网上绝大部分都在说在重定向printf时候只要重写fputc函数并勾选微库来实现
但是那是keil才有的微库，如果不勾选微库，就得先停用标准库的半主机模式，再重写。。。
但是对于stm32cubeide和clion这种目前不是主流但是体验很好的armgcc编译器来说，上述方法完全不管用，题主在很长一段时间内只能用自带的haltransmit发送。字符串倒无所谓，变量真的是麻烦。
于是，看见知乎某篇帖子（应该是知乎）写的很详细，也是关于这个问题的解决方法
在其基础上优化一下，用于契合clion的用户
首先创建一个c和h文件，名字随便取名，我的直接复制的帖子中原帖的
retarget.h和retarget.c
retarget.h如下
`// All credit to Carmine Noviello for this code
// https://github.com/cnoviello/mastering-stm32/blob/master/nucleo-f030R8/system/include/retarget/retarget.h
ifndef RETARGET_H_
define RETARGET_H_
include "stm32f4xx_hal.h"
include <sys/stat.h>
void RetargetInit(UART_HandleTypeDef huart);
int _isatty(int fd);
int _write(int fd, char ptr, int len);
int _close(int fd);
int _lseek(int fd, int ptr, int dir);
int _read(int fd, char* ptr, int len);
int _fstat(int fd, struct stat* st);
endif //#ifndef RETARGET_H_`
retarget.c如下
`// All credit to Carmine Noviello for this code
// https://github.com/cnoviello/mastering-stm32/blob/master/nucleo-f030R8/system/src/retarget/retarget.c
include <_ansi.h>
include <_syslist.h>
include <errno.h>
include <sys/time.h>
include <sys/times.h>
include <limits.h>
include <signal.h>
include "retarget.h"
include <stdint.h>
include <stdio.h>
if !defined(OS_USE_SEMIHOSTING)
define STDIN_FILENO 0
define STDOUT_FILENO 1
define STDERR_FILENO 2
UART_HandleTypeDef *gHuart;
void RetargetInit(UART_HandleTypeDef *huart) {
gHuart = huart;
/* Disable I/O buffering for STDOUT stream, so that* chars are sent out as soon as they are printed. */
setvbuf(stdout, NULL, _IONBF, 0);
}
int _isatty(int fd) {
if (fd >= STDIN_FILENO && fd <= STDERR_FILENO)
return 1;
errno = EBADF;
return 0;
}
int _write(int fd, char* ptr, int len) {
HAL_StatusTypeDef hstatus;
if (fd == STDOUT_FILENO || fd == STDERR_FILENO) {
// hstatus = HAL_UART_Transmit_DMA(gHuart, (uint8_t *) ptr, len);
hstatus = HAL_UART_Transmit(gHuart, (uint8_t *) ptr, len, HAL_MAX_DELAY);
if (hstatus == HAL_OK)
return len;
else
return EIO;
}
errno = EBADF;
return -1;
}
int _close(int fd) {
if (fd >= STDIN_FILENO && fd <= STDERR_FILENO)
return 0;
errno = EBADF;
return -1;
}
int _lseek(int fd, int ptr, int dir) {
(void) fd;
(void) ptr;
(void) dir;
errno = EBADF;
return -1;
}
int _read(int fd, char* ptr, int len) {
HAL_StatusTypeDef hstatus;
if (fd == STDIN_FILENO) {hstatus = HAL_UART_Receive(gHuart, (uint8_t *) ptr, 1, HAL_MAX_DELAY);if (hstatus == HAL_OK)return 1;elsereturn EIO;
}
errno = EBADF;
return -1;
}
int _fstat(int fd, struct stat* st) {
if (fd >= STDIN_FILENO && fd <= STDERR_FILENO) {
st->st_mode = S_IFCHR;
return 0;
}
errno = EBADF;
return 0;
}
endif //#if !defined(OS_USE_SEMIHOSTING)`
这时候，主函数加上
RetargetInit(&huart1);
编译的时候会报错，说函数重定义，进去syscalls.c文件，把报错的函数直接注释掉即可
csdn的也是我本人，所以带了水印