[m-rev.] for review: emit errors about purity mismatches with foreign clauses

[Ian MacLarty]

On Thu, Jul 06, 2006 at 02:14:34PM +1000, Julien Fischer wrote:
> 
> On Thu, 6 Jul 2006, Ian MacLarty wrote:
> 
> > On Thu, Jul 06, 2006 at 12:13:59PM +1000, Julien Fischer wrote:
> > >
> > > > Actually there seems to be another bug because while the compiler reports a
> > > > warning, it doesn't generate an executable and a non-zero exit status is
> > > > returned (even with --no-halt-at-warn).  Try compiling the following program
> > > > to see what I mean:
> > > >
> > > > :- module pure.
> > > >
> > > > :- interface.
> > > >
> > > > :- import_module io.
> > > >
> > > > :- pred main(io::di, io::uo) is det.
> > > >
> > > > :- implementation.
> > > >
> > > > main(!IO) :-
> > > >         nl(!IO).
> > > >
> > > > :- pragma promise_pure(p/0).
> > > >
> > > > :- impure pred p is det.
> > > >
> > > > :- pragma foreign_proc("C",
> > > >         p,
> > > >         [will_not_call_mercury],
> > > > "
> > > >         printf(\"hello\");
> > > > ").
> > >
> > > That is a purity error.
> > >
> >
> > Why does the compiler emit a warning then?
> >
> 
> Hmmm ... so it does.  It appears that the code for handling that particular
> error/warning (in compiler/purity.m) is a bit confused and can't decide which
> one it is - it seems to have taken the approach that it is both an error *and*
> a warning (at least w.r.t the exit status).
> 
> Any opinions on which it should be?
> 

I'd say it should be an error.

Ian.
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