[reSIProcate] VS2005 crashing with DUM

[Derek MacDonald]

Pehaps david meant that auto_ptr can cause problems when pointed to a base
class w/ non-virtual destructors, and left a word out?

PS - adam, you can climb down from the watchtower.

On 10/24/07, Adam Roach <adam at nostrum.com> wrote:
>
> On 10/23/07 11:00 PM, Adam Roach wrote:
> > david Butcher wrote:
> >
> >> auto_ptr is not compatible with virtual destructors. that may be the
> odd bit.
> >>
> >>
> >
> > What?
> >
> >
>
> Let me be more explicit.
>
> Stroustrup [1] doesn't mention anything about this in his treatment of
> auto_ptr. In fact, his examples include putting the base class of
> polymorphic objects into auto_ptrs -- which is going to lead to improper
> release of resources without virtual destructors.
>
> Also, extensive searches on Google failed to turn anything up that might
> be interpreted as a general prohibition against using auto_ptr with
> objects that have virtual destructors.
>
> In fact, the only thing I turned up has to do with a really obscure bug
> in Visual C++ 8.0, apparently having to do with errant coercion paths
> [2]; it sound like it impacts all virtual methods, not just destructors.
> It should be noted that the code that causes these problems shouldn't
> compile under real C++ compilers (although I suppose there's a chance
> that this coercion path is preferred by the compiler over another
> implicit path that other compilers use for the specific code in question
> -- meaning it would compile in both environments, but trigger the
> "virtual methods crash" bug described in the article I cite).
>
> Finally, I've demonstrated to myself that things work just fine with
> auto_ptr and virtual destructors under g++ in the trivial case with a
> tiny program:
>
> #include <iostream>
> #include <memory>
>
> class A
> {
>   public:
>     A(){}
>     virtual ~A();
> };
>
> A::~A()
> {
>   std::cout << "A is going away" << std::endl;
> }
>
> class B : public A
> {
>   public:
>     B(){}
>     virtual ~B();
> };
>
> B::~B()
> {
>   std::cout << "B is going away" << std::endl;
> }
>
> int main(int argc, char **argv)
> {
>   std::auto_ptr<A> ptr(new B());
>   ptr.reset();
>   return 0;
> }
>
>
> So, david: could you please clarify what you mean? It's not clear to me,
> and I've had a number of developers send me private mail asking, "is
> this right?"
>
> /a
>
> ---
> [1] Soustrup, Bjarne, "The C++ Programming Language", 3rd Edition,
> Addison Wesley, 1997
>
> [2] Bottom of page:
> <
> http://www.codeproject.com/Feature/SubtleBugs.asp?select=2053685&df=100&forumid=343280&exp=0&fr=183.5
> >
>
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>
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