[PATCH] D122273: [clang][dataflow] Fix handling of base-class fields

[Yitzhak Mandelbaum via Phabricator via cfe-commits]

ymandel added a comment.

Thanks for the reviews.



================
Comment at: clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp:185
+      // base classes, because they are not visible in derived classes.
+      getFieldsFromClassHierarchy(Base.getType(), /*IgnorePrivateFields=*/true,
+                                  Fields);
----------------
xazax.hun wrote:
> Will this work well for all cases of diamond shape inheritance?
> 
> E.g.:
> ```
> struct A { int a; };
> struct B : virtual A { int b; };
> struct C : virtual A { int c; };
> struct D : B, C { int d; };
> ```
> 
> In the above code, I would expect the field `a` to appear only once. I guess this should work well because of the set representation although we will visit A twice.
> 
> On the other hand, consider:
> ```
> struct A { int a; };
> struct B : A { int b; };
> struct C : A { int c; };
> struct D : B, C { int d; };
> ```
> 
> Here, in fact, we have 2 instances of the field `a`. Both `B::a` and `C::a` are part of `D`. I suspect that the current implementation might not handle this.
Good point, no. But, I'm not sure that fixing this here would be enough - I think we'd also need to revisit how we model structs, since `getChild` takes a decl as argument -- it doesn't support multiple versions of the same field decl.

I added a FIXME since this seems a larger issue, but let me know if you think it needs fixing now.


================
Comment at: clang/unittests/Analysis/FlowSensitive/TransferTest.cpp:1014
+  std::string Code = R"(
+    struct A {
+      int Bar;
----------------
sgatev wrote:
> Add a similar test with `class` instead of `struct`?
I went with a simpler test for struct, only verifying that the default is understood correctly (and differently than class), but happy to expand it.


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  https://reviews.llvm.org/D122273/new/

https://reviews.llvm.org/D122273