Recommit r148056 with fixes to deal with weirdness with bitfields in unions.

Original message: Make sure adding a field to a struct never reduces its size.  PR11745.

llvm-svn: 148070

2 files changed, 15 insertions, 4 deletions

diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index 43dee104ba3..5223219a306 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -1869,12 +1869,12 @@ void RecordLayoutBuilder::LayoutField(const FieldDecl *D) {
   // Reserve space for this field.
   uint64_t FieldSizeInBits = Context.toBits(FieldSize);
   if (IsUnion)
-    setSize(std::max(getSizeInBits(), FieldSizeInBits));
+    setDataSize(std::max(getDataSizeInBits(), FieldSizeInBits));
   else
-    setSize(FieldOffset + FieldSize);
+    setDataSize(FieldOffset + FieldSize);
 
-  // Update the data size.
-  setDataSize(getSizeInBits());
+  // Update the size.
+  setSize(std::max(getSizeInBits(), getDataSizeInBits()));
 
   // Remember max struct/class alignment.
   UpdateAlignment(FieldAlign, UnpackedFieldAlign);
diff --git a/clang/test/SemaCXX/empty-class-layout.cpp b/clang/test/SemaCXX/empty-class-layout.cpp
index 0b46bf045ac..c68f2bb6fb0 100644
--- a/clang/test/SemaCXX/empty-class-layout.cpp
+++ b/clang/test/SemaCXX/empty-class-layout.cpp
@@ -144,3 +144,14 @@ struct B : Empty, A { };
 SA(0, sizeof(B) == 16);
 
 }
+
+namespace Test7 {
+  // Make sure we reserve enough space for both bases; PR11745.
+  struct Empty { };
+  struct Base1 : Empty { };
+  struct Base2 : Empty { };
+  struct Test : Base1, Base2 {
+    char c;
+  };
+  SA(0, sizeof(Test) == 2);
+}