Ada subtypes and base types

[Zdenek Dvorak]

Hello,

> Jeffrey A Law wrote:
> > Another possibility is to simply not allow conversions between a
> > subtype and basetype. 
> 
> Such a patch also solves the problem.  But I'm not sure to understand
> the impact on other codes.  Is this kind of conversion between a type
> and its basetype specific to Ada?

this still seems unnecessarily conservative to me.  I would just check
for types whose TYPE_MIN and TYPE_MAX do not match the natural values
derived from the type precision (i.e., those returned by
upper_bound_in_type (type, type) and lower_bound_in_type (type, type)).

Zdenek

> Index: tree-chrec.c
> ===================================================================
> --- tree-chrec.c	(revision 111416)
> +++ tree-chrec.c	(working copy)
> @@ -1207,7 +1207,9 @@ chrec_convert_aggressive (tree type, tre
>      return NULL_TREE;
>  
>    inner_type = TREE_TYPE (chrec);
> -  if (TYPE_PRECISION (type) > TYPE_PRECISION (inner_type))
> +  if (TYPE_PRECISION (type) > TYPE_PRECISION (inner_type)
> +      /* Conversions between a subtype and its basetype are not allowed.  */
> +      || TREE_TYPE (type) == TREE_TYPE (chrec))
>      return NULL_TREE;
>  
>    left = CHREC_LEFT (chrec);