5
Value = 0x0
Value = 0x1
Value = 0x2
Value = 0x3
Value = 0x4
Value = 0x5
Value = 0x6
Value = 0x7
Value = 0x8
Value = 0x9

After I remove the Microsoft ABI definition __attribute__((ms_abi)) above 
Foo_va_list () in the code, the output will become correct. I find GCC also have
similar wrong behavior with __attribute__((ms_abi)). I don’t know how to make
the __attribute__((ms_abi)) work correctly with va_arg.  I appreciate if any
suggestion.






Steven Shi
Intel\SSG\STO\UEFI Firmware

Tel: +86 021-61166522<tel:%2B86%20021-61166522>
iNet: 821-6522


_______________________________________________
cfe-dev mailing list
cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev

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Richard Smith via llvm-dev

2016-Jan-09 09:18 UTC

head link

[llvm-dev] [cfe-dev] Is it a va_arg bug in clang?

You need a newer version of clang for these builtins.
On Jan 8, 2016 7:15 PM, "Shi, Steven via cfe-dev" <cfe-dev at
lists.llvm.org>
wrote:
> Hi Richard,
>
> Thank you for the info.  I build my code in Ubuntu-64bits with simply
> commands: “clang X64.c”, then run “./a.out” to see the output. If I
> replace my va_list, va_start, va_arg va_end with __builtin_ms_va_list,
> __builtin_ms_va_start, __builtin_ms_va_arg, __builtin_ms_va_end, my code
> will build fail in Ubuntu with below message. Do you suggest I should build
> it in windows and not in Linux? Or did I miss any build option here?
> Appreciate if you could let me know the correct build steps.
>
>
>
>
>
>
>
> jshi19 at jshi19-Intel:/mnt/disk3$ clang X64.c
>
> *X64.c:12:2: *error: *unknown type name '__builtin_ms_va_list'; did
you
> mean*
>
> *      '__builtin_va_list'?*
>
>         __builtin_ms_va_list   Marker;
>
>         ^~~~~~~~~~~~~~~~~~~~
>
>         __builtin_va_list
>
> note: '__builtin_va_list' declared here
>
> *X64.c:15:2: *error: *use of unknown builtin
'__builtin_ms_va_start'*
>
> *      [-Wimplicit-function-declaration]*
>
>         __builtin_ms_va_start (Marker, Format);
>
>         ^
>
> *X64.c:17:11: *error: *use of unknown builtin
'__builtin_ms_va_arg'*
>
> *      [-Wimplicit-function-declaration]*
>
>                 Value = __builtin_ms_va_arg (Marker, int);
>
>                         ^
>
> *X64.c:17:11: *note: did you mean '__builtin_ms_va_start'?
>
> *X64.c:15:2: *note: '__builtin_ms_va_start' declared here
>
>         __builtin_ms_va_start (Marker, Format);
>
>         ^
>
> *X64.c:17:40: *error: *expected expression*
>
>                 Value = __builtin_ms_va_arg (Marker, int);
>
>                                                      ^
>
> *X64.c:20:2: *error: *use of unknown builtin '__builtin_ms_va_end'*
>
> *      [-Wimplicit-function-declaration]*
>
>         __builtin_ms_va_end  (Marker);
>
>         ^
>
> *X64.c:20:2: *note: did you mean '__builtin_ms_va_arg'?
>
> *X64.c:17:11: *note: '__builtin_ms_va_arg' declared here
>
>                 Value = __builtin_ms_va_arg (Marker, int);
>
>                         ^
>
> 5 errors generated.
>
>
>
>
>
>
>
>
>
>
>
> *Steven Shi*
>
> *Intel\SSG\STO\UEFI Firmware*
>
>
>
> Tel: +86 021-61166522
>
> iNet: 821-6522
>
>
>
> *From:* metafoo at gmail.com [mailto:metafoo at gmail.com] *On Behalf Of
*Richard
> Smith
> *Sent:* Saturday, January 09, 2016 3:26 AM
> *To:* Shi, Steven
> *Cc:* cfe-dev at lists.llvm.org; llvm-dev at lists.llvm.org
> *Subject:* Re: [cfe-dev] Is it a va_arg bug in clang?
>
>
>
> On Thu, Jan 7, 2016 at 11:15 PM, Shi, Steven via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
> For the variadic function error with AMD64 abi and windows calling
> convention on 64bits x86, I find it has been tracked in Bug 20847 (
