Index: lib/StaticAnalyzer/Core/CallEvent.cpp
===================================================================
--- lib/StaticAnalyzer/Core/CallEvent.cpp
+++ lib/StaticAnalyzer/Core/CallEvent.cpp
@@ -387,23 +387,24 @@
 
 RuntimeDefinition AnyFunctionCall::getRuntimeDefinition() const {
   const FunctionDecl *FD = getDecl();
+  if (!FD)
+    return {};
+
   // Note that the AnalysisDeclContext will have the FunctionDecl with
   // the definition (if one exists).
-  if (FD) {
-    AnalysisDeclContext *AD =
-      getLocationContext()->getAnalysisDeclContext()->
-      getManager()->getContext(FD);
-    bool IsAutosynthesized;
-    Stmt* Body = AD->getBody(IsAutosynthesized);
-    DEBUG({
-        if (IsAutosynthesized)
-          llvm::dbgs() << "Using autosynthesized body for " << FD->getName()
-                       << "\n";
-    });
-    if (Body) {
-      const Decl* Decl = AD->getDecl();
-      return RuntimeDefinition(Decl);
-    }
+  AnalysisDeclContext *AD =
+    getLocationContext()->getAnalysisDeclContext()->
+    getManager()->getContext(FD);
+  bool IsAutosynthesized;
+  Stmt* Body = AD->getBody(IsAutosynthesized);
+  DEBUG({
+      if (IsAutosynthesized)
+        llvm::dbgs() << "Using autosynthesized body for " << FD->getName()
+                     << "\n";
+  });
+  if (Body) {
+    const Decl* Decl = AD->getDecl();
+    return RuntimeDefinition(Decl);
   }
 
   SubEngine *Engine = getState()->getStateManager().getOwningEngine();
@@ -411,7 +412,7 @@
 
   // Try to get CTU definition only if CTUDir is provided.
   if (!Opts.naiveCTUEnabled())
-    return RuntimeDefinition();
+    return {};
 
   cross_tu::CrossTranslationUnitContext &CTUCtx =
       *Engine->getCrossTranslationUnitContext();
Index: test/Analysis/undef-call.c
===================================================================
--- test/Analysis/undef-call.c
+++ test/Analysis/undef-call.c
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -fsyntax-only -analyze -analyzer-checker=debug.ExprInspection -analyzer-config experimental-enable-naive-ctu-analysis=true -analyzer-config ctu-dir=%T/ctudir -verify %s
+// expected-no-diagnostics
+
+struct S {
+  void (*fp)();
+};
+
+int main() {
+  struct S s;
+  // This will cause the analyzer to look for a function definition that has
+  // no FunctionDecl. It used to cause a crash in AnyFunctionCall::getRuntimeDefinition.
+  // It would only occur when CTU analysis is enabled.
+  s.fp();
+}