Read access violation

[Descensum]

Hello! New to this forum.

My code compiles properly and both requesting and withdrawing functions work properly. When I go to display the landing times/flight numbers, I get the error: std::_String_alloc<std::_String_base_types<char,std::allocator<char> > >::_Mysize(...) returned 0xCDCDCDE1.

No clue what error this is. I've been trying to figure it out but have had no success so far.

#include <iostream>
#include <malloc.h>
#include <stdlib.h>
#include <string>

using namespace std;

typedef struct flights
{
	int landingTime;
	string* flightNumber;
	flights* next;
};

int main()
{
	int k;
	cout << "Please enter a K value: ";
	cin >> k;

	flights *head = NULL;
	int choice;
	cout << "-------------------------------------------------" << endl;
	cout << "1. Request Landing" << endl;
	cout << "2. Withdraw Landing Request" << endl;
	cout << "3. List of landing times and the flight number" << endl;
	cout << "4. Quit" << endl;
	cout << "-------------------------------------------------" << endl;
	cout << "What operation would you like to perform? ";
	cin >> choice;

	while (true)
	{
		if (choice == 1)
		{
			if (head == NULL)
			{
				head = (flights*)malloc(sizeof(flights));
				cout << "Please enter the landing time: ";
				cin >> head->landingTime;

				if (head->landingTime >= k)
				{
					cout << "Please enter the flight number: ";
					head->flightNumber = new string;
					cin >> *head->flightNumber;
					head->next = NULL;
					cout << "-------------------------------------------------" << endl;
				}

				else
				{
					cout << "Does not satisfy given K constraint." << endl;
					free(head);
					cout << "-------------------------------------------------" << endl;
				}
			}

			else
			{
				flights *upcomingFlight = head;

				while (upcomingFlight->next != NULL)
				{
					upcomingFlight = upcomingFlight->next;
				}

				flights *newFlight = (flights*)malloc(sizeof(flights));
				cout << "Please enter the landing time: ";
				cin >> newFlight->landingTime;
				bool insertCheck = false;

				if (head->landingTime - newFlight->landingTime >= k && newFlight->landingTime >= k)
				{
					cout << "Please enter the flight number: ";
					head->flightNumber = new string;
					cin >> *head->flightNumber;
					newFlight->next = head;
					head = newFlight;
					insertCheck = true;
					cout << "-------------------------------------------------" << endl;
				}

				else if (newFlight->landingTime - upcomingFlight->landingTime >= k)
				{
					cout << "Please enter the flight number: ";
					head->flightNumber = new string;
					cin >> *head->flightNumber;
					newFlight->next = NULL;
					upcomingFlight->next = newFlight;
					insertCheck = true;
					cout << "-------------------------------------------------" << endl;
				}

				else
				{
					flights *previousFlight = head;
					upcomingFlight = head->next;

					while (upcomingFlight != NULL)
					{
						if (newFlight->landingTime - previousFlight->landingTime >= k && upcomingFlight->landingTime - newFlight->landingTime >= k)
						{
							cout << "Please enter the flight number: ";
							head->flightNumber = new string;
							cin >> *head->flightNumber;
							previousFlight->next = newFlight;
							newFlight->next = upcomingFlight;
							insertCheck = true;
							break;
							cout << "-------------------------------------------------" << endl;
						}

						upcomingFlight = newFlight->next;
						previousFlight = previousFlight->next;

					}

					if (!insertCheck)
					{
						cout << "Does not satisfy given K constraint." << endl;
						free(newFlight);
						cout << "-------------------------------------------------" << endl;
					}
				}
			}
		}

		else if (choice == 2)
		{
			int landingTime;
			flights *prevFlight = head;
			flights *nextFlight = head->next;

			cout << "Please enter the landing time of the flight request you would like to withdraw: ";
			cin >> landingTime;

			if (head->landingTime == landingTime)
			{
				head = head->next;
				free(prevFlight);
				cout << "Flight request has been removed." << endl;
				cout << "-------------------------------------------------" << endl;
			}

			else
			{
				bool withdrawCheck = false;

				while (nextFlight != NULL)
				{
					if (nextFlight->landingTime == landingTime)
					{
						prevFlight->next = nextFlight->next;
						free(nextFlight);
						withdrawCheck = true;
						break;

					}

					prevFlight = prevFlight->next;
					nextFlight = nextFlight->next;
				}

				if (!withdrawCheck)
				{
					cout << "The landing Time you entered was not found." << endl;
					cout << "-------------------------------------------------" << endl;
				}
			}

		}

		else if (choice == 3)
		{
			flights *nextFlight = head;

			if (nextFlight == NULL)
			{
				cout << "There are currently no flights." << endl;
				cout << "-------------------------------------------------" << endl;
			}

			else
			{
				while (nextFlight != NULL)
				{
					cout << "Flight Number: " << *nextFlight->flightNumber << endl;
					cout << "Landing Time: " << nextFlight->landingTime << endl;
					nextFlight = nextFlight->next;
					cout << "-------------------------------------------------" << endl;
				}
			}
		}

		else if (choice == 4)
		{
			break;
		}

		else
		{
			cout << "Not a valid input. Please choose an option from 1-4." << endl;
			cout << "-------------------------------------------------" << endl;
		}

		cout << "What operation would you like to perform? ";
		cin >> choice;
	}

	return 0;
}

[DTM256]

Do you have a line number for that error?

Second, you might want to use a switch statement instead of If else if.

[Descensum]

Just checked and I get the error on line 102.

[ne555]

provide an example input.

I see malloc, new, free (but no delete), a hand made list, lack of functions.
those are your bullets and you're playing russian roulette

[Thomas1965]

I got a crash at line 188 cout << "Flight Number: " << *nextFlight->flightNumber << endl; when *nextFlight->flightNumber == 0xcdcdcdcd {...} so filghtNumber is invalid

It happend after insering two flight and then choosing "List of landing times and the flight number"

[Descensum]

It seems like every time I try to display the landing times and flight numbers, It'll always crash with the same error. Doesn't seem to matter what inputs I put in. The inputs I put in were:

1
5
1
1
9
2
3

and then it crashes. Tested with other numbers and it still gives the same error.