> https://llvm.org/bugs/show_bug.cgi?id=20847) (
> http://reviews.llvm.org/D1622#inline-9345). Do we still plan to fix it?
>
>
>
> You know, I meet exactly same va_arg mistake with llvm3.7 when I enable
> the Uefi firmware (http://www.uefi.org/) build with clang. The ms_abi is
> the Uefi firmware binary module standard interface. I really hope this bug
> fix can been checked in as soon as possible. If we cannot fix it in short
> time, could we offer a temporary fix patch based on llvm3.7?
>
>
>
> This is already fixed in clang trunk. Your code is rejected as follows:
>
>
>
> <stdin>:15:17: error: 'va_start' used in Win64 ABI function
>
>                 va_start (Marker, Format);
>
>                 ^
>
>
>
> You need to use __builtin_ms_va_list, __builtin_ms_va_start,
> __builtin_ms_va_end to use ms_abi varargs semantics. (In particular, note
> that __builtin_ms_va_list is a different type from va_list, so this
can't
> "just work" in the way you expect it to.)
>
>
>
> *Steven Shi*
>
> *Intel\SSG\STO\UEFI Firmware*
>
>
>
> Tel: +86 021-61166522
>
> iNet: 821-6522
>
>
>
> *From:* Shi, Steven
> *Sent:* Thursday, January 07, 2016 11:07 PM
> *To:* 'cfe-dev at lists.llvm.org'
> *Subject:* Is it a va_arg bug in clang?
>
>
>
> Hello,
>
> I’m trying to use the clang3.7 to compile  64bits x86 code with Microsoft
> ABI in Ubuntu 64bit, but I find the va_arg get the wrong variable argument
> from the va_list. Below is my test code.
>
>
>
> #include <stdio.h>
>
> #include <stdarg.h>
>
>
>
> void
>
> __attribute__((ms_abi))
>
> Foo_va_list (
>
>     int                       VaNum,
>
>     const char  *Format,
>
>   ...
>
>   )
>
> {
>
>                 va_list  Marker;
>
>                 long long    Value;
>
>
>
>                 va_start (Marker, Format);
>
>                 for (int i = 0; i < VaNum; i++ ) {
>
>                                 Value = va_arg (Marker, int);
>
>                                 printf("Value = 0x%llx\n",
Value);
>
>                 }
>
>                 va_end (Marker);
>
> }
>
>
>
>
>
> int main()
>
> {
>
>   Foo_va_list (16, "0123456789abcdef= %x%x%x%x%x%x%x%x%x%x%x%x%x%x%x%x
> \n", 0,1,2,3,4,5,6,7,8,9,0xa,0xb,0xc,0xd,0xe,0xf);
>
>   return 0;
>
> }
>
>
>
> The expected output are:
>
> Value = 0x0
>
> Value = 0x1
>
> Value = 0x2
>
> Value = 0x3
>
> Value = 0x4
>
> Value = 0x5
>
> Value = 0x6
>
> Value = 0x7
>
> Value = 0x8
>
> Value = 0x9
>
> Value = 0xa
>
> Value = 0xb
>
> Value = 0xc
>
> Value = 0xd
>
> Value = 0xe
>
> Value = 0xf
>
>
>
> But the real output are:
>
> Value = 0x0
>
> Value = 0x1
>
> Value = 0x2
>
> Value = 0x3
>
> Value = 0x4
>
> Value = 0x5
>
> Value = 0x0
>
> Value = 0x1
>
> Value = 0x2
>
> Value = 0x3
>
> Value = 0x4
>
> Value = 0x5
>
> Value = 0x6
>
> Value = 0x7
>
> Value = 0x8
>
> Value = 0x9
>
>
>
> After I remove the Microsoft ABI definition __attribute__((ms_abi)) above
>  Foo_va_list () in the code, the output will become correct. I find GCC
> also have similar wrong behavior with __attribute__((ms_abi)). I don’t know
> how to make the __attribute__((ms_abi)) work correctly with va_arg.  I
> appreciate if any suggestion.
>
>
>
>
>
>
>
>
>
>
>
>
>
> *Steven Shi*
>
> *Intel\SSG\STO\UEFI Firmware*
>
>
>
> Tel: +86 021-61166522
>
> iNet: 821-6522
>
>
>
>
> _______________________________________________
> cfe-dev mailing list
> cfe-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>
>
>
> _______________________________________________
> cfe-dev mailing list
> cfe-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>
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Shi, Steven via llvm-dev

