当前位置:网站首页>C杂讲 浅拷贝 与 深拷贝
C杂讲 浅拷贝 与 深拷贝
2022-07-06 09:04:00 【Bright-SKY】
目录
知识点1【知识点的引入】
1、当结构体中存在指针成员变量时,进行结构体变量拷贝操作时,存在浅拷贝与深拷贝差别问题。
即:浅拷贝时,拷贝后两个结构体变量中指针成员变量指向同一个地址
深拷贝时,拷贝后两个结构体变量中指针成员变量指向不同地址
typedef struct
{
int num;
char *name;//指针变量作为 结构体的成员
}DATA;
void test01()
{
DATA data={100,"hehehehaha"};
printf("%d\n",sizeof(DATA));//8字节
printf("num = %d\n",data.num);
//指针变量作为结构体的成员 保存的是空间的地址
printf("name = %s\n",data.name);
}
2、指针变量 作为结构体的成员 操作前 必须有合法的空间
void test02()
{
DATA data;
printf("%d\n",sizeof(DATA));
printf("num = %d\n",data.num);
//指针变量 作为结构体的成员 操作前 必须有合法的空间
//data.name = "hehe";
//给name 事先申请 一块 堆区空间
data.name = (char *)calloc(1,10);
strcpy(data.name,"hahaha");
printf("name = %s\n",data.name);
//如果name指向堆区空间 一定要记得释放
if(data.name != NULL)
{
free(data.name);
data.name = NULL;
}
}
原理图分析:
3、指针变量 作为结构体的成员 结构体变量间的赋值操作 容易导致“浅拷贝”发生
void test03()
{
DATA data1;
DATA data2;
data1.num = 100;
data1.name = (char *)calloc(1,10);
strcpy(data1.name,"my data");
printf("data1:num = %d, name = %s\n",data1.num, data1.name);
//指针变量 作为结构体的成员 结构体变量间的赋值操作 容易导致“浅拷贝”发生
data2 = data1;//“浅拷贝”
printf("data2: num = %d, name = %s\n",data2.num, data2.name);
if(data1.name != NULL)
{
free(data1.name);
data1.name = NULL;
}
if(data2.name != NULL)
{
free(data2.name);
data2.name = NULL;
}
}
运行结果 出现段错误
知识点2【深拷贝】
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
typedef struct
{
int num;
char *name;
}DATA;
void test01()
{
DATA data1;
DATA data2;
data1.num = 100;
data1.name = (char *)calloc(1,12);
strcpy(data1.name, "my data");
data2.num = data1.num;
//为结构体变量 申请 独立的空间
data2.name = (char *)calloc(1,12);
strcpy(data2.name, data1.name);
printf("data1:num = %d, name=%s\n", data1.num, data1.name);
printf("data2:num = %d, name=%s\n", data2.num, data2.name);
if(data1.name != NULL)
{
free(data1.name);
data1.name = NULL;
}
if(data2.name != NULL)
{
free(data2.name);
data2.name = NULL;
}
}
int main(int argc,char *argv[])
{
test01();
return 0;
}
运行结果:
知识点3【总结】
前提就是指针变量 作为 结构体的成员
浅拷贝:两个结构体变量 中的 指针成员 指向 同一块堆区空间。
深拷贝:两个结构体变量 中的 指针成员 指向 各自的堆区空间。
边栏推荐
- Research and implementation of hospital management inpatient system based on b/s (attached: source code paper SQL file)
- [Chongqing Guangdong education] reference materials for nine lectures on the essence of Marxist Philosophy in Wuhan University
- CANoe仿真功能之自动化序列(Automation Sequences )
- tn-c为何不可用2p断路器?
- What are the models of data modeling
- 单片机实现模块化编程:思维+实例+系统教程(实用程度令人发指)
- [CV] target detection: derivation of common terms and map evaluation indicators
- Embedded development is much more difficult than MCU? Talk about SCM and embedded development and design experience
- Summary of May training - from a Guang
- Automation sequences of canoe simulation functions
猜你喜欢
Interview shock 62: what are the precautions for group by?
小白带你重游Spark生态圈!
Use of activiti7 workflow
A wave of open source notebooks is coming
Selection of software load balancing and hardware load balancing
Combined search /dfs solution - leetcode daily question - number of 1020 enclaves
机械工程师和电气工程师方向哪个前景比较好?
嵌入式开发中的防御性C语言编程
MapReduce working mechanism
【深度学习】语义分割:论文阅读:(2021-12)Mask2Former
随机推荐
软件负载均衡和硬件负载均衡的选择
The real future of hardware engineers may not be believed by you if I say so
嵌入式開發中的防禦性C語言編程
Mapreduce实例(七):单表join
[one click] it only takes 30s to build a blog with one click - QT graphical tool
Libuv thread
Defensive C language programming in embedded development
手把手教您怎么编写第一个单片机程序
Take you back to spark ecosystem!
【深度学习】语义分割:论文阅读(NeurIPS 2021)MaskFormer: per-pixel classification is not all you need
[deep learning] semantic segmentation - source code summary
C#/. Net phase VI 01C Foundation_ 01: running environment, process of creating new C program, strict case sensitivity, meaning of class library
VH6501学习系列文章
小白带你重游Spark生态圈!
Webrtc blog reference:
嵌入式开发中的防御性C语言编程
May brush question 01 - array
Vs All comments and uncomments
June brush question 01 - array
Use of activiti7 workflow