[x264-devel] Failure to build x264 with ASM on i386

[Brad Smith]

On 18/02/14 2:35 AM, Martin Storsjö wrote:
> On Mon, 17 Feb 2014, Brad Smith wrote:
>
>> On 04/02/14 5:04 PM, Loren Merritt wrote:
>>> On Tue, 4 Feb 2014, Martin Storsjö wrote:
>>>> On Mon, 3 Feb 2014, Dimitry Andric wrote:
>>>>> On 03 Feb 2014, at 18:39, Loren Merritt <lorenm at u.washington.edu>
>>>>> wrote:
>>>>> ...
>>>>> The reason is that gcc assumes a 16 byte stack alignment on i386,
>>>>> which
>>>>> is only valid for Linux after ~2006, not most BSDs.  If you force
>>>>> gcc to
>>>>> assume a 4 byte stack alignment, it also cannot compile the inline
>>>>> assembly:
>>>>
>>>> FWIW, the similar cases within libav are handled by adding
>>>> __attribute__((force_align_arg_pointer)) to all public entry points
>>>> into the
>>>> libraries, which adds a special prologue to these functions that
>>>> realign the
>>>> stack to 16 bytes, and adding -mincoming-stack-boundary=4 to the
>>>> cflags,
>>>> telling the compiler to assume a 16 byte aligned stack in all
>>>> functions, so
>>>> only the public ones need to care about fixing the alignment.
>>>
>>> x264 does in fact realign the stack at all entrypoints (using yasm
>>> rather
>>> than force_align_arg_pointer since we added that feature before
>>> force_align_arg_pointer existed). And yes we do that so that we can
>>> tell the compiler to assume aligned stack even if the OS doesn't provide
>>> it. I didn't previously know that about BSD, but Win32 also doesn't.
>>
>> Still looking for any possible options that could result in being able
>> to build x264 on i386. I haven't seen any suggestions yet that would
>> help.
>
> Did you try adding -mincoming-stack-boundary=4 to the cflags?

$ clang -mincoming-stack-boundary=4
clang-3.5: error: unknown argument: '-mincoming-stack-boundary=4'


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