How do I link object files in C? Fails with “Undefined symbols for architecture x86_64”

Question

So I\'m trying trying to use a function defined in another C (file1.c) file in my file (file2.c). I\'m including the header of file1 (file1.h) in order to do this.

H

Answer 1

Add foo1.c , foo2.c , foo3.c and makefile in one folder the type make in bash

if you do not want to use the makefile, you can run the command

gcc -c foo1.c foo2.c foo3.c

then

gcc -o output foo1.o foo2.o foo3.o

foo1.c

#include 
#include 

void funk1();

void funk1() {
    printf ("\nfunk1\n");
}


int main(void) {

    char *arg2;
    size_t nbytes = 100;

    while ( 1 ) {

        printf ("\nargv2 = %s\n" , arg2);
        printf ("\n:> ");
        getline (&arg2 , &nbytes , stdin);
        if( strcmp (arg2 , "1\n") == 0 ) {
            funk1 ();
        } else if( strcmp (arg2 , "2\n") == 0 ) {
            funk2 ();
        } else if( strcmp (arg2 , "3\n") == 0 ) {
            funk3 ();
        } else if( strcmp (arg2 , "4\n") == 0 ) {
            funk4 ();
        } else {
            funk5 ();
        }
    }
}

foo2.c

#include 
void funk2(){
    printf("\nfunk2\n");
}
void funk3(){
    printf("\nfunk3\n");
}

foo3.c

#include 

void funk4(){
    printf("\nfunk4\n");
}
void funk5(){
    printf("\nfunk5\n");
}

makefile

outputTest: foo1.o foo2.o foo3.o
    gcc -o output foo1.o foo2.o foo3.o
    make removeO

outputTest.o: foo1.c foo2.c foo3.c
    gcc -c foo1.c foo2.c foo3.c

clean:
    rm -f *.o output

removeO:
    rm -f *.o