Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -352,11 +352,16 @@
 if(EXISTS ${COMPILER_RT_LIBCXX_PATH}/)
   set(COMPILER_RT_HAS_LIBCXX_SOURCES TRUE)
 else()
-  set(COMPILER_RT_LIBCXX_PATH ${LLVM_MAIN_SRC_DIR}/../libcxx)
+  set(COMPILER_RT_LIBCXX_PATH ${LLVM_MAIN_SRC_DIR}/runtimes/libcxx)
   if(EXISTS ${COMPILER_RT_LIBCXX_PATH}/)
     set(COMPILER_RT_HAS_LIBCXX_SOURCES TRUE)
   else()
-    set(COMPILER_RT_HAS_LIBCXX_SOURCES FALSE)
+    set(COMPILER_RT_LIBCXX_PATH ${LLVM_MAIN_SRC_DIR}/../libcxx)
+    if(EXISTS ${COMPILER_RT_LIBCXX_PATH}/)
+      set(COMPILER_RT_HAS_LIBCXX_SOURCES TRUE)
+    else()
+      set(COMPILER_RT_HAS_LIBCXX_SOURCES FALSE)
+    endif()
   endif()
 endif()
 
Index: lib/fuzzer/CMakeLists.txt
===================================================================
--- lib/fuzzer/CMakeLists.txt
+++ lib/fuzzer/CMakeLists.txt
@@ -32,6 +32,10 @@
 
 set(LIBFUZZER_CFLAGS ${SANITIZER_COMMON_CFLAGS})
 
+if(CMAKE_CXX_COMPILER_ID MATCHES Clang AND COMPILER_RT_HAS_LIBCXX_SOURCES)
+  list(APPEND LIBFUZZER_CFLAGS -stdlib=libc++ -D_LIBCPP_ABI_VERSION=Fuzzer)
+endif()
+
 append_list_if(COMPILER_RT_HAS_OMIT_FRAME_POINTER_FLAG -fno-omit-frame-pointer LIBFUZZER_CFLAGS)
 
 if (CMAKE_CXX_FLAGS MATCHES "fsanitize-coverage")
@@ -74,6 +78,24 @@
   CFLAGS ${LIBFUZZER_CFLAGS}
   PARENT_TARGET fuzzer)
 
+if(CMAKE_CXX_COMPILER_ID MATCHES Clang AND COMPILER_RT_HAS_LIBCXX_SOURCES)
+  foreach(arch ${FUZZER_SUPPORTED_ARCH})
+    get_target_flags_for_arch(${arch} TARGET_CFLAGS)
+    set(LIBCXX_PREFIX ${CMAKE_CURRENT_BINARY_DIR}/libcxx_fuzzer_${arch})
+    add_custom_libcxx(libcxx_fuzzer_${arch} ${LIBCXX_PREFIX}
+      CFLAGS ${TARGET_CFLAGS} -D_LIBCPP_ABI_VERSION=Fuzzer)
+    add_dependencies(clang_rt.fuzzer-${arch} libcxx_fuzzer_${arch})
+    add_custom_command(TARGET clang_rt.fuzzer-${arch} POST_BUILD
+      COMMAND
+        ${PYTHON_EXECUTABLE} ${COMPILER_RT_LIBCXX_PATH}/utils/merge_archives.py
+      ARGS
+        -o $<TARGET_LINKER_FILE:clang_rt.fuzzer-${arch}>
+        "$<TARGET_LINKER_FILE:clang_rt.fuzzer-${arch}>"
+        "${CMAKE_CURRENT_BINARY_DIR}/libcxx_fuzzer_${arch}/lib/libc++.a"
+    )
+  endforeach()
+endif()
+
 if(COMPILER_RT_INCLUDE_TESTS)
   add_subdirectory(tests)
 endif()
Index: lib/fuzzer/tests/CMakeLists.txt
===================================================================
--- lib/fuzzer/tests/CMakeLists.txt
+++ lib/fuzzer/tests/CMakeLists.txt
@@ -18,6 +18,10 @@
   list(APPEND LIBFUZZER_UNITTEST_LINK_FLAGS -lstdc++ -lpthread)
 endif()
 
+if(CMAKE_CXX_COMPILER_ID MATCHES Clang AND COMPILER_RT_HAS_LIBCXX_SOURCES)
+  list(APPEND LIBFUZZER_UNITTEST_CFLAGS -stdlib=libc++ -D_LIBCPP_ABI_VERSION=Fuzzer)
+endif()
+
 foreach(arch ${FUZZER_SUPPORTED_ARCH})
   set(LIBFUZZER_TEST_RUNTIME RTFuzzerTest.${arch})
   if(APPLE)
@@ -33,14 +37,20 @@
     ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
     FOLDER "Compiler-RT Runtime tests")
 
+  if(CMAKE_CXX_COMPILER_ID MATCHES Clang AND COMPILER_RT_HAS_LIBCXX_SOURCES)
+    set(LIBFUZZER_TEST_RUNTIME_DEPS libcxx_fuzzer_${arch})
+    set(LIBFUZZER_TEST_RUNTIME_LINK_FLAGS
+      "${CMAKE_CURRENT_BINARY_DIR}/../libcxx_fuzzer_${arch}/lib/libc++.a")
+  endif()
+
   set(FuzzerTestObjects)
   generate_compiler_rt_tests(FuzzerTestObjects
     FuzzerUnitTests "Fuzzer-${arch}-Test" ${arch}
     SOURCES FuzzerUnittest.cpp ${COMPILER_RT_GTEST_SOURCE}
     RUNTIME ${LIBFUZZER_TEST_RUNTIME}
-    DEPS gtest
+    DEPS gtest ${LIBFUZZER_TEST_RUNTIME_DEPS}
     CFLAGS ${LIBFUZZER_UNITTEST_CFLAGS}
-    LINK_FLAGS ${LIBFUZZER_UNITTEST_LINK_FLAGS})
+    LINK_FLAGS ${LIBFUZZER_UNITTEST_LINK_FLAGS} ${LIBFUZZER_TEST_RUNTIME_LINK_FLAGS})
   set_target_properties(FuzzerUnitTests PROPERTIES
     RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
 endforeach()