Failing to compile a multifile program in c with make - c

Question

I am trying to compile the following multi-file program (taken from the book Programming: a Modern approach, second edition By K. N. King) with a Makefile, but the compilation fails and I get the following warnings and don't understand why:
clang: warning: readline.o: 'linker' input unused [-Wunused-command-line-argument]
clang: warning: inventory2.o: 'linker' input unused [-Wunused-command-line-argument]
clang: warning: argument unused during compilation: '-Wall' [-Wunused-command-line-argument]
here is the makefile:
############
# makefile #
############
CC = gcc
CFLAGS = -c -Wall
BIN=inventory2
$(BIN): $(BIN).o readline.o #readline.h
$(CC) $(CFLAGS) readline.o $(BIN).o -o $(BIN)
$(BIN).o: $(BIN).c
$(CC) $(CFLAGS) $(BIN).c -o $(BIN).o
readline.o: readline.c readline.h
$(CC) $(CFLAGS) readline.c -o readline.o
clean:
$(RM) -rf $(BIN) *.dSYM
$(RM) -rf readline.o
$(RM) -rf $(BIN).o
run: all
./$(BIN)
Here are the source files (inventory2.c, readline.c and readline.h)
/*********************************************************
* From C PROGRAMMING: A MODERN APPROACH, Second Edition *
* By K. N. King *
* Copyright (c) 2008, 1996 W. W. Norton & Company, Inc. *
* All rights reserved. *
* This program may be freely distributed for class use, *
* provided that this copyright notice is retained. *
*********************************************************/
/* inventory.c (Chapter 16, page 391) */
/* Maintains a parts database (array version) */
#include <stdio.h>
#include "readline.h"
#define NAME_LEN 25
#define MAX_PARTS 100
struct part {
int number;
char name[NAME_LEN+1];
int on_hand;
} inventory[MAX_PARTS];
int num_parts = 0; /* number of parts currently stored */
int find_part(int number);
void insert(void);
void search(void);
void update(void);
void print(void);
/**********************************************************
* main: Prompts the user to enter an operation code, *
* then calls a function to perform the requested *
* action. Repeats until the user enters the *
* command 'q'. Prints an error message if the user *
* enters an illegal code. *
**********************************************************/
int main(void)
{
char code;
for (;;) {
printf("Enter operation code: ");
scanf(" %c", &code);
while (getchar() != '\n') /* skips to end of line */
;
switch (code) {
case 'i': insert();
break;
case 's': search();
break;
case 'u': update();
break;
case 'p': print();
break;
case 'q': return 0;
default: printf("Illegal code\n");
}
printf("\n");
}
}
/**********************************************************
* find_part: Looks up a part number in the inventory *
* array. Returns the array index if the part *
* number is found; otherwise, returns -1. *
**********************************************************/
int find_part(int number)
{
int i;
for (i = 0; i < num_parts; i++)
if (inventory[i].number == number)
return i;
return -1;
}
/**********************************************************
* insert: Prompts the user for information about a new *
* part and then inserts the part into the *
* database. Prints an error message and returns *
* prematurely if the part already exists or the *
* database is full. *
**********************************************************/
void insert(void)
{
int part_number;
if (num_parts == MAX_PARTS) {
printf("Database is full; can't add more parts.\n");
return;
}
printf("Enter part number: ");
scanf("%d", &part_number);
if (find_part(part_number) >= 0) {
printf("Part already exists.\n");
return;
}
inventory[num_parts].number = part_number;
printf("Enter part name: ");
read_line(inventory[num_parts].name, NAME_LEN);
printf("Enter quantity on hand: ");
scanf("%d", &inventory[num_parts].on_hand);
num_parts++;
}
/**********************************************************
* search: Prompts the user to enter a part number, then *
* looks up the part in the database. If the part *
* exists, prints the name and quantity on hand; *
* if not, prints an error message. *
**********************************************************/
void search(void)
{
int i, number;
printf("Enter part number: ");
scanf("%d", &number);
i = find_part(number);
if (i >= 0) {
printf("Part name: %s\n", inventory[i].name);
printf("Quantity on hand: %d\n", inventory[i].on_hand);
} else
printf("Part not found.\n");
}
/**********************************************************
* update: Prompts the user to enter a part number. *
* Prints an error message if the part doesn't *
* exist; otherwise, prompts the user to enter *
* change in quantity on hand and updates the *
* database. *
**********************************************************/
void update(void)
{
int i, number, change;
printf("Enter part number: ");
scanf("%d", &number);
i = find_part(number);
if (i >= 0) {
printf("Enter change in quantity on hand: ");
scanf("%d", &change);
inventory[i].on_hand += change;
} else
printf("Part not found.\n");
}
/**********************************************************
* print: Prints a listing of all parts in the database, *
* showing the part number, part name, and *
* quantity on hand. Parts are printed in the *
* order in which they were entered into the *
* database. *
**********************************************************/
void print(void)
{
int i;
printf("Part Number Part Name "
"Quantity on Hand\n");
for (i = 0; i < num_parts; i++)
printf("%7d %-25s%11d\n", inventory[i].number,
inventory[i].name, inventory[i].on_hand);
}
File readline.c:
/*********************************************************
* From C PROGRAMMING: A MODERN APPROACH, Second Edition *
* By K. N. King *
* Copyright (c) 2008, 1996 W. W. Norton & Company, Inc. *
* All rights reserved. *
* This program may be freely distributed for class use, *
* provided that this copyright notice is retained. *
*********************************************************/
/* readline.c (Chapter 16, page 395) */
#include <ctype.h>
#include <stdio.h>
#include "readline.h"
int read_line(char str[], int n)
{
int ch, i = 0;
while (isspace(ch = getchar()))
;
while (ch != '\n' && ch != EOF) {
if (i < n)
str[i++] = ch;
ch = getchar();
}
str[i] = '\0';
return i;
}
and readline.h:
/*********************************************************
* From C PROGRAMMING: A MODERN APPROACH, Second Edition *
* By K. N. King *
* Copyright (c) 2008, 1996 W. W. Norton & Company, Inc. *
* All rights reserved. *
* This program may be freely distributed for class use, *
* provided that this copyright notice is retained. *
*********************************************************/
/* readline.h (Chapter 16, page 395) */
#ifndef READLINE_H
#define READLINE_H
/**********************************************************
* read_line: Skips leading white-space characters, then *
* reads the remainder of the input line and *
* stores it in str. Truncates the line if its *
* length exceeds n. Returns the number of *
* characters stored. *
**********************************************************/
int read_line(char str[], int n);
#endif

