On Wed, May 22, 2013 at 11:08:40PM -0400, Jason Merrill wrote:
> Another issue with delayed folding of sizeof. On the trunk, we
> should fold everything before passing it on to
> warnings_for_convert_and_check; on the branch, I'm inclined to be
> conservative and only fold SIZEOF_EXPR.
>
> Jakub, do you have an opinion about whether this should go into
> 4.8.1 or 4.8.2?
I'd say it can wait for 4.8.2 if you don't mind.
> commit 0477e34118f5bdbdb4d93c795f59d122dca02f36
> Author: Jason Merrill <ja...@redhat.com>
> Date: Wed May 22 10:10:49 2013 -0400
>
> PR c++/56930
> * call.c (convert_like_real): Use cp_convert_and_check.
> * cvt.c (cp_convert_and_check): Use maybe_constant_value.
> * semantics.c (cxx_eval_constant_expression): Handle LTGT_EXPR.
> (potential_constant_expression_1): Handle OMP_ATOMIC*.
>
> diff --git a/gcc/cp/call.c b/gcc/cp/call.c
> index 71a1589..0b6a83f 100644
> --- a/gcc/cp/call.c
> +++ b/gcc/cp/call.c
> @@ -6199,10 +6199,10 @@ convert_like_real (conversion *convs, tree expr, tree
> fn, int argnum,
> if (convs->check_narrowing)
> check_narrowing (totype, expr);
>
> - if (issue_conversion_warnings && (complain & tf_warning))
> - expr = convert_and_check (totype, expr);
> + if (issue_conversion_warnings)
> + expr = cp_convert_and_check (totype, expr, complain);
> else
> - expr = convert (totype, expr);
> + expr = cp_convert (totype, expr, complain);
>
> return expr;
> }
> diff --git a/gcc/cp/cvt.c b/gcc/cp/cvt.c
> index 93be76a..d9e905e 100644
> --- a/gcc/cp/cvt.c
> +++ b/gcc/cp/cvt.c
> @@ -624,10 +624,20 @@ cp_convert_and_check (tree type, tree expr,
> tsubst_flags_t complain)
> result = cp_convert (type, expr, complain);
>
> if ((complain & tf_warning)
> - && c_inhibit_evaluation_warnings == 0
> - && !TREE_OVERFLOW_P (expr)
> - && result != error_mark_node)
> - warnings_for_convert_and_check (type, expr, result);
> + && c_inhibit_evaluation_warnings == 0)
> + {
I'm surprised there is no fold_nondependent_expr_sfinae (expr, tf_none);
first, we had to add that before to similar maybe_constant_value calls
for -Wdiv-by-zero, shift warnings etc. Perhaps we can have a helper
that will call the above, maybe_constant_value and strip the possible
NOP_EXPR that maybe_constant_value can add, and use that in all the places
where we want for diagnostic purposes try to fold everything as much as
possible.
> + tree folded = maybe_constant_value (expr);
> + tree stripped = folded;
> + tree folded_result = cp_convert (type, folded, complain);
> +
> + /* maybe_constant_value wraps an INTEGER_CST with TREE_OVERFLOW in a
> + NOP_EXPR so that it isn't TREE_CONSTANT anymore. */
> + STRIP_NOPS (stripped);
> +
> + if (!TREE_OVERFLOW_P (stripped)
> + && folded_result != error_mark_node)
> + warnings_for_convert_and_check (type, folded, folded_result);
> + }
> --- a/gcc/cp/cvt.c
> +++ b/gcc/cp/cvt.c
> @@ -620,6 +620,9 @@ cp_convert_and_check (tree type, tree expr,
> tsubst_flags_t complain)
>
> if (TREE_TYPE (expr) == type)
> return expr;
> +
> + if (TREE_CODE (expr) == SIZEOF_EXPR)
> + expr = maybe_constant_value (expr);
Is this sufficient though? What if the testcase is:
int main()
{
int x = sizeof(int) + 1;
int y { sizeof(int) * __CHAR_BIT__ };
int z = sizeof(int) + 2 * sizeof(y) + 3 * sizeof (x);
}
Jakub
