On Tue, Feb 21, 2017 at 4:27 PM, Martin Sebor <mse...@gmail.com> wrote:
>> Ah, I see, your patch changes attribute unused handling for local
>> variables from tracking TREE_USED to lookup_attribute. I'm not
>> opposed to this change, but I'd like to understand why the TREE_USED
>> handling wasn't working.
>
>
> In the test case in the bug:
>
> template <class T>
> void g ()
> {
> T t; // warning, ok
>
> typedef T U;
> U u; // no warning, bug
> }
>
> template void g<int>();
>
> both TREE_USED(T) and TREE_USED(t) are zero in initialize_local_var
> so the function doesn't set already_used or TREE_USED(t) and we get
> a warning as expected.
>
> But because TREE_USED(U) is set to 1 in maybe_record_typedef_use
> (to implement -Wunused-local-typedefs), initialize_local_var then
> sets already_used to 1 and later also TREE_USED(u) to 1, suppressing
> the warning.
Hmm, I would expect maybe_record_typedef_use to set TREE_USED on the
TYPE_DECL, not on the *_TYPE which initialize_local_var checks.
Jason
