C++ String to Integer Conversion

I'm working on a C++ program where I need to convert a string containing a numeric value into an integer. I want to ensure that this conversion is handled correctly and safely, especially when dealing with potential exceptions or invalid input.

Here's a simplified example of what I'm trying to do:

#include <iostream>
#include <string>

int main() {
    std::string str = "12345"; // This could be any numeric string.

    // How can I safely convert the string 'str' to an integer?

    int num = ???; // The converted integer should be stored here.

    std::cout << "Converted integer: " << num << std::endl;

    return 0;
}

In this code, I have a string str containing a numeric value. I want to convert this string into an integer variable num. However, I want to handle potential issues gracefully, such as cases where the string is not a valid integer. Could you offer a C++ code sample illustrating the proper and secure approach to convert a string to an integer while managing any potential exceptions or errors? I appreciate you helping me. I attempted to visit multiple sources to locate the answer, but I was unable to do so. Thank you.