MS ABI: Fix inheritance model calculation in CRTP

CRTP-like patterns involve a class which inherits from another class
using itself as a template parameter.

However, the base class itself may try to create a pointer-to-member
which involves the derived class.  This is problematic because we
may not have finished parsing the most derived classes' base specifiers
yet.

It turns out that MSVC simply uses the unspecified inheritance model
instead of doing anything fancy.

This fixes PR19987.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@210886 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 35 insertions, 7 deletions

diff --git a/include/clang/AST/DeclCXX.h b/include/clang/AST/DeclCXX.h
index 56bbbb1691..72fad7c28e 100644
--- a/include/clang/AST/DeclCXX.h
+++ b/include/clang/AST/DeclCXX.h
@@ -462,6 +462,9 @@ class CXXRecordDecl : public RecordDecl {
     /// \brief Whether this class describes a C++ lambda.
     bool IsLambda : 1;
 
+    /// \brief Whether we are currently parsing base specifiers.
+    bool IsParsingBaseSpecifiers : 1;
+
     /// \brief The number of base class specifiers in Bases.
     unsigned NumBases;
 
@@ -685,6 +688,12 @@ public:
     return data().Polymorphic || data().NumVBases != 0;
   }
 
+  void setIsParsingBaseSpecifiers() { data().IsParsingBaseSpecifiers = true; }
+
+  bool isParsingBaseSpecifiers() const {
+    return data().IsParsingBaseSpecifiers;
+  }
+
   /// \brief Sets the base classes of this struct or class.
   void setBases(CXXBaseSpecifier const * const *Bases, unsigned NumBases);
 
diff --git a/lib/AST/DeclCXX.cpp b/lib/AST/DeclCXX.cpp
index 0ac8b73e30..43d0fca9f9 100644
--- a/lib/AST/DeclCXX.cpp
+++ b/lib/AST/DeclCXX.cpp
@@ -70,7 +70,8 @@ CXXRecordDecl::DefinitionData::DefinitionData(CXXRecordDecl *D)
     ImplicitCopyAssignmentHasConstParam(true),
     HasDeclaredCopyConstructorWithConstParam(false),
     HasDeclaredCopyAssignmentWithConstParam(false),
-    IsLambda(false), NumBases(0), NumVBases(0), Bases(), VBases(),
+    IsLambda(false), IsParsingBaseSpecifiers(false), NumBases(0), NumVBases(0),
+    Bases(), VBases(),
     Definition(D), FirstFriend() {
 }
 
@@ -334,8 +335,10 @@ CXXRecordDecl::setBases(CXXBaseSpecifier const * const *Bases,
     addedClassSubobject(BaseClassDecl);
   }
   
-  if (VBases.empty())
+  if (VBases.empty()) {
+    data().IsParsingBaseSpecifiers = false;
     return;
+  }
 
   // Create base specifier for any direct or indirect virtual bases.
   data().VBases = new (C) CXXBaseSpecifier[VBases.size()];
@@ -346,6 +349,8 @@ CXXRecordDecl::setBases(CXXBaseSpecifier const * const *Bases,
       addedClassSubobject(Type->getAsCXXRecordDecl());
     data().getVBases()[I] = *VBases[I];
   }
+
+  data().IsParsingBaseSpecifiers = false;
 }
 
 void CXXRecordDecl::addedClassSubobject(CXXRecordDecl *Subobj) {
diff --git a/lib/AST/MicrosoftCXXABI.cpp b/lib/AST/MicrosoftCXXABI.cpp
index 359e864827..6870315b21 100644
--- a/lib/AST/MicrosoftCXXABI.cpp
+++ b/lib/AST/MicrosoftCXXABI.cpp
@@ -93,7 +93,7 @@ static bool usesMultipleInheritanceModel(const CXXRecordDecl *RD) {
 }
 
 MSInheritanceAttr::Spelling CXXRecordDecl::calculateInheritanceModel() const {
-  if (!hasDefinition())
+  if (!hasDefinition() || isParsingBaseSpecifiers())
     return MSInheritanceAttr::Keyword_unspecified_inheritance;
   if (getNumVBases() > 0)
     return MSInheritanceAttr::Keyword_virtual_inheritance;
diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index 57e6550cec..ed7908dfc9 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/lib/Sema/SemaDeclCXX.cpp
@@ -1431,6 +1431,9 @@ Sema::ActOnBaseSpecifier(Decl *classdecl, SourceRange SpecifierRange,
   if (!Class)
     return true;
 
+  // We haven't yet attached the base specifiers.
+  Class->setIsParsingBaseSpecifiers();
+
   // We do not support any C++11 attributes on base-specifiers yet.
   // Diagnose any attributes we see.
   if (!Attributes.empty()) {
diff --git a/test/CodeGenCXX/microsoft-abi-member-pointers.cpp b/test/CodeGenCXX/microsoft-abi-member-pointers.cpp
index 48bc2c721f..18e8c827ee 100644
--- a/test/CodeGenCXX/microsoft-abi-member-pointers.cpp
+++ b/test/CodeGenCXX/microsoft-abi-member-pointers.cpp
@@ -1,7 +1,7 @@
-// RUN: %clang_cc1 -fno-rtti -emit-llvm %s -o - -triple=i386-pc-win32 -fms-extensions | FileCheck %s
-// RUN: %clang_cc1 -fno-rtti -emit-llvm %s -o - -triple=x86_64-pc-win32 -fms-extensions | FileCheck %s -check-prefix=X64
-// RUN: %clang_cc1 -fno-rtti -emit-llvm %s -o - -triple=i386-pc-win32 -DINCOMPLETE_VIRTUAL -fms-extensions -verify
-// RUN: %clang_cc1 -fno-rtti -emit-llvm %s -o - -triple=i386-pc-win32 -DINCOMPLETE_VIRTUAL -DMEMFUN -fms-extensions -verify
+// RUN: %clang_cc1 -std=c++11 -fno-rtti -emit-llvm %s -o - -triple=i386-pc-win32 -fms-extensions | FileCheck %s
+// RUN: %clang_cc1 -std=c++11 -fno-rtti -emit-llvm %s -o - -triple=x86_64-pc-win32 -fms-extensions | FileCheck %s -check-prefix=X64
+// RUN: %clang_cc1 -std=c++11 -fno-rtti -emit-llvm %s -o - -triple=i386-pc-win32 -DINCOMPLETE_VIRTUAL -fms-extensions -verify
+// RUN: %clang_cc1 -std=c++11 -fno-rtti -emit-llvm %s -o - -triple=i386-pc-win32 -DINCOMPLETE_VIRTUAL -DMEMFUN -fms-extensions -verify
 // FIXME: Test x86_64 member pointers when codegen no longer asserts on records
 // with virtual bases.
 
@@ -630,6 +630,17 @@ void test() { void (B::*a)() = &B::f; }
 // CHECK: store i8* bitcast (void (%"struct.pr20007_kw::A"*)* @"\01?f@A@pr20007_kw@@QAEXXZ" to i8*)
 }
 
+namespace pr19987 {
+template <typename T>
+struct S {
+  int T::*x;
+};
+
+struct U : S<U> {};
+
+static_assert(sizeof(S<U>::x) == 12, "");
+}
+
 #else
 struct __virtual_inheritance A;
 #ifdef MEMFUN