想用sprintf打印浮点数时出现问题

发布于 2011-04-11 23:12:38 浏览：11990 订阅该版

大家好，刚接触RTT，第一感觉shell做的很好，调试起来很方便，所以开始在这个平台上做一些东西。
现在我遇到一个问题：
我想用sprintf把浮点数打印出来的时候就出现hard fault。
代码如下：
```c
void ds18b20_thread_entry(void * parameter)
{
  char __string[10];
  float __T;

ds18b20_init();
  while(ds18b20_check() == 0)
  {
    lcd_showString(30,110,"DS18B20 detecting..");
    rt_thread_delay(100);
  }
  lcd_showString(30,110,"DS18B20 detected   ");
  lcd_showString(30,130,"Temperate:");
  while(1)
  {
    __T = ds18b20_getTemp();
    sprintf(__string, "%f", __T);
    lcd_showString(110,130,(const char*)__string);
    rt_thread_delay(200);
  }
}
```

编译器：Sourcery G++ Lite 2009q3-68
注：线程创建时使用动态内存方式。

使用sprintf打印浮点编译时提示缺少函数_sbrk。于是从网上找了一下这个函数。加进去重新编译通过，但运行完sprintf()，再接着跑rt_thread_delay()的时候就出现hard fault了。
```c
#include <sys/types.h>

extern int  __HEAP_START;

caddr_t _sbrk ( int incr )
{
  static unsigned char *heap = NULL;
  unsigned char *prev_heap;

if (heap == NULL)
  {
    heap = (unsigned char *)&__HEAP_START;
  }
  prev_heap = heap;
  /* check removed to show basic approach */

heap += incr;

return (caddr_t) prev_heap;
}
```
__HEAP_START在linkerscript里面定义的
```c
......
        /* This is used by the startup in order to initialize the .bss secion */
        _ebss = . ;
        _estack = .;
        
        *(.bss.init)
    } > DATA
    __bss_end = .;

_end = .;
    PROVIDE(__HEAP_START = _end );

/* Stabs debugging sections.  */
    .stab          0 : { *(.stab) }
    .stabstr       0 : { *(.stabstr) }
......
```

不知道是不是`_sbrk ()`定义的heap跟系统用的heap重叠了，请问问题主要出在哪里，还有其他方法打印浮点数吗？
谢谢
![file.png](/uploads/2392_1bd2f84b86fdf84ce755f22d2daca095.png)
![file.png](/uploads/2392_2a53336e39358ad2860ffb161b5f46a3.png)

8 个回答

bernard 2011-04-12

这家伙很懒，什么也没写！

020gzh 2011-04-12

这家伙很懒，什么也没写！

bernard 2011-04-12

这家伙很懒，什么也没写！

020gzh 2011-04-12

这家伙很懒，什么也没写！

bernard 2011-04-12

这家伙很懒，什么也没写！

020gzh 2011-04-13

这家伙很懒，什么也没写！

我把RT_USING_NEWLIB给define了，然后再把componentslibc
ewlib下的代码加入，重新编译。得到很多implicit declaration of function 的警告以及以下的错误:

```
undefined reference to `mkdir'	syscalls.c	/STM32_test/program/os/components/libc/newlib	line 0	C/C++ Problem
undefined reference to `rt_console_init'	libc.c	/STM32_test/program/os/components/libc/newlib	line 0	C/C++ Problem
```

