error C2011: '' : 'class' type redefinition

Question

One of the header files is as follows -

#include "stdafx.h"

class AAA
{
public:
    std::string strX;
    std::string strY;
};

When I try to compile the project, I get the error

error C2011: 'AAA' : 'class' type redefinition

Nowhere else in my program have I redefined the class AAA. How do I fix this?

You need to use include guards. – juanchopanza Sep 07 '14 at 19:03 — juanchopanza, Sep 07 '14 at 19:03

score 55 · Accepted Answer · answered Sep 07 '14 at 19:06

55

Change to code to something like this:

#ifndef AAA_HEADER
#define AAA_HEADER

#include "stdafx.h"

class AAA
{
public:
    std::string strX;
    std::string strY;
};

#endif

If you include this header file more than once in some source file, include guards will force compiler to generate class only once so it will not give class redefinition error.

answered Sep 07 '14 at 19:06

Ashot

10,807
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Is AAA_HEADER the AAA.h file? – user3164272 Sep 08 '14 at 12:42
3

AAA_HEADER is just unique string to identify the file. Read about include guards here http://stackoverflow.com/questions/8020113/c-include-guards – Ashot Sep 08 '14 at 12:48
The nice thing about this solution is that it will work for all C++ compilers, not just Microsoft's. – empty Oct 19 '18 at 16:46

empty · Answer 2 · 2018-10-19T16:45:19.350

37

Adding

#pragma once

to the top of your AAA.h file should take care of the problem.

like this

#include "stdafx.h"
#pragma once

class AAA
{
public:
    std::string strX;
    std::string strY;
};

edited Oct 19 '18 at 16:45

answered Jun 07 '16 at 18:09

empty

5,194
3
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3

Should it be more likely at the very top of the file (at first line) not after some includes? – Sandburg May 04 '18 at 09:58

score 5 · Answer 3 · answered Sep 07 '14 at 20:17

5

In addition to the suggested include guards you need to move #include "stdafx.h" out of the header. Put it at the top of the cpp file.

answered Sep 07 '14 at 20:17

ScottMcP-MVP

10,337
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score 1 · Answer 4 · edited Oct 05 '21 at 13:31

1

I met this problem today in VS 2017. I added #pragma once, but it didn't work until I added a macro definition:

    // does not work    
    #pragma once
        
    // works with or without #pragma once
    #ifndef _HEADER_AAA
    #define _HEADER_AAA
    //
    // my code here....
    //
    #endif

I have no clue how to explain this, but it is a solution for me.

edited Oct 05 '21 at 13:31

Yun

3,056
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answered Sep 15 '21 at 05:48

Chaohsiung Huang

154
1
4

Mike Garrison · Answer 5 · 2023-02-10T03:22:07.163

There are two ways to go about this but you can't use both. Make sure to wrap the class definition with a compiler directive that the class declaration only gets compiled once:

#include "stdafx.h"

#pragma once

class AAA{
public:
    std::string strX;
    std::string strY;
};

-or-

   #include "stdafx.h"
    
    #ifndef AAA_HEADER_
    #define AAA_HEADER_
    
    class AAA
    {
    public:
    
        std::string strX;
        std::string strY;
    
    };
    
    #endif

Also: note the class import statement should be at the top of your file.

error C2011: '' : 'class' type redefinition

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