结构体中指针

结构体中带有指针的情况

#include<stdio.h>struct man
{char *name;int age;
};int main()
{struct man m = {"tom",20};printf("name = %s, age = %d\n",m.name,m.age);return 0;
}

运行结果：

exbot@ubuntu:~/wangqinghe/C/20190714$ gcc struct.c -o struct

exbot@ubuntu:~/wangqinghe/C/20190714$ ./struct

name = tom, age = 20

如果修改m.name的值

#include<stdio.h>
#include<string.h>struct man
{char *name;int age;
};int main()
{struct man m = {"tom",20};strcpy(m.name,"mike");printf("name = %s, age = %d\n",m.name,m.age);return 0;
}

exbot@ubuntu:~/wangqinghe/C/20190714$ gcc struct.c -o struct

exbot@ubuntu:~/wangqinghe/C/20190714$ ./struct

段错误 (核心已转储)

会出现以上错误。

将指针改位数组：

#include<stdio.h>
#include<string.h>struct man
{char name[256];int age;
};int main()
{struct man m = {"tom",20};strcpy(m.name,"mike");printf("name = %s, age = %d\n",m.name,m.age);return 0;
}

编译运行：

exbot@ubuntu:~/wangqinghe/C/20190714$ gcc struct.c -o struct

exbot@ubuntu:~/wangqinghe/C/20190714$ ./struct

name = mike, age = 20

分析：

常量内存中的数值是不能修改的。

#include<stdio.h>
#include<string.h>
#include<stdlib.h>struct man
{char *name;int age;
};int main()
{//struct man m = {"tom",20};struct man m;m.name = malloc(sizeof(char) * 100);m.age = 20;strcpy(m.name,"mike");printf("name = %s, age = %d\n",m.name,m.age);return 0;
}

编译运行：

exbot@ubuntu:~/wangqinghe/C/20190714$ gcc struct.c -o struct

exbot@ubuntu:~/wangqinghe/C/20190714$ ./struct

name = mike, age = 20

#include<stdio.h>
#include<string.h>
#include<stdlib.h>struct man
{char *name;int age;
};int main()
{struct man *p = malloc(sizeof(struct man));p->name = malloc(sizeof(char) * 100);strcpy(p->name,"tom");p->age = 30;printf("name = %s, age = %d\n",p->name,p->age);free(p->name);free(p);return 0;
}