[llvm-branch-commits] [clang] [LifetimeSafety] Track per-field origins for record types (PR #195603)

[Zhijie Wang via llvm-branch-commits]

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@@ -131,6 +131,20 @@ class OriginNode {
     return nullptr;
   }
 
+  /// To reach the record, peels the base's outer origin when the
+  /// base is a glvalue (`IsGLValue`) and one more level for an arrow access
+  /// (`IsArrow`), then looks up `FD`. Returns null if `FD` is not reachable.
+  OriginNode *resolveMemberField(const FieldDecl *FD, bool IsGLValue,
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aeft wrote:

> I think in that case the responsibilities here might not be correct. The caller should know exactly  if this is the arrow or the dot accessor, so maybe we should have either a bool argument to tell which one or two separate methods and that would enable the caller to be always precise. What do you think?

I get your point. We can pass two bool values to explicitly peel the origins: one `IsGLValue` peels the outermost origin, one `IsArrow` peels the pointer indirection. The reason it's two and not just the accessor: the accessor only fixes the indirection jump, while the outermost jump depends on the base's value category, e.g. `p->v` is 2 hops but `getP()->v` is 1 hop with the same arrow. This way we handle both cases in one method and the caller can be precise about what to peel and locate the field.

> I am not sure I follow the second point. Is this about differentiating between p.s and *p.s?

Here I mean differentiating two cases:

1. `p->v` pointer indirection (this adds a pointee edge, FD=nullptr)
2. lvalue storage wrap (this also adds a pointee edge for now, FD=nullptr):

These can be two EdgeKind: `Pointee` and `StorageWrap`. But actually we may have a third one: `ReferenceWrap` (now it belongs to pointee edge, e.g., `rs.v` where `rs` is a reference). As an alternative to the two-bool approach above: if we attach EdgeKind to the edges, `StorageWrap`/`ReferenceWrap` become self-identifying, so we always peel those first and use `IsArrow` only for the pointer indirection, no `IsGLValue` needed. (We may ignore this for now if the first method looks reasonable to you)  
  
cc @Xazax-hun 

https://github.com/llvm/llvm-project/pull/195603