1 files changed, 33 insertions, 0 deletions
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index bcb9f05ca3c..21dd5425834 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -3913,6 +3913,39 @@ bool FieldDecl::isZeroLengthBitField(const ASTContext &Ctx) const {
          getBitWidthValue(Ctx) == 0;
 }
 
+bool FieldDecl::isZeroSize(const ASTContext &Ctx) const {
+  if (isZeroLengthBitField(Ctx))
+    return true;
+
+  // C++2a [intro.object]p7:
+  //   An object has nonzero size if it
+  //     -- is not a potentially-overlapping subobject, or
+  if (!hasAttr<NoUniqueAddressAttr>())
+    return false;
+
+  //     -- is not of class type, or
+  const auto *RT = getType()->getAs<RecordType>();
+  if (!RT)
+    return false;
+  const RecordDecl *RD = RT->getDecl()->getDefinition();
+  if (!RD) {
+    assert(isInvalidDecl() && "valid field has incomplete type");
+    return false;
+  }
+
+  //     -- [has] virtual member functions or virtual base classes, or
+  //     -- has subobjects of nonzero size or bit-fields of nonzero length
+  const auto *CXXRD = cast<CXXRecordDecl>(RD);
+  if (!CXXRD->isEmpty())
+    return false;
+
+  // Otherwise, [...] the circumstances under which the object has zero size
+  // are implementation-defined.
+  // FIXME: This might be Itanium ABI specific; we don't yet know what the MS
+  // ABI will do.
+  return true;
+}
+
 unsigned FieldDecl::getFieldIndex() const {
   const FieldDecl *Canonical = getCanonicalDecl();
   if (Canonical != this)