CODEWITHSUNDEEP
c
Johhny Bravo
Johhny Bravo

Reputation: 199

Compiling multiple files error

So I have created couple of files:

file1.c

#include "file2.h"
...
int *p; <-GLOBAL VARIABLE
...
void main(){
     printer();
}

file2.c

 #include "file1.h"

 void printer(){
     *p = 5;
      printf("%d",*p);
 }

file1.h

 extern int *p;

file2.h

 extern void printer(void);

Code compiles. However, when I run it, I get segmentation error. I have tried to look for the solution everywhere, but couldn't find a good one.

I tried replacing printer(void) in file2.h with printer() no result (and not sure if it is correct, either).

Does anyone possibly see a solution to my issue?

Upvotes: 0

Views: 33

Answers (2)

Goodies
Goodies

Reputation: 4681

Think of this in terms of one file:

#include <stdio.h>
int *p; <-GLOBAL VARIABLE

void printer();

void main(){
    printer();
}

void printer(){
    *p = 5;
    printf("%d",*p);
}

What you've done is taken an initialized but undefined variable of a pointer that points to an integer. When you go to set that pointer, it is not initialized. You need to either initialize it and reference it with &, or better yet, allocate memory for it dynamically.

Perhaps in your main function, you can do something like:

int main(){
    p = calloc(1, sizeof(int));
    printer();
    free(p);
}

Upvotes: 1

Dave Costa
Dave Costa

Reputation: 48121

You've never allocated memory for p to reference, or otherwise initialized it as a reference to properly-allocated memory. When you do *p = 5, you are trying to reference memory you aren't allowed access to.

A typical solution would be to dynamically allocate memory, e.g.:

p = malloc( sizeof(int) );

Upvotes: 1

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