Re: [Boost-users] Visual Studio 2005 ptr_list visualizer?

From: Filip Konvička (filip.konvicka_at_[hidden])
Date: 2007-08-02 19:43:46

Hi Bill,

(please don't top post, thanks!)
> I have written visualizers for the other pointer containers, but realize
> that I had forgotten about ptr_list. I previously posted the visualizer code
> for ptr_vector, ptr_map, ptr_multimap, ptr_set, ptr_multiset, and also
> array. If you don't have it I can easily post it again.
>   
Thanks for sharing your work! Once the wiki + repository are ready, 
people will hopefully find things more easily.
> I took a quick stab at ptr_list, but I think I may have run into a
> limitation (or bug) in the visualizer. It's not letting me cast the final
> expression to the templated parameter. I tried it with a direct cast and
> that worked, but it seems to lose the template information in the resulting
> expression.
>
> The problem is in the expression ($T1*)$e._Myval. It seems that $T1 (the
> template parameter) is not valid at this point. If, for example the list is
> defined as ptr_list<int>, then the expression (int*)$e._Myval will work, but
> obviously we can't hard code that here. Any one have any ideas here?
>   
Yes, this is a bit tricky... the problem is not $T1 being invalid in the 
context, it rather is in how pattern matching works. I suspect that the 
rule pattern matching is string-based. In this case, it is useful to 
look (via a watch) at the exact type being matched. In the case of 
ptr_list<int>, it is

   boost::ptr_list<int,boost::heap_clone_allocator,std::allocator<void *> >

which apparently matches your filter

  boost::ptr_list<*>

since you see some effects in the watch window. Hence $T1 = 
"int,boost::heap_clone_allocator,std::allocator<void *>", which does not 
make sense after substitution. So, to fix your rule, it suffices to 
rewrite the pattern as

  boost::ptr_list<*,*,*>

(in fact, boost::ptr_list<*,*> would work as well, justifying my above 
guess...but it is clearly not as clean).

Cheers,
Filip