~CXTPControlCustom() should be virtual!

Hi,

If there is no "virtual" keyword it doesn't mean its not virtual ;-)

ps. Don't worry, its virtual.

Oleg, Support Team
CODEJOCK SOFTWARE SOLUTIONS

Try this sample

struct A

{

A() {}

virtual ~A() {}

};

struct B : public A

{

B() {}

~B() {} // destructor B will be virtual even without virtual keyword

};

A *a = new B;

delete a;

Trust me, I now what is "virtual" keyword and how it used :)

p.s. See 10.3.1 of ANSI C++ International Standard

Oleg, Support Team
CODEJOCK SOFTWARE SOLUTIONS

Hi,

So you want to compete in C++ knowledge ? :)

www.brainbench.com -> C++ Fundametals.

Test:	C++ Fundamentals
Date:	10-Feb-2009
Score:	4.76
Weights:	100% C++ Fundamentals
Elapsed time:	49 min 19 sec

C++ Fundamentals
Score:	4.76
Percentile:	Scored higher than 97% of previous examinees

Demonstrates understanding of most advanced concepts within the subject area. Appears capable of mentoring others on the most complex projects.
Strong Areas	Data Handling Flow Control Functions Building C++ Programs Templates
Weak Areas	None noted

try to score more :)

ps. I bet 100$ that you didn't try last sample.

Try this.

struct A
{
A() {}
virtual ~A() {printf("Called ~A\n");}
};

struct B : public A
{
B() {}
~B() { printf("Called ~B\n");} // destructor B will be virtual even without virtual keyword
};

struct C : public B
{
~C() { printf("Called ~C\n");} // destructor B will be virtual even without virtual keyword

};

int main(int argc, char* argv[])
{

B *b = new C;
delete b; // no leak. no crash.

return 0;
}

Oleg, Support Team
CODEJOCK SOFTWARE SOLUTIONS

Ok, so the destructor in A saves you in this case, but that doesn't motivate leaving out the "virtual" keyword. I ain't gonna compete with my master (though Anakin will become stronger one day).

However...

International Standard ISO/IEC 14882: http://www.gisinvestor.ru/?module=File&action=Download&id=8

If the object being deleted has incomplete class type at the point of deletion and the complete class has a nontrivial destructor or a deallocation function the behavior is undefined.

Q: Why would you NOT explicitly make the destructor virtual? If CXTPControlCustom was some day changed to inherit some other class there is a high risk the class causes problems when derived!

My answer: Public destructors should always be explicitly declared virtual. Just like you check pointers before using them, this is a way to avoid problems.

PokerMemento - http://www.pokermemento.com/