在 Contiki 程序中使用 malloc

考虑以下 Contiki 程序。

#include<stdio.h>
#include"contiki.h"
#include <stdlib.h>

static char *mem;
static int x;
/*---------------------------------------------------------------------------*/
PROCESS(test, "test");
AUTOSTART_PROCESSES(&test);
/*---------------------------------------------------------------------------*/
PROCESS_THREAD(test, ev, data)
{
  PROCESS_BEGIN();
  printf("before malloc\n");
  mem=(char*)malloc(10);
  for(x=0;x<10;x++)
     mem[x]=x+1;
  printf("after malloc\n");
  PROCESS_END();
}

当这个程序为native/z1/wismote/cooja编译时，它执行得很好，并且两个printf语句都被执行，但是当为mbxxx目标编译，然后在硬件上执行时，只有第一个printf语句被执行并且代码被卡住在malloc中。这种行为背后有什么猜测或原因吗？我还在这里附上了 GDB 跟踪。

(gdb) mon reset init
target state: halted
target halted due to debug-request, current mode: Thread 
xPSR: 0x01000000 pc: 0x08000efc msp: 0x20000500
(gdb) b test.c:16
Breakpoint 1 at 0x8000ec8: file test.c, line 16.
(gdb) b test.c:17
Breakpoint 2 at 0x8000ece: file test.c, line 17.
(gdb) b test.c:18
Breakpoint 3 at 0x8000ed8: file test.c, line 18.
(gdb) load
Loading section .isr_vector, size 0x84 lma 0x8000000
Loading section .text, size 0xc5c4 lma 0x8000084
Loading section .data, size 0x660 lma 0x800c648
Start address 0x8000084, load size 52392
Transfer rate: 15 KB/sec, 8732 bytes/write.
(gdb) c
Continuing.
Note: automatically using hardware breakpoints for read-only addresses.

Breakpoint 1, process_thread_test (process_pt=0x2000050c <test+12>, ev=129 '\201', data=0x0) at test.c:16
16      printf("before malloc\n");
(gdb) c
Continuing.

Breakpoint 2, process_thread_test (process_pt=0x2000050c <test+12>, ev=<optimized out>, 
    data=<optimized out>) at test.c:17
17  mem=(char*)malloc(10);
(gdb) c
Continuing.
^C
Program received signal SIGINT, Interrupt.
Default_Handler () at ../../cpu/stm32w108/hal/micro/cortexm3/stm32w108/crt-stm32w108.c:87
87  {
(gdb) bt
#0  Default_Handler () at ../../cpu/stm32w108/hal/micro/cortexm3/stm32w108/crt-stm32w108.c:87
#1  <signal handler called>
#2  0x08000440 in _malloc_r ()
#3  0x08000ed4 in process_thread_test (process_pt=0x2000050c <certificate_check+12>, ev=<optimized out>, 
    data=<optimized out>) at test.c:17
#4  0x0800272c in call_process (p=0x20000500 <test>, ev=<optimized out>, data=<optimized out>)
    at ../../core/sys/process.c:190
#5  0x080028e6 in process_post_synch (p=<optimized out>, ev=ev@entry=129 '\201', data=<optimized out>)
    at ../../core/sys/process.c:366
#6  0x0800291a in process_start (p=<optimized out>, arg=arg@entry=0x0) at ../../core/sys/process.c:120
#7  0x08002964 in autostart_start (processes=<optimized out>) at ../../core/sys/autostart.c:57
#8  0x08001134 in main () at ../../platform/mbxxx/./contiki-main.c:210
(gdb)

啊啊……终于解决问题了。之所以存在这个特殊问题，是因为 stm32w108 未配置为使用动态内存。

所需要做的就是打开以下文件： contiki-2.7/cpu/stm32w108/hal/micro/cortexm3/stm32w108/crt-stm32w108.c 并在文件顶部或 _sbrk 实现之前添加 #define USE_HEAP！堆大小也可以在这里修改，而不是从链接描述文件中修改，尽管堆栈大小

附注： 在嵌入式系统中使用动态内存分配是一个非常糟糕的主意，所以要避免它！它肮脏相信我！最终我还将删除所有动态内存分配引用！ :)