gdbsupport: add support for references to checked_static_cast

Add a checked_static_cast overload that works with references.  A bad
dynamic cast with references throws std::bad_cast, it would be possible
to implement the new overload based on that, but it seemed simpler to
just piggy back off the existing function.

I found some potential uses of this new overload in amd-dbgapi-target.c,
update them to illustrate the use of the new overload.  To build
amd-dbgapi-target.c, on needs the amd-dbgapi library, which I don't
expect many people to have.  But I have it, and it builds fine here.  I
did test the new overload by making a purposely bad cast and it did
catch it.

Change-Id: Id6b6a7db09fe3b4aa43cddb60575ff5f46761e96
Reviewed-By: Lancelot SIX <lsix@lancelotsix.com>
Reviewed-By: Andrew Burgess <aburgess@redhat.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/gdbsupport/gdb-checked-static-cast.h b/gdbsupport/gdb-checked-static-cast.h
index bc75244..e9127b9 100644
--- a/gdbsupport/gdb-checked-static-cast.h
+++ b/gdbsupport/gdb-checked-static-cast.h
@@ -66,6 +66,22 @@ checked_static_cast (V *v)
   return result;
 }
 
+/* Same as the above, but to cast from a reference type to another.  */
+
+template<typename T, typename V, typename = gdb::Requires<std::is_reference<T>>>
+T
+checked_static_cast (V &v)
+{
+  static_assert (std::is_reference<T>::value, "target must be a reference type");
+
+  using T_no_R = typename std::remove_reference<T>::type;
+  using T_P = typename std::add_pointer<T_no_R>::type;
+
+  using V_no_R = typename std::remove_reference<V>::type;
+
+  return *checked_static_cast<T_P, V_no_R> (&v);
+}
+
 }
 
 #endif /* COMMON_GDB_CHECKED_DYNAMIC_CAST_H */