2 files changed, 31 insertions, 0 deletions
diff --git a/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp b/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp
index 6502af74a33..f4aa56f2750 100644
--- a/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp
+++ b/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp
@@ -42,19 +42,30 @@ void ExprEngine::performTrivialCopy(NodeBuilder &Bldr, ExplodedNode *Pred,
                                     const CallEvent &Call) {
   SVal ThisVal;
   bool AlwaysReturnsLValue;
+  const CXXRecordDecl *ThisRD = nullptr;
   if (const CXXConstructorCall *Ctor = dyn_cast<CXXConstructorCall>(&Call)) {
     assert(Ctor->getDecl()->isTrivial());
     assert(Ctor->getDecl()->isCopyOrMoveConstructor());
     ThisVal = Ctor->getCXXThisVal();
+    ThisRD = Ctor->getDecl()->getParent();
     AlwaysReturnsLValue = false;
   } else {
     assert(cast<CXXMethodDecl>(Call.getDecl())->isTrivial());
     assert(cast<CXXMethodDecl>(Call.getDecl())->getOverloadedOperator() ==
            OO_Equal);
     ThisVal = cast<CXXInstanceCall>(Call).getCXXThisVal();
+    ThisRD = cast<CXXMethodDecl>(Call.getDecl())->getParent();
     AlwaysReturnsLValue = true;
   }
 
+  assert(ThisRD);
+  if (ThisRD->isEmpty()) {
+    // Do nothing for empty classes. Otherwise it'd retrieve an UnknownVal
+    // and bind it and RegionStore would think that the actual value
+    // in this region at this offset is unknown.
+    return;
+  }
+
   const LocationContext *LCtx = Pred->getLocationContext();
 
   ExplodedNodeSet Dst;
diff --git a/clang/test/Analysis/ctor.mm b/clang/test/Analysis/ctor.mm
index 5ef2beea496..cfae8ed4ed0 100644
--- a/clang/test/Analysis/ctor.mm
+++ b/clang/test/Analysis/ctor.mm
@@ -729,3 +729,23 @@ namespace NoCrashOnEmptyBaseOptimization {
     S s;
   }
 }
+
+namespace EmptyBaseAssign {
+struct B1 {};
+struct B2 { int x; };
+struct D: public B1, public B2 {
+const D &operator=(const D &d) {
+  *((B2 *)this) = d;
+  *((B1 *)this) = d;
+  return *this;
+}
+};
+
+void test() {
+  D d1;
+  d1.x = 1;
+  D d2;
+  d2 = d1;
+  clang_analyzer_eval(d2.x == 1); // expected-warning{{TRUE}}
+}
+}