stackoverflow https://stackoverflow.com/questions/52305098/makefile-fails-implicit-rule-compiles-one-object-file-but-doesnt-compile-the

defs.h

#ifndef DEFS_H
#define DEFS_H

#ifdef __cplusplus
extern "C" {
#endif

#ifdef __cplusplus
}
#endif

#endif /* DEFS_H */

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

hello.c

#include "defs.h"

void display_hello()
{
    printf("Hello!\n");
}

hello.h

#ifndef HELLO_H
#define HELLO_H

#ifdef __cplusplus
extern "C" {
#endif

#ifdef __cplusplus
}
#endif

#endif /* HELLO_H */

void display_hello();

main.c

#include "defs.h"
#include "hello.h"

int main(int argc, char** argv) {
   display_hello();
   return (EXIT_SUCCESS);
}

Makefile

objects = main.o hello.o
hello : $(objects)
	cc -o hello $(objects)

hello.o : defs.h
main.o : defs.h hello.h

.PHONY : clean
clean :
	-rm hello $(objects)