Question

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <vector>
using namespace std;
  struct student
  {
    char name[50];
    char lname[50];
    int id;
    float GPA;
  };
void toAdd(vector<student*> *plist);
void toDelete(vector<student*>* plist);
void toPrint(vector<student*>* plist);
int main(){
  vector<student*> list;
  vector<student*>* plist = &list;
  char input[80];
  bool running = true;
  while (running == true){
    cout << "What would you like to do?" << endl;
    cin.getline (input,80);
    if(strcmp (input, "ADD") == 0){
      toAdd(plist);
    }
    else if(strcmp (input, "DELETE") == 0){
    }
    else if(strcmp (input, "PRINT") == 0){
    }
    else{
      cout << "That is not a valid response!" << endl;
        }
  }
}

void toAdd(vector<student*> *plist){
  student* stu;
  cout << "What a test!" << endl;
  cout << "First Name: ";
  cin.getline(stu->name,20);
  cout << "Last Name: ";
  cin.getline(stu->lname,20);
  cout << "ID: ";
  cin.getline(stu->id);
  cout << "GPA: ";
  cin.getline(stu->GPA);
  plist->push_back(stu);
}
void toDelete(){

}
void toPrint(){
}

我不明白我做错了什么。我已经花了几个小时看这段代码，真的需要一些帮助。我收到错误“Segmentation Fault（core dumped）”当我运行代码并尝试输入名称时。我觉得这可能很简单，但在线解释都没有帮助我。：（

Answer 1

取消引用未初始化的指针。在你打电话之前

cin.getline(stu->name,20);

您需要先使用new

分配内存

student* stu = new student;

Answer 2

当您尝试访问不允许的内存位置（读取或写入）区域时，通常会导致Seg错误。在下面的行中，在toAdd（）方法中：

# https://matplotlib.org/api/dates_api.html
# https://matplotlib.org/examples/api/date_demo.html

import datetime as dt

import matplotlib.dates as mdates
import matplotlib.cbook as cbook

import matplotlib.dates as mpd


years = mdates.YearLocator()   # every year
months = mdates.MonthLocator()  # every month
yearsFmt = mdates.DateFormatter('%Y')


majorLocator = years
majorFormatter = yearsFmt #FormatStrFormatter('%d')
minorLocator = months


y1 = np.arange(100)*0.14+1
y2 = -(np.arange(100)*0.04)+12

"""neither of these indices works"""
x = pd.date_range(start='4/1/2012', periods=len(y1))
#x = map(mpd.date2num, pd.date_range(start='4/1/2012', periods=len(y1)))

fig, ax = plt.subplots()
ax.plot(x,y1)
ax.plot(x,y2)

ax.xaxis.set_major_locator(years)
ax.xaxis.set_major_formatter(yearsFmt)
ax.xaxis.set_minor_locator(months)

datemin = x[0]   
datemax = x[-1]  
ax.set_xlim(datemin, datemax)
fig.autofmt_xdate()
plt.show()

stu-＆gt; name，它等效于：（* stu）.name试图取消引用未初始化的指针。

此外，建议使用智能指针（Wrapper用于原始（常规）指针），因为它允许您更有效地管理为该指针分配的内存。您可以选择唯一或共享智能指针。

为什么我的指针导致段错误？

2 个答案: