Re: different x86_64 ABIs

[Sebastian Biallas <sb at biallas dot net>]

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Andrew Haley wrote:
> Sebastian Biallas writes:
>  > Andrew Haley wrote:
>  > > Sebastian Biallas writes:
>  > >  > Hello everyone,
>  > >  > 
>  > >  > I'm working on a x86_64 project which has mixed C and assembly code. The
>  > >  > program should (ultimatively) run on all major x86_64 platforms but
>  > >  > currently I'm facing the problem that x86_64 has a completely different
>  > >  > ABI on e.g. Linux and Windows. This makes interfacing between C and
>  > >  > assembler impossible in a portable manner.
>  > >  > 
>  > >  > So I either need to provide the assembly files in different flavours or
>  > >  > (which is why I ask here) gcc provides some __attribute__((elf_abi)) or
>  > >  > __attribute__((linux_abi)) or something like that.
>  > >  > 
>  > >  > Is the already such an attribute or is it planned? Or this there another
>  > >  >  solution for the problem?
>  > > 
>  > > Make life easy for yourself: Write different assembly code.  
>  > 
>  > Well, actually it would be much easier for me if gcc could handle
>  > this :)
> 
> Mostly it can.  That's what inline asm is for.

Well, I haven't told the whole story. Actually it's some sort of JIT
which generated tons of machine code, which also wants to interface with
C code.

> 
>  > Keeping 2500 lines of assembly code in sync is not really easy.
> 
> I would have thought it'd be easier to fix that by not using so much
> assembler code, 

I know. But in this case it's really necessary to have this support code
in assembler (because I have to rely on certain things).

> but I don't know your application area.
> 
>  > > The ABI is different, and to work fully with gcc, assembly code
>  > > really needs DWARF2 unwinder data, and that makes no sense at all
>  > > to Windows.
>  > 
>  > Huh? I thought unwind data is only needed for C++-Exceptions, isn't it?
> 
> We use it everywhere, even for C code.  You can probably get away
> without it.

Some pointer for further reading?

Sebastian
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