Index: lib/ubsan/ubsan_handlers_cxx.cc
===================================================================
--- lib/ubsan/ubsan_handlers_cxx.cc
+++ lib/ubsan/ubsan_handlers_cxx.cc
@@ -18,6 +18,8 @@
 #include "ubsan_type_hash.h"
 
 #include "sanitizer_common/sanitizer_common.h"
+#include "sanitizer_common/sanitizer_stacktrace.h"
+#include "sanitizer_common/sanitizer_symbolizer.h"
 
 using namespace __sanitizer;
 using namespace __ubsan;
@@ -26,9 +28,33 @@
   extern const char *TypeCheckKinds[];
 }
 
+#define MAX_STACK_DUMP_DEPTH 50
+
+int ubsan_vptr_inited = 0;
+
+static void DumpCurrentCallStack() {
+  StackTrace stack;
+  stack.Unwind(MAX_STACK_DUMP_DEPTH, GET_CALLER_PC(), GET_CURRENT_FRAME(), 0, 0, 0, false);
+  stack.Print();
+}
+
+static void ubsan_vptr_init() {
+  // Initialize symbolizer with an empty string to avoid aggressive online symbolizations.
+  Symbolizer::Init();
+
+  // FIXME: ubsan_vptr_init() is not thread safe.
+  ubsan_vptr_inited = 1;
+}
+
 static void HandleDynamicTypeCacheMiss(
     DynamicTypeCacheMissData *Data, ValueHandle Pointer, ValueHandle Hash,
     bool Abort) {
+
+  // Proactively trying to initialize since UBsan does not interpose any
+  // starting functions.
+  if (ubsan_vptr_inited == 0)
+    ubsan_vptr_init();
+
   if (checkDynamicType((void*)Pointer, Data->TypeInfo, Hash))
     // Just a cache miss. The type matches after all.
     return;
@@ -60,6 +86,8 @@
       << MangledName(DTI.getSubobjectTypeName())
       << Range(Pointer, Pointer + sizeof(uptr), "vptr for %2 base class of %1");
 
+  DumpCurrentCallStack();
+
   if (Abort)
     Die();
 }