std::exception

Overview

Instead of throwing raw integers or strings, C++ provides a standard library of exception classes (`<stdexcept>`). All of them inherit from `std::exception`.

Syntax

cpp

#include <stdexcept>

try {
    throw std::invalid_argument("Input cannot be negative");
} 
// Catching by reference to avoid copying
catch (const std::exception& e) {
    // e.what() returns the error message
    std::cout << "Error: " << e.what() << std::endl;
}

Common Pitfalls

Using `v[10]` instead of `v.at(10)`. The `[]` operator does not check bounds and will NOT throw an exception, resulting in silent memory corruption.

Interview Tips

Always catch exceptions by `const reference` (const std::exception&). If you catch by value, you suffer from 'Object Slicing', where derived exception data is lost.

Real-World Example

Using standard out_of_range exception with vectors.

example

cpp

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

int main() {
    vector<int> v = {1, 2, 3};
    
    try {
        // v.at() performs bounds checking and throws out_of_range
        cout << v.at(10) << endl; 
    } 
    catch (const std::out_of_range& e) {
        cout << "Bounds Error: " << e.what() << endl;
    }
    catch (const std::exception& e) {
        cout << "Generic Error: " << e.what() << endl;
    }
    return 0;
}

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