nitvm: Throw an error when trying to read an uninitialized attribute

Signed-off-by: Julien Pagès <julien.projet@gmail.com>

diff --git a/src/vm.nit b/src/vm.nit
index fd27117..92d2d1f 100644 (file)
--- a/src/vm.nit
+++ b/src/vm.nit
@@ -148,21 +148,22 @@ class VirtualMachine super NaiveInterpreter
 
                assert(recv isa MutableInstance)
 
-               recv.internal_attributes = init_internal_attributes(null_instance, recv.mtype.as(MClassType).mclass.all_mattributes(mainmodule, none_visibility).length)
+               recv.internal_attributes = init_internal_attributes(initialization_value, recv.mtype.as(MClassType).mclass.all_mattributes(mainmodule, none_visibility).length)
                super
        end
 
        # Initialize the internal representation of an object (its attribute values)
-       private fun init_internal_attributes(null_instance: Instance, size: Int): Pointer
+       # `init_instance` is the initial value of attributes
+       private fun init_internal_attributes(init_instance: Instance, size: Int): Pointer
                import Array[Instance].length, Array[Instance].[] `{
 
                Instance* attributes = malloc(sizeof(Instance) * size);
 
                int i;
                for(i=0; i<size; i++)
-                       attributes[i] = null_instance;
+                       attributes[i] = init_instance;
 
-               Instance_incr_ref(null_instance);
+               Instance_incr_ref(init_instance);
                return attributes;
        `}
 
@@ -180,6 +181,12 @@ class VirtualMachine super NaiveInterpreter
                var i = read_attribute_ph(recv.internal_attributes, recv.vtable.internal_vtable,
                                        recv.vtable.mask, id, mproperty.offset)
 
+               # If we get a `MInit` value, throw an error
+               if i == initialization_value then
+                       fatal("Uninitialized attribute {mproperty.name}")
+                       abort
+               end
+
                return i
        end