Understanding Makefiles: undefined symbols for x86_64 (Mac) - c

Question

This following is an OS simulator called USLOSS. The main.c is executed in the phase1.a library, and this is the 4th phase of the project. Below is generated from a call to make test00
gcc -Wall -g -I./usloss/include -D_XOPEN_SOURCE -D_XOPEN_SOURCE -L. -L./usloss/lib testcases/test00.c -o testcases/test00
testcases/test00.c:18:5: warning: implicit declaration of function
'GetTimeofDay' is invalid in C99 [-Wimplicit-function-declaration]
GetTimeofDay(&begin);
^
testcases/test00.c:30:5: warning: implicit declaration of function 'Terminate'
is invalid in C99 [-Wimplicit-function-declaration]
Terminate(1);
^
testcases/test00.c:44:5: warning: implicit declaration of function 'Spawn' is
invalid in C99 [-Wimplicit-function-declaration]
Spawn("Child1", Child, "1", USLOSS_MIN_STACK, 4, &pid);
^
testcases/test00.c:49:5: warning: implicit declaration of function 'Wait' is
invalid in C99 [-Wimplicit-function-declaration]
Wait(&pid, &status);
^
4 warnings generated.
Undefined symbols for architecture x86_64:
"_GetTimeofDay", referenced from:
_Child in test00-4284b8.o
"_Sleep", referenced from:
_Child in test00-4284b8.o
"_Spawn", referenced from:
_start4 in test00-4284b8.o
"_Terminate", referenced from:
_Child in test00-4284b8.o
_start4 in test00-4284b8.o
"_USLOSS_Console", referenced from:
_Child in test00-4284b8.o
_start4 in test00-4284b8.o
"_Wait", referenced from:
_start4 in test00-4284b8.o
"_main", referenced from:
implicit entry/start for main executable
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [testcases/test00] Error 1
make test00 should create an executable version of the test00.c file, but I don't understand why the program is failing to link. Supplied is my Makefile
TARGET = libphase4.a
ASSIGNMENT = 452phase1
CC = gcc
AR = ar
COBJS = phase4.o libuser.o
CSRCS = ${COBJS:.o=.c}
#PHASE1LIB = phase1
#PHASE2LIB = phase2
#PHASE3LIB = phase3
PHASE1LIB = phase1debug
PHASE2LIB = phase2debug
PHASE3LIB = phase3debug
HDRS = phase1.h phase2.h phase3.h phase4.h libuser.h provided_prototypes.h
INCLUDE = ./usloss/include
CFLAGS = -Wall -g -I${INCLUDE}
CFLAGS += -D_XOPEN_SOURCE
UNAME := $(shell uname -s)
ifeq ($(UNAME), Darwin)
CFLAGS += -D_XOPEN_SOURCE # use for Mac, NOT for Linux!!
endif
LDFLAGS = -L. -L./usloss/lib
PHASE4 = /home/cs452/fall15/phase4
ifeq ($(PHASE4), $(wildcard $(PHASE4)))
LDFLAGS += -L$(PHASE4)
endif
TESTDIR = testcases
TESTS = test00 test01 test02 test03 test04 test05 test06 test07 test08 \
test09 test10 test11 test12 test13 test14 test15 test16 test17 \
test18 test19 test20 test21 test22
LIBS = -lusloss -l$(PHASE1LIB) -l$(PHASE2LIB) -l$(PHASE3LIB) -lphase4
$(TARGET): $(COBJS)
$(AR) -r $# $(COBJS)
#$(TESTS): $(TARGET) $(TESTDIR)/$$#.c
$(TESTS): $(TARGET)
$(CC) $(CFLAGS) -I. -c $(TESTDIR)/$#.c
$(CC) $(LDFLAGS) -o $# $#.o $(LIBS)
clean:
rm -f $(COBJS) $(TARGET) test??.o test?? core term*.out
phase4.o: phase4.c libuser.c
submit: $(CSRCS) $(HDRS) Makefile
tar cvzf phase4.tgz $(CSRCS) $(HDRS) Makefile
I don't understand Makefiles well enough to understand what is happening with the linker. Also supplied is the test00.c
#include <stdlib.h>
#include <stdio.h>
#include <usloss.h>
#include "phase1.h"
#include "phase2.h"
#include <usyscall.h>
#include "libuser.h"
#include <assert.h>
#define ABS(a,b) a-b > 0 ? a-b : -(a-b)
int Child(char *arg)
{
int begin, end, time;
int me = atoi(arg);
USLOSS_Console("Child%d(): Going to sleep for 10 seconds\n", me);
GetTimeofDay(&begin);
Sleep(10);
GetTimeofDay(&end);
time = end - begin;
time = ABS(10000000, time);
if (time > 1000000) {
USLOSS_Console("Child%d(): Sleep bad: %d %d\n",
me, time, ABS(10000000, time));
}
else {
USLOSS_Console("Child%d(): Sleep done at time %d\n", me, end);
}
Terminate(1);
return 0;
} /* Child */
int start4(char *arg)
{
int pid, status;
USLOSS_Console("start4(): Start 5 children who all sleep for 10 seconds. Upon\n");
USLOSS_Console(" waking up, each child checks if its sleep time was at\n");
USLOSS_Console(" least 10 seconds.\n");
Spawn("Child1", Child, "1", USLOSS_MIN_STACK, 4, &pid);
Spawn("Child2", Child, "2", USLOSS_MIN_STACK, 4, &pid);
Spawn("Child3", Child, "3", USLOSS_MIN_STACK, 4, &pid);
Spawn("Child4", Child, "4", USLOSS_MIN_STACK, 4, &pid);
Spawn("Child5", Child, "5", USLOSS_MIN_STACK, 4, &pid);
Wait(&pid, &status);
Wait(&pid, &status);
Wait(&pid, &status);
Wait(&pid, &status);
Wait(&pid, &status);
USLOSS_Console("start4(): Test sleep done.\n");
Terminate(0);
return 0;
}
Why does this linker error happen and what can I do to fix it and test my files? The result should be an executable .o file to run and see the output.

Answer 1

I'm in your class. It looks like you need to use the MacOSX libraries.