Re: [RFA] Add language-dependent post-parser

[Daniel Jacobowitz <drow at false dot org>]

On Wed, Mar 31, 2004 at 10:30:04AM -0500, Daniel Jacobowitz wrote:
> On Wed, Mar 31, 2004 at 03:02:45AM -0500, Paul Hilfinger wrote:
> > 
> > Daniel,
> > 
> > > I don't see why you can't do it, for instance, here:
> > > simple_exp :    simple_exp '(' arglist ')'
> > >                        { 
> > >                          write_exp_elt_opcode (OP_FUNCALL);
> > >                          write_exp_elt_longcst ($3);
> > >				/* check arguments */
> > >                          write_exp_elt_opcode (OP_FUNCALL);
> > >                        }
> > >        ;
> > 
> > > You'd have to wiggle the expression machinery to give you back the
> > > expression node for the function name, probably by making the
> > > write_exp_* functions return a pointer.  But that's less intrusive and
> > > more efficient than adding a second pass.
> > 
> > Yes, that's exactly how I'd LIKE to do it. And I would, but for one
> > miserable little fact: the expression at this point is in POSTFIX
> > form.  So, for example, I can't use evaluate_type or the evaluate_exp
> > member of exp_descriptor, both of which work on PREFIX form.
> 
> How much work would it be to duplicate and prefixify them, then? 
> prefixify_subexp has the right interface already; if you write out the
> OP_FUNCALL, you could then call a function which returns a new struct
> expression in prefix form containing just the call and its arguments.
> It would just need to allocate enough memory (could be generous about
> it and just use the size of the original expression), call
> prefixify_subexp, and fiddle out->nelts.
> 
> OK, it's not so _efficient_, but... it could be made efficient if
> someone overhauls the representation at some point.

But I guess the point is, this is no more elegant than a second pass,
and whatever you implement I should probably use for C++ anyway so it
won't be an Ada-specific hook.  Does anyone else have an opinion?

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer