Look through missing intermediate bases when interposing subclasses.

library/VTableInterpose.cpp

@@ -281,9 +281,10 @@ VMethodInterposeLinkBase *VMethodInterposeLinkBase::get_first_interpose(virtual_
     return item;
 }
 
-void VMethodInterposeLinkBase::find_child_hosts(virtual_identity *cur, void *vmptr)
+bool VMethodInterposeLinkBase::find_child_hosts(virtual_identity *cur, void *vmptr)
 {
     auto &children = cur->getChildren();
+    bool found = false;
 
     for (size_t i = 0; i < children.size(); i++)
     {
@@ -298,17 +299,32 @@ void VMethodInterposeLinkBase::find_child_hosts(virtual_identity *cur, void *vmp
                 continue;
 
             child_next.insert(base);
+            found = true;
         }
-        else
+        else if (child->vtable_ptr)
         {
             void *cptr = child->get_vmethod_ptr(vmethod_idx);
             if (cptr != vmptr)
                 continue;
 
             child_hosts.insert(child);
+            found = true;
+
             find_child_hosts(child, vmptr);
         }
+        else
+        {
+            // If this vtable is not known, but any of the children
+            // have the same vmethod, this one definitely does too
+            if (find_child_hosts(child, vmptr))
+            {
+                child_hosts.insert(child);
+                found = true;
+            }
+        }
     }
+
+    return found;
 }
 
 void VMethodInterposeLinkBase::on_host_delete(virtual_identity *from)

library/include/VTableInterpose.h

@@ -159,7 +159,7 @@ namespace DFHack
         void on_host_delete(virtual_identity *host);
 
         VMethodInterposeLinkBase *get_first_interpose(virtual_identity *id);
-        void find_child_hosts(virtual_identity *cur, void *vmptr);
+        bool find_child_hosts(virtual_identity *cur, void *vmptr);
     public:
         VMethodInterposeLinkBase(virtual_identity *host, int vmethod_idx, void *interpose_method, void *chain_mptr, int priority);
         ~VMethodInterposeLinkBase();