On Mon, Jan 25, 2016 at 04:00:48PM +0100, Nicolai Stange wrote:
> Currently, the determination of a __builtin_offsetof() expressions'
> constness flags is done in two steps:
> - Several flags are speculatively set at expression parsing time
> - and possibly cleared again at evaluation if the member expression
> includes a non-const array index like in
> __builtin_offsetof(struct A, a.b[non_const_foo])
>
> For consistency with other expression types' evaluation, defer the
> determination of a __builtin_offsetof() expression's constness to
> evaluation time, too.
>
> Furthermore, carry an array index expression's constness flags
> through the implicit cast to size_t type.
Better to split this into two patches.
> @@ -3028,13 +3026,18 @@ static struct symbol *evaluate_offsetof(struct expression *expr)
> } else {
> struct expression *idx = expr->index, *m;
> struct symbol *i_type = evaluate_expression(idx);
> + unsigned old_idx_flags;
> int i_class = classify_type(i_type, &i_type);
> +
> if (!is_int(i_class)) {
> expression_error(expr, "non-integer index");
> return NULL;
> }
> unrestrict(idx, i_class, &i_type);
> + old_idx_flags = idx->flags;
> idx = cast_to(idx, size_t_ctype);
> + idx->flags |= old_idx_flags;
> + expr_flags_decay_consts(&idx->flags);
> m = alloc_const_expression(expr->pos,
> bits_to_bytes(ctype->bit_size));
> m->ctype = size_t_ctype;
It's not clear at all to me why this is needed.
Why cast_to() can't set itself the right value for idx->flags?
Luc
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