gistfile1.txt

ristian@luke:~$ cat foo.c
#include <stdio.h>

void test_function(int i)
{
	printf("This function does nothing\n");
}

int main(void)
{
	printf("test\n");
}
kristian@luke:~$ gcc foo.c

kristian@luke:~$ gcc -Wall foo.c
foo.c: In function ‘main’:
foo.c:11:1: warning: control reaches end of non-void function [-Wreturn-type]

kristian@luke:~$ gcc -Wall -Wextra foo.c
foo.c: In function ‘test_function’:
foo.c:3:24: warning: unused parameter ‘i’ [-Wunused-parameter]
foo.c: In function ‘main’:
foo.c:11:1: warning: control reaches end of non-void function [-Wreturn-type]

kristian@luke:~$ gcc -Wall -Wextra -Wmissing-prototypes foo.c
foo.c:3:6: warning: no previous prototype for ‘test_function’ [-Wmissing-prototypes]
foo.c: In function ‘test_function’:
foo.c:3:24: warning: unused parameter ‘i’ [-Wunused-parameter]
foo.c: In function ‘main’:
foo.c:11:1: warning: control reaches end of non-void function [-Wreturn-type]