cin.get() 的运行时错误 [重复]

Question

#include<iostream>
#include<string>
#include<cstring>

using namespace std;
void cpp_string();
void cstyle_string();

int main()
{
  cpp_string();
  cstyle_string();

  system("pause");
  return 0;
}

void cpp_string()
{
  string fName, lName;
  char grade;
  int age;

  cout << "What is your first name?";
  getline(cin, fName);
  cout << "What is your last name?";
  getline(cin, lName);
  cout << "What letter grade do you deserve?";
  cin >> grade;
  cout << "What is your age?";
  cin >> age;

  cout << "Name: " << fName << ", " << lName << endl;
  cout << "Grade: " << grade << endl;
  cout << "Age: " << age << endl;

  return;
}

void cstyle_string()
{
  char fNm[20], lNm[20];
  char grade;
  int age;

  cout << "What is your first name?";
  cin.get(fNm, 20).get();
  cin.clear();
  cout << "What is your last name?";
  cin.get(lNm, 20).get();
  cout << "What letter grade do you deserve?";
  cin >> grade;
  cout << "What is your age?";
  cin >> age;

  cout << "Name: " << fNm << ", " << lNm << endl;
  cout << "Grade: " << grade << endl;
  cout << "Age: " << age << endl;

  return;
}

我得到的输出是

What is your first name?demiurge conon  
What is your last name?no  
What letter grade do you deserve?a  
What is your age?22  
Name: demiurge conon, no  
Grade: a  
Age: 22  
What is your first name?What is your last name?What letter grade do you deserve?What is your age?Name: ,  
Grade: ╠ 
Age: -858993460 
Press any key to continue . . . 

但如果我在不同的文件中运行cstyle_string()，那么我不会收到任何错误代码可以完美运行。

我想知道为什么会这样？

Answer 1

有两个问题。

1. 冗余\n

2. cin的状态

cpp_string 中的最后一个cin 是cin >> age。

它会留下一个\n 未被提取。

cstyle_string 的第一个是cin.get(fNm, 20).get();

如果找到分隔符，则不会从输入序列中提取，而是保留在那里作为要从流中提取的下一个字符

cin.get(FNm, 20) 将在\n 之前解析空输入，实际上流中没有可用的字符。在这种情况下，failbit 标志将被设置，接下来所有的cin >> 运算符都将失败。

你只能打电话cstyle_string直接回车，会发生同样的事情。