newlib中malloc如何获取heap地址

newlib代码：

caddr_t
_sbrk (int incr)
{
  extern char   end asm ("end");    /* Defined by the linker.  */
  static char * heap_end;
  char *        prev_heap_end;

  if (heap_end == NULL)
    heap_end = & end;
  
  prev_heap_end = heap_end;
  
  if (heap_end + incr > stack_ptr)
    {
      /* Some of the libstdc++-v3 tests rely upon detecting
     out of memory errors, so do not abort here.  */
#if 0
      extern void abort (void);

      _write (1, "_sbrk: Heap and stack collision\n", 32);
      
      abort ();
#else
      errno = ENOMEM;
      return (caddr_t) -1;
#endif
    }
  
  heap_end += incr;

  return (caddr_t) prev_heap_end;
}

第一次调用使用end符号获取堆的起始地址，因此只需要在链接文件中在heap起始地址定义end标号即可。

   .heap 0x00200000 (NOLOAD):
    {
        . = ALIGN(64);
    __heap_start = .;
        PROVIDE(end = .);
        . = . + 0xA0000;
    __end__ = .;
    }

如上，使用PROVIDE声明了end标号。

标签：__,malloc,end,newlib,incr,char,abort,heap
来源： https://blog.csdn.net/qq_14892521/article/details/118753374