But this doesn't scale well to larger hierarchies, because it only
defines ::test for an argument that is exactly “symtab_node *”
(and not for example “const symtab_node *” or something that
comes between cgraph_node and symtab_node in the hierarchy).
For example:
struct A { int x; };
struct B : A {};
struct C : B {};
It also adds a general specialisation of is_a_helper for const
pointers. Together, this makes both of the above examples work.
gcc/
* is-a.h (reinterpret_is_a_helper): New class.
(static_is_a_helper): Likewise.
(is_a_helper): Inherit from reinterpret_is_a_helper.
(is_a_helper<const T *>): New specialization.