C语言结构体赋值和有指针成员的结构体赋值

曾经终败给现在 2022-12-21 04:51 256阅读 0赞

1  结构体赋值

#include <windows.h>
     
    struct MyStruct
    {
        int a;
        int b;
        char c[20];
    };
     
    int APIENTRY WinMain(HINSTANCE hInstance,
                         HINSTANCE hPrevInstance,
                         LPSTR     lpCmdLine,
                         int       nCmdShow)
    {
    	char szBuffer[100];
        struct MyStruct t1 = {101, 202, "hello struct"};
        struct MyStruct t2 = t1;
    	wsprintf(szBuffer, "MyStruct t1: %d, %d, %s",t1.a, t1.b, t1.c);
    	MessageBox(NULL,szBuffer,TEXT("结构体赋值"),0);
    	wsprintf(szBuffer, "MyStruct t2: %d, %d, %s",t2.a, t2.b, t2.c);
    	MessageBox(NULL,szBuffer,TEXT("结构体赋值"),0);
    	return 0;
    }

结构体成员直接赋值；也可以把一个结构体变量赋值给另一个同类型的结构体变量，t2 = t1；

![20201114204153655.png][]

![20201114204203783.png][]

2 有指针成员的结构体赋值

#include <windows.h>
     
    struct MyStruct
    {
        int a;
        int b;
        char* c;
    };
     
    int APIENTRY WinMain(HINSTANCE hInstance,
                         HINSTANCE hPrevInstance,
                         LPSTR     lpCmdLine,
                         int       nCmdShow)
    {
    	char szBuffer[100];
        struct MyStruct t1;
        t1.a = 101;
        t1.b = 202;
        // 为指针区域赋值
        char *p = (char*)malloc(10*sizeof(char));
        strcpy(p, "hellostru");
        t1.c = p;
        struct MyStruct t2;
        t2 = t1;
        
    	wsprintf(szBuffer, "MyStruct t1: %d, %d, %s",t1.a, t1.b, t1.c);
    	MessageBox(NULL,szBuffer,TEXT("结构体赋值"),0);
    	wsprintf(szBuffer, "MyStruct t2: %d, %d, %s",t2.a, t2.b, t2.c);
    	MessageBox(NULL,szBuffer,TEXT("结构体赋值"),0);
    
        wsprintf(szBuffer, "t1 pointer addr: %x",t1.c);
        MessageBox(NULL,szBuffer,TEXT("结构体赋值"),0);
        wsprintf(szBuffer, "t2 pointer addr: %x",t2.c);
        MessageBox(NULL,szBuffer,TEXT("结构体赋值"),0);
    	    
    	return 0;
    }

运行如下；后两个消息框输出的是指针地址；

![20201114204657562.png][]

![20201114204708268.png][]

![20201114204717213.png][]

![20201114204727823.png][]

有指针成员的结构体；t2=t1，会直接将t1的指针变量赋值给t2.c，代码不会出错；

如果我们在赋值之后将t1所用的资源释放掉，那么使用t2的话则可能导致内存泄漏了。

[20201114204153655.png]: /images/20221120/ae451ec6dbf04b0084f2599402bbef29.png
[20201114204203783.png]: /images/20221120/3208f0bdd8d2445bacdd6696a32c124d.png
[20201114204657562.png]: https://img-blog.csdnimg.cn/20201114204657562.png
[20201114204708268.png]: https://img-blog.csdnimg.cn/20201114204708268.png
[20201114204717213.png]: https://img-blog.csdnimg.cn/20201114204717213.png
[20201114204727823.png]: https://img-blog.csdnimg.cn/20201114204727823.png