Index: cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- cmake/modules/HandleLLVMOptions.cmake
+++ cmake/modules/HandleLLVMOptions.cmake
@@ -555,6 +555,8 @@
       append_common_sanitizer_flags()
       append("-fsanitize=undefined -fno-sanitize=vptr,function -fno-sanitize-recover=all"
               CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+      append(" -fsanitize-blacklist=${CMAKE_SOURCE_DIR}/utils/sanitizers/ubsan_blacklist.txt"
+	      CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
     elseif (LLVM_USE_SANITIZER STREQUAL "Thread")
       append_common_sanitizer_flags()
       append("-fsanitize=thread" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
Index: utils/sanitizers/ubsan_blacklist.txt
===================================================================
--- /dev/null
+++ utils/sanitizers/ubsan_blacklist.txt
@@ -0,0 +1,5 @@
+# This blacklist should be applied when LLVM is built
+# with -fsanitize=undefined instrumentation. It exists
+# because libstdc++ has some undefined behavior issues
+# in some of the headers, in particular, stl_tree.h.
+src:*bits/stl_tree.h