AMDG Tiago Alves wrote:
Hi, and sorry for the probable newbieness of this question!
I want to put weak_ptr into a piece of memory previously allocated.
this is my code:
// construct a weak_ptr from a share_ptr boost::weak_ptr<Obj>* cameraPtr = new boost::weak_ptr<Obj>(obj_share_ptr); // lua_newuserdata allocs memory and returns a pointer to it, just like malloc. boost::weak_ptr<Obj>* camera = static_cast<boost::weak_ptr<Obj>*>(lua_newuserdata(pLuaState,sizeof(boost::weak_ptr<Obj>)));
Now i want camera to be a weak_ptr of ObjPtr. I tried different ways to do this, such as *camera = boost::weak_ptr<Obj>(obj_share_ptr); or camera->swap(*cameraPtr); or *camera = *cameraPtr;
I think none of these work because in fact they all do a swap() between camera and cameraPtr. Since camera is just an malloc, it will try to swap dirty memory and segfault sometimes (yes, sometimes this worked).
Out of desperation, i did this: memcpy(camera,cameraPtr,sizeof(boost::weak_ptr<Obj>));
Which seems to work but it stinks. It's copying an object with memcpy instead of using its constructor.
Is there a better way to do this?
Use placement new. new(camara) boost::weak_ptr<Obj>(obj_share_ptr); In Christ, Steven Watanabe