[PATCH] D146329: [Clang] Fix defaulted equality operator so that it does not attempt to compare unnamed bit-fields

[Shafik Yaghmour via Phabricator via cfe-commits]

shafik created this revision.
shafik added reviewers: aaron.ballman, erichkeane, rsmith.
Herald added a project: All.
shafik requested review of this revision.

If we look at class.bit p2 <https://eel.is/c++draft/class.bit#2.sentence-2> it tells us that that unnamed bit-fields are not members and class.compare.default p5 <https://eel.is/c++draft/class.compare.default#5.sentence-1> tells us that we should only non-static data members of the class.

This fixes: https://github.com/llvm/llvm-project/issues/61335 and https://github.com/llvm/llvm-project/issues/61417


https://reviews.llvm.org/D146329

Files:
  clang/lib/Sema/SemaDeclCXX.cpp
  clang/test/CXX/class/class.compare/class.compare.default/p1.cpp


Index: clang/test/CXX/class/class.compare/class.compare.default/p1.cpp
===================================================================
--- clang/test/CXX/class/class.compare/class.compare.default/p1.cpp
+++ clang/test/CXX/class/class.compare/class.compare.default/p1.cpp
@@ -226,3 +226,26 @@
   (void)(b == 0);
 }
 } // namespace p2085_2
+
+namespace GH61417 {
+struct A {
+  unsigned x : 1;
+  unsigned   : 0;
+  unsigned y : 1;
+
+  constexpr A() : x(0), y(0) {}
+  bool operator==(const A& rhs) const noexcept = default;
+};
+
+void f1() {
+  constexpr A a, b;
+  constexpr bool c = (a == b); // no diagnostic, we should not be comparing the
+                               // unnamed bit-field which is indeterminate
+}
+
+void f2() {
+    A a, b;
+    bool c = (a == b); // no diagnostic nor crash during codegen attempting to
+                       // access info for unnamed bit-field
+}
+}
Index: clang/lib/Sema/SemaDeclCXX.cpp
===================================================================
--- clang/lib/Sema/SemaDeclCXX.cpp
+++ clang/lib/Sema/SemaDeclCXX.cpp
@@ -7755,6 +7755,10 @@
 
     //   followed by the non-static data members of C
     for (FieldDecl *Field : Record->fields()) {
+      // C++23 [class.bit]p2:
+      //   Unnamed bit-fields are not members ...
+      if (Field->isUnnamedBitfield())
+        continue;
       // Recursively expand anonymous structs.
       if (Field->isAnonymousStructOrUnion()) {
         if (visitSubobjects(Results, Field->getType()->getAsCXXRecordDecl(),


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