c - 如何正确计算结构数组的大小?我这样做对吗?

Question

我正在尝试获取结构数组的总字节数。1 个结构的总字节数为 96 个字节。我把 int 放在第一位以避免填充字节。我真的不知道我正在做的是否正确，但我知道根据我粘贴在此处的示例分配 struct[MAX] 将是 96 字节 * 50。我得到大约 700 万个字节，或者一些垃圾值。任何人都可以帮我在代码中计算MAX = 50 struct address addr[MAX]的数量.这是完整的示例。谢谢大家！

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

#define MAX 50  //for structure
struct address {
     int zip;   // 4 bytes
     char name[20];      // 20 bytes
     char street[40];    // 40 bytes
     char city[16];      // 16 bytes
     char state[4];      // 4 bytes
     char country[10];   // 10 bytes
};
int main()
{
    struct address addr[MAX];
    unsigned int *allocation;
    allocation = malloc(MAX * sizeof(struct address));
    if (!allocation) {
        printf("Memory allocation errornn");
        exit(1);
    } else {
        printf("address start: 0x%x08 - size in bytes: %dn", &addr, sizeof(struct address));
        printf("sizeof zip %dn", sizeof(addr[0].zip));
        printf("sizeof name %dn", sizeof(addr[0].name));
        printf("sizeof street %dn", sizeof(addr[0].street));
        printf("sizeof city %dn", sizeof(addr[0].city));
        printf("sizeof state %dn", sizeof(addr[0].state));
        printf("sizeof country %dn", sizeof(addr[0].country));
        printf("total size of structure is %dn", allocation);
    }
    free(allocation);
    system("PAUSE");
    return 0;
}

Answer 1

这一行：

   printf("total size of structure is %dn", allocation);

不正确allocation因为指针。要获得总大小，只需执行以下操作：

#include <stdio.h>
#define MAX 50  //for structure
struct address{
     int zip;   // 4 bytes
     char name[20];      // 20 bytes
     char street[40];    // 40 bytes
     char city[16];      // 16 bytes
     char state[4];      // 4 bytes
     char country[10];   // 10 bytes
};
int main()
{
    struct address addr[MAX];
    printf("Size %zun", sizeof(addr));
    return 0;
}

Answer 2

struct address addr[MAX]

使用此行，您将结构从 addr[0] 分配给 addr[49]