================
@@ -450,6 +453,116 @@ class StmtComparer {
};
} // namespace
+static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
+ const Attr *Attr1, const Attr *Attr2) {
+ // Two attributes are structurally equivalent if they are the same kind
+ // of attribute, spelled with the same spelling kind, and have the same
+ // arguments. This means that [[noreturn]] and __attribute__((noreturn)) are
+ // not structurally equivalent, nor are [[nodiscard("foo")]] and
+ // [[nodiscard("bar")]].
+ if (Attr1->getKind() != Attr2->getKind())
+ return false;
+
+ if (Attr1->getSyntax() != Attr2->getSyntax())
+ return false;
+
+ if (Attr1->getSpellingListIndex() != Attr2->getSpellingListIndex())
+ return false;
+
+ auto GetAttrName = [](const Attr *A) {
+ if (const IdentifierInfo *II = A->getAttrName())
+ return II->getName();
+ return StringRef{};
+ };
+
+ if (GetAttrName(Attr1) != GetAttrName(Attr2))
+ return false;
+
+ // FIXME: check the attribute arguments. Attr does not track the arguments on
+ // the base class, which makes this awkward. We may want to tablegen a
+ // comparison function for attributes? In the meantime, we're doing this the
+ // cheap way by pretty printing the attributes and checking they produce
----------------
AaronBallman wrote:
> I am slightly uncomfortable using pretty printing, I mean theoretically we
> usually don't consider pretty printing load bearing as such. This is probably
> an ok short-term trade off but this feels potentially fragile.
Agreed, hence the FIXME. It's a temporary practical solution, but we don't have
the underlying machinery to compare attribute arguments generically and that's
far outside of the scope of this already large patch.
> Agreed. I also have design concerns. N3037 is silent on attributes.
Mismatched attributes are UB by omission, so I went with the most conservative
model which is: all attributes have to be identical across objects to be
structurally equivalent.
> ```
> struct S;
> struct [[deprecated]] S { // fine
> int a;
> };
>```
Correct.
> ```
> struct S { // not fine?
> [[deprecated]] int a; // not fine?
> };
> ```
Also correct.
https://github.com/llvm/llvm-project/pull/132939
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