gcc4.0 откуда варнинги? o_O

на gcc version 4.0.2 20051125 (Red Hat 4.0.2-8)


инклюды такие

#include <stdio.h>              // Standard i/o header file
#include <sys/types.h>          // File typedefs header file
#include <sys/socket.h>         // Socket structure header file
#include <signal.h>
#include <unistd.h>
#include <math.h>
#ifndef LINUXPC
#include <sys/filio.h>
#include <string.h>
#endif
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <netdb.h>
#include <time.h>
#include <sys/time.h>
#include <errno.h>
#include <strings.h>

теперь делаем make:


cc -DLINUXPC   -c -o socket_demo.o socket_demo.c
socket_demo.c: In function 'main':
socket_demo.c:632: warning: incompatible implicit declaration of built-in function 'exit'
socket_demo.c:640: warning: incompatible implicit declaration of built-in function 'exit'
socket_demo.c: In function 'server':
socket_demo.c:971: warning: incompatible implicit declaration of built-in function 'strcpy'
socket_demo.c:973: warning: incompatible implicit declaration of built-in function 'strlen'
socket_demo.c:994: warning: pointer targets in passing argument 3 of 'accept' differ in signedness
socket_demo.c: In function 'chk_imalive':
socket_demo.c:2715: warning: incompatible implicit declaration of built-in function 'strcpy'
socket_demo.c:2730: warning: incompatible implicit declaration of built-in function 'strcpy'
socket_demo.c:2740: warning: incompatible implicit declaration of built-in function 'strcpy'
socket_demo.c: In function 'e_mail_alert':
socket_demo.c:2761: warning: incompatible implicit declaration of built-in function 'strcpy'
socket_demo.c:2785: warning: incompatible implicit declaration of built-in function 'strcat'
gcc socket_demo.o -o socket_demo


========================
joe +632 socket_demo.c

сожержит строку
...
        exit(1);
...
========================

cat Makefile


CFLAGS = -DLINUXPC

all: socket_demo

socket_demo: socket_demo.o
        gcc socket_demo.o -o socket_demo

clean:
        rm -f socket_demo socket_demo.o



что бы это значило?