下面是rtconfig.h的内容

```
/* RT-Thread config file */
#ifndef __RTTHREAD_CFG_H__
#define __RTTHREAD_CFG_H__

/* RT_NAME_MAX*/
#define RT_NAME_MAX	10

/* RT_ALIGN_SIZE*/
#define RT_ALIGN_SIZE	4

/* PRIORITY_MAX */
#define RT_THREAD_PRIORITY_MAX	32

/* Tick per Second */
#define RT_TICK_PER_SECOND	100

/* SECTION: RT_DEBUG */
/* Thread Debug */
#define RT_DEBUG
#define RT_THREAD_DEBUG

#define RT_USING_OVERFLOW_CHECK

/* Using Hook */
//#define RT_USING_HOOK

/* Using Software Timer */
/* #define RT_USING_TIMER_SOFT */
#define RT_TIMER_THREAD_PRIO		4
#define RT_TIMER_THREAD_STACK_SIZE	512
#define RT_TIMER_TICK_PER_SECOND	10

/* SECTION: IPC */
/* Using Semaphore*/
#define RT_USING_SEMAPHORE

/* Using Mutex */
#define RT_USING_MUTEX

/* Using Event */
#define RT_USING_EVENT

/* Using MailBox */
#define RT_USING_MAILBOX

/* Using Message Queue */
#define RT_USING_MESSAGEQUEUE

/* SECTION: Memory Management */
/* Using Memory Pool Management*/
#define RT_USING_MEMPOOL

/* Using Dynamic Heap Management */
#define RT_USING_HEAP

/* Using Small MM */
#define RT_USING_SMALL_MEM

/* SECTION: Device System */
/* Using Device System */
#define RT_USING_DEVICE
#define RT_USING_UART1

/* SECTION: Console options */
#define RT_USING_CONSOLE
/* the buffer size of console*/
#define RT_CONSOLEBUF_SIZE	128

/* SECTION: finsh, a C-Express shell */
#define RT_USING_FINSH
/* Using symbol table */
#define FINSH_USING_SYMTAB
#define FINSH_USING_DESCRIPTION

/* SECTION: the runtime libc library */
/* the runtime libc library */
#define RT_USING_NEWLIB
#define RT_USING_DFS_DEVFS

/* SECTION: device filesystem */
//#define RT_USING_DFS
//#define RT_USING_DFS_ELMFAT

/* the max number of mounted filesystem */
//#define DFS_FILESYSTEMS_MAX			2
/* the max number of opened files 		*/
//#define DFS_FD_MAX					4
/* the max number of cached sector 		*/
//#define DFS_CACHE_MAX_NUM   		4

/* SECTION: lwip, a lighwight TCP/IP protocol stack */
//#define RT_USING_LWIP
/* LwIP uses RT-Thread Memory Management */
//#define RT_LWIP_USING_RT_MEM
/* Enable ICMP protocol*/
//#define RT_LWIP_ICMP
/* Enable UDP protocol*/
//#define RT_LWIP_UDP
/* Enable TCP protocol*/
//#define RT_LWIP_TCP
/* Enable DNS */
//#define RT_LWIP_DNS

/* the number of simulatenously active TCP connections*/
//#define RT_LWIP_TCP_PCB_NUM	5

/* ip address of target*/
//#define RT_LWIP_IPADDR0	192
//#define RT_LWIP_IPADDR1	168
//#define RT_LWIP_IPADDR2	1
//#define RT_LWIP_IPADDR3	30

/* gateway address of target*/
//#define RT_LWIP_GWADDR0	192
//#define RT_LWIP_GWADDR1	168
//#define RT_LWIP_GWADDR2	1
//#define RT_LWIP_GWADDR3	1

/* mask address of target*/
//#define RT_LWIP_MSKADDR0	255
//#define RT_LWIP_MSKADDR1	255
//#define RT_LWIP_MSKADDR2	255
//#define RT_LWIP_MSKADDR3	0

/* tcp thread options */
//#define RT_LWIP_TCPTHREAD_PRIORITY		12
//#define RT_LWIP_TCPTHREAD_MBOX_SIZE		4
//#define RT_LWIP_TCPTHREAD_STACKSIZE		1024

/* ethernet if thread options */
//#define RT_LWIP_ETHTHREAD_PRIORITY		15
//#define RT_LWIP_ETHTHREAD_MBOX_SIZE		4
//#define RT_LWIP_ETHTHREAD_STACKSIZE		512

#endif
```

我现在只加了kernel，finsh，和newlib的代码到里面

![](http://www.rt-thread.org/phpBB3/download/file.php?mode=view&id=586&sid=d87071bad3cd17a2bb34dd191df0b70d)

![](http://www.rt-thread.org/phpBB3/download/file.php?mode=view&id=587&sid=d87071bad3cd17a2bb34dd191df0b70d)