cython fails to compile pyx after version bump

I currently use Cython 0.17 and have a large codebase in Cython that I want to upgrade to the latest version. From that codebase I extracted the following simple example to demonstrate the failure.

example.hpp:

#include <stdint.h>

class MyBool {
public:
  MyBool(void) : m_value(0) {}
  MyBool(bool value) : m_value(value) {}
  operator bool() const { return bool(m_value); }

private:
  uint8_t m_value;
}

example.pyx:

cdef extern from "example.hpp":
    cdef cppclass MyBool_c "MyBool"

cdef class MyBoolArray(object):
    def __getitem__(self, key):
        cdef MyBool_c* my_bool = <MyBool_c*>0
        my_bool[0] = <MyBool_c>(0)
        return <bint>(my_bool[0])

Until Cython=0.20, everything works fine. From 0.21 to 0.22 the following error occurs:

Error compiling Cython file:
------------------------------------------------------------
...

cdef class MyBoolArray(object):
    def __getitem__(self, key):
        cdef MyBool_c* my_bool = <MyBool_c*>0
        my_bool[0] = <MyBool_c>(0)
        return <bint>(my_bool[0])
                            ^
------------------------------------------------------------

example.pyx:8:29: Type 'MyBool_c' not acceptable as a boolean

Error compiling Cython file:
------------------------------------------------------------
...

cdef class MyBoolArray(object):
    def __getitem__(self, key):
        cdef MyBool_c* my_bool = <MyBool_c*>0
        my_bool[0] = <MyBool_c>(0)
        return <bint>(my_bool[0])
                            ^
------------------------------------------------------------

example.pyx:8:29: Cannot convert 'MyBool_c' to Python object

From 0.23 an on, I got a different crash:

Error compiling Cython file:
------------------------------------------------------------
...
    cdef cppclass MyBool_c "MyBool"

cdef class MyBoolArray(object):
    def __getitem__(self, key):
        cdef MyBool_c* my_bool = <MyBool_c*>0
        my_bool[0] = <MyBool_c>(0)
                    ^
------------------------------------------------------------

example.pyx:7:21: Compiler crash in AnalyseExpressionsTransform

ModuleNode.body = StatListNode(example.pyx:1:0)
StatListNode.stats[1] = CClassDefNode(example.pyx:4:5,
    as_name = u'MyBoolArray',
    class_name = u'MyBoolArray',
    module_name = u'',
    visibility = u'private')
CClassDefNode.body = StatListNode(example.pyx:5:4)
StatListNode.stats[0] = DefNode(example.pyx:5:4,
    modifiers = [...]/0,
    name = u'__getitem__',
    num_required_args = 2,
    py_wrapper_required = True,
    reqd_kw_flags_cname = '0',
    used = True)
File 'Nodes.py', line 430, in analyse_expressions: StatListNode(example.pyx:6:8,
    is_terminator = True)
File 'Nodes.py', line 4774, in analyse_expressions: SingleAssignmentNode(example.pyx:7:21)
File 'Nodes.py', line 4920, in analyse_types: SingleAssignmentNode(example.pyx:7:21)

Compiler crash traceback from this point on:
  File "/home/asaf/miniconda2/lib/python2.7/site-packages/Cython/Compiler/Nodes.py", line 4920, in analyse_types
    op = env.lookup_operator_for_types(self.pos, '=', [self.lhs.type, self.rhs.type])
  File "/home/asaf/miniconda2/lib/python2.7/site-packages/Cython/Compiler/Symtab.py", line 844, in lookup_operator_for_types
    return self.lookup_operator(operator, operands)
  File "/home/asaf/miniconda2/lib/python2.7/site-packages/Cython/Compiler/Symtab.py", line 829, in lookup_operator
    method = obj_type.scope.lookup("operator%s" % operator)
AttributeError: 'NoneType' object has no attribute 'lookup'

I also tried to read the changelog to see which change could lead for this kind of error, but I didn’t find anything. Any idea what could have happened or how the problem can be solved?

[da-woods]

No but cdef MyBool_c* my_bool = <MyBool_c*>0 creates a NULL pointer and then my_bool[0] attempts to use that pointer.

I do agree with your suggestions on how to change it so it’ll compile. I just think it will crash when run.

[asafkahlon]

I updated example.pyx to this:

cdef extern from "<stdint.h>" nogil:
    ctypedef unsigned char  uint8_t

from libcpp cimport bool as boolean

cdef extern from "example.hpp":
    cdef cppclass MyBool_c:
        MyBool()
        MyBool(boolean value)
        uint8_t m_value

cdef class MyBoolArray(object):
    def __getitem__(self, key):
        cdef MyBool_c* my_bool = <MyBool_c*>0
        my_bool[0] = <MyBool_c>(0)
        return <boolean> (my_bool[0])

This file works also on the newest version. Pay attention - I still got the second error if call the constructor directly as you suggested before. It works only with the original usage. Do you still think I should call the constructor directly? Should there be any difference?