我在尝试使用 STM32CubeIDE（通常是 STM32CubeIDE 的标准安装）在 STM32 上运行 std::cout 时遇到问题。
我已经查阅了许多有关出于 stdio.h 和 printf 目的而重定向 UART 的资料，但我正在尝试使用 std::cout 在 C++ 环境中实现这一切。 我找到的主要来源在这里：https://www.keil.com/support/man/docs/armlib/armlib_chr1358938931411.htm
根据包含标题的方式和时间，我会收到不同的错误，这是我尝试过的：
重定向.h：
#ifndef _RETARGET_H__
#define _RETARGET_H__
#include "stm32f1xx_hal.h"
#include <sys/stat.h>
#include <stdio.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);
namespace std {
int fputc(int, FILE *);
}
#endif //#ifndef _RETARGET_H__
retarget.cc（删减了一点）[更正这是一个 C++ 文件]
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 _write(int fd, char* ptr, int len) {
HAL_StatusTypeDef hstatus;
if (fd == STDOUT_FILENO || fd == STDERR_FILENO) {
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;
}
namespace std {
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 __stdout;
FILE __stdin;
FILE __stderr;
int fputc(int c, FILE *stream)
{
char tOut = c;
return _write(STDOUT_FILENO, &tOut, 1);
/* Your implementation of fputc(). */
}
}
和 main.cpp（也被剪掉了一点）：
#include "retarget.h"
#include <iostream>
int main(void)
{
/* HAL Init stuff Clipped */
RetargetInit(&huart1);
std::cout << "\n\nSTM32 main.c Startup\n" << std::endl;
while(1){
std::cout << "*";
HAL_Delay(1000);
}
}
如果我使用 printf（将 std::cout 更改为 printf），则一切正常，因此 _write 函数可以正确发送到 UART，所以我知道一切正常。
现在，来看看错误。
如所呈现的，编译器抛出：
In file included from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\ext\string_conversions.h:43,
from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\bits\basic_string.h:6557,
from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\string:55,
from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\bits\locale_classes.h:40,
from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\bits\ios_base.h:41,
from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\ios:42,
from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\ostream:38,
from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\iostream:39,
from ../Core/Src/main.cc:26:
c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\cstdio:111:11: error: 'int fputc(int, FILE*)' conflicts with a previous declaration
111 | using ::fputc;
| ^~~~~
In file included from ../Core/Src/main.cc:25:
../Core/Inc/retarget.h:23:5: note: previous declaration 'int std::fputc(int, FILE*)'
23 | int fputc(int, FILE *);
| ^~~~~
make: *** [Core/Src/subdir.mk:41: Core/Src/main.o] Error 1
如果我翻转 main.cc 文件中的包含内容，以便首先拉入 iostream，我会得到：
In file included from ../Core/Src/main.cc:26:
../Core/Inc/retarget.h:23:22: error: 'int std::fputc(int, FILE*)' conflicts with a previous declaration
23 | int fputc(int, FILE *);
| ^
In file included from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\cstdio:42,
from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\ext\string_conversions.h:43,
from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\bits\basic_string.h:6557,
from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\string:55,
from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\bits\locale_classes.h:40,
from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\bits\ios_base.h:41,
from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\ios:42,
from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\ostream:38,
from c:{stm32 tools path snipped}arm-none-eabi\include\c++\10.3.1\iostream:39,
from ../Core/Src/main.cc:25:
c:{stm32 tools path snipped}arm-none-eabi\include\stdio.h:214:5: note: previous declaration 'int fputc(int, FILE*)'
214 | int fputc (int, FILE *);
| ^~~~~
make: *** [Core/Src/subdir.mk:41: Core/Src/main.o] Error 1
有什么建议吗？ 预先感谢。
终于偶然发现了解决方案，归结为
_write()所以，解决方案，就我而言：
我将
retarget.ccretarget.cretarget.cretarget.h对于
retarget.hretarget.h#ifndef _RETARGET_H__
#define _RETARGET_H__
#include "stm32f1xx_hal.h"
#include <sys/stat.h>
#include <stdio.h>
#ifdef __cplusplus
extern "C"
{
#endif
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);
#ifdef __cplusplus
} //extern "C"
#endif
#endif //#ifndef _RETARGET_H__
现在一切都按预期进行 -
std::cout << "Working now!" << std::endl;std 流缓冲区函数（如 _write()）的重定向会影响其他流缓冲区处理，例如如果您在项目的其他地方使用 ostraem...
因此我的方法是：创建一个单独的流缓冲区类，其中根据您的需要处理写入事件函数。当构造函数被调用时，转发要修改的ostream并覆盖它的流缓冲区。缺点是原始流缓冲区保留为未使用的静态内存分配。
template <class Elem = char, class Tr = std::char_traits<Elem> >
class redirectostream : public std::basic_streambuf<Elem, Tr>
{
public:
redirectostream(std::ostream &streamToChange)
{
//redirect the ostream
streamToChange.rdbuf(this);
};
std::streamsize xsputn(const Elem *_Ptr, std::streamsize _Count)
{
HAL_StatusTypeDef status = HAL_UART_Transmit_IT(&huart1, _Ptr, _Count);
return HAL_OK == status ? _Count: 0;
}
};
//redirect std::cout
redirectostream<> redirectCoutObj(std::cout);
UART 初始化后，您可以按照习惯使用 std:cout。
#include <iostream>
int main(void)
{
HAL_Init();
SystemClock_Config();
MX_USART2_UART_Init();
std::cout << "Hallo World!";
while (1)
{
HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);
HAL_Delay(500);
}
}