2016-Jan-10 09:30 UTC

head link

[llvm-dev] [cfe-dev] Is it a va_arg bug in clang?

Hi Richard,
I tried latest 3.7.1 release, the clang has same build failure and don’t know
__builtin_ms_va_list at all. I compared the llvm trunk with 3.7.1 and find the
trunk has a VA commit from Davis which is not included in the 3.7.1 release. So,
I guess I need to directly build the latest trunk instead of the 3.7.1 release.
(why 3.7.1 release doesn’t include this patch?)

commit 7e96f0f6fffbdebfdac238ae76cc3a791acfa23e
Author: Charles Davis <cdavis5x at gmail.com>
Date:   Tue Aug 25 23:27:41 2015 +0000

    Make variable argument intrinsics behave correctly in a Win64 CC function.

    Summary:
    This change makes the variable argument intrinsics, `llvm.va_start` and
    `llvm.va_copy`, and the `va_arg` instruction behave as they do on Windows
    inside a `CallingConv::X86_64_Win64` function. It's needed for a Clang
patch
    I have to add support for GCC's `__builtin_ms_va_list` constructs.



But when I try to configure the trunk build with cmake, the cmake report
failures as below. I can pass configure the 3.7.1 release with the same command.
Could you let me know the right configure or build steps for llvm trunk?
Appreciate your continues help!

My cmake command:
cmake ../llvm -G "Unix Makefiles"
-DCMAKE_BUILD_TYPE="Release" -DLLVM_TARGETS_TO_BUILD="X86"
-DCMAKE_VERBOSE_MAKEFILE=ON -DCMAKE_CXX_COMPILER="/usr/bin/g++"
-DCMAKE_C_COMPILER="/usr/bin/gcc"

cmake failure output:
… …
-- Performing Test HAS_MAYBE_UNINITIALIZED
-- Performing Test HAS_MAYBE_UNINITIALIZED - Success
/mnt/disk3/llvmtruck/llvm/autoconf/config.guess: 6:
/mnt/disk3/llvmtruck/llvm/au: not foundig.guess:
/mnt/disk3/llvmtruck/llvm/autoconf/config.guess: 8:
/mnt/disk3/llvmtruck/llvm/au: not foundig.guess:
/mnt/disk3/llvmtruck/llvm/autoconf/config.guess: 28:
/mnt/disk3/llvmtruck/llvm/a: not foundfig.guess:
/mnt/disk3/llvmtruck/llvm/autoconf/config.guess: 29:
/mnt/disk3/llvmtruck/llvm/a: not foundfig.guess:
/mnt/disk3/llvmtruck/llvm/autoconf/config.guess: 40:
/mnt/disk3/llvmtruck/llvm/a: not foundfig.guess:
/mnt/disk3/llvmtruck/llvm/autoconf/config.guess: 42:
/mnt/disk3/llvmtruck/llvm/a: not foundfig.guess:
/mnt/disk3/llvmtruck/llvm/autoconf/config.guess: 54:
/mnt/disk3/llvmtruck/llvm/a: not foundfig.guess:
/mnt/disk3/llvmtruck/llvm/autoconf/config.guess: 65:
/mnt/disk3/llvmtruck/llvm/a: not foundfig.guess:
/mnt/disk3/llvmtruck/llvm/autoconf/config.guess: 68:
/mnt/disk3/llvmtruck/llvm/a: not foundfig.guess:
/mnt/disk3/llvmtruck/llvm/autoconf/config.guess: 71:
/mnt/disk3/llvmtruck/llvm/autoconf/config.guess: Syntax error: word unexpected
(expecting "in")
CMake Error at cmake/modules/GetHostTriple.cmake:24 (message):
  Failed to execute /mnt/disk3/llvmtruck/llvm/autoconf/config.guess
Call Stack (most recent call first):
  cmake/config-ix.cmake:331 (get_host_triple)
  CMakeLists.txt:407 (include)




