Compiler crash in AnalyseExpressionsTransform

[Czarek Tomczak]

Hi,

I'm getting this crash while compiling with Cython:

web_request.pyx:54:19: Compiler crash in AnalyseExpressionsTransform
ModuleNode.body = StatListNode(cefpython.pyx:42:0)
StatListNode.stats[11] = StatListNode(cefpython.pyx:77:4)
StatListNode.stats[4] = StatListNode(web_request.pyx:14:0)
StatListNode.stats[2] = CFuncDefNode(web_request.pyx:49:5,
    args = [...]/2,
    modifiers = [...]/0,
    visibility = u'private')
File 'Nodes.py', line 387, in analyse_expressions: StatListNode(web_request.pyx:51:4)
File 'Nodes.py', line 4403, in analyse_expressions: SingleAssignmentNode(web_request.pyx:54:47)
File 'Nodes.py', line 4509, in analyse_types: SingleAssignmentNode(web_request.pyx:54:47)
File 'ExprNodes.py', line 2750, in analyse_target_types: IndexNode(web_request.pyx:54:19,
    result_is_used = True,
    use_managed_ref = True)
File 'ExprNodes.py', line 3178, in is_lvalue: IndexNode(web_request.pyx:54:19,
    result_is_used = True,
    use_managed_ref = True)
Compiler crash traceback from this point on:
  File "/usr/local/lib/python2.7/dist-packages/Cython/Compiler/ExprNodes.py", line 3178, in is_lvalue
    return not base_type.base_type.is_array
AttributeError: 'CppClassType' object has no attribute 'base_type'

The code is:

cdef cpp_map[int, void*] g_pyWebRequests
cdef PyWebRequest webRequest = PyWebRequest(request, webRequestClient) 
g_pyWebRequests[1] = <void*>webRequest

PyWebRequest is a cdef class.

What to do?

A side note:

I have to keep PyWebRequests in C++ map as I do not want to increase references

to these objects, I need to access them from C++ and I do not have control over

their lifetime, keeping them in a Python dict would make them live forever and the

memory would never be freed.

Using latest Cython 0.19.1

Thanks for help.

Regards,

Czarek

[Nikita Nemkin]

On Wed, 22 May 2013 23:18:53 +0600, Czarek Tomczak
<czarek....@gmail.com> wrote:

> I have to keep PyWebRequests in C++ map as I do not want to increase
> references
> to these objects, I need to access them from C++ and I do not have
> control over their lifetime, keeping them in a Python dict would make
> them live forever and the memory would never be freed.

Weak references exist specifically for this purpose.
They are also much safer, because they are cleared automatically
when the pointed object dies.
Take a look at WeakValueDictionary in the standard lib.

Note: cdef classes need an additional member ("cdef __weakref__")
in order to support weak references.
(http://docs.cython.org/src/reference/extension_types.html#weak-referencing)

Language-level weakref support and weakref optimizations are on my
personal Cython wishlist...

Best regards,
Nikita Nemkin

[Czarek Tomczak]

Replacing Cython.Shadow.void* with libc.stdint.uintptr_t in the C++ map 

gets rid of the compiler crash, I will just use this fix.

Regards,

Czarek

[Czarek Tomczak]

Nikita, thank you for the guide on weak references, I will take a look at it.

Right now I'm removing objects from a C++ map in the __dealloc__ method

of the cdef class, which is called when object lifetime ends, so it works.

Regards,

Czarek

[Czarek Tomczak]

I had further problems with using uintptr_t instead of void*, casting python object

to uintptr_t threw some errors, I ended up using weak references and it works great.

Best regards,

Czarek