Unconditionally use modified PyType_Ready.

This fixes github issue #4106.

Cython/Compiler/Nodes.py

@@ -5246,13 +5246,13 @@ class CClassDefNode(ClassDefNode):
                 self.type_init_args.generate_disposal_code(code)
                 self.type_init_args.free_temps(code)
 
-            self.generate_type_ready_code(self.entry, code, True)
+            self.generate_type_ready_code(self.entry, code)
         if self.body:
             self.body.generate_execution_code(code)
 
     # Also called from ModuleNode for early init types.
     @staticmethod
-    def generate_type_ready_code(entry, code, heap_type_bases=False):
+    def generate_type_ready_code(entry, code):
         # Generate a call to PyType_Ready for an extension
         # type defined in this module.
         type = entry.type
@@ -5288,15 +5288,10 @@ class CClassDefNode(ClassDefNode):
             code.putln("#else")
             for slot in TypeSlots.slot_table:
                 slot.generate_dynamic_init_code(scope, code)
-            if heap_type_bases:
             code.globalstate.use_utility_code(
                 UtilityCode.load_cached('PyType_Ready', 'ExtensionTypes.c'))
-                readyfunc = "__Pyx_PyType_Ready"
-            else:
-                readyfunc = "PyType_Ready"
             code.putln(
-                "if (%s(&%s) < 0) %s" % (
-                    readyfunc,
+                "if (__Pyx_PyType_Ready(&%s) < 0) %s" % (
                     typeobj_cname,
                     code.error_goto(entry.pos)))
             # Don't inherit tp_print from builtin types in Python 2, restoring the
@@ -5375,7 +5370,6 @@ class CClassDefNode(ClassDefNode):
                         type.vtabptr_cname,
                         code.error_goto(entry.pos)))
                 code.putln("#endif")
-                if heap_type_bases:
                 code.globalstate.use_utility_code(
                     UtilityCode.load_cached('MergeVTables', 'ImportExport.c'))
                 code.putln("if (__Pyx_MergeVtables(&%s) < 0) %s" % (

tests/run/cdef_multiple_inheritance_cimport.srctree

+# Test for https://github.com/cython/cython/issues/4106
+
+PYTHON setup.py build_ext --inplace
+PYTHON -c "import sub"
+
+######## setup.py ########
+
+from Cython.Build import cythonize
+from distutils.core import setup
+
+setup(
+  ext_modules = cythonize("*.pyx"),
+)
+
+######## base.pxd ########
+
+cdef class A:
+  cdef dict __dict__
+  cdef int a(self)
+
+cdef class B(A):
+  cdef int b(self)
+
+######## base.pyx ########
+
+cdef class A:
+  cdef int a(self):
+    return 1
+
+class PyA:
+  pass
+
+cdef class B(A, PyA):
+  cdef int b(self):
+    return 2
+
+######## sub.pyx ########
+
+from base cimport B
+print(B)
+
+cdef class C(B):
+  cdef int c(self):
+    return 3