Deal with virtual function calls with no candidate targets

During virtual method resolution, if a virtual function call has no
candidate targets then we add the class it was called on as an
instantiated class.

Author: Owen Jones

src/java_bytecode/ci_lazy_methods.cpp

@@ -123,7 +123,9 @@ bool ci_lazy_methodst::operator()(
   std::unordered_set<irep_idt> methods_already_populated;
   std::unordered_set<exprt, irep_hash> virtual_function_calls;
 
-  bool any_new_methods = true;
+  bool any_new_classes = true;
+  while(any_new_classes)
+  {bool any_new_methods = true;
   while(any_new_methods)
   {
     any_new_methods=false;
@@ -153,16 +155,58 @@ bool ci_lazy_methodst::operator()(
       }
     }
 
-    // Given the object types we now know may be created, populate more
-    // possible virtual function call targets:
+      // Given the object types we now know may be created, populate more
+      // possible virtual function call targets:
 
-    debug() << "CI lazy methods: add virtual method targets ("
-            << virtual_function_calls.size() << " callsites)" << eom;
+      debug() << "CI lazy methods: add virtual method targets ("
+              << virtual_function_calls.size() << " callsites)" << eom;
 
-    for(const exprt &function : virtual_function_calls)
+      for(const exprt &function : virtual_function_calls)
+      {
+        get_virtual_method_targets(
+          function,
+          instantiated_classes,
+          methods_to_convert_later,
+          symbol_table);
+      }
+    }
+
+    any_new_classes = false;
+
+    // Look for virtual callsites with no candidate targets. If we have
+    // invokevirtual A.f and we don't believe either A or any of its children
+    // may exist, we assume specifically A is somehow instantiated. Note this
+    // may result in an abstract class being classified as instantiated, which
+    // stands in for some unknown concrete subclass: in this case the called
+    // method will be a stub.
+    for(const exprt &virtual_function_call : virtual_function_calls)
     {
+      std::unordered_set<irep_idt> candidate_target_methods;
       get_virtual_method_targets(
-        function, instantiated_classes, methods_to_convert_later, symbol_table);
+        virtual_function_call,
+        instantiated_classes,
+        candidate_target_methods,
+        symbol_table);
+
+      if(!candidate_target_methods.empty())
+        continue;
+
+      // Add the call class to instantiated_classes and assert that it
+      // didn't already exist
+      const irep_idt &call_class = virtual_function_call.get(ID_C_class);
+      auto ret_class = instantiated_classes.insert(call_class);
+      CHECK_RETURN(ret_class.second);
+      any_new_classes = true;
+
+      // Check that `get_virtual_method_target` returns a method now
+      const irep_idt &call_basename =
+        virtual_function_call.get(ID_component_name);
+      const irep_idt method_name = get_virtual_method_target(
+        instantiated_classes, call_basename, call_class, symbol_table);
+      CHECK_RETURN(!method_name.empty());
+
+      // Add what it returns to methods_to_convert_later
+      methods_to_convert_later.insert(method_name);
     }
   }