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.
Martin
