MS ABI: Pure virtual functions don't contribute to vtordisps

Usually, overriding a virtual function defined in a virtual base
required emission of a vtordisp slot in the record.  However no vtordisp
is needed if the overriding function is pure; it should be impossible to
observe the pure virtual method.

This fixes PR21046.

llvm-svn: 218340

1 files changed, 26 insertions, 0 deletions

diff --git a/clang/test/Layout/ms-x86-vtordisp.cpp b/clang/test/Layout/ms-x86-vtordisp.cpp
index 60779fb1975..1b78d9fe843 100644
--- a/clang/test/Layout/ms-x86-vtordisp.cpp
+++ b/clang/test/Layout/ms-x86-vtordisp.cpp
@@ -416,6 +416,31 @@ struct HC : virtual HB {};
 // CHECK-X64-NEXT:      | [sizeof=32, align=8
 // CHECK-X64-NEXT:      |  nvsize=8, nvalign=8]
 
+struct IA {
+  virtual void f();
+};
+struct __declspec(dllexport) IB : virtual IA {
+  virtual void f() = 0;
+  IB() {}
+};
+
+// CHECK: *** Dumping AST Record Layout
+// CHECK: *** Dumping AST Record Layout
+// CHECK-NEXT:    0 | struct IB
+// CHECK-NEXT:    0 |   (IB vbtable pointer)
+// CHECK-NEXT:    4 |   struct IA (virtual base)
+// CHECK-NEXT:    4 |     (IA vftable pointer)
+// CHECK-NEXT:      | [sizeof=8, align=4
+// CHECK-NEXT:      |  nvsize=4, nvalign=4]
+// CHECK-X64: *** Dumping AST Record Layout
+// CHECK-X64: *** Dumping AST Record Layout
+// CHECK-X64-NEXT:    0 | struct IB
+// CHECK-X64-NEXT:    0 |   (IB vbtable pointer)
+// CHECK-X64-NEXT:    8 |   struct IA (virtual base)
+// CHECK-X64-NEXT:    8 |     (IA vftable pointer)
+// CHECK-X64-NEXT:      | [sizeof=16, align=8
+// CHECK-X64-NEXT:      |  nvsize=8, nvalign=8]
+
 int a[
 sizeof(A)+
 sizeof(C)+
@@ -428,4 +453,5 @@ sizeof(pragma_test3::C)+
 sizeof(pragma_test4::C)+
 sizeof(GD)+
 sizeof(HC)+
+sizeof(IB)+
 0];