Steven Shi
Intel\SSG\STO\UEFI Firmware

Tel: +86 021-61166522
iNet: 821-6522

From: metafoo at gmail.com [mailto:metafoo at gmail.com] On Behalf Of Richard
Smith
Sent: Saturday, January 09, 2016 5:18 PM
To: Shi, Steven
Cc: Clang Dev; llvm-dev
Subject: Re: [cfe-dev] Is it a va_arg bug in clang?


You need a newer version of clang for these builtins.
On Jan 8, 2016 7:15 PM, "Shi, Steven via cfe-dev" <cfe-dev at
lists.llvm.org<mailto:cfe-dev at lists.llvm.org>> wrote:
Hi Richard,
Thank you for the info.  I build my code in Ubuntu-64bits with simply commands:
“clang X64.c”, then run “./a.out” to see the output. If I replace my va_list,
va_start, va_arg va_end with __builtin_ms_va_list, __builtin_ms_va_start,
__builtin_ms_va_arg, __builtin_ms_va_end, my code will build fail in Ubuntu with
below message. Do you suggest I should build it in windows and not in Linux? Or
did I miss any build option here? Appreciate if you could let me know the
correct build steps.



jshi19 at jshi19-Intel:/mnt/disk3$ clang X64.c
X64.c:12:2: error: unknown type name '__builtin_ms_va_list'; did you
mean
      '__builtin_va_list'?
        __builtin_ms_va_list   Marker;
        ^~~~~~~~~~~~~~~~~~~~
        __builtin_va_list
note: '__builtin_va_list' declared here
X64.c:15:2: error: use of unknown builtin '__builtin_ms_va_start'
      [-Wimplicit-function-declaration]
        __builtin_ms_va_start (Marker, Format);
        ^
X64.c:17:11: error: use of unknown builtin '__builtin_ms_va_arg'
      [-Wimplicit-function-declaration]
                Value = __builtin_ms_va_arg (Marker, int);
                        ^
X64.c:17:11: note: did you mean '__builtin_ms_va_start'?
X64.c:15:2: note: '__builtin_ms_va_start' declared here
        __builtin_ms_va_start (Marker, Format);
        ^
X64.c:17:40: error: expected expression
                Value = __builtin_ms_va_arg (Marker, int);
                                                     ^
X64.c:20:2: error: use of unknown builtin '__builtin_ms_va_end'
      [-Wimplicit-function-declaration]
        __builtin_ms_va_end  (Marker);
        ^
X64.c:20:2: note: did you mean '__builtin_ms_va_arg'?
X64.c:17:11: note: '__builtin_ms_va_arg' declared here
                Value = __builtin_ms_va_arg (Marker, int);
                        ^
5 errors generated.





Steven Shi
Intel\SSG\STO\UEFI Firmware

Tel: +86 021-61166522<tel:%2B86%20021-61166522>
iNet: 821-6522

From: metafoo at gmail.com<mailto:metafoo at gmail.com> [mailto:metafoo at
gmail.com<mailto:metafoo at gmail.com>] On Behalf Of Richard Smith
Sent: Saturday, January 09, 2016 3:26 AM
To: Shi, Steven
Cc: cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>; llvm-dev
at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>
Subject: Re: [cfe-dev] Is it a va_arg bug in clang?

