Why does this throw an exeption?

Question

0.00/5 (No votes)

See more:

I'm a 13 year old who's just tring to experiment with things in C++. I declared a vector for storing the contents of a file and a pointer with dynamically allocated memmory. With this, I could perhaps make some sort of an local account database. Although when comparing the two, I get thrown an exeption (Segmentation fault) did some research and I think it means I'm writing or reading from a memmory illegally?

C++

          std::string* user_details_confirmation = new std::string[3];
    
                  
                    for (int i = 0; i < 6; i++){ std::cout << " "; }
                    std::cout << "First Name : ";

                    std::cin >> user_details_confirmation[0];
                    if(user_details_confirmation[0] == setup_file_contents_vec[0]) {};
                    system("cls");
<pre lang="C++">

What I have tried:

I changed both of the variables to vectors.
Code was originally in a loop (Got rid of it).

Posted 13-Oct-21 6:22am

apetrai

Updated 13-Oct-21 7:00am

v3

Add a Solution

5 solutions

Solution 3

Given that you've defined setup_file_contents_vec, but not initialized it, then setup_file_contents_vec[0] does not exist. So trying to assign a value to it results in a run-time error. You probably want to be using the std::vector push_back() method to add new items to the vector.

Posted 13-Oct-21 6:48am

k5054

Comments

apetrai 13-Oct-21 12:55pm

Initializing the vector lead to my console crashing instantly.

Solution 1

Where is the definition of "setup_file_contents_vec"?
Is it initialized?

Posted 13-Oct-21 6:36am

Brian Pendleton

Comments

apetrai 13-Oct-21 12:40pm

@BrianPendleton It's not, std::vector<std::string>setup_file_contents_vec{};

Solution 2

In that case, that's most likely your problem. The vector "setup_file_contents_vec" has zero elements with your definition.

Posted 13-Oct-21 6:44am

Brian Pendleton

Comments

apetrai 13-Oct-21 12:48pm

Although it is later defined:

std::string temp_var_to_vec;

while(setup_file_required_scan >> temp_var_to_vec) { setup_file_contents_vec.push_back(temp_var_to_vec); }

Solution 4

Also, I am not certain that you can read directly into a vector like that without creating that element first. This worked for me, tested here[^] :

#include <iostream>
#include <iomanip>
#include <vector>

using namespace std;

int main()
{
    std::vector<std::string> user_details_confirmation{""};
    std::vector<std::string>setup_file_contents_vec{ "timmy", "jimmy" };
    
    for(auto& iter : setup_file_contents_vec)
    {
        cout << "   setup_file_contents_vec: " << iter << std::endl;
    }
    
    std::cout << "First Name : ";
    std::cin >> user_details_confirmation[0];

    std::cout << "user_details_confirmation: " << user_details_confirmation[0] << std::endl;
    std::cout << "setup_file_contents_vec: " << setup_file_contents_vec[0] << std::endl;
    
    
    if(user_details_confirmation[0] == setup_file_contents_vec[0]) 
    {
        std::cout << "EQUAL";
    }
    
    
    return 0;
}

Posted 13-Oct-21 6:52am

Brian Pendleton

Comments

apetrai 13-Oct-21 12:56pm

Initializing the vector lead to my console crashing immediately.

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Brian Pendleton · Accepted Answer · 2021-10-13T07:00:00

Sorry, that wasn't meant to be a solution; just informative. Personally, I'd probably create a temp variable for the input, then use the push_back method, like k5054 suggested.

Something like this, perhaps:

#include <iostream>
#include <iomanip>
#include <vector>

using namespace std;

int main()
{
    std::vector<std::string> user_details_confirmation{};
    std::vector<std::string>setup_file_contents_vec{ "timmy", "jimmy" };
    
    for(auto& iter : setup_file_contents_vec)
    {
        cout << "   setup_file_contents_vec: " << iter << std::endl;
    }
    
    std::string input_value;
    std::cout << "First Name : ";
    std::cin >> input_value;
    
    user_details_confirmation.push_back(input_value);

    std::cout << "user_details_confirmation: " << user_details_confirmation[0] << std::endl;
    std::cout << "setup_file_contents_vec: " << setup_file_contents_vec[0] << std::endl;
    
    
    if(user_details_confirmation[0] == setup_file_contents_vec[0]) 
    {
        std::cout << "EQUAL";
    }
    
    
    return 0;
}