Question

I have a question regarding memory deallocation and exceptions. when I use delete to delete an object created on the heap . If an exception occurs before this delete is the memory going to leak or this delete is going to execute ?

Answer 1

This depends on where that delete is. If it’s inside the catch that catches the exception, it might invoke.

try {
    f();  // throws
} catch( ... ) {
    delete p;  // will delete
}

If it’s after the catch that catches the exception and that catch doesn’t return from the function (i.e. allows execution flow to proceed after the catch block) then the delete might be called.

try {
    f();  // throws
} catch( ... ) {
    // execution proceeds beyond catch
}
delete p;  // will delete

If the delete is not in a catch block or after a catch block that allows execution to proceed then the delete will not call.

try {
    f();  // throws
    delete p;  // will not delete
}  // ...

As you may imagine, in the two first cases above the delete will not be invoked if there is a throw before the delete:

try {
    f();  // throws
} catch( ... ) {
    g();  // throws
    delete p;  // will not delete
}