[clang] [C23] Implement WG14 N3037 (PR #132939)

[via cfe-commits]

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@@ -1905,54 +2073,84 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
 
   // Compare the definitions of these two enums. If either or both are
   // incomplete (i.e. forward declared), we assume that they are equivalent.
+  // In C23, the order of the enumerations does not matter, only the names and
+  // values do.
   D1 = D1->getDefinition();
   D2 = D2->getDefinition();
   if (!D1 || !D2)
     return true;
 
-  EnumDecl::enumerator_iterator EC2 = D2->enumerator_begin(),
-                                EC2End = D2->enumerator_end();
-  for (EnumDecl::enumerator_iterator EC1 = D1->enumerator_begin(),
-                                     EC1End = D1->enumerator_end();
-       EC1 != EC1End; ++EC1, ++EC2) {
+  if (Context.LangOpts.C23 &&
+      !CheckStructurallyEquivalentAttributes(Context, D1, D2))
+    return false;
+
+  llvm::SmallVector<const EnumConstantDecl *, 8> D1Enums, D2Enums;
+  auto CopyEnumerators =
+      [](auto &&Range, llvm::SmallVectorImpl<const EnumConstantDecl *> &Cont) {
+        for (const EnumConstantDecl *ECD : Range)
+          Cont.push_back(ECD);
+      };
+  CopyEnumerators(D1->enumerators(), D1Enums);
+  CopyEnumerators(D2->enumerators(), D2Enums);
+
+  // In C23 mode, the order of the enumerations does not matter, so sort them
+  // by name to get them both into a consistent ordering.
+  if (Context.LangOpts.C23) {
+    auto Sorter = [](const EnumConstantDecl *LHS, const EnumConstantDecl *RHS) {
+      return LHS->getName() < RHS->getName();
+    };
+    llvm::sort(D1Enums, Sorter);
+    llvm::sort(D2Enums, Sorter);
+  }
+
+  auto EC2 = D2Enums.begin(), EC2End = D2Enums.end();
+  for (auto EC1 = D1Enums.begin(), EC1End = D1Enums.end(); EC1 != EC1End;
+       ++EC1, ++EC2) {
     if (EC2 == EC2End) {
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Sirraide wrote:

Here too perhaps?

https://github.com/llvm/llvm-project/pull/132939