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Full Discussion: C program multiple definition error during linking time
Top Forums Programming C program multiple definition error during linking time Post 302785717 by royalibrahim on Tuesday 26th of March 2013 08:38:20 AM
Old 03-26-2013
C program multiple definition error during linking time
Hi,

I have the following files:

// file.h
HTML Code:
void foo();
int i = 5; // should be just declared as extern int i;
// file1.c
Code:
#include <stdio.h>
#include "file.h"

void foo() {
    i = 10;
    printf("%d\n", i);
}

// file2.c
Code:
#include <stdio.h>
#include "file.h"

int main() {
    foo();
    printf("%d\n", i);
}

When I compiled the above files using gcc compiler, I got the following linker error

gcc -c file1.c
gcc -c file2.c
gcc -o a.out file*.o // linker error: file2.o: multiple definition of 'i'

After searching in the google, I got below links where I found the solution
Solving multiple definition - C++ Forum
multiple definition of 'variable_name'
"multiple definition" error - C++ Forum

Now, I have changed the code in the file.h as:
Code:
extern int i;

Now, my question is, if I want to print the value of i before calling the foo() function in the file2.c, what should I do in order to not to end up in the linker error?

// file2.c
Code:
#include <stdio.h>
#include "file.h"

i = 20; // treats as an altogether a new definition of i, implicitly adds int keyword before i
int main() {
        i = 20; // multiple definition error
        printf("%d\n", i);
        foo();
        printf("%d\n", i);
}

Last edited by royalibrahim; 03-27-2013 at 03:54 AM..
 

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LEARN ABOUT MINIX

zdiff

ZDIFF(1)                                                      General Commands Manual                                                     ZDIFF(1)

NAME

       zcmp, zdiff - compare compressed files

SYNOPSIS

       zcmp [ cmp_options ] file1 [ file2 ]
       zdiff [ diff_options ] file1 [ file2 ]

DESCRIPTION

       Zcmp  and  zdiff are used to invoke the cmp or the diff program on files compressed via gzip.  All options specified are passed directly to
       cmp or diff.  If only file1 is specified, it is compared to the uncompressed contents of file1.gz.  If two files are specified, their  con-
       tents  (uncompressed  if  necessary)  are  fed to cmp or diff.  The input files are not modified.  The exit status from cmp or diff is pre-
       served.

SEE ALSO

       cmp(1), diff(1), zmore(1), zgrep(1), znew(1), zforce(1), gzip(1), gzexe(1)

BUGS

       Messages from the cmp or diff programs may refer to file names such as "-" instead of to the file names specified.

                                                                                                                                          ZDIFF(1)
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