Keil C51调试

*** WARNING L15: MULTIPLE CALL TO SEGMENT
SEGMENT: ?PR?PRINTF?PRINTF
CALLER1: ?C_C51STARTUP
CALLER2: ?PR?INT0?TEXT4
Program Size: data=51.2 xdata=0 code=1173
Target not created
怎么会这样子的??
问题补充：#include <reg51.h>
#include<stdio.h>
Uart_Init();
main()
{ Uart_Init();
EX0=1;
EA=1;
while(1);
}
void int0() interrupt 0 using 0
{ printf("External Interrupt 0 responded\n");
}
Uart_Init()
{SCON = 0x52; /* 设置串行口控制寄存器SCON*/
TMOD = 0x20; /* 12M时钟时波特率为2400 */
TCON = 0x69; /* TCON */
TH1 = 0xf3; /* TH1 */
}