From a1f7764bca6dd333f9dc6913ee213b22829d824b Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Sun, 22 May 2016 05:34:26 +0000
Subject: [PATCH] [AST] Cleanup comments regarding CXXRecordDecl::isEmpty

We were missing references to the standard, some of our home-grown
verbiage didn't make any sense.

No functional change is intended.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@270353 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/AST/DeclCXX.h |  7 ++++---
 lib/AST/DeclCXX.cpp         | 19 +++++++++++--------
 2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/include/clang/AST/DeclCXX.h b/include/clang/AST/DeclCXX.h
index cd1e1d6b8d..a5cf9ca992 100644
--- a/include/clang/AST/DeclCXX.h
+++ b/include/clang/AST/DeclCXX.h
@@ -1139,9 +1139,10 @@ public:
   /// \brief Determine whether this is an empty class in the sense of
   /// (C++11 [meta.unary.prop]).
   ///
-  /// A non-union class is empty iff it has a virtual function, virtual base,
-  /// data member (other than 0-width bit-field) or inherits from a non-empty
-  /// class.
+  /// The CXXRecordDecl is a class type, but not a union type,
+  /// with no non-static data members other than bit-fields of length 0,
+  /// no virtual member functions, no virtual base classes,
+  /// and no base class B for which is_empty<B>::value is false.
   ///
   /// \note This does NOT include a check for union-ness.
   bool isEmpty() const { return data().Empty; }
diff --git a/lib/AST/DeclCXX.cpp b/lib/AST/DeclCXX.cpp
index 9dc0771ead..45205e8b20 100644
--- a/lib/AST/DeclCXX.cpp
+++ b/lib/AST/DeclCXX.cpp
@@ -172,8 +172,6 @@ CXXRecordDecl::setBases(CXXBaseSpecifier const * const *Bases,
     CXXRecordDecl *BaseClassDecl
       = cast<CXXRecordDecl>(BaseType->getAs<RecordType>()->getDecl());
 
-    // A class with a non-empty base class is not empty.
-    // FIXME: Standard ref?
     if (!BaseClassDecl->isEmpty()) {
       if (!data().Empty) {
         // C++0x [class]p7:
@@ -187,6 +185,9 @@ CXXRecordDecl::setBases(CXXBaseSpecifier const * const *Bases,
         data().IsStandardLayout = false;
       }
 
+      // C++14 [meta.unary.prop]p4:
+      //   T is a class type [...] with [...] no base class B for which
+      //   is_empty<B>::value is false.
       data().Empty = false;
       data().HasNoNonEmptyBases = false;
     }
@@ -238,9 +239,9 @@ CXXRecordDecl::setBases(CXXBaseSpecifier const * const *Bases,
       if (SeenVBaseTypes.insert(C.getCanonicalType(BaseType)).second)
         VBases.push_back(Base);
 
-      // C++11 [meta.unary.prop] is_empty:
-      //    T is a class type, but not a union type, with ... no virtual base
-      //    classes
+      // C++14 [meta.unary.prop] is_empty:
+      //   T is a class type, but not a union type, with ... no virtual base
+      //   classes
       data().Empty = false;
 
       // C++1z [dcl.init.agg]p1:
@@ -458,8 +459,8 @@ void CXXRecordDecl::addedMember(Decl *D) {
       //   A POD-struct is an aggregate class...
       data().PlainOldData = false;
       
-      // Virtual functions make the class non-empty.
-      // FIXME: Standard ref?
+      // C++14 [meta.unary.prop]p4:
+      //   T is a class type [...] with [...] no virtual member functions...
       data().Empty = false;
 
       // C++ [class.virtual]p1:
@@ -938,7 +939,9 @@ void CXXRecordDecl::addedMember(Decl *D) {
     if (!data().HasNoNonEmptyBases)
       data().IsStandardLayout = false;
 
-    // If this is not a zero-length bit-field, then the class is not empty.
+    // C++14 [meta.unary.prop]p4:
+    //   T is a class type [...] with [...] no non-static data members other
+    //   than bit-fields of length 0...
     if (data().Empty) {
       if (!Field->isBitField() ||
           (!Field->getBitWidth()->isTypeDependent() &&
-- 
2.40.0