Re: libffi stdcall closures

[Timothy Wall <twalljava at dev dot java dot net>]

On Nov 13, 2007, at 4:08 PM, Tom Tromey wrote:

> > > > > > "Timothy" == Timothy Wall <twalljava@dev.java.net> writes:
>
> Timothy> Here's the patch for stdcall closures, including a basic  
> test.  The
> Timothy> diff is against the JNA repo; I can probably do one  
> against a gcc
> Timothy> checkout if necessary.
>
> I'm not really an x86 expert, so perhaps a port maintainer could look
> it over.  The test case also looked good at first blush, but Andreas
> is really the person for that...

Should I ping him directly?

> I have a couple nits to pick, but nothing major.
>
> FWIW there are other areas where you may run into problems.  The
> biggest one is varargs -- libffi basically doesn't support this at
> all.  I'm sure there are more obscure ones, too, involving any new ABI
> additions... maybe vectors, or decimal float, or I don't know what.

Do you mean varargs out or varargs in closures?  I'm not too worried  
about varargs in closures, and varargs calls through libffi seem to  
work ok in the platforms we've tried so far.


> Timothy> +#ifdef X86_WIN32
> Timothy> +  if (cif->abi == FFI_STDCALL) {
> Timothy> +    FFI_INIT_TRAMPOLINE_STDCALL (&closure->tramp[0],    \
> Timothy> +                                 &ffi_closure_STDCALL,  \
> Timothy> +                                 (void*)closure, cif- 
> >bytes);
> Timothy> +  }
> Timothy> +#endif
>
> You don't need the backslashes here.  I see them elsewhere in the
> file, but they are bogus.  Also the "{" should be on its own line.
>
> Also, it looks to me as though there's a missing 'else' in
> here... shouldn't we call either FFI_INIT_TRAMPOLINE_STDCALL or
> FFI_INIT_TRAMPOLINE, but not both?

That's just me trying to avoid intersecting conditional code with  
logic constructs.

Following is a better construct, dropping the somewhat useless  
ASSERTions:

>   if (cif->abi == FFI_SYSV)
>     {
>       FFI_INIT_TRAMPOLINE (&closure->tramp[0],
>                            &ffi_closure_SYSV,
>                            (void*)closure);
>     }
> #ifdef X86_WIN32
>   else if (cif->abi == FFI_STDCALL)
>     {
>       FFI_INIT_TRAMPOLINE_STDCALL (&closure->tramp[0],
>                                    &ffi_closure_STDCALL,
>                                    (void*)closure, cif->bytes);
>     }
> #endif
>   else
>     {
>       return FFI_BAD_ABI;
>     }

I'm looking over the JNA standalone libffi config changes and will  
post those separately.