[PATCH] D49438: [analyzer][UninitializedObjectChecker] New flag to turn off dereferencing

[Umann Kristóf via Phabricator via cfe-commits]

Szelethus added a comment.

In https://reviews.llvm.org/D49438#1189772, @george.karpenkov wrote:

> > I think what pointer chasing should do, is check whether that pointer owns the pointee
>
> But ownership is a convention, and it's not always deducible from a codebase.


How about the following case:

  struct A {
    struct B {
      int b;
    };
    std::unique_ptr<B> ptr;
    A() : ptr(new B) {}
  };
  
  A a;

Here, `a->ptr->b` is clearly uninitialized, and I think it's fine to assume in most cases that no other pointer points to it right after `a`'s construction.

> I think of those as two separate checks, and I think we should only talk about enabling the pointer-chasing after we had established that just checking for uninitialized fields finds lots of valid bugs (and we can only do that after it gets enabled for many projects)

I think in the earlier case `*this->ptr` should be regarded as a regular field, and it could be analyzed without fear of spamming too many reports. Currently the biggest problem is that many objects could contain references to the same object:

  struct A { int x; };
  struct B {
    A &a;
    B(A &a) : a(a) {}
  };
  struct C {
    A &a;
    C(A &a) : a(a) {}
  };
  
  A a;
  B b(a);
  C c(a); // a.x reported twice


https://reviews.llvm.org/D49438