On Mon, Feb 01, 2016 at 03:42:59AM +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.
I don't think that consistency is the good/real reason,
you're doing it for the same reason as the others: so that
the expression is recognized as an integer constant expression.
> Furthermore, carry an array index expression's constness flags
> through the implicit cast to size_t type.
>
> Signed-off-by: Nicolai Stange <nicstange@xxxxxxxxx>
> ---
> diff --git a/evaluate.c b/evaluate.c
> index 7a4af39..0101e61 100644
> --- a/evaluate.c
> +++ b/evaluate.c
> @@ -3031,25 +3031,29 @@ 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->constexpr_flags;
> idx = cast_to(idx, size_t_ctype);
> + idx->constexpr_flags = old_idx_flags;
This saving/restoring of teh flags is annoying.
Why is it needed? Can it be solved in another way?
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