fix memory leak for memory views in extension subtypes

CHANGES.rst

@@ -15,6 +15,10 @@ Features added
 Bugs fixed
 ----------
 
+* Memory leak when extension subtypes add a memory view as attribute
+  to those of the parent type without having Python object attributes
+  or a user provided dealloc method.
+
 * Compiler crash on readonly properties in "binding" mode.
 
 * Auto-encoding with ``c_string_encoding=ascii`` failed in Py3.3.

Cython/Compiler/Symtab.py

@@ -1768,6 +1768,7 @@ class CClassScope(ClassScope):
     #  method_table_cname    string
     #  getset_table_cname    string
     #  has_pyobject_attrs    boolean  Any PyObject attributes?
+    #  has_memoryview_attrs  boolean  Any memory view attributes?
     #  has_cyclic_pyobject_attrs    boolean  Any PyObject attributes that may need GC?
     #  property_entries      [Entry]
     #  defined               boolean  Defined in .pxd file
@@ -1777,6 +1778,7 @@ class CClassScope(ClassScope):
     is_c_class_scope = 1
 
     has_pyobject_attrs = False
+    has_memoryview_attrs = False
     has_cyclic_pyobject_attrs = False
     defined = False
     implemented = False
@@ -1850,7 +1852,9 @@ class CClassScope(ClassScope):
             entry = self.declare(name, cname, type, pos, visibility)
             entry.is_variable = 1
             self.var_entries.append(entry)
-            if type.is_pyobject and name != '__weakref__':
+            if type.is_memoryviewslice:
+                self.has_memoryview_attrs = True
+            elif type.is_pyobject and name != '__weakref__':
                 self.has_pyobject_attrs = True
                 if (not type.is_builtin_type
                         or not type.scope or type.scope.needs_gc()):

Cython/Compiler/TypeSlots.py

@@ -353,6 +353,7 @@ class ConstructorSlot(InternalMethodSlot):
         if (self.slot_name != 'tp_new'
                 and scope.parent_type.base_type
                 and not scope.has_pyobject_attrs
+                and not scope.has_memoryview_attrs
                 and not scope.lookup_here(self.method)):
             # if the type does not have object attributes, it can
             # delegate GC methods to its parent - iff the parent

tests/memoryview/memoryview_in_subclasses.pyx

+"""
+Test for memory leaks when adding more memory view attributes in subtypes.
+"""
+
+import gc
+
+from cython.view cimport array
+
+
+def count_memoryviews():
+    gc.collect()
+    return sum([1 if 'memoryview' in str(type(o)) else 0
+                for o in gc.get_objects()])
+
+
+def run_test(cls, num_iters):
+    orig_count = count_memoryviews()
+    def f():
+        x = cls(1024)
+    for i in range(num_iters):
+        f()
+    return count_memoryviews() - orig_count
+
+
+cdef class BaseType:
+    """
+    >>> run_test(BaseType, 10)
+    0
+    """
+    cdef double[:] buffer
+
+    def __cinit__(self, n):
+        self.buffer = array((n,), sizeof(double), 'd')
+
+
+cdef class Subtype(BaseType):
+    """
+    >>> run_test(Subtype, 10)
+    0
+    """
+    cdef double[:] buffer2
+
+    def __cinit__(self, n):
+        self.buffer2 = array((n,), sizeof(double), 'd')
+
+
+cdef class SubtypeWithUserDealloc(BaseType):
+    """
+    >>> run_test(SubtypeWithUserDealloc, 10)
+    0
+    """
+    cdef double[:] buffer2
+
+    def __cinit__(self, n):
+        self.buffer2 = array((n,), sizeof(double), 'd')
+
+    def __dealloc__(self):
+        pass