On Thu, Jan 28, 2016 at 11:11 AM, Florian Weimer <fwei...@redhat.com> wrote:
> On 01/27/2016 04:17 PM, Richard Biener wrote:
>
>> We are trying to support
>>
>> t.c
>> ---
>> void *foo();
>>
>> int bar()
>> {
>> return ((int (*)())foo) ();
>> }
>>
>> t2.c
>> -----
>> int foo () { return 0; }
>>
>> thus doing a direct call to a function with a (wrong) prototype via a
>> function
>> pointer cast to the correct type and having a matching implementation of
>> that function elsewhere.
>
> I suspect Ada needs something like this already. I expect the following
> to work (although it is quite hideous).
>
> with System;
>
> package Import is
>
> function Foo return System.Address;
> pragma Import (C, Foo);
>
> function Bar return Integer;
>
> end Import;
>
> package body Import is
>
> function Bar return Integer is
> function Foo_2 return Integer;
> pragma Import (C, Foo_2);
> for Foo_2'Address use Foo'Address;
> begin
> return Foo_2;
> end Bar;
>
> end Import;
Heh. Well, the real reason for officially (aka in GCCs middle-end)
supporting this
is LTO and cross-language calls. You hardly can get 1:1 matching declarations
there and penaltizing all of them by forcing us to go through indirect calls
(which backends handle just fine) is no good.
What the middle-end policy does is simply that the generated code should
match the source input call ABI used (which is specified by the function
type a call is carried out on). That makes sense from a QOI perspective anyway.
And yes, it looks like the m68k backend is simply buggy here.
Richard.
>
> Florian
