[PATCH] D16403: Add scope information to CFG

[Maxim Ostapenko via Phabricator via llvm-commits]

m.ostapenko added a comment.

In https://reviews.llvm.org/D16403#992452, @NoQ wrote:

> Thank you, this explanation looks very reasonable.
>
> All right, so right after the termination of the loop we have
>
>   [B1]
>   1: ForStmt (LoopExit)
>   2: [B4.5].~A() (Implicit destructor)
>   3: [B5.3].~A() (Implicit destructor)
>   4: CFGScopeEnd(a)
>   5: CFGScopeEnd(b)
>
>
> ... where `[B4.5]` is `A b = a;` and `[B5.3]` is `A a;`. Am i understanding correctly that while destroying `a` you can still use the storage of `b` safely? Or should `a` go out of scope before `b` gets destroyed?


AFAIU, when we destroying `a` we can still use the storage of `b` because nothing can be allocated into b's storage between calling destructors for `b` and `a`. So, imho the sequence should look like:

  [B4.5].~A() (Implicit destructor)
  [B5.3].~A() (Implicit destructor)
  CFGScopeEnd(b)
  CFGScopeEnd(a)



> Also, is the order of scope ends actually correct here - shouldn't `b` go out of scope earlier? Given that they are in very different lifetime scopes (`a` is one for the whole loop, `b` is per-loop-iteration). I guess the order would matter for the analyzer.

Yeah, this is a bug in a current implementation. Will fix this in the next patch version.


Repository:
  rL LLVM

https://reviews.llvm.org/D16403