Getting error: ISO C++ forbids declaration of with no type

问题

I'm getting the following errors:

ISO C++ forbids declaration of ttTreeInsert with no type

ISO C++ forbids declaration of ttTreeDelete with no type

ISO C++ forbids declaration of ttTreePrint with no type

prototype for int ttTree::ttTreePrint() does not match any in class ttTree

candidate is: void ttTree::ttTreePrint()

Here is my header file:

#ifndef ttTree_h
#define ttTree_h

class ttTree 
{
public:
  ttTree(void);
  int ttTreeInsert(int value);
  int ttTreeDelete(int value);
  void ttTreePrint(void);

};

#endif

Here is my .cpp file:

#include "ttTree.h"

ttTree::ttTree(void)
{

}

ttTree::ttTreeInsert(int value)
{
}

ttTree::ttTreeDelete(int value)
{
}

ttTree::ttTreePrint(void)
{
}

Can anyone point out what is causing these errors? Thank you!

回答1:

You forgot the return types in your member function definitions:

int ttTree::ttTreeInsert(int value) { ... }
^^^               

and so on.

回答2:

Your declaration is int ttTreeInsert(int value);

However, your definition/implementation is

ttTree::ttTreeInsert(int value)
{
}

Notice that the return type int is missing in the implementation. Instead it should be

int ttTree::ttTreeInsert(int value)
{
    return 1; // or some valid int
}

来源：https://stackoverflow.com/questions/23314409/getting-error-iso-c-forbids-declaration-of-with-no-type