Exception Handling & Error Management Flashcards

What happens when an exception is thrown inside a destructor that is already executing due to stack unwinding?

Answer: std::terminate() is called

If a destructor throws while another exception is being propagated (stack unwinding), std::terminate() is called because two exceptions cannot be active simultaneously.

Which of the following correctly creates a custom exception class that follows best practices?

Answer: class MyEx : public std::exception { public: const char* what() const noexcept override { return "error"; } };

Best practice is to inherit publicly from std::exception and override what() as const noexcept to match the base class contract.

What does the noexcept specifier guarantee when applied to a function?

Answer: The compiler optimizes the function assuming no exceptions will propagate out

noexcept tells the compiler no exceptions will propagate out, enabling optimizations; if one does, std::terminate() is called.

What is the output of: try { throw 42; } catch (double d) { cout << "double"; } catch (...) { cout << "other"; }

Answer: other

An int literal 42 does not match catch(double), so the catch-all handler catch(...) executes.

Which function can be used to rethrow the currently active exception inside a catch block?

Answer: throw;

A bare throw; statement inside a catch block rethrows the currently active exception preserving its original type.

What is std::exception_ptr used for?

Answer: Storing and transporting exceptions across threads

std::exception_ptr captures an exception with std::current_exception() and allows rethrowing it later, even in a different thread.

In a catch clause, what is the advantage of catching by reference (catch(std::exception& e)) over catching by value?

Answer: It prevents object slicing when catching derived exceptions through a base reference

Catching by reference prevents slicing, ensuring the derived type's what() and virtual methods are called correctly.