A union can have a constexpr defaulted default constructor, if it has an

in-class initializer for one of its fields. Value-initialization of such
a type should use the in-class initializer!

The former was just a bug, the latter is a (reported) standard defect.

llvm-svn: 156274

5 files changed, 15 insertions, 10 deletions

diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index 6ecc4890c9c..87e5e533d3f 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -1852,6 +1852,7 @@ bool ASTNodeImporter::ImportDefinition(RecordDecl *From, RecordDecl *To,
     ToData.HasPublicFields = FromData.HasPublicFields;
     ToData.HasMutableFields = FromData.HasMutableFields;
     ToData.HasOnlyCMembers = FromData.HasOnlyCMembers;
+    ToData.HasInClassInitializer = FromData.HasInClassInitializer;
     ToData.HasTrivialDefaultConstructor = FromData.HasTrivialDefaultConstructor;
     ToData.HasConstexprNonCopyMoveConstructor
       = FromData.HasConstexprNonCopyMoveConstructor;
diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
index e27d880ecf9..0c78abb8135 100644
--- a/clang/lib/AST/DeclCXX.cpp
+++ b/clang/lib/AST/DeclCXX.cpp
@@ -43,6 +43,7 @@ CXXRecordDecl::DefinitionData::DefinitionData(CXXRecordDecl *D)
     Abstract(false), IsStandardLayout(true), HasNoNonEmptyBases(true),
     HasPrivateFields(false), HasProtectedFields(false), HasPublicFields(false),
     HasMutableFields(false), HasOnlyCMembers(true),
+    HasInClassInitializer(false),
     HasTrivialDefaultConstructor(true),
     HasConstexprNonCopyMoveConstructor(false),
     DefaultedDefaultConstructorIsConstexpr(true),
@@ -818,17 +819,19 @@ NotASpecialMember:;
       data().HasNonLiteralTypeFieldsOrBases = true;
 
     if (Field->hasInClassInitializer()) {
-      // C++0x [class]p5:
+      data().HasInClassInitializer = true;
+
+      // C++11 [class]p5:
       //   A default constructor is trivial if [...] no non-static data member
       //   of its class has a brace-or-equal-initializer.
       data().HasTrivialDefaultConstructor = false;
 
-      // C++0x [dcl.init.aggr]p1:
+      // C++11 [dcl.init.aggr]p1:
       //   An aggregate is a [...] class with [...] no
       //   brace-or-equal-initializers for non-static data members.
       data().Aggregate = false;
 
-      // C++0x [class]p10:
+      // C++11 [class]p10:
       //   A POD struct is [...] a trivial class.
       data().PlainOldData = false;
     }
@@ -920,7 +923,7 @@ NotASpecialMember:;
         //    -- every constructor involved in initializing non-static data
         //       members [...] shall be a constexpr constructor
         if (!Field->hasInClassInitializer() &&
-            !FieldRec->hasConstexprDefaultConstructor())
+            !FieldRec->hasConstexprDefaultConstructor() && !isUnion())
           // The standard requires any in-class initializer to be a constant
           // expression. We consider this to be a defect.
           data().DefaultedDefaultConstructorIsConstexpr = false;
@@ -944,7 +947,7 @@ NotASpecialMember:;
         data().DefaultedDefaultConstructorIsConstexpr = false;
         data().DefaultedCopyConstructorIsConstexpr = false;
         data().DefaultedMoveConstructorIsConstexpr = false;
-      } else if (!Field->hasInClassInitializer())
+      } else if (!Field->hasInClassInitializer() && !isUnion())
         data().DefaultedDefaultConstructorIsConstexpr = false;
     }
 
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 0ef1b1e81f3..66cc1e14e54 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -3642,11 +3642,10 @@ static void TryValueInitialization(Sema &S,
       //    user-provided or deleted default constructor, then the object is
       //    zero-initialized and, if T has a non-trivial default constructor,
       //    default-initialized;
-      if ((ClassDecl->getTagKind() == TTK_Class ||
-           ClassDecl->getTagKind() == TTK_Struct)) {
-        Sequence.AddZeroInitializationStep(Entity.getType());
-        return TryConstructorInitialization(S, Entity, Kind, 0, 0, T, Sequence);
-      }
+      // FIXME: The 'non-union' here is a defect (not yet assigned an issue
+      // number). Update the quotation when the defect is resolved.
+      Sequence.AddZeroInitializationStep(Entity.getType());
+      return TryConstructorInitialization(S, Entity, Kind, 0, 0, T, Sequence);
     }
   }
 
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 1c5b6584699..9ead7947acd 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -1090,6 +1090,7 @@ void ASTDeclReader::ReadCXXDefinitionData(
   Data.HasPublicFields = Record[Idx++];
   Data.HasMutableFields = Record[Idx++];
   Data.HasOnlyCMembers = Record[Idx++];
+  Data.HasInClassInitializer = Record[Idx++];
   Data.HasTrivialDefaultConstructor = Record[Idx++];
   Data.HasConstexprNonCopyMoveConstructor = Record[Idx++];
   Data.DefaultedDefaultConstructorIsConstexpr = Record[Idx++];
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 29ea01b9145..62154edf658 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -4310,6 +4310,7 @@ void ASTWriter::AddCXXDefinitionData(const CXXRecordDecl *D, RecordDataImpl &Rec
   Record.push_back(Data.HasPublicFields);
   Record.push_back(Data.HasMutableFields);
   Record.push_back(Data.HasOnlyCMembers);
+  Record.push_back(Data.HasInClassInitializer);
   Record.push_back(Data.HasTrivialDefaultConstructor);
   Record.push_back(Data.HasConstexprNonCopyMoveConstructor);
   Record.push_back(Data.DefaultedDefaultConstructorIsConstexpr);