Makefile fails on ubuntu 14.04 - undefined reference

Question

I can't get this Makefile to work. This is the simplest example. Below is the code and error:

main.c

#include <stdio.h>
#include <stdlib.h>
#include "hello.h"

int main(){
    hello();
    return EXIT_SUCCESS;
}

hello.c

#include<stdio.h>
#include "hello.h"

void hello(void){
    printf("Hello World\n");
}

hello.h

#ifndef _HELLO_H
#define _HELLO_H

void hello(void);

#endif

Makefile

CC=gcc -Wall -pedantic 

prog: main.o hello.o
    ${CC} -o prog main.o hello.o
main.o: main.c hello.h
    ${CC} -o main.o main.c
hello.o: hello.c hello.h
    ${CC} -o hello.o hello.c

Error:

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

Simply writing

gcc -o prog main.c hello.c

works.

Answer 1

您忘记告诉编译器在生成目标文件时只希望进行部分编译（即不进行链接）。

    ${CC} -c -o xxx.o xxx.c