C99中结构体最后一个成员允许一个大小未知的数组
sizeof 返回的这种结构大小不包括柔性数组的内存
            
            
              c
              
              
            
          
          struct s
{
	int n; 
	int arr[];//柔性数组成员
};
int main()
{
	int sz = sizeof(struct  s);
	printf("%d\n", sz); //4
	return 0;
}包含柔性数组成员的结构用malloc ()函数进行内存的动态分配,并且分配的内存应该大于结构的大 小,以适应柔性数组的预期大小。
两种实现,推荐第一种
第一种
            
            
              c
              
              
            
          
          	struct s* ps = (struct s*)malloc(sizeof(struct s) + 40);
	if (ps == NULL)
		return 1;
	ps->n == 100;
	int i = 0;
	for (i = 0; i < 10; i++)
	{
		ps->arr[i] = i;
	}
	for (i = 0; i < 10; i++)
	{
		printf("%d ", ps->arr[i]);
	}
	struct s* ptr = realloc(ps, sizeof(struct s) + 80);
	if (ptr != NULL)
	{
		ps = ptr;
	}
	free(ps);
	ps = NULL;第二种
            
            
              c
              
              
            
          
          struct s
{
	int n;
	int* arr;
};
int main()
{
	struct s* ps = (struct s*)malloc(sizeof(struct s));
	if (ps == NULL)
		return 1;
	ps->n = 100;
	ps->arr = (int*)malloc(40);
	if (ps->arr == NULL)
		return 1;
	int i = 0;
	for (i = 0; i < 10; i++)
	{
		ps->arr[i] = i;
	}
	for (i = 0; i < 10; i++)
	{
		printf("%d ", ps->arr[i]);
	}
	
	//扩容
	int* ptr = (int*)realloc(ps->arr,80);
	if (ptr == NULL)
		return 1;
	else
		ps = ptr;
	//释放
	free(ps->arr);
	free(ps);
	ps = NULL;
	return 0;
}