The consequences of the # include in C + +

This is the problem that is encountered when making a module today. Abstract, the code is as follows:

File structure:

Error:

The error appears to be that the code in the Box.h is problematic. In fact, the root cause of the problem lies in the redundant Cup.h "Box.h" (because Box.h has # include "Cup.h", so it constitutes a loop resulting in an error! ）

The solution, of course, is to delete the superfluous # include directive.

Feel C + + compiler basically error if you encounter more complicated situation, the error message basically has no reference value, in addition to misleading is misleading, so, in writing C + + must be careful and careful ah!

Code:

Box.h

#ifndef Box_h #define Box_h"Cup.h"class  box{    public:        Box ();         ~Box ();}; Cup* getcup (); void Deletecup (Cup *p); #endif // Box_h

Box.cpp

#include"Box.h"#include<iostream>using namespacestd; Box::box () {cout<<"Box Cons"<<Endl;} Box::~Box () {cout<<"Box des"<<Endl;} Cup*Getcup () {return NewCup ();}voidDeletecup (Cup *p) {delete p;}

Cup.h

#ifndef Cup_h #define Cup_h"Box.h"class  cup{    friend Cup* getcup ();      Public :         ~Cup ();     Private :        Cup ();}; #endif // Cup_h

Cup.cpp

" Cup.h "  <iostream>usingnamespace  std; Cup::cup () {    "Cup cons" << Endl;} Cup::~Cup () {    "Cup des" << Endl;}

Main.cpp

" Box.h "  "Cup.h"int  main () {    *p = getcup ();    box box;    Deletecup (P);}

The consequences of the # include in C + +