C++ Language & SafetyLesson 22 of 441 min read6 questions

Exceptions & try/catch

Throw signals an error; catch handles it; uncaught = abort.

Concept core idea Watch out easy to get wrong

Concept

Key concepts

throw raises an exception; a matching catch handles it. .at() throws std::out_of_range on a bad index.
An uncaught exception propagates to std::terminate → 'Aborted (core dumped)'. That crash means nobody handled it.
Wrap risky code in try { ... } catch (const std::exception& e) { ... }; e.what() gives the message.
Catch by const reference (avoids slicing and copies).

C++

try { a.at(10) = 4; }              // throws
catch (const std::out_of_range& e){
  std::cout << e.what();           // handled — program continues
}

Watch out

uncaught throw vs bug in .at()

The abort is from nobody catching the exception — .at() did its job by detecting the bad index.

catch by value vs by reference

Catch by const& — catching by value can slice the exception object and copies it.

6 questions on this lesson. Write your answers from memory, then compare them with the model answers side by side.