前言
- 有童鞋说在gcc下，vsnprintf来替代rt_vsnprintf来打印浮点会引发死机
- 经过实际验证，没有发现死机
- 但并不建议直接用vsnprintf来替代rt_vsnprintf，打印浮点多半用于调试，可以独立成一个专门的打印函数
- vsnprintf只是用于把浮点格式化到字符串，只要字符串长度不溢出，理论上不会造成死机
- 如果发现死机，需要确认打印的环境，如中断中，尤其在串口输出的情况下
- RT-Thread Studio
arm-none-eabi-gcc环境：未发现死机现象 - Keil MDK5 环境：未发现死机现象
- cygwin gcc 环境：未发现死机现象
- 可以正常的用于浮点数的调试打印
/*
* Copyright (c) 2006-2018, RT-Thread Development Team
*
* SPDX-License-Identifier: Apache-2.0
*
* Change Logs:
* DateAuthorNotes
* 2018-11-06SummerGiftchange to new framework
*/#include
#include
#include
#include "drv_gpio.h"
/* defined the LED0 pin: PA5 */
#define LED0_PINGET_PIN(A, 5)#include #define DBG_BUFF_MAX_LEN256/* debug print : support float double */
int dbg_printf(const char *fmt, ...)
{
va_list args;
static char rt_log_buf[DBG_BUFF_MAX_LEN] = { 0 };
va_start(args, fmt);
int length = vsnprintf(rt_log_buf, sizeof(rt_log_buf) - 1, fmt, args);
rt_kputs(rt_log_buf);
return length;
}int main(void)
{
double a = 334455.00123345;
double b = 667788.14234234;
dbg_printf("double a = %lf\r\n", a);
int count = 1;
/* set LED0 pin mode to output */
rt_pin_mode(LED0_PIN, PIN_MODE_OUTPUT);
while (count++)
{
rt_pin_write(LED0_PIN, PIN_HIGH);
dbg_printf("double a + b = %lf\r\n", a+b+count);
rt_thread_mdelay(1000);
rt_pin_write(LED0_PIN, PIN_LOW);
rt_thread_mdelay(2000);
}return RT_EOK;
}
- cygwin的测试
/* vsnprintf example */
#include
#include #define DBG_BUFF_MAX_LEN256/* debug print : support float double */
int dbg_printf(const char *fmt, ...)
{
va_list args;
static char rt_log_buf[DBG_BUFF_MAX_LEN] = { 0 };
va_start(args, fmt);
int length = vsnprintf(rt_log_buf, sizeof(rt_log_buf) - 1, fmt, args);
printf("%s\r\n", rt_log_buf);
return length;
}
int main ()
{
double a = 123453.0001444;
dbg_printf("%lf", a);
return 0;
}
输出效果
msh >
\ | /
- RT -Thread Operating System
/ | \4.1.0 build Feb3 2022 21:11:28
2006 - 2022 Copyright by RT-Thread team
double a = 334455.001233
double a + b = 1002245.143576
msh >double a + b = 1002246.143576
double a + b = 1002247.143576
double a + b = 1002248.143576
double a + b = 1002249.143576
double a + b = 1002250.143576
double a + b = 1002251.143576
double a + b = 1002252.143576
double a + b = 1002253.143576
double a + b = 1002254.143576
double a + b = 1002255.143576
double a + b = 1002256.143576
double a + b = 1002257.143576
double a + b = 1002258.143576
double a + b = 1002259.143576
double a + b = 1002260.143576
double a + b = 1002261.143576
- cygwin的打印：
$ ./a.exe
123453.000144
小结
- rt_kprintf，采用不依赖标准C库的方式，主要目的是为了减少ROM（Flash）的占用
- 如果实际中需要浮点打印（如打印到串口、打印到文件），可以基于
vsnprintf编写一个简单的全功能格式打印函数 - RT-Thread ulog可以开启浮点支持，开启后使用：
vsnprintf
