[cfe-dev] Is it a va_arg bug in clang?
Richard Smith via cfe-dev
cfe-dev at lists.llvm.org
Sat Jan 9 01:18:28 PST 2016
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
>
>
>
>
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>
>
>
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