[CMake][compiler-rt] Support for using in-tree libc++

[phosek]

Summary

compiler-rt build has several options for choosing C++ ABI and C++
library for testing. These options are inadequate and incorrect as they
don't set the dependencies correctly when using in-tree libc++ and don't
support runtimes like ORC or XRay that use C++ library.

This change replaces these options with COMPILER_RT_USE_LIBCXX that
determines whether to use in-tree libc++ or not. If yes, it correctly
sets the dependendencies using generator expresions. If not, users
should use standard flags like CMAKE_CXX_FLAGS to select their preferred
C++ standard library.

[ldionne]

I like this, however IMO it would be better to instead have something like

COMPILER_RT_CXX_LIBRARY="libc++|system-libc++|libstdc++|..."

That way, this can be extended to support other C++ libraries without having to add new boolean options, and without forcing folks to use ad-hoc CMAKE_CXX_FLAGS in their builds. WDYT?

compiler-rt/CMakeLists.txt

479–481

I'm not sure I follow here -- we don't support using LLVM_ENABLE_PROJECTS=libcxx anymore.

483–500

Is there any reason why this can't be hardcoded to ${LLVM_MAIN_SRC_DIR}/.../libcxx? Why do we need to handle the other layouts?

Edit: Oh, I see, this was only moved around. I assume you prefer making these other changes in separate patches.

[smeenai]

(clearing my queue while there are unaddressed comments)

[phosek]

compiler-rt/CMakeLists.txt

479–481

I cleaned this in D126905.

483–500

I have created D126905 to clean up these flags.

[phosek]

This was broken up into a series of smaller changes which landed separately.

clang/cmake/caches/Fuchsia-stage2.cmake

if(LINUX_${target}_SYSROOT)
     set(RUNTIMES_${target}_CMAKE_C_FLAGS "--target=${target}" CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_CXX_FLAGS "--target=${target}" CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_ASM_FLAGS "--target=${target}" CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_SYSROOT ${LINUX_${target}_SYSROOT} CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_SHARED_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_MODULE_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_EXE_LINKER_FLAGS "-fuse-ld=lld" CACHE STRING "")
     set(RUNTIMES_${target}_COMPILER_RT_USE_BUILTINS_LIBRARY ON CACHE BOOL "")
+    set(RUNTIMES_${target}_COMPILER_RT_USE_LIBCXX ON CACHE BOOL "")
+    set(RUNTIMES_${target}_COMPILER_RT_ENABLE_STATIC_LIBCXX ON CACHE BOOL "")
     set(RUNTIMES_${target}_COMPILER_RT_CAN_EXECUTE_TESTS ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBUNWIND_ENABLE_SHARED OFF CACHE BOOL "")
     set(RUNTIMES_${target}_LIBUNWIND_USE_COMPILER_RT ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXXABI_USE_COMPILER_RT ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXXABI_ENABLE_SHARED OFF CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXXABI_USE_LLVM_UNWINDER ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXXABI_ENABLE_STATIC_UNWINDER ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXXABI_INSTALL_LIBRARY OFF CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXX_USE_COMPILER_RT ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXX_ENABLE_SHARED OFF CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXX_ENABLE_STATIC_ABI_LIBRARY ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXX_ABI_VERSION 2 CACHE STRING "")
     set(RUNTIMES_${target}_LLVM_ENABLE_ASSERTIONS OFF CACHE BOOL "")
-    set(RUNTIMES_${target}_SANITIZER_CXX_ABI "libc++" CACHE STRING "")
-    set(RUNTIMES_${target}_SANITIZER_CXX_ABI_INTREE ON CACHE BOOL "")
-    set(RUNTIMES_${target}_SANITIZER_TEST_CXX "libc++" CACHE STRING "")
-    set(RUNTIMES_${target}_SANITIZER_TEST_CXX_INTREE ON CACHE BOOL "")
     set(RUNTIMES_${target}_COMPILER_RT_TEST_COMPILER_CFLAGS "--unwindlib=libunwind -static-libgcc" CACHE STRING "")
     set(RUNTIMES_${target}_SANITIZER_COMMON_TEST_TARGET_CFLAGS "--unwindlib=libunwind -static-libgcc" CACHE STRING "")
     set(RUNTIMES_${target}_TSAN_TEST_TARGET_CFLAGS "--unwindlib=libunwind -static-libgcc" CACHE STRING "")
     set(RUNTIMES_${target}_LLVM_TOOLS_DIR "${CMAKE_BINARY_DIR}/bin" CACHE BOOL "")
     set(RUNTIMES_${target}_LLVM_ENABLE_RUNTIMES "compiler-rt;libcxx;libcxxabi;libunwind" CACHE STRING "")
 
     # Use .build-id link.
     list(APPEND RUNTIME_BUILD_ID_LINK "${target}")
foreach(target x86_64-unknown-fuchsia;aarch64-unknown-fuchsia)
     set(RUNTIMES_${target}_CMAKE_ASM_FLAGS ${FUCHSIA_${target}_COMPILER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_C_FLAGS ${FUCHSIA_${target}_COMPILER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_CXX_FLAGS ${FUCHSIA_${target}_COMPILER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_SHARED_LINKER_FLAGS ${FUCHSIA_${target}_LINKER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_MODULE_LINKER_FLAGS ${FUCHSIA_${target}_LINKER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_EXE_LINKER_FLAGS ${FUCHSIA_${target}_LINKER_FLAGS} CACHE STRING "")
     set(RUNTIMES_${target}_CMAKE_SYSROOT ${FUCHSIA_${target}_SYSROOT} CACHE PATH "")
     set(RUNTIMES_${target}_COMPILER_RT_USE_BUILTINS_LIBRARY ON CACHE BOOL "")
+    set(RUNTIMES_${target}_COMPILER_RT_USE_LIBCXX ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBUNWIND_USE_COMPILER_RT ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBUNWIND_HIDE_SYMBOLS ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBUNWIND_INSTALL_STATIC_LIBRARY OFF CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXXABI_USE_COMPILER_RT ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXXABI_USE_LLVM_UNWINDER ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXXABI_ENABLE_STATIC_UNWINDER ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXXABI_HERMETIC_STATIC_LIBRARY ON CACHE BOOL "")
     set(RUNTIMES_${target}_LIBCXXABI_INSTALL_STATIC_LIBRARY OFF CACHE BOOL "")

