Index: cmake/Modules/AddCompilerRT.cmake
===================================================================
--- cmake/Modules/AddCompilerRT.cmake
+++ cmake/Modules/AddCompilerRT.cmake
@@ -491,6 +491,7 @@
                -DCMAKE_INSTALL_PREFIX:PATH=<INSTALL_DIR>
                -DLLVM_PATH=${LLVM_MAIN_SRC_DIR}
                -DLIBCXX_STANDALONE_BUILD=On
+               -DLIBCXX_CXX_ABI=none
     LOG_BUILD 1
     LOG_CONFIGURE 1
     LOG_INSTALL 1
Index: lib/fuzzer/CMakeLists.txt
===================================================================
--- lib/fuzzer/CMakeLists.txt
+++ lib/fuzzer/CMakeLists.txt
@@ -32,6 +32,10 @@
 
 set(LIBFUZZER_CFLAGS ${SANITIZER_COMMON_CFLAGS})
 
+if(COMPILER_RT_HAS_LIBCXX_SOURCES)
+  list(APPEND LIBFUZZER_CFLAGS -nostdinc++ -D_LIBCPP_NAMESPACE=__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 +78,40 @@
   CFLAGS ${LIBFUZZER_CFLAGS}
   PARENT_TARGET fuzzer)
 
+if(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 ${TARGET_CFLAGS} -D_LIBCPP_NAMESPACE=__Fuzzer)
+    add_dependencies(RTfuzzer.${arch} libcxx_fuzzer_${arch})
+    add_dependencies(RTfuzzer_main.${arch} libcxx_fuzzer_${arch})
+    target_compile_options(RTfuzzer.${arch} PRIVATE
+      -isystem ${CMAKE_CURRENT_BINARY_DIR}/libcxx_fuzzer_${arch}/include/c++/v1
+    )
+    target_compile_options(RTfuzzer_main.${arch} PRIVATE
+      -isystem ${CMAKE_CURRENT_BINARY_DIR}/libcxx_fuzzer_${arch}/include/c++/v1
+    )
+    set(cxx_${arch}_merge_dir "${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/cxx_${arch}_merge.dir")
+    file(MAKE_DIRECTORY ${cxx_${arch}_merge_dir})
+    add_custom_command(TARGET clang_rt.fuzzer-${arch} POST_BUILD
+    COMMAND
+      ${CMAKE_AR}
+    ARGS
+      x ${CMAKE_CURRENT_BINARY_DIR}/libcxx_fuzzer_${arch}/lib/libc++.a
+    COMMAND
+      ${CMAKE_AR}
+    ARGS
+      x "$<TARGET_LINKER_FILE:clang_rt.fuzzer-${arch}>"
+    COMMAND
+      ${CMAKE_AR}
+    ARGS
+      qcs "$<TARGET_LINKER_FILE:clang_rt.fuzzer-${arch}>" *.o*
+    WORKING_DIRECTORY ${cxx_${arch}_merge_dir}
+    )
+  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(COMPILER_RT_HAS_LIBCXX_SOURCES)
+  list(APPEND LIBFUZZER_UNITTEST_CFLAGS -nostdinc++ -D_LIBCPP_NAMESPACE=__Fuzzer)
+endif()
+
 foreach(arch ${FUZZER_SUPPORTED_ARCH})
   set(LIBFUZZER_TEST_RUNTIME RTFuzzerTest.${arch})
   if(APPLE)
@@ -33,14 +37,22 @@
     ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
     FOLDER "Compiler-RT Runtime tests")
 
