C header issue: #include and "undefined reference"

Question

Alright, I've been trying to work with this for the longest time, and I simply can't seem to get it to work right. I have three files, main.c, hello_world.c, and hello_world.h. For whatever reason they don't seem to compile nicely, and I really just can't figure out why...

Here are my source files. First hello_world.c:

#include <stdio.h> #include "hello_world.h"  int hello_world(void) {   printf("Hello, Stack Overflow!\n");   return 0; } 

Then hello_world.h, simple:

int hello_world(void); 

And then finally main.c:

#include "hello_world.h"  int main() {   hello_world();   return 0; } 

When I put it into GCC, this is what I get:

 cc     main.c   -o main /tmp/ccSRLvFl.o: In function `main': main.c:(.text+0x5): undefined reference to `hello_world' collect2: ld returned 1 exit status make: *** [main] Error 1 

Anyone able to help me out? I'm really stuck on this, but I'm 99 percent sure it's a really simple fix.

Answer 1

gcc main.c hello_world.c -o main 

Also, always use header guards:

#ifndef HELLO_WORLD_H #define HELLO_WORLD_H  /* header file contents go here */  #endif /* HELLO_WORLD_H */ 

Answer 2

You are not including hello_world.c in compilation.

   gcc hello_world.c main.c   -o main