Re: How to fix the following problem?

From:

red floyd <no.spam.here@example.com>

Newsgroups:

comp.lang.c++

Date:

Wed, 03 Sep 2008 20:27:11 -0700

Message-ID:

<FyIvk.12196$vn7.8201@flpi147.ffdc.sbc.com>

Daniel T. wrote:

SamuelXiao <foolsmart2005@gmail.com> wrote:

-----------------------Lab002.h------------------------------
#ifndef _LAB_002_
#define _LAB_002_

class base{
    char *msg;
public:
    base(char *);
    ~base();
    void print(void);
};

class derived1 : base{
public:
    derived1(char *);
    ~derived1();
};

class derived2 : derived1{
public:
    derived2(char *);
    ~derived2();
};
#endif

----------------------------main.cpp------------------------------
#include <iostream>
#include "Lab002.h"
using namespace std;

void main(void){
    derived2 x("X");
    {
        derived2 y("Y");
    }
    derived2 z("Z");
}

-------------compiler complaint------------------------------------

main.obj : error LNK2019: unresolved external symbol "public: __thiscall
derived2::~derived2(void)" (??1derived2@@QAE@XZ) referenced in function
_main

1>main.obj : error LNK2019: unresolved external symbol "public:
__thiscall derived2::derived2(char *)" (??0derived2@@QAE@PAD@Z)
referenced in function _main

what 's wrong with it?

There are two things wrong with the above code.
1) 'main' returns an int, not void.

2) 'main' attempts to create several derived2 objects by using the
derived2::derived2(char*) constructor, unfortunately according to the
linker, no such constructor has been provided.

[MONTY-PYTHON]
There are THREE things wrong with the above code.
[/MONTY-PYTHON]

3) The identifier for the include guard _LAB_002_ is reserved to the
implementation. You may not use it for your own purposes like that.

[MONTY-PYTHON]
There are THREE AND A HALF things wrong with the above code.
[/MONTY-PYTHON]

3.5) the (void) argument list is a C-ism, discouraged in C++. Avoid
its use.

As a side note, the contents of <iostream> are not used, and the
"using namespace std;" is unnecessary, since no members of std:: are
used.