Answer 1

You can simplify your Makefile by using implicit rules:
CC = gcc
CFLAGS = -Wall
BIN = inventory2
.PHONY: run clean
$(BIN): $(BIN).o readline.o
readline.o: readline.h
clean:
$(RM) $(BIN) *.o
run: $(BIN)
-./$(BIN)

Answer 2

Look at the Make output:
cc -c -Wall inventory2.c -o inventory2.o
cc -c -Wall readline.c -o readline.o
cc -c -Wall readline.o inventory2.o -o inventory2
cc: warning: readline.o: linker input file unused because linking not done
cc: warning: inventory2.o: linker input file unused because linking not done
The command you are using to attempt to link the executable includes a -c. That's because you have -c in the flags.
Also the run recipe depends on a non-existing target.
Remove the -o from the compilationg commands and the -c from the linking commands.
############
# makefile #
############
CC=cc
CFLAGS=-Wall
BIN=inventory2
$(BIN): $(BIN).o readline.o #readline.h
$(CC) $(CFLAGS) readline.o $(BIN).o -o $(BIN)
$(BIN).o: $(BIN).c
$(CC) $(CFLAGS) $(BIN).c -c
readline.o: readline.c readline.h
$(CC) $(CFLAGS) readline.c -c
clean:
$(RM) -rf $(BIN) *.dSYM
$(RM) -rf readline.o
$(RM) -rf $(BIN).o
run: $(BIN)
./$(BIN)