Custom exception class - weird behavior

Question

I've created a custom exception class testException.

throw creates a testException object which upon creation receives the desired name of the exception.

When a testException is caught (by reference) it should return the name of the exception by using the member function Get.Exception.

For some reason the function isn't called and instead I get the error:

terminate called after throwing an instance of testException

I saw a similar example here, which supposedly should work.

Why do I get the above error?

Code:

Exception.h

#include <iostream>
#include <string>
#ifndef TESTEXCEPTION_H
#define TESTEXCEPTION_H

using std::cout;
using std::cin;
using std::endl;
using std::string;

class testException {
public:
    testException(string);
    string GetException();
    ~testException();
protected:
private:
    string myexception;
};

#endif // TESTEXCEPTION_H

Exception.cpp

#include "testException.h"

testException::testException(string temp) : myexception(temp) {
    // ctor
}

string testException::GetException() {
    return myexception;
}

testException::~testException() {
    // dtor
}

main.h

#include <iostream>
#include "testException.h"

using std::cout;
using std::cin;
using std::endl;

int main() {
    throw testException ("Test");
    try {
        // Shouldn't be printed if exception is caught:
        cout << "Hello World" << endl;
    } catch (testException& first) {
        std::cerr << first.GetException();
    }
    return 0;
}

Felix Glas · Accepted Answer · 2014-07-31 11:49:59Z

3

You are throwing the exception outside of the try block.

int main() {
    throw testException("Test"); // Thrown in main function scope.
                                  // Will result in call to terminate.
    try {
        /* ... */
    } catch (testException& first) {
        // Only catches exceptions thrown in associated 'try' block.
        std::cerr << first.GetException();
    }
    /* ... */
}

An exception can only be caught when thrown inside of a try-catch clause. Throwing an exception in the main function scope will result in a call to terminate.

A try block will "try" to execute everything inside and if any exceptions are thrown along the way, they will be caught if the the associated exception handler takes a parameter with a type that the thrown exception is implicitly convertible to.

Once an exception is thrown the rest of the remaining statements inside of the try block will be skipped, all objects with automatic storage duration will be destroyed and the exception will be handled accordingly.

Live example with throw statement moved inside try-catch clause

edited Jul 31, 2014 at 11:49

answered Jul 31, 2014 at 11:03

Felix Glas

15.5k8 gold badges59 silver badges84 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Medvednic Over a year ago

When I tried to throw it inside the try block - same thing happened. AFAIK - once an exception has been thrown (even if it is outside of a try block), a stack unwinding occurs until it is caught or a termination happens.

Felix Glas Over a year ago

@Medvednic See the live example. Works as expected when the throw statement is moved inside the try-catch clause.

Medvednic Over a year ago

Thanks! silly me - I misunderstood the tutorial. it said that exceptions don't have to be explicitly thrown inside the try block it self, what they actually meant is that a function inside a try block can throw exception.

Edward · Accepted Answer · 2014-07-31 11:03:23Z

2

move throwing line: throw testException ("Test"); into try {} catch(catch (testException& first) {} block.

answered Jul 31, 2014 at 11:03

Edward

3042 silver badges16 bronze badges

Collectives™ on Stack Overflow

Custom exception class - weird behavior

2 Answers 2

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related