Fix template cypclass field reference counting

Cython/Compiler/ExprNodes.py

@@ -7759,8 +7759,9 @@ class AttributeNode(ExprNode):
             elif self.type.is_cyp_class:
                 rhs.make_owned_reference(code)
                 rhs.generate_giveref(code)
-                code.put_gotref(select_code, self.type)
-                code.put_xdecref(select_code, self.type)
+                if not self.entry.is_specialised:
+                    code.put_gotref(select_code, self.type)
+                    code.put_xdecref(select_code, self.type)
 
             if not self.type.is_memoryviewslice:
                 code.putln(

Cython/Compiler/Nodes.py

@@ -6022,7 +6022,12 @@ class SingleAssignmentNode(AssignmentNode):
                 not rhs.is_name and not rhs.is_literal and
                 (rhs.type.is_pyobject or rhs.type.is_cyp_class)):
             # things like (cdef) attribute access are not safe (traverses pointers)
-            rhs = rhs.coerce_to_temp(env)
+            if rhs.is_attribute and rhs.type.is_cyp_class and rhs.entry.is_specialised:
+                rhs = rhs.coerce_to_temp(env)
+                # cypclass fields specialised from a template do their own reference counting.
+                rhs.use_managed_ref = False
+            else:
+                rhs = rhs.coerce_to_temp(env)
         elif rhs.type.is_pyobject:
             rhs = rhs.coerce_to_simple(env)
         self.rhs = rhs
@@ -6576,7 +6581,10 @@ class DelStatNode(StatNode):
                 arg.free_temps(code)
             elif arg.type.is_cyp_class:
                 arg.generate_evaluation_code(code)
-                code.put_xdecref_clear(arg.result(), arg.type)
+                if arg.is_attribute and arg.entry.is_specialised:
+                    code.putln("%s = nullptr;" % arg.result())
+                else:
+                    code.put_xdecref_clear(arg.result(), arg.type)
                 arg.generate_disposal_code(code)
                 arg.free_temps(code)
             # else error reported earlier

Cython/Compiler/Symtab.py

@@ -182,6 +182,8 @@ class Entry(object):
     # active_entry     Entry      Entry for the active version of an asyncable cypclass method
     #
     # is_consumed      boolean    The entry is the operand of a 'consume' expression.
+    #
+    # is_specialised   boolean    The entry is a template specialisation.
 
     # TODO: utility_code and utility_code_definition serves the same purpose...
 
@@ -261,6 +263,7 @@ class Entry(object):
     original_name = None
     active_entry = None
     is_consumed = False
+    is_specialised = False
 
     def __init__(self, name, cname, type, pos = None, init = None):
         self.name = name
@@ -3136,11 +3139,12 @@ class CppClassScope(Scope):
                                             e.cname,
                                             utility_code=e.utility_code)
             else:
-                scope.declare_var(entry.name,
+                e = scope.declare_var(entry.name,
                                   entry.type.specialize(values),
                                   entry.pos,
                                   entry.cname,
                                   entry.visibility)
+                e.is_specialised = True
 
         return scope
 

tests/run/cypclass_template_refcounting.pyx

@@ -129,3 +129,57 @@ def test_getting_and_setting():
         if Cy_GETREF(v) != 3:
             return -(i+2)
     return 0
+
+def test_field_getting():
+    """
+    >>> test_field_getting()
+    Template destroyed
+    Value destroyed
+    0
+    """
+    v = Value()
+    h = Template[Value](v)
+    if Cy_GETREF(v) != 3:
+        return -1
+
+    for i in range(10):
+        v = h.value
+        if Cy_GETREF(v) != 3:
+            return -(i+2)
+    return 0
+
+def test_field_setting():
+    """
+    >>> test_field_setting()
+    Template destroyed
+    Value destroyed
+    0
+    """
+    h = Template[Value](NULL)
+    v = Value()
+
+    for i in range(10):
+        h.value = v
+        if Cy_GETREF(v) != 3:
+            return -(i+1)
+    return 0
+
+def test_field_deleting():
+    """
+    >>> test_field_deleting()
+    Template destroyed
+    Value destroyed
+    0
+    """
+    v = Value()
+    h = Template[Value](v)
+    if Cy_GETREF(v) != 3:
+        return -1
+
+    del h.value
+    if Cy_GETREF(v) != 2:
+        return -1
+
+    del h
+
+    return 0