On Thu, Jan 7, 2016 at 11:15 PM, Shi, Steven via cfe-dev <cfe-dev at
lists.llvm.org<mailto:cfe-dev at lists.llvm.org>> wrote:
For the variadic function error with AMD64 abi and windows calling convention on
64bits x86, I find it has been tracked in Bug 20847
(https://llvm.org/bugs/show_bug.cgi?id=20847)
(http://reviews.llvm.org/D1622#inline-9345). Do we still plan to fix it?

You know, I meet exactly same va_arg mistake with llvm3.7 when I enable the Uefi
firmware (http://www.uefi.org/) build with clang. The ms_abi is the Uefi
firmware binary module standard interface. I really hope this bug fix can been
checked in as soon as possible. If we cannot fix it in short time, could we
offer a temporary fix patch based on llvm3.7?

This is already fixed in clang trunk. Your code is rejected as follows:

<stdin>:15:17: error: 'va_start' used in Win64 ABI function
                va_start (Marker, Format);
                ^

You need to use __builtin_ms_va_list, __builtin_ms_va_start, __builtin_ms_va_end
to use ms_abi varargs semantics. (In particular, note that __builtin_ms_va_list
is a different type from va_list, so this can't "just work" in the
way you expect it to.)

Steven Shi
Intel\SSG\STO\UEFI Firmware

Tel: +86 021-61166522<tel:%2B86%20021-61166522>
iNet: 821-6522

From: Shi, Steven
Sent: Thursday, January 07, 2016 11:07 PM
To: 'cfe-dev at lists.llvm.org<mailto:cfe-dev at lists.llvm.org>'
Subject: Is it a va_arg bug in clang?

Hello,
I’m trying to use the clang3.7 to compile  64bits x86 code with Microsoft ABI in
Ubuntu 64bit, but I find the va_arg get the wrong variable argument from the
va_list. Below is my test code.

#include <stdio.h>
#include <stdarg.h>

void
__attribute__((ms_abi))
Foo_va_list (
    int                       VaNum,
    const char  *Format,
  ...
  )
{
                va_list  Marker;
                long long    Value;

                va_start (Marker, Format);
                for (int i = 0; i < VaNum; i++ ) {
                                Value = va_arg (Marker, int);
                                printf("Value = 0x%llx\n", Value);
                }
                va_end (Marker);
}


int main()
{
  Foo_va_list (16, "0123456789abcdef= %x%x%x%x%x%x%x%x%x%x%x%x%x%x%x%x
\n", 0,1,2,3,4,5,6,7,8,9,0xa,0xb,0xc,0xd,0xe,0xf);
  return 0;
}

The expected output are:
Value = 0x0
Value = 0x1
Value = 0x2
Value = 0x3
Value = 0x4
Value = 0x5
Value = 0x6
Value = 0x7
Value = 0x8
Value = 0x9
Value = 0xa
Value = 0xb
Value = 0xc
Value = 0xd
Value = 0xe
Value = 0xf

But the real output are:
Value = 0x0
Value = 0x1
Value = 0x2
Value = 0x3
Value = 0x4
Value = 0x5
Value = 0x0
Value = 0x1
Value = 0x2
Value = 0x3
Value = 0x4
Value = 0x5
Value = 0x6
Value = 0x7
Value = 0x8
Value = 0x9

After I remove the Microsoft ABI definition __attribute__((ms_abi)) above 
Foo_va_list () in the code, the output will become correct. I find GCC also have
similar wrong behavior with __attribute__((ms_abi)). I don’t know how to make
the __attribute__((ms_abi)) work correctly with va_arg.  I appreciate if any
suggestion.






Steven Shi
Intel\SSG\STO\UEFI Firmware

Tel: +86 021-61166522<tel:%2B86%20021-61166522>
iNet: 821-6522


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