+  if(COMPILER_RT_HAS_LIBCXX_SOURCES)
+    set(LIBFUZZER_TEST_RUNTIME_DEPS libcxx_fuzzer_${arch})
+    set(LIBFUZZER_TEST_RUNTIME_CFLAGS
+      -isystem ${CMAKE_CURRENT_BINARY_DIR}/../libcxx_fuzzer_${arch}/include/c++/v1)
+    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
-    CFLAGS ${LIBFUZZER_UNITTEST_CFLAGS}
-    LINK_FLAGS ${LIBFUZZER_UNITTEST_LINK_FLAGS})
+    DEPS gtest ${LIBFUZZER_TEST_RUNTIME_DEPS}
+    CFLAGS ${LIBFUZZER_UNITTEST_CFLAGS} ${LIBFUZZER_TEST_RUNTIME_CFLAGS}
+    LINK_FLAGS ${LIBFUZZER_UNITTEST_LINK_FLAGS} ${LIBFUZZER_TEST_RUNTIME_LINK_FLAGS})
   set_target_properties(FuzzerUnitTests PROPERTIES
     RUNTIME_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
 endforeach()
Index: test/CMakeLists.txt
===================================================================
--- test/CMakeLists.txt
+++ test/CMakeLists.txt
@@ -8,6 +8,8 @@
 # BlocksRuntime (and most of builtins) testsuites are not yet ported to lit.
 # add_subdirectory(BlocksRuntime)
 
+pythonize_bool(COMPILER_RT_HAS_STDLIB_LIBCXX)
+
 set(SANITIZER_COMMON_LIT_TEST_DEPS)
 
 if(COMPILER_RT_BUILD_PROFILE AND COMPILER_RT_HAS_PROFILE)
Index: test/fuzzer/CMakeLists.txt
===================================================================
--- test/fuzzer/CMakeLists.txt
+++ test/fuzzer/CMakeLists.txt
@@ -19,20 +19,24 @@
   list(APPEND LIBFUZZER_TESTSUITES ${CMAKE_CURRENT_BINARY_DIR}/unit)
 endif()
 
-foreach(arch ${FUZZER_SUPPORTED_ARCH})
-  set(LIBFUZZER_TEST_COMPILER ${COMPILER_RT_TEST_COMPILER})
-  get_test_cc_for_arch(${arch} LIBFUZZER_TEST_COMPILER LIBFUZZER_TEST_FLAGS)
-
-  string(TOUPPER ${arch} ARCH_UPPER_CASE)
-  set(CONFIG_NAME ${ARCH_UPPER_CASE}${OS_NAME}Config)
-
-  # LIT-based libFuzzer tests.
-  configure_lit_site_cfg(
-    ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.in
-    ${CMAKE_CURRENT_BINARY_DIR}/${CONFIG_NAME}/lit.site.cfg
-    )
-  list(APPEND LIBFUZZER_TESTSUITES ${CMAKE_CURRENT_BINARY_DIR}/${CONFIG_NAME})
-
+foreach(stdlib IN ITEMS stdlibc++)
+  foreach(arch ${FUZZER_SUPPORTED_ARCH})
+    set(LIBFUZZER_TEST_COMPILER ${COMPILER_RT_TEST_COMPILER})
+    get_test_cc_for_arch(${arch} LIBFUZZER_TEST_COMPILER LIBFUZZER_TEST_FLAGS)
+
+    set(LIBFUZZER_TEST_STDLIB ${stdlib})
+    string(TOUPPER ${stdlib} STDLIB_UPPER_CASE)
+
+    string(TOUPPER ${arch} ARCH_UPPER_CASE)
+    set(CONFIG_NAME ${ARCH_UPPER_CASE}${STDLIB_UPPER_CASE}${OS_NAME}Config)
+
+    # LIT-based libFuzzer tests.
+    configure_lit_site_cfg(
+      ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.in
+      ${CMAKE_CURRENT_BINARY_DIR}/${CONFIG_NAME}/lit.site.cfg
+      )
+    list(APPEND LIBFUZZER_TESTSUITES ${CMAKE_CURRENT_BINARY_DIR}/${CONFIG_NAME})
+  endforeach()
 endforeach()
 
 set(EXCLUDE_FROM_ALL ON)
Index: test/fuzzer/lit.site.cfg.in
===================================================================
--- test/fuzzer/lit.site.cfg.in
+++ test/fuzzer/lit.site.cfg.in
@@ -5,6 +5,7 @@
 config.cpp_compiler = "@LIBFUZZER_TEST_COMPILER@"
 config.target_flags = "@LIBFUZZER_TEST_FLAGS@"
 config.c_compiler = "@LIBFUZZER_TEST_COMPILER@"
+config.stdlib = "@LIBFUZZER_TEST_STDLIB@"
 
 config.osx_sysroot_flag = "@OSX_SYSROOT_FLAG@"
 config.cmake_binary_dir = "@CMAKE_BINARY_DIR@"