On 5/5/07, Jeff Garland <jeff@crystalclearsoftware.com> wrote:
Jonathan Franklin wrote:
For example, GCC has a
warning about a derived class whose base doesn't have a virtual dtor. It's actually *impossible* (not just inefficient or convoluted) to implement is_polymorphic without generating that warning.
Interesting. I'm obviously flaunting my ignorance, but I didn't realize that inheriting from a class sans virtual dtor was ever a Good Thing. I'll have to read up on the issues WRT is_polymorphic.
Sorry, I slightly misspoke. What I meant to type was that I didn't realize that inheriting from a class with virtual methods sans virtual dtor was ever a Good Thing. AFAICT gcc will only gripe if the base class defines virtual methods but no virtual dtor. Perhaps this isn't the case with older versions of the compiler. I still need to read up on the issues WRT is_polymorphic, since they obviously exist given David's previous statements. I find inheriting without virtual functions quite useful. I agree wholeheartedly. In general, it's hard to ensure your
derived classes won't need the destructor called and hence the rule. However, if Derived happens to have a trivial/empty destructor then, really there's no reason to call it.
True. The first case *usually* (but not always) trumps the second, for the reason that you mentioned, and additionally, just because when you wrote the derived class with an empty/trivial dtor doesn't mean that someone else won't add something non-trivial later and forget to add 'virtual' to the base class dtor. Jon