Multiple catch blocks in C++ - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of multiple catch blocks with integer exception

What is the output of this C++ code when an integer exception is thrown?

C++

#include <iostream>
using namespace std;

int main() {
    try {
        throw 10;
    } catch (double e) {
        cout << "Caught double: " << e << endl;
    } catch (int e) {
        cout << "Caught int: " << e << endl;
    } catch (...) {
        cout << "Caught unknown exception" << endl;
    }
    return 0;
}

A Caught double: 10

B Caught unknown exception

C Caught int: 10

D Compilation error

💡 Hint

Remember that catch blocks are checked in order and the first matching type handles the exception.

The thrown exception is an int (10). The catch block for double does not match, so it is skipped. The catch block for int matches and handles the exception, printing "Caught int: 10".

❓ Predict Output

intermediate

Output when throwing a string literal with multiple catch blocks

What will this C++ program output when it throws a string literal exception?

C++

#include <iostream>
using namespace std;

int main() {
    try {
        throw "error";
    } catch (int e) {
        cout << "Caught int: " << e << endl;
    } catch (const char* e) {
        cout << "Caught const char*: " << e << endl;
    } catch (...) {
        cout << "Caught unknown exception" << endl;
    }
    return 0;
}

A Caught const char*: error

B Caught unknown exception

C Caught int: error

D Runtime error

💡 Hint

Check which catch block matches the thrown type exactly.

The thrown exception is a string literal, which is of type const char*. The catch block for int does not match, so the second catch block catches the exception and prints "Caught const char*: error".

🔧 Debug

advanced

Identify the error in multiple catch blocks

What error will this C++ code produce when compiled?

C++

#include <iostream>
using namespace std;

int main() {
    try {
        throw 5.5;
    } catch (int e) {
        cout << "Caught int: " << e << endl;
    } catch (double e) {
        cout << "Caught double: " << e << endl;
    } catch (double e) {
        cout << "Caught another double: " << e << endl;
    }
    return 0;
}

A Output: Caught double: 5.5

B Runtime error: ambiguous catch block

C Output: Caught int: 5

D Compilation error: duplicate catch block for double

💡 Hint

Check if catch blocks have unique exception types.

The code has two catch blocks for the same type (double), which is not allowed and causes a compilation error.

🧠 Conceptual

advanced

Behavior of catch(...) block in multiple catch blocks

Consider the following C++ code snippet. What will be the output if an exception of type std::string is thrown?

C++

#include <iostream>
#include <string>
using namespace std;

int main() {
    try {
        throw string("error");
    } catch (int e) {
        cout << "Caught int: " << e << endl;
    } catch (...) {
        cout << "Caught unknown exception" << endl;
    }
    return 0;
}

A Caught unknown exception

B Program terminates without output

C Compilation error due to missing catch block for std::string

D Caught int: error

💡 Hint

The catch(...) block catches any exception not caught by previous catch blocks.

The thrown exception is std::string, which does not match the int catch block. The catch(...) block catches all other exceptions, so it prints "Caught unknown exception".

❓ Predict Output

expert

Output of nested try-catch with multiple catch blocks

What is the output of this C++ program with nested try-catch blocks and multiple catch handlers?

C++

#include <iostream>
using namespace std;

int main() {
    try {
        try {
            throw 'a';
        } catch (int e) {
            cout << "Inner caught int: " << e << endl;
        } catch (...) {
            cout << "Inner caught unknown" << endl;
            throw;
        }
    } catch (char e) {
        cout << "Outer caught char: " << e << endl;
    } catch (...) {
        cout << "Outer caught unknown" << endl;
    }
    return 0;
}

A

Inner caught int: a
Outer caught char: a

B

Inner caught unknown
Outer caught char: a

C

Inner caught unknown
Outer caught unknown

D Compilation error due to throw in catch block

💡 Hint

Look at how the inner catch rethrows the exception and how the outer catch handles it.

The inner try throws a char 'a'. The inner catch for int does not match, so the catch(...) block catches it, prints "Inner caught unknown", then rethrows. The outer catch for char matches and prints "Outer caught char: a".