Exception handling and Debug Assertion Failed Window

[FairMeaty]

Greetings.
I am learning about exception handling.
The following code will give an out-of-range error. When I tried to execute the code, it pops out the "Debug Assertion Failed" window. However whatever specified in catch(){} was not executed.

  #include <vector>
#include <iostream>
using namespace std;

int main() 
{
    vector<int> v;
    for (int i; cin >> i;)
        v.push_back(i);
    try 
        {
            for (int i = 0; i <= v.size(); i++)
                cout << v[i] << endl; 
        }
    
    catch(out_of_range& oor)
        {
            cerr << "out of range error detected" << '\n'<<oor.what()<<endl;
        }
    system("pause");
    return 0;
}

What needs to be done, if I want the actions specified in catch(){} to be executed and show up in console terminal and not show the "Debug Assertion Failed" dialog box?

[Handy Andy]

Hekko FairMeaty,

in the catch part try catch (const std::exception& e) untested.

In your try block you are not thronging the proper error for the "catch" to catch.

If the above code does not work add another "catch" block catch (...).

I do not use the try/catch very often, so I will have t do a little research.

Andy

[Handy Andy]

Hekko FairMeaty,

It took a bit, but I finally ended up with this:

#include <iostream>
#include <vector>

using namespace std;

int main()
{
    vector<int> v;

    //for (int lc{}, input; lc < 3; lc++)
    //{
    //    std::cout << " Enter number " << lc + 1 << ": ";  // <--- The "cin" ALWAYS needs a prompt.
    //    std::cin >> input;

    //    v.push_back(input);
    //}

    for (int lc{}; lc < 5; lc++)  // <--- Quick way for testing. Delete When finished.
    {
        v.push_back(lc);
    }
    
    try
    {
        for (int i = 0; i <= v.size(); i++)
            cout << v.at(i) << endl;  // <--- Changed.
    }

    catch (const std::exception& e)
    {
        cerr << "\n     Out of range error detected\n     " << e.what() << '\n';  // <--- Changed.
    }



    //system("pause");

    // <--- Keeps console window open when running in debug mode on Visual Studio. Or a good way to pause the program.
    // The next line may not be needed. If you have to press enter to see the prompt it is not needed.
    //std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');  // <--- Requires header file <limits>.
    std::cout << "\n\n Press Enter to continue: ";
    std::cin.get();

    return 0;  // <--- Not required, but makes a good break point.
}

// This is code I found for testing. https://en.cppreference.com/w/cpp/language/try_catch

    //try
    //{
    //    std::cout << "Creating a vector of size 5... \n";
    //    std::vector<int> v(5);
    //    std::cout << "Accessing the 11th element of the vector...\n";
    //    std::cout << v.at(10); // vector::at() throws std::out_of_range
    //}
    //catch (const std::exception& e)
    //{  // caught by reference to base
    //    std::cout << " a standard exception was caught, with message '"
    //        << e.what() << "'\n";
    //} 

Normally you do not need to use the ".at()" in a for loop, but since the (<=) does 1 more loop than needed the ".at()" throws an exception that the "catch" will catch.

Andy

[thmm]

@OP,
did you run the code in DEBUG mode in Visual Studio?
In DEBUG mode the vector subscript operator in VS doesn't throw exceptions you can catch but uses assertions.