我认为我的开关盒有问题

我正在从一个txt文件中读取字符串，然后通过开关大小写将其与关键字列表（bubby、bonny、computer）匹配，然后初始化一个结构。但我得到了以下错误。

+        _struct    0x00efb7b0 {g=<Error reading characters of string.> HL=-431602080. mg_i=-431602080. ...}    D * 

#include <iostream>
#include <stdio.h>
#include <ctime>
#include <windows.h>
#include <fstream>
#include <string>
using namespace std;

struct D
{
    string g;
    float HL, mg_i, mg_m, t;
    float tau = HL / abs(log(0.5));
};


void scan(string, int&);

ifstream rlog;
ofstream wlog;
string line;
int main()
{
    int ptr;
    string month[] = { "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec" };
    //time_t t_i, t_f = time(0);
    //tm *ltm = localtime(&t_f);
    rlog.open("log.txt");
    scan(" :", ptr);

    string _list[3] = {"bubby", "bonny", "computer"};
    int j = 0;
    for (int i = 0; i < 2; i++){
        if (line.find(_list[i]) < line.length()){
            j++;
        }
    }
    D *_struct = (D*)malloc(j*sizeof(D));
    for (int i = 0; i < j; i++){
        if (line.find(_list[i]) < line.length()){
            switch (i){
            case '1':
                (_struct + i)->g = "bubby";
                _struct[i].HL = 9.0;
                _struct[i].mg_m = 150;
                break;
            case '2':
                (_struct + i)->g = "bonny";
                _struct[i].HL = 8.5;
                _struct[i].mg_m = 450;
                break;
            case '3':
                (_struct + i)->g = "computer";
                _struct[i].HL = 48.755;
                _struct[i].mg_m = 360;
                break;
            }
        }
    }

    return 0;
}

void scan(string s, int &i)
{
    while (!rlog.eof()){
        getline(rlog, line);        //READ IN
        if (line.find(s) > line.length()){}
        else{
            i = line.find(s);
            break;
        }                //EXIT FUNCT WEN FOUND
    }
}

提前感谢