[cfe-commits] r61147 - in /cfe/trunk: lib/Analysis/CFRefCount.cpp test/Analysis/uninit-vals-ps.c

[Ted Kremenek]

On Mar 9, 2009, at 10:48 PM, Zhongxing Xu wrote:

> Hi Ted,
>
> We don't have any casts for this example. So why would p and q point  
> to different region?
>
> typedef struct s* MyPointer;
>
> struct s* foo();
>
> void bar() {
>   MyPointer p = foo();
>   struct s* q = p;
> }


That's a fair point.  There are no casts in this example.  That  
doesn't mean, however, that we don't have to reason about them when  
they are present.  Put another way, I'm not convinced it isn't a  
problem.

For example, considered the following contrived example:

   struct s* p = ...
   p->f = 5;

   void* r = p;
   MyPointer *q = r;
   if (q->f == 5)
     // do something

   if (q == p)
     // do something

While contrived, we should be able to readily determine that q->f is  
indeed 5 at the first branch as well as the fact that q == p at the  
second branch.  We have a variety of hacks in place to handle some of  
these cases; it would be nice if there was just a clear, consistent  
model of what different kinds of region views mean and how they should  
be interpreted.

The point of having a clear model for region views and their semantics  
that handles all cases consistently (and inductively) means that the  
corner cases just get naturally handled without us having to  
specifically consider them.