From 58bd603109e4e6ca214712ca897d024bed07ef0f Mon Sep 17 00:00:00 2001
From: Erich Keane <erich.keane@intel.com>
Date: Fri, 15 Sep 2017 16:03:35 +0000
Subject: Fix the __interface inheritence rules to work better with IUnknown
 and IDispatch

__interface objects in MSVC are permitted to inherit from __interface types,
and interface-like types.

Additionally, there are two default interface-like types
(IUnknown and IDispatch) that all interface-like
types must inherit from.

Differential Revision: https://reviews.llvm.org/D37308

llvm-svn: 313364
---
 clang/lib/AST/DeclCXX.cpp      | 47 ++++++++++++++++++++++++++++++++++++++++++
 clang/lib/Sema/SemaDeclCXX.cpp |  2 +-
 2 files changed, 48 insertions(+), 1 deletion(-)

(limited to 'clang/lib')

diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
index 5782b7b56c9..d63d42c66ff 100644
--- a/clang/lib/AST/DeclCXX.cpp
+++ b/clang/lib/AST/DeclCXX.cpp
@@ -1470,6 +1470,53 @@ bool CXXRecordDecl::isAnyDestructorNoReturn() const {
   return false;
 }
 
+bool CXXRecordDecl::isInterfaceLike() const {
+  assert(hasDefinition() && "checking for interface-like without a definition");
+  // All __interfaces are inheritently interface-like.
+  if (isInterface())
+    return true;
+
+  // Interface-like types cannot have a user declared constructor, destructor,
+  // friends, VBases, conversion functions, or fields.  Additionally, lambdas
+  // cannot be interface types.
+  if (isLambda() || hasUserDeclaredConstructor() ||
+      hasUserDeclaredDestructor() || !field_empty() || hasFriends() ||
+      getNumVBases() > 0 || conversion_end() - conversion_begin() > 0)
+    return false;
+
+  // No interface-like type can have a method with a definition.
+  for (const auto *const Method : methods())
+    if (Method->isDefined())
+      return false;
+
+  // Check "Special" types.
+  const auto *Uuid = getAttr<UuidAttr>();
+  if (Uuid && isStruct() && getDeclContext()->isTranslationUnit() &&
+      ((getName() == "IUnknown" &&
+        Uuid->getGuid() == "00000000-0000-0000-C000-000000000046") ||
+       (getName() == "IDispatch" &&
+        Uuid->getGuid() == "00020400-0000-0000-C000-000000000046"))) {
+    if (getNumBases() > 0)
+      return false;
+    return true;
+  }
+
+  // FIXME: Any access specifiers is supposed to make this no longer interface
+  // like.
+
+  // If this isn't a 'special' type, it must have a single interface-like base.
+  if (getNumBases() != 1)
+    return false;
+
+  const auto BaseSpec = *bases_begin();
+  if (BaseSpec.isVirtual() || BaseSpec.getAccessSpecifier() != AS_public)
+    return false;
+  const auto *Base = BaseSpec.getType()->getAsCXXRecordDecl();
+  if (Base->isInterface() || !Base->isInterfaceLike())
+    return false;
+  return true;
+}
+
 void CXXRecordDecl::completeDefinition() {
   completeDefinition(nullptr);
 }
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 941930c51ae..a9ef333c66e 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -2388,7 +2388,7 @@ bool Sema::AttachBaseSpecifiers(CXXRecordDecl *Class,
       if (const RecordType *Record = NewBaseType->getAs<RecordType>()) {
         const CXXRecordDecl *RD = cast<CXXRecordDecl>(Record->getDecl());
         if (Class->isInterface() &&
-              (!RD->isInterface() ||
+              (!RD->isInterfaceLike() ||
                KnownBase->getAccessSpecifier() != AS_public)) {
           // The Microsoft extension __interface does not permit bases that
           // are not themselves public interfaces.
-- 
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