二级指针的应用场景之一：在函数外定义指针，在函数中对指针进行赋值，函数调用结束后，实现指针赋值；指针引用代替二级指针实现函数内指针赋值。

hardGreenRookie

于 2019-07-03 20:46:19 发布

阅读量476

点赞数

分类专栏： C/C++ 文章标签：笔记

本文链接：https://blog.youkuaiyun.com/qq_40945306/article/details/94589509

版权

C/C++ 专栏收录该内容

8 篇文章

订阅专栏

本文详细介绍了如何使用C++中的指针进行内存分配与回收，通过具体示例展示了如何利用二级指针和指针引用在函数间传递并修改结构体指针，确保资源的有效管理和避免内存泄漏。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

函数内二级指针完成函数外定义指针赋值：

struct teacher{
	int id;
	char name[64];
};

int get_mem(struct teacher **tpp){
	struct teacher *tp = NULL;
	tp = (struct teacher*)malloc(sizeof(struct teacher));
	if(tp == NULL){
		return -1;
	}
	tp->id = 100;
	strcpy(tp->name,"lisi");
	*tpp = tp;
	return 0;
}

int get_mem2(struct teacher* &tpp){
	tpp = (struct teacher*)malloc(sizeof(struct teacher));
	if(tpp == NULL){
		return -1;
	}
	tpp->id = 1000;
	strcpy(tpp->name,"wang5");
	return 0;
}

void free_teacher(struct teacher **tpp){
	if(tpp == NULL)
		return;
	struct teacher *tp = *tpp;
	if(tp != NULL){
		free(tp);
		*tpp = NULL;
	}
}
int main(void){
	
	struct teacher *tp = NULL;
	get_mem(&tp);
	cout<<tp->id<<" "<<tp->name<<endl;
	free_teacher(&tp);
	return 0;
}

用指针引用实现函数外定义指针，在函数内对指针赋值：

struct teacher{
	int id;
	char name[64];
};


int get_mem2(struct teacher* &tpp){
	tpp = (struct teacher*)malloc(sizeof(struct teacher));
	if(tpp == NULL){
		return -1;
	}
	tpp->id = 1000;
	strcpy(tpp->name,"wang5");
	return 0;
}

void free_teacher2(struct teacher* &tpp){
	if(tpp != NULL){
		free(tpp);
		tpp = NULL;
	}
}
int main(void){
	
	struct teacher *tp = NULL;
	get_mem2(tp);
	cout<<tp->id<<" "<<tp->name<<endl;
	free_teacher2(tp);
	return 0;
}