怎么解决STM32（MDK）中不能使用printf()函数的问题

#ifdef __GNUC__ 

/* With GCC/RAISONANCE, small printf (option LD Linker->Libraries->Small printf 

     set to 'Yes') calls __io_putchar() */ 

#define PUTCHAR_PROTOTYPE int __io_putchar(int ch) 

#else 

#define PUTCHAR_PROTOTYPE int fputc(int ch, FILE *f) 

#endif /* __GNUC__ */ 

PUTCHAR_PROTOTYPE 

{ 

/* Place your implementation of fputc here */ 

/* e.g. write a character to the USART */ 

USART_SendData(USART1, (uint8_t) ch); 

/* Loop until the end of transmission */ 

while (USART_GetFlagStatus(USART1, USART_FLAG_TC) == RESET); 

return ch; 

} 

#pragma import(__use_no_semihosting)  

_sys_exit(int x)  

{  

x = x;  

}  

struct __FILE  

{  

int handle;  

/* Whatever you require here. If the only file you are using is */  

/* standard output using printf() for debugging, no file handling */  

/* is required. */  

};  

/* FILE is typedef’ d in stdio.h. */  

FILE __stdout; 

#pragma import(__use_no_semihosting)   

/******************************************************************************   

*标准库需要的支持函数   

******************************************************************************/   

struct __FILE   

{   

int handle;   

/* Whatever you require here. If the only file you are using is */   

/* standard output using printf() for debugging, no file handling */   

/* is required. */   

};   

/* FILE is typedef’ d in stdio.h. */   

FILE __stdout;   



/// <summary>   

/// 定义_sys_exit()以避免使用半主机模式   

/// </summary>   

/// <param name="x"></param>   

/// <returns></returns>   

_sys_exit(int x)   

{   

x = x;   

}   







int fputc(int ch, FILE *f)  

{  

    //USART_SendData(USART1, (u8) ch);  

    USART1->DR = (u8) ch;  

      

    /* Loop until the end of transmission */  

    while(USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET) 

    {  

    }  



    return ch;  

}  

externvoidsendchar(char*ch); 

intfputc(intch,FILE*f) 

｛/*e.g.writeacharactertoanUART*/ 

chartempch=ch; 

sendchar(&tempch); 

returnch; 

｝