Re: [RFA] Allow casting of object pointers for method calls

[Daniel Jacobowitz <drow at mvista dot com>]

Committed, thanks.

On Fri, Dec 21, 2001 at 03:05:26PM -0500, Jim Blandy wrote:
> 
> Please commit this.  Thanks!
> 
> Daniel Jacobowitz <drow@mvista.com> writes:
> 
> > 
> > I'd like to commit this.
> > 
> > >From the comment on value_virtual_fn_field:
> >    VALUEP is a pointer to a pointer to a value, holding the object
> >    whose virtual function we want to invoke.  If the ABI requires a
> >    virtual function's caller to adjust the `this' pointer by an amount
> >    retrieved from the vtable before invoking the function (i.e., we're
> >    not using "vtable thunks" to do the adjustment automatically), then
> >    this function may set *VALUEP to point to a new object with an
> >    appropriately tweaked address.
> > 
> > find_overload_match went out of its way to prevent this from working.  The
> > cast at the end is unpleasant but, as far as I can see, correct;
> > value_find_oload_method_list tends to dereference pointers, and if we don't
> > return this rather than *this things die.
> > 
> > With this patch, all virtfunc tests other than:
> > XFAIL: gdb.c++/virtfunc.exp: print pEe->D::vg()
> > 
> > pass using g++ 2.95.  No other regressions.  I'll submit a separate patch to
> > remove their XFAILs.  This is also necessary for my g++ 3.0 support stuff,
> > which is pretty trivial after Jason's gcc work and this values patchs.
> > 
> > Anyone, comments?  I think the hack is (for now at least, maybe with a
> > FIXME) tolerable.
> > 
> > -- 
> > Daniel Jacobowitz                           Carnegie Mellon University
> > MontaVista Software                         Debian GNU/Linux Developer
> > 
> > 2001-12-03  Daniel Jacobowitz  <drow@mvista.com>
> > 
> > 	* valops.c (find_overload_match): Accept obj as a
> > 	reference parameter.  Update it before returning.
> > 	* value.h (find_overload_match): Update prototype.
> > 	* eval.c (evaluate_subexp_standard): Pass object to
> > 	find_overload_match by reference.
> > 
> > Index: eval.c
> > ===================================================================
> > RCS file: /cvs/src/src/gdb/eval.c,v
> > retrieving revision 1.16
> > diff -u -p -r1.16 eval.c
> > --- eval.c	2001/11/12 21:20:18	1.16
> > +++ eval.c	2001/12/03 15:27:58
> > @@ -845,7 +845,7 @@ evaluate_subexp_standard (struct type *e
> >  
> >  	      (void) find_overload_match (arg_types, nargs, tstr,
> >  				     1 /* method */ , 0 /* strict match */ ,
> > -					  arg2 /* the object */ , NULL,
> > +					  &arg2 /* the object */ , NULL,
> >  					  &valp, NULL, &static_memfuncp);
> >  
> >  
> > Index: valops.c
> > ===================================================================
> > RCS file: /cvs/src/src/gdb/valops.c,v
> > retrieving revision 1.41
> > diff -u -p -r1.41 valops.c
> > --- valops.c	2001/11/13 16:44:13	1.41
> > +++ valops.c	2001/12/03 15:27:58
> > @@ -2618,12 +2618,13 @@ value_find_oload_method_list (value_ptr 
> >  
> >  int
> >  find_overload_match (struct type **arg_types, int nargs, char *name, int method,
> > -		     int lax, value_ptr obj, struct symbol *fsym,
> > +		     int lax, value_ptr *objp, struct symbol *fsym,
> >  		     value_ptr *valp, struct symbol **symp, int *staticp)
> >  {
> >    int nparms;
> >    struct type **parm_types;
> >    int champ_nparms = 0;
> > +  struct value *obj = (objp ? *objp : NULL);
> >  
> >    short oload_champ = -1;	/* Index of best overloaded function */
> >    short oload_ambiguous = 0;	/* Current ambiguity state for overload resolution */
> > @@ -2847,6 +2848,15 @@ find_overload_match (struct type **arg_t
> >        xfree (func_name);
> >      }
> >  
> > +  if (objp)
> > +    {
> > +      if (TYPE_CODE (VALUE_TYPE (temp)) != TYPE_CODE_PTR
> > +	  && TYPE_CODE (VALUE_TYPE (*objp)) == TYPE_CODE_PTR)
> > +	{
> > +	  temp = value_addr (temp);
> > +	}
> > +      *objp = temp;
> > +    }
> >    return oload_incompatible ? 100 : (oload_non_standard ? 10 : 0);
> >  }
> >  
> > Index: value.h
> > ===================================================================
> > RCS file: /cvs/src/src/gdb/value.h,v
> > retrieving revision 1.22
> > diff -u -p -r1.22 value.h
> > --- value.h	2001/10/16 01:58:07	1.22
> > +++ value.h	2001/12/03 15:27:58
> > @@ -386,7 +386,7 @@ extern struct fn_field *value_find_oload
> >  
> >  extern int find_overload_match (struct type **arg_types, int nargs,
> >  				char *name, int method, int lax,
> > -				value_ptr obj, struct symbol *fsym,
> > +				value_ptr *obj, struct symbol *fsym,
> >  				value_ptr * valp, struct symbol **symp,
> >  				int *staticp);
> >  
> > 
> 

-- 
Daniel Jacobowitz                           Carnegie Mellon University
MontaVista Software                         Debian GNU/Linux Developer