Cocos2d-x runtimes rely on the spine-c runtimes which are up-to-date. Cocos2d-x has a wrapper that performs the rendering/updating and it is also up-to-date as far as meshes are concerned.
Because Cocos2d-x uses spine-c, you could conceivably create a c++ tool to generate bodies/fixtures/etc... for a whole slew of runtimes.
Approach 1
I've been thinking about this all day, but I would bet the best approach would be to create a body for each bone with the mesh hulls as the fixtures. The bone positions would be the joint positions and the IK Constraints could give you some hints for the joint properties.
Check out this ground constraint video: viewtopic.php?f=3&t=3318 The SkeletonUtilityConstraints in Unity simply performs an updateWorldTransforms() after the bone is repositioned to resolve the IK constraints. The (simplified) order of operations is something along the lines of:
Apply Animation
UpdateWorld Transforms
Resolve Bone Position <- Your Physics Step
UpdateWorld Transforms (resolving IK) <- probably creating more collisions
render
Approach 2
The other approach would be to create fixtures from all the attachments and make the root bone the physics body. It's simpler, and it solves a lot of other problems, but it would make the animation very static looking, and the IK resolving wouldn't be necessary.
hull
Also, as a hint, the first N vertices in the sp(Skinned)MeshAttachment_ComputeWorldVertices() are the polygon HULL for the mesh, where N is sp(Skinned)MeshAttachment::hullLength. That should make building your fixtures easier.
Are you using Box2d as the engine?