Recover in C++

#include <iostream>
#include <stdexcept>
#include <functional>

// This function throws an exception.
void mayThrow() {
    throw std::runtime_error("a problem");
}

int main() {
    // In C++, we use try-catch blocks for exception handling.
    // This is similar to the deferred function with recover in the original example.
    try {
        // The std::function wrapper allows us to catch any exception
        // that might be thrown within the lambda.
        std::function<void()> f = [] {
            try {
                mayThrow();
            } catch (const std::exception& e) {
                std::cout << "Caught exception. Error:\n" << e.what() << std::endl;
            }
        };
        
        f();

        // This code will run, unlike in the original example,
        // because C++ exceptions are caught and don't stop program execution.
        std::cout << "After mayThrow()" << std::endl;
    } catch (...) {
        // This catch-all block is analogous to a recover that catches any panic.
        std::cout << "Caught unknown exception" << std::endl;
    }

    return 0;
}

In C++, we don’t have a direct equivalent to Go’s panic and recover mechanisms. Instead, we use exception handling with try, catch, and throw.

The mayThrow function simulates the mayPanic function from the original example by throwing an exception instead of panicking.

In the main function, we wrap our code in a try block. Inside this block, we define a lambda function that calls mayThrow and catches any exceptions it might throw. This lambda is wrapped in a std::function to allow catching exceptions from within the lambda.

The catch block in the lambda function is analogous to the recover in the original example. It catches any std::exception (which includes std::runtime_error) and prints the error message.

Unlike in the original example, the code after mayThrow() will actually execute in this C++ version, because exceptions are caught and don’t terminate the program.

The outer catch (...) block is a catch-all that would handle any exceptions not caught by the inner catch block. This is somewhat analogous to a recover that catches any panic.

To run this program:

$ g++ -std=c++11 exception_handling.cpp -o exception_handling
$ ./exception_handling
Caught exception. Error:
a problem
After mayThrow()

This example demonstrates how C++ uses exception handling to manage and recover from runtime errors, which is conceptually similar to Go’s panic and recover mechanism, albeit with different syntax and behavior.