[Bug c/50476] Warn of pointer set to object whose lifetime is limited

["manu at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50476

Manuel LÃpez-IbÃÃez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |manu at gcc dot gnu.org

--- Comment #2 from Manuel LÃpez-IbÃÃez <manu at gcc dot gnu.org> 2012-05-09 11:05:39 UTC ---
I think it is only undefined behaviour to access the pointer after the
life-time of y has finished, however, the following probably isn't, no?

void g()
{
  ...
   *x = 2;
   ...
}

void f()
{
   ...
   x = &y;
   ...
   g();
   ...
   x = NULL;
}

The C/C++ FE cannot distinguish between these two cases. 

Do you have a suggestion about how to implement this? 

I think it would require some kind of constant propagation to know that the
final value of x is safe, but no existing contributor is interested in
implementing such thing, so someone new has to step up and do the work.