cannot resolve LNK2005 multiply defined symbols

Question

Windows 11, Visual Studio 2019, C++
I started getting this error:

1>ripemd_160_test_data.obj : error LNK2005: "char (* ripemd_input)[90]" (?ripemd_input@@3PAY0FK@DA) already defined in ripemd_160_13.obj

1>E:\WX\ripemd_160_13\Debug\ripemd_160_13.exe : fatal error LNK1169: one or more multiply defined symbols found

I have removed almost all the code with only one instance of that item and still get the error. Here is the main project file:

include <iostream>

include "ripemd_160_test_data.h"

int main()
{
std::cout << "Hello World!\n";
}

Yeah, that it. Here is the utility include file.

#pragma once  
#ifndef RIPEMD_160_TEST_DATA_H  
#define RIPEMD_160_TEST_DATA_H  

#include <stdint.h>  
#include <string>  

const size_t rm_count = 8;  
const size_t max_in = 90;  

char ripemd_input[rm_count ][ max_in ] =  
{  
   { "a" }  
// deleted stuff  
};  

#endif  

Please note the #pragma and the #define.
And here is the cpp file.

// test data for RIPEMD-160 test data  
// A RIPEMD-160 output is always the same length.  

#include "ripemd_160_test_data.h"  

Yeah, it down to just that.

I have done a clean and build and continue to get that same error. There is nothing left to remove.
What am I doing wrong.

Edit: I did use the "101010" tool to mark the code as such and it did not work.
Edit: And I started a new console project and added just those two files to the project, nothing else. The error is still there.

Answer 1

Hi, @Bryan Kelly

The problem is that global variable is being accessed by multiple files.

Modified snippet:
ripemd_160_test_data.h

extern char ripemd_input[rm_count][max_in];   

ripemd_160_test_data.cpp

#include "ripemd_160_test_data.h"  

char ripemd_input[rm_count ][ max_in ] =  
{  
{ "a" }  
// deleted stuff  
};  

Best regards,

Minxin Yu

---

If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Answer 2

Did you look at the "#pragma once"
Did you look at the "#ifndef ..."
Both of those commands to the compiler were designed to prevent it from creating the item multiple times.
I started using that stuff back in the 1980s and 1990s.

If it is declared "external" in the h file, then it is "external" to the h file, and every file that incorporates the h file sees it declared external, and there is nothing left to actually create that entity.

Answer 3

I stepped away for a while and thought about this deeply. Your point(s) are getting through to me.
Thank you for your time and patience.