[Patch] Support DEC-C extensions

[Gabriel Dos Reis]

On Tue, Oct 4, 2011 at 4:59 AM, Pedro Alves <pedro@codesourcery.com> wrote:
> On Monday 03 October 2011 21:23:43, Joseph S. Myers wrote:
>> On Mon, 3 Oct 2011, Douglas Rupp wrote:
>>
>> > On 9/30/2011 8:19 AM, Joseph S. Myers wrote:
>> > > On Fri, 30 Sep 2011, Tristan Gingold wrote:
>> > >
>> > > > If you prefer a target hook, I'm fine with that.  I will write such a
>> > > > patch.
>> > > >
>> > > > I don't think it must be restricted to system headers, as it is possible
>> > > > that the user 'imports' such a function (and define it in one of VMS
>> > > > favorite languages such as macro-32 or bliss).
>> > > If it's not restricted to system headers, then probably the option is
>> > > better than the target hook.
>> > >
>> > I'm not sure I understand the reasoning here.  This seems fairly VMS specific
>> > so what is the downside for a target hook and user written headers?
>>
>> The language accepted by the compiler in the user's source code (as
>> opposed to in system headers) shouldn't depend on the target except for
>> certain well-defined areas such as target attributes and built-in
>> functions; behaving the same across different systems is an important
>> feature of GCC.  This isn't one of those areas of target-dependence; it's
>> generic syntax rather than e.g. exploiting a particular processor feature.
>
> So I take it a `void foo(...);' declaration to mean the same thing
> as an unprototyped `void foo();'?  (If so, I think that should be
> explicit in the documentation).  That is, decc system headers are
> probably declaring with:
>
> extern void foo(...);
>
> and then the function is defined somewhere with, say:
>
> void foo(int a, int b, void *c)
> {
>  ...
> }
>
> Do we need to consider ABIs that have calling conventions that
> treat unprototyped and varargs functions differently? (is there any?)

Could you elaborate on the equivalence of these declarations?