結構體中帶有指針的情況

#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; }

運行結果：

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

段錯誤 (核心已轉儲)

?

會出現以上錯誤。

?

將指針改位數組：

#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; }

編譯運行：

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

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

name = mike, age = 20

?

分析：

常量內存中的數值是不能修改的。

#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; }

編譯運行：

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; }

指針在內存的存儲方式：

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

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

name = tom, age = 30

?

END

轉載于:https://www.cnblogs.com/wanghao-boke/p/11183110.html

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