ftime() 함수 포함된 소스파일로 make 명령 실행시 오류가 발생합니다.

[cshuap@users ~/paws]$ make
gcc -c -O2 client.c
gcc -o paws_client client.o -lm -O2
client.o(.text+0x25e4): In function `worm_infectee_scan':
: undefined reference to `ftime'
client.o(.text+0x2601): In function `worm_infectee_scan':
: undefined reference to `ftime'
client.o(.text+0x31b5): In function `main':
: undefined reference to `ftime'
client.o(.text+0x31fa): In function `main':
: undefined reference to `ftime'
*** Error code 1

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <netdb.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/timeb.h>
 
int main(int argc, char** argv)
{
  register u_int i, j, k, r, m, n;
  u_int uns;
  FILE *infile;
  char buf1[256], buf2[256], str[64];
  char *cptr1, *cptr2;
  struct timeb start_t, end_t;
  u_int *as_size;
  int i1, i2;
 
 //길어서 생략 합니다.
 
  ftime(&start_t); //simulation start time
  printf("_____________________________________________________\n");
  printf("Time\tInf\tUpdate\tDropped\tPassed\tBuffered_scans\n");
  i = 0;
  while (i < SIMULATION_DURATION) {
    worm_infectee_scan(i);
    i++;
  }
  ftime(&end_t);
  j = end_t.time*1000 + end_t.millitm - start_t.time*1000 - start_t.millitm;
  printf("Real time used on machine <%d>: %dh%dm%d\n", host_id, j/3600000, j%3600000/60000, j%60000/1000);
  printf("Total time used for communication: %dm%ds\n", com_time/60000, com_time/60000%1000);
  fflush(stdout);
}