It’s the array that’s causing trouble in: void print_graph(g_node graph_node[], double weight[][], int nodes); The second and subsequent dimensions must be given: void print_graph(g_node graph_node[], double weight[][32], int nodes); Or you can just give a pointer to pointer: void print_graph(g_node graph_node[], double **weight, int nodes); However, although they look similar, those are very different internally. … Read more
At the time you declare your member, you are still defining the A class, so the type A is still undefined. However, when you write A*, the compiler already knows that A stands for a class name, and so the type “pointer to A” is defined. That’s why you can embed a pointer to the … Read more
Clang is wrong. [dcl.fct.def.general] 2 The type of a parameter or the return type for a function definition shall not be a (possibly cv-qualified) class type that is incomplete or abstract within the function body unless the function is deleted ([dcl.fct.def.delete]). That’s pretty clear I think. A deleted definition allows for an incomplete class type. … Read more
The correct writing should be: List<List<Integer>> ret = new ArrayList<List<Integer>>(); Since in this way, you can add not only ArrayList but also LinkedList to ret
A class is allowed to have a static member of the same type. However, a class is incomplete until the end of its definition, and an object cannot be defined with incomplete type. You can declare an object with incomplete type, and define it later where it is complete (outside the class). struct Size { … Read more
This paper was adopted into C++17 which allows incomplete types to be used in certain STL containers. Prior to that, it was Undefined Behavior. To quote from the paper: Based on the discussion on the Issaquah meeting, we achieved the consensus to proceed* with the approach – “Containers of Incomplete Types”, but limit the scope … Read more
Here are some examples of std::unique_ptr with incomplete types. The problem lies in destruction. If you use pimpl with unique_ptr, you need to declare a destructor: class foo { class impl; std::unique_ptr<impl> impl_; public: foo(); // You may need a def. constructor to be defined elsewhere ~foo(); // Implement (with {}, or with = default;) … Read more