incomplete-type

问题 Related questions: one, two After trying to understand CRTP for several days it seems that now I understand even less than before:) Consider the following code: 01 #include <iostream> 02 03 template <class IMPL> 04 class Interace 05 { 06 public: 07 typedef typename IMPL::TYPE TYPE; // ERROR: "...invalid use of incomplete type..." 08 void foo() { IMPL::impl(); } // then why does this work? 09 }; 10 11 class Implementation : public Interface<Implementation> 12 { 13 public: 14 typedef int TYPE;

问题 I am getting the following error from this piece of code, I am new to C and learning as I go along! cc -g -I /usr/lib/i386-linux-gnu -c anld.c anld.c: In function ‘main’: anld.c:379:11: error: dereferencing pointer to incomplete type Main .C file bridge_t *bridge_p = bridge_new(); //Create / init our bridge bridge_p->s = server_connect(options.server_p, options.dest_port, options.ifname_p, options.gateway_p); bridge .C file struct bridge { int s; }; bridge_t *bridge_new(void) { bridge_t

问题 I'm getting a incomplete type error for the 'next' and 'previous' variables. I'm not sure what I am doing wrong because I am very rusty on writing classes in C++. Any help would be appreciated! Thanks. #include<iostream> using namespace std; class LinearNode { public: //Constructor for the LinearNode class that takes no arguments LinearNode(); //Constructor for the LinearNode class that takes the element as an argument LinearNode(int el); //returns the next node in the set. LinearNode getNext

问题 I have a class that should have a private member of the same class, something like: class A { private: A member; } But it tells me that member is an incomplete type. Why? It doesn't tell me incomplete type if I use a pointer, but I'd rather not use a pointer. Any help is appreciated 回答1: 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

问题 Given the following class template: template<typename T> struct Outer { struct Inner; auto f(Inner) -> void; }; we define Inner separately for each specialization of Outer : template<> struct Outer<int>::Inner {}; template<> struct Outer<double>::Inner {}; and then define the member function f once for all specializations of Outer : auto Outer<T>::f(Inner) -> void { } but Clang (9.0.0) complains: error: variable has incomplete type 'Outer::Inner' auto Outer<T>::f(Inner) -> void ^ We can evade

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: What leads to incomplete types? (QGraphicsItem: Source or target has incomplete type) I started out with this question: What leads to incomplete types? (QGraphicsItem: Source or target has incomplete type) As mentioned there, I got the following error (partly my own translation): C664: Conversion of parameter 1 from 'Qt::CursorShape' to 'const QCursor &' not possible. Source or target has incomplete type. While

问题 This question already has an answer here : incomplete type error (1 answer) Closed 4 years ago . I want to build a tree using level order traversal. When I declare my Queue object in the private scope, I get the error "field 'q' has incomplete type 'Queue'. My program works if I declare a Queue in the addTreeNode(int integer) function, but when I move it to the header file, I get the new error. From what I have read it seems that the Tree class does not know how much memory to allocate to the

问题 Where does the recursion in the definition of cycle break ? #include <iostream> using namespace std; template<typename T> struct Recursive { using cycle = struct X : Recursive<X> {}; // would work for Recursive<T> as well }; int main() { Recursive<int> x; return 0; } To my surprise the above code compiles - Is it a valid piece of code and if yes what's the meaning (a brief description) of the type cycle ? 回答1: The struct X : Recursive<X> is an example of the Curiously Recurring Template

问题 I was recently surprised to know that this code compiles (at least on gcc and MSVC++): template<typename T> class A { public: T getT() { return T(); } }; class B : public A<B> { }; When this doesn't: class A; class B : public A { }; class A { public: B getB() { return B(); } }; It seems weird to me that a template class could take an incomplete type as a template parameter and have a function that returned one by calling its constructor and still compile. So where exactly are complete types

问题 Reference here That destructor will also implicitly call the destructor of the auto_ptr object. And that will delete the pointer it holds, that points to the C object - without knowing the definition of C! That appeared in the .cpp file where struct A's constructor is defined. This was curious and then 5.3.5/5 states - "If the object being deleted has incomplete class type at the point of deletion and the complete class has a non-trivial destructor or a deallocation function, the behavior is