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I get the “access violation writing location c++” error as the title says. How can I fix it so the error goes away? Here is my detail:
#include <vector>
#include <string>
#include <fstream>
class ElemAlg
{
private:
std::string difficultlyLevel, question, answerToRead;
std::vector<std::string> questions, answers;
std::vector<std::string> GetQuiz(int);
};#include "elemalg.h"
std::vector<std::string> ElemAlg::GetQuiz(int difficulty)
{
if (difficulty == 1) { difficultyLevel = "algE"; }
if (difficulty == 2) { difficultyLevel = "algM"; }
if (difficulty == 3) { difficultyLevel = "algH"; }
if (difficulty == 4) { difficultyLevel = "algVH"; }
std::ifstream fin(difficultyLevel + ".txt");
while (std::getline(fin, question)) { questions.push_back(question); }
fin.close();
std::ifstream fin2(difficultyLevel + "Answers.txt");
while (std::getline(fin2, answerToRead)) { answers.push_back(answerToRead); }
fin2.close();
return questions;
}#includes etc
ElemAlg *ea;
ea->GetQuiz(1);When I operated it, I received the error text:
C++: Access violation writing locationI appreciate any help from you.
The cause: I think here is your problem:
Because an instance of
ElemAlgisn’t created, you are calling a member function on an uninitialized pointer.The compiler won’t have to do any runtime lookup because the member function you’re calling isn’t virtual, which is why the call goes to
GetQuiz. However, because ea is uninitialized,thispointer will be garbage, resulting in undefined behavior when you access a member variable (such asdifficultyLevel). That undefined behavior results in an access violation.Solution: You can solve this error by initializing
ea:or