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Re: [Patch] Support DEC-C extensions


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?)

-- 
Pedro Alves


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