On Fri, Nov 20, 2009 at 12:59 PM, Peter Kasting <pkast...@google.com> wrote:
> On Fri, Nov 20, 2009 at 12:42 PM, Mark Mentovai <m...@chromium.org> wrote: > >> As Evan points out, there are some cases when it's not absolutely >> necessary to have a base or interface class declare a virtual >> destructor. > > > For a concrete example, take AutocompleteEditController, which is declared > in autocomplete_edit.h. This is an abstract base class that names several > different methods. The purpose of the class is to insulate the > functionality the edit needs from whatever code actually implements that > functionality. However, the edit doesn't create or own pointers to its > controller, and never deletes its controller, so this abstract class doesn't > have a virtual destructor. The pattern here is "implements interface X" as > opposed to the "is a specialized type of an X" pattern of parent and child > classes. > What's the benefit of omitting the virtual destructor? This seems inherently error-prone since you are relying on users of the class to stick to a behavior that is subtle (never destroy through a pointer to the base class), undocumented, and impossible for the compiler to enforce. Alternately, you could have the compiler enforce that an object of this type is never deleted through a pointer to the base class by declaring a protected destructor, instead of leaving in the compiler-defined public default one. I'm not sure why you would want to do this over just declaring a virtual d'tor. - James > > PK > > -- > Chromium Developers mailing list: chromium-dev@googlegroups.com > View archives, change email options, or unsubscribe: > http://groups.google.com/group/chromium-dev > -- Chromium Developers mailing list: chromium-dev@googlegroups.com View archives, change email options, or unsubscribe: http://groups.google.com/group/chromium-dev
