8.7

8.7/Makefile

+CC=gcc
+OBJS=main.o func.o
+
+test: $(OBJS)
+	$(CC) -o $@ $^
+
+id: main.o id_func.o
+	$(CC) -o test $(OBJS)
+
+main.o: main.c
+	$(CC) -c main.c
+
+func.o: func.c
+	$(CC) -c func.c
+
+id_func.o: func.c
+	$(CC) -DPRINT_ID -c func.c
+	
+clean:
+	rm $(OBJS) test

8.7/func.c

+#include <stdio.h>
+#include "func.h"
+
+int func_name_or_id()
+{
+#ifdef PRINT_ID
+	printf("201920756\n");
+	return 0;
+#else
+	printf("Jangwon Lee\n");
+	return 1;
+#endif
+}

8.7/func.h

+#pragma once
+
+extern int func_name_or_id();

8.7/main.c

+#include "func.h"
+
+int main()
+{
+	func_name_or_id();
+}