结构体的深拷贝与浅拷贝

#define _CRT_SECURE_NO_WARNINGS

#include<stdio.h>
#include<string.h>

typedef struct Student {
       char* name;
       int age;
}Student;

void deepCopyStu(Student* from, Student* to) {
       //malloc分配的内存需要包括字符串的末尾空字符 '\0',否则，strcpy 会试图写入超出分配内存的空间，从而导致未定义行为或崩溃。
       to->name = malloc(strlen(from->name)+1);
       strcpy(to->name,from->name);
       to->age = from->age;
}

void main(){

       Student stu1;
       stu1.name = (char*)malloc(100);
       strcpy(stu1.name,"Yaphets");
       stu1.age = 20;
       printf("stu1: name = %s, age = %d\n",stu1.name,stu1.age);

       //浅拷贝1
       Student stu2;
       stu2.name = stu1.name;
       stu2.age = stu1.age;
       printf("%p,%p\n", &stu1, &stu2);
       printf("stu2: name = %s, age = %d\n", stu2.name, stu2.age);

       Student stu3;
       //浅拷贝2
       stu3 = stu1;
       printf("%p,%p\n", &stu1, &stu3);
       printf("stu3: name = %s, age = %d\n", stu3.name, stu3.age);
       strcpy(stu1.name, "Teddy");
       printf("stu1: name = %p\n", stu1.name);
       printf("stu2: name = %p\n", stu2.name);
       printf("After modifying stu1.name:\n");
       printf("stu1: name = %s, age = %d\n", stu1.name, stu1.age);
       printf("stu2: name = %s, age = %d\n", stu2.name, stu2.age);
       printf("stu3: name = %s, age = %d\n", stu3.name, stu3.age);

       Student stu4;
       //深拷贝
       deepCopyStu(&stu1, &stu4);
       strcpy(stu1.name, "Bob");
       printf("After modifying stu1.name:\n");
       printf("%p,%p,%p,%p\n", &stu1, &stu2, &stu3, &stu4);
       printf("stu1: name = %p\n", stu1.name);
       printf("stu4: name = %p\n", stu4.name);
       printf("stu1: name = %s, age = %d\n", stu1.name, stu1.age);
       printf("stu2: name = %s, age = %d\n", stu2.name, stu2.age);
       printf("stu3: name = %s, age = %d\n", stu3.name, stu3.age);
       printf("stu4: name = %s, age = %d\n", stu4.name, stu4.age);
       free(stu1.name);
       free(stu4.name);
       getchar();
}

运行结果

stu1: name = Yaphets, age = 20
0075FC3C,0075FC2C
stu2: name = Yaphets, age = 20
0075FC3C,0075FC1C
stu3: name = Yaphets, age = 20
stu1: name = 00C1BB80
stu2: name = 00C1BB80
After modifying stu1.name://浅拷贝改变stu1的string内容，stu2和stu3的string内容会跟着改
stu1: name = Teddy, age = 20
stu2: name = Teddy, age = 20
stu3: name = Teddy, age = 20
After modifying stu1.name:
0075FC3C,0075FC2C,0075FC1C,0075FC0C
stu1: name = 00C1BB80
stu4: name = 00C1BA20//深拷贝时重新分配的内存
stu1: name = Bob, age = 20
stu2: name = Bob, age = 20
stu3: name = Bob, age = 20
stu4: name = Teddy, age = 20//修改stu1的string内容后不影响stu4的string内容