c - 如何打印结构并对其进行 memcpy？

Question

我有以下结构 -

struct data
{
unsigned char r;
int f;
};

然后我尝试打印它，但在打印语句中出现段错误。我做错了什么以及如何进行 memcpy 和打印？

struct data *data1;
char temp[10];
data1->r = 1; data1->f = 2;                                                           
memcpy(temp,(char *)(struct data *)data1, sizeof(struct data));
printf("buffer is %s\n",temp );

Answer 1

您缺少内存分配。检查此代码并让我知道任何问题:

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

struct data{
    unsigned char r;
    int f;
};

int main(){
    struct data *data1=(struct data*)malloc(sizeof(struct data));
    char temp[100];

    data1->r = 255; data1->f = 1;                                                           
    memcpy(temp, data1, sizeof(struct data));

    printf("size of struct: %d\n", (int)sizeof(struct data));
    printf("buffer is: \n");
    //code to print the buffer in binary in chunks of 4
    for(int i=0; i<sizeof(struct data); i++){
        char v=temp[i];
        for(int j=0; j<8*sizeof(char); j++){
            if(v & 1)
                printf("1");
            else
                printf("0");
            v>>=1;
        }
        if((i+1)%4==0) printf("\n");
        else printf(" ");
    }
    printf("\n");
};

输出:

size of struct: 8
buffer is:
11111111 00000000 00000000 00000000 //r
10000000 00000000 00000000 00000000 //f

数据实际上被复制了