Re: pure virtual method called

[Jan Hubicka <hubicka@ucw.cz>]

Hi,
the testcase would be wonderful - those bugs are hard to catch. I fixed some issues
recently, so you may try recent snapshot if you didn't.
You may try -fno-devirtualize to see if the bug goes away (likely it will) and you
may try to look in -fdump-tree-all -fdump-ipa-all dumps where cxa_pure_virtual call
appears in the program and send me some context.

Honza
> Hi Jan,
> 
>     I hope to report a bug soon, but in the meantime I wanted to let
> you know that for the last month or so, the 4.9 branch has (I think)
> a bug at O3, where my program gets:
> 
> pure virtual method called
> terminate called without an active exception
> Aborted
> 
> 4.8 works fine.
> 
>     I am guessing this is related to your devirt work.  I haven't
> been able to produce a reduce testcase yet (sorry!), but here is
> some code that illustrates the C++ type for the object whose virtual
> table is (?) messed up.  (Note: this code compiles but does NOT
> crash.)
> 
>     Again, sorry for not having a testcase.  I'll make one soon.
> Hopefully it is helpful to know that bugs still exist.
> 
> -BenRI
> 
> #include <vector>
> 
> class Object
> {
>   virtual Object* clone() const =0;
> };
> 
> template <typename T>
> class Box: public Object, public T
> {
> public:
>   Box<T>* clone() const {return new Box<T>(*this);}
> };
> 
> template <typename T>
> using Vector = Box<std::vector<T>>;
> 
> int main()
> {
>   Vector<int> v;
>   v.clone();
> }
> 
> -BenRI
> 
> P.S. The bug exists in debian gcc snapshots taken on 2014-02-12 and
> 2014-01-22, Linux AMD64.