Write indefinite length struct in C

indefine_struct.c

#include <stdio.h>

struct Node
{
        int data;
        int length;
        char buffer[0];
};

int main()
{
        int buffer_len = 100;
        struct Node *node = (struct Node *)malloc(sizeof(struct Node) + buffer_len);

        node->length = 100;

        printf("len of struct:%d\n", sizeof(struct Node));
        printf("len of buffer:%d\n", node->length);

        return 0;
}