Multiple catch blocks in C++ - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of multiple catch blocks in C++?

Multiple catch blocks allow a program to handle different types of exceptions separately, providing specific responses based on the exception type.

beginner

How does C++ decide which catch block to execute when an exception is thrown?

C++ checks the type of the thrown exception and matches it with the first compatible catch block in order. It executes the first matching catch block it finds.

intermediate

Can you have a catch block that catches all exceptions regardless of type? How?

Yes, by using a catch block with ellipsis syntax: catch(...). This block catches any exception not caught by previous catch blocks.

intermediate

What happens if no catch block matches the thrown exception?

If no catch block matches, the program calls std::terminate() and usually ends abruptly, unless the exception is caught elsewhere.

beginner

Write a simple example of multiple catch blocks handling different exception types.

Example:<br><pre>try {
  throw 10;
} catch (int e) {
  std::cout << "Caught int: " << e << std::endl;
} catch (const std::exception& e) {
  std::cout << "Caught std::exception: " << e.what() << std::endl;
} catch (...) {
  std::cout << "Caught unknown exception" << std::endl;
}</pre>

What keyword is used to handle exceptions in C++?

A catch

B try

C throw

D except

The catch keyword is used to define blocks that handle exceptions thrown in the try block.

Which catch block will handle an exception of type std::runtime_error if multiple catch blocks exist?

A None, it will be ignored

B The last catch block

C The catch block with ellipsis <code>catch(...)</code>

D The first catch block matching <code>std::runtime_error</code> or its base classes

C++ matches the thrown exception type to the first compatible catch block, including base classes.

What does catch(...) do?

A Catches all exceptions not caught by previous catch blocks

B Catches only exceptions of type ellipsis

C Is invalid syntax

D Catches exceptions of type <code>std::exception</code>

The ellipsis catch block is a catch-all for any exception type not previously caught.

If no catch block matches the thrown exception, what happens?

A Exception is ignored and program continues

B Program calls <code>std::terminate()</code> and ends

C Exception is automatically handled by the OS

D Program retries the try block

Without a matching catch block, the program terminates abruptly by calling std::terminate().

Can multiple catch blocks be used to handle different exception types in the same try block?

A No, only one catch block is allowed per try

B Yes, but only if exceptions are of the same type

C Yes, each catch block handles a specific exception type

D No, catch blocks must be nested

Multiple catch blocks allow handling different exception types separately from the same try block.

Explain how multiple catch blocks work in C++ and why they are useful.

Think about how you might want to respond differently to different problems.

Write a short code snippet using multiple catch blocks to handle an integer exception and a standard exception.

Start with try, throw an int, then catch int and std::exception separately.