Question

这是我在这里的第一篇文章。我是C ++中相对新手编程的人，这个错误令我感到难过。

我的程序应该从几个空格分隔的文本文件中获取输入并吐出一个csv文件。

我的代码编译得很好，但程序崩溃了，我能够检索到以下错误：

正在调试的程序在从GDB调用的函数中发出信号。 GDB已将上下文恢复到调用之前的状态。要更改此行为，请使用“set unwindonsignal off”。评估包含该功能的表达（std :: string :: size（）const）将被放弃。程序接收信号SIGSEGV，分段故障。 0x00423576在std :: string :: size（）const（）

中

错误发生在此代码的第16行：

#include "arrayUtils.h"
#include "enrollment.h"
#include <string>
#include <iostream>

using namespace std;


/*
 * Read the course names and max enrollments. Keep the courses
 * in alphabetic order by course name.
 */
void readCourses (istream& courseFile, int numCourses,
          string* courseNames, int* maxEnrollments)
{
  string courseNameValue = ""; // PROBLEMS START HERE
  int maxEnrollmentValue = 0;

  while (courseFile){
    courseFile >> courseNameValue;
    addInOrder(courseNames, numCourses, courseNameValue); //PROGRAM CRASHES HERE

    courseFile >> ws;

    courseFile >> maxEnrollmentValue;
    addInOrder(maxEnrollments, numCourses, maxEnrollmentValue);
  }
}

/*
 * Read the enrollment requests, processing each one and tracking
 * the number of students successfully enrolled into each course.
 */
void processEnrollmentRequests (istream& enrollmentRequestsFile,
                int numCourses,
                string* courseNames,
                int* maxEnrollments,
                int* enrollments)
{
  // Start the enrollment counters at zero
  for (int pos = 0; pos < numCourses; ++pos)
  {
      enrollments[pos] = 0;
  }

  // Read the requests, one at a time, serving each one
  string courseName;
  int courseIndex = 0;

  enrollmentRequestsFile >> courseName;
  while (enrollmentRequestsFile) {
    enrollmentRequestsFile >> ws;
    string studentName;
    getline (enrollmentRequestsFile, studentName);

    courseIndex = binarySearch(courseNames, numCourses, courseName);

    if (courseIndex >= 0)
    {
        if (maxEnrollments[courseIndex] >= enrollments[courseIndex])
        {
            ++enrollments[courseIndex];
            cout << studentName << " has enrolled in " << courseName << "\n";
        }
        else
        {
            cout << studentName << " cannot be enrolled in " << courseName << "\n";
        }
    }
    else
    {
        cout << studentName << " cannot be enrolled in " << courseName << "\n";
    }

    enrollmentRequestsFile >> courseName;
   }
}


/*
 * Write a CSV report listing each course and its enrollment.
 */
void generateReport (ostream& reportFile,
             int numCourses,
             string* courseNames,
             int* enrollments)
{
  for (int pos = 0; pos < numCourses; ++pos)
  {
      reportFile << "\"" << courseNames[pos] << "\"," << enrollments << "\n";
  }
}


void processEnrollments (istream& courseFile, istream& enrollmentRequestsFile,
             ostream& reportFile)
{ 
  int numCourses = 0;
  int arraySize = 0;
  courseFile >> numCourses;

  arraySize = numCourses + 1;

  // Create the arrays we need
  string courseNames[arraySize];
  int maxEnrollments[arraySize];
  int enrollments[arraySize];

  // Process the enrollments
  readCourses (courseFile, numCourses, courseNames, maxEnrollments);
  processEnrollmentRequests (enrollmentRequestsFile, numCourses,
                 courseNames, maxEnrollments, enrollments);
  generateReport (reportFile, numCourses, courseNames, enrollments);
}

我调用的用于组织字符串数组的函数是：

// Assume the elements of the array are already in order
// Find the position where value could be added to keep
//    everything in order, and insert it there.
// Return the position where it was inserted
//  - Assumes that we have a separate integer (size) indicating how
//     many elements are in the array
//  - and that the "true" size of the array is at least one larger
//      than the current value of that counter
template <typename T>
int addInOrder (T* array, int& size, T value)
{
  // Make room for the insertion
  int toBeMoved = size - 1;
  while (toBeMoved >= 0 && value < array[toBeMoved]) {
    array[toBeMoved+1] = array[toBeMoved];
    --toBeMoved;
  }
  // Insert the new value
  array[toBeMoved+1] = value;
  ++size;
  return toBeMoved+1;
}

请帮忙！我不知道该怎么做才能解决这个问题，该计划即将推出！

编辑：

主程序如下：

#include <cstdlib>
#include <iostream>
#include <string>
#include <fstream>

#include "enrollment.h"


using namespace std;


int main (int argc, char** argv)
{
  if (argc != 4)
    {
      cerr << "Usage: " << argv[0] << " courseFile enrollmentFile reportFile" << endl;
      return -1;
    }

  // Take input and output file names from the command line
  ifstream coursesIn (argv[1]);
  ifstream enrollmentIn (argv[2]);
  ofstream reportOut (argv[3]);

  processEnrollments (coursesIn, enrollmentIn, reportOut);

  coursesIn.close();
  enrollmentIn.close();
  reportOut.close();

  return 0;
}

Answer 1

在addInOrder函数中：

int toBeMoved = size - 1;
while (toBeMoved >= 0 && value < array[toBeMoved]) {
  array[toBeMoved+1] = array[toBeMoved];

toBeMoved 在第一次迭代中变为 size ，超出了数组范围。

Answer 2

扩展Jermaine Xu的回答：

解决方案：

使用std::vector<T>而不是数组/指针。它负责动态调整大小和移除..你的程序也会更清晰（也可能更高效）

Answer 3

您没有正确使用addInOrder功能。

string courseNames[numCourses + 1];

courseNames数组定义如上，然后直接将courseName和numCourses传递给addInOrder。在addInOrder中你做了：

courseName[numCourses]  //toBeMoved = size - 1; toBeMoved+1

您从courseName数组边界访问的内容实际上是访问last element of courseName。

因此，您需要一个额外的变量来记住您当前的数组大小。像这样：

void readCourses (istream& courseFile, int numCourses,
          string* courseNames, int* maxEnrollments)
{
  string courseNameValue = ""; 
  int maxEnrollmentValue = 0;

  int index = 0;           // index to how many real courses are added to courseName array
  while (courseFile){
    if (index == numCourses){  // courseName array is full, break out
        break;
    }
    courseFile >> courseNameValue;
    addInOrder(courseNames, index , courseNameValue);  // pass in index, not array size

    courseFile >> ws;

    courseFile >> maxEnrollmentValue;
    addInOrder(maxEnrollments, numCourses, maxEnrollmentValue);
  }
}

希望这有帮助！

程序接收信号SIGSEGV，分段故障

3 个答案: