提示double转换到int，可能丢失数据

Question

int binToDec(string bin)
{
int sum = 0;
for (int i = 0; i < bin.size(); i++)
{
if (bin[i] == '0' || bin[i] == '1')
{
sum += (bin[i] - '0') * pow(2, bin.size() - i - 1);
}
else
{
cout << "非法二进制字符！" << endl;
return 0;
}
}
return sum;