[clang][MSExtentions] Fix invalid overload failure about the loss of __unaligned qualifier (#65248)

hazohelet · web-flow · commit cf51876dd909 · 2023-09-08T13:22:07.000+09:00
Loss of `__unaligned` qualifier does not invalidate overload candidates. This fixes a regression reported in https://reviews.llvm.org/D153690 Reviewed By: cor3ntin, AaronBallman PR: #65248
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
@@ -216,6 +216,8 @@ Bug Fixes in This Version
   local structs.
 - Correctly parse non-ascii identifiers that appear immediately after a line splicing
   (`#65156 <https://github.com/llvm/llvm-project/issues/65156>`_`)
+- Clang no longer considers the loss of ``__unaligned`` qualifier from objects as
+  an invalid conversion during method function overload resolution.
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
@@ -5556,9 +5556,11 @@ TryObjectArgumentInitialization(Sema &S, SourceLocation Loc, QualType FromType,
 
   // First check the qualifiers.
   QualType FromTypeCanon = S.Context.getCanonicalType(FromType);
-  if (ImplicitParamType.getCVRQualifiers()
-                                    != FromTypeCanon.getLocalCVRQualifiers() &&
-      !ImplicitParamType.isAtLeastAsQualifiedAs(FromTypeCanon)) {
+  // MSVC ignores __unaligned qualifier for overload candidates; do the same.
+  if (ImplicitParamType.getCVRQualifiers() !=
+          FromTypeCanon.getLocalCVRQualifiers() &&
+      !ImplicitParamType.isAtLeastAsQualifiedAs(
+          withoutUnaligned(S.Context, FromTypeCanon))) {
     ICS.setBad(BadConversionSequence::bad_qualifiers,
                FromType, ImplicitParamType);
     return ICS;
diff --git a/clang/test/SemaCXX/MicrosoftExtensions.cpp b/clang/test/SemaCXX/MicrosoftExtensions.cpp
@@ -589,6 +589,18 @@ namespace PR42089 {
   __attribute__((nothrow)) void S::Bar(){}
 }
 
+namespace UnalignedConv {
+struct S {
+  bool operator==(int) const;
+};
+
+int func() {
+  S __unaligned s;
+  return s == 42;
+}
+}
+
+
 #elif TEST2
 
 // Check that __unaligned is not recognized if MS extensions are not enabled
