From: Eli Friedman <eli.friedman@gmail.com>
Date: Thu, 1 Dec 2011 00:37:01 +0000 (+0000)
Subject: Fix MSVC class layout for empty classes.  Patch by Dmitry Sokolov.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=901dd668931a70932ad09092959c42693409a3cd;p=clang

Fix MSVC class layout for empty classes.  Patch by Dmitry Sokolov.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@145544 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/AST/RecordLayoutBuilder.cpp b/lib/AST/RecordLayoutBuilder.cpp
index 60a7c2d1fe..88a90a4172 100644
--- a/lib/AST/RecordLayoutBuilder.cpp
+++ b/lib/AST/RecordLayoutBuilder.cpp
@@ -1399,10 +1399,8 @@ void RecordLayoutBuilder::Layout(const CXXRecordDecl *RD) {
   }
 
   // Finally, round the size of the total struct up to the alignment
-  // of the struct itself.  Amazingly, this does not occur in the MS
-  // ABI after virtual base layout.
-  if (!isMicrosoftCXXABI() || RD->getNumVBases())
-    FinishLayout(RD);
+  // of the struct itself.
+  FinishLayout(RD);
 
 #ifndef NDEBUG
   // Check that we have base offsets for all bases.
@@ -1882,6 +1880,13 @@ void RecordLayoutBuilder::FinishLayout(const NamedDecl *D) {
     else
       setSize(CharUnits::One());
   }
+
+  // MSVC doesn't round up to the alignment of the record with virtual bases.
+  if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(D)) {
+    if (isMicrosoftCXXABI() && RD->getNumVBases())
+      return;
+  }
+
   // Finally, round the size of the record up to the alignment of the
   // record itself.
   uint64_t UnpaddedSize = getSizeInBits() - UnfilledBitsInLastByte;
diff --git a/test/Sema/ms_class_layout.cpp b/test/Sema/ms_class_layout.cpp
index 66d711fb43..ea3f899ea2 100644
--- a/test/Sema/ms_class_layout.cpp
+++ b/test/Sema/ms_class_layout.cpp
@@ -95,6 +95,7 @@ struct P : public M, public virtual L {
   int p;
 };
 
+struct R {};
 
 #pragma pack(pop)
 
@@ -111,6 +112,7 @@ int main() {
   N* n;
   O* o;
   P* p;
+  R* r;
   return 0;
 }
 
@@ -325,3 +327,9 @@ int main() {
 // CHECK-NEXT: nvsize=12, nvalign=4
 
 //CHECK: %struct.P = type { %struct.M.base, i32, %struct.K, %struct.L }
+
+// CHECK:       0 | struct R (empty)
+// CHECK-NEXT:  sizeof=1, dsize=0, align=1
+// CHECK-NEXT:  nvsize=0, nvalign=1
+
+//CHECK: %struct.R = type { i8 }