need a little help with linking error for CRC

[liftthis]

I need some help with compiler error.
error link2005: _crcTable already defined in crc.obj


I attach the zip file below:

[cilu]

You're CRC header has no guards. Use one of these two:

#ifndef _CRC_H_
#define _CRC_H_

// header content goes here

#endif

or (only for Microsoft compilers)

#pragma once 

// header content goes here

You should try defining your table as constant:

const unsigned long  crcTable[256] =
{
};

[liftthis]

Still need to address the error link2005: _crcTable already defined in crc.obj,

I can't see it.

[GCDEF]

Did you try what he said?

[liftthis]

Yes I did with and without the #pragma once and still have a problem

[Philip Nicoletti]

1) in crc.h , you can just declare the variable

extern unsigned long  crcTable[256];

2) in crc.c you define the variable

#include "crc.h"

unsigned long  crcTable[256] =
{
 0x00000000L, 0x00B20606L, 0x01640C0CL, 0x01D60A0AL,
/* etc */

3) You should put header guards in all .h files (not needed in your simple example).

[liftthis]

Thanks that helped. How do know if the CRC generated is correct?

[liftthis]

I am having trouble trying to get the CRC append to the test data, and print out the data with the appended crc.


#include <stdio.h>
#include <string.h>

#include "crc.h"

static unsigned long crcSum;

void
main(void)
{
// unsigned char test[] = "123456789";
unsigned char test[13] = {0x1,0x2,0x3,0x4,0x5,0x6,0x7,0x8,0x9};


/*
* Print the check value for the selected CRC algorithm.
*/

printf("Payload: 0x%X\n", test);
printf("The crcFast() of \"123456789\" is 0x%X\n", crcFast(test, strlen(test)));

crcSum = crcFast(test, strlen(test));
// printf("Payload is 0x%X\n", test);
// printf("CRC is 0x%X\n", crcSum);

// Add CRC To message
*(unsigned long *)&test[9] = (unsigned long)crcSum /*crcSum*/;

printf("Payload with CRC Appended: 0x%X\n", *(unsigned long *)&test[9]);




} /* main() */

[hoxsiew]

"test" is not a C-string (no NULL terminator) so you get undefined behavior when you try to use calls like printf() and strlen().

[JohnW@Wessex]

Thanks that helped. How do know if the CRC generated is correct?

This may help