I ran across a question the other day that I didn’t know the answer to, so I thought I would look it up. Namely: what happens to objects on the stack as a c++ exception is handled. Continue reading to find out.
class YourClass {
public:
YourClass() {
cout << "YourClass() Called" << endl;
}
~YourClass() {
cout << "~YourClass() Called" << endl;
}
};
void DoStuff() {
cout << "DoStuff entered" << endl;;
MyClass m;
try {
YourClass y;
cout << "Throwing int exception" << endl;
throw (15);
cout << "Exception thrown" << endl;
} catch (int i) {
cout << "int Exception caught " << i << endl;
} catch (...) {
cout << "unknown exception caught" << endl;
}
try {
MyClass m2;
cout << "Throwing MyClass exception" << endl;
throw (&m2);
} catch (MyClass *m) {
//BZZT invalid pointer m!
//(see the debug output destructor already called
cout << "MyClass exception caught" << endl;
} catch (...) {
cout << "unkown exception caught" << endl;
}
cout << "DoStuff exiting" << endl;
}
int main(int, char *[])
{
cout << "main entered" << endl;
DoStuff();
cout << "main exiting" << endl;
}
When main executes, the following is printed out:
main entered
DoStuff entered
MyClass() Called
YourClass() Called
Throwing int exception
~YourClass() Called
int Exception caught 15
MyClass() Called
Throwing MyClass exception
~MyClass() Called
MyClass exception caught
DoStuff exiting
~MyClass() Called
main exiting
Notice that anything created on the stack inside the try {} block is popped off BEFORE catch{} gets called.