compiler-rt/CMakeLists.txt

 option(SANITIZER_ALLOW_CXXABI "Allow use of C++ ABI details in ubsan" ON)
 
 set(SANITIZER_CAN_USE_CXXABI OFF)
 if (cxxabi_supported AND SANITIZER_ALLOW_CXXABI)
   set(SANITIZER_CAN_USE_CXXABI ON)
 endif()
 pythonize_bool(SANITIZER_CAN_USE_CXXABI)
 
-macro(handle_default_cxx_lib var)
-  # Specifying -stdlib= in CMAKE_CXX_FLAGS overrides the defaults.
-  if (CMAKE_CXX_FLAGS MATCHES "-stdlib=([a-zA-Z+]*)")
-    set(${var}_LIBNAME "${CMAKE_MATCH_1}")
-    set(${var}_SYSTEM 1)
-  elseif (${var} STREQUAL "default")
-    if (APPLE OR CMAKE_SYSTEM_NAME MATCHES "FreeBSD")
-      set(${var}_LIBNAME "libc++")
-      set(${var}_SYSTEM 1)
-    elseif (FUCHSIA)
-      set(${var}_LIBNAME "libc++")
-      set(${var}_INTREE 1)
-    else()
-      set(${var}_LIBNAME "libstdc++")
-      set(${var}_SYSTEM 1)
-    endif()
-  else()
-    set(${var}_LIBNAME "${${var}}")
-    set(${var}_SYSTEM 1)
-  endif()
-endmacro()
-
-# This is either directly the C++ ABI library or the full C++ library
-# which pulls in the ABI transitively.
-set(SANITIZER_CXX_ABI "default" CACHE STRING
-    "Specify C++ ABI library to use.")
-set(CXXABIS none default libstdc++ libc++ libcxxabi)
-set_property(CACHE SANITIZER_CXX_ABI PROPERTY STRINGS ;${CXXABIS})
-handle_default_cxx_lib(SANITIZER_CXX_ABI)
-
-# This needs to be a full C++ library for linking gtest and unit tests.
-set(SANITIZER_TEST_CXX "default" CACHE STRING
-    "Specify C++ library to use for tests.")
-set(CXXLIBS none default libstdc++ libc++)
-set_property(CACHE SANITIZER_TEST_CXX PROPERTY STRINGS ;${CXXLIBS})
-handle_default_cxx_lib(SANITIZER_TEST_CXX)
-
 set(DEFAULT_SANITIZER_USE_STATIC_LLVM_UNWINDER OFF)
 if (FUCHSIA)
   set(DEFAULT_SANITIZER_USE_STATIC_LLVM_UNWINDER ON)
 elseif (DEFINED LIBUNWIND_ENABLE_SHARED AND NOT LIBUNWIND_ENABLE_SHARED)
   set(DEFAULT_SANITIZER_USE_STATIC_LLVM_UNWINDER ON)
 endif()
 
 option(SANITIZER_USE_STATIC_LLVM_UNWINDER

 else()
   set(SANITIZER_NO_UNDEFINED_SYMBOLS_DEFAULT OFF)
 endif()
 option(SANITIZER_NO_UNDEFINED_SYMBOLS "Report error on unresolved symbol references" ${SANITIZER_NO_UNDEFINED_SYMBOLS_DEFAULT})
 if (SANITIZER_NO_UNDEFINED_SYMBOLS)
   list(APPEND SANITIZER_COMMON_LINK_FLAGS -Wl,-z,defs)
 endif()
 
-# TODO: COMPILER_RT_COMMON_CFLAGS and COMPILER_RT_COMMON_LINK_FLAGS are
-# intended for use in non-sanitizer runtimes such as libFuzzer, profile or XRay,
-# move these higher to include common flags, then derive SANITIZER_COMMON_CFLAGS
-# and SANITIZER_COMMON_LINK_FLAGS from those and append sanitizer-specific flags.
-set(COMPILER_RT_COMMON_CFLAGS ${SANITIZER_COMMON_CFLAGS})
-set(COMPILER_RT_COMMON_LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS})
-
-# We don't use the C++ standard library, so avoid including it by mistake.
-append_list_if(COMPILER_RT_HAS_NOSTDINCXX_FLAG -nostdinc++ SANITIZER_COMMON_CFLAGS)
-append_list_if(COMPILER_RT_HAS_NOSTDLIBXX_FLAG -nostdlib++ SANITIZER_COMMON_LINK_FLAGS)
-
-# Remove -stdlib= which is unused when passing -nostdinc++...
-string(REGEX MATCHALL "-stdlib=[a-zA-Z+]*" stdlib_flag "${CMAKE_CXX_FLAGS}")
-string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
-
-# ...we need it to build some runtimes and tests so readd it where appropriate.
-list(APPEND COMPILER_RT_COMMON_CFLAGS ${stdlib_flag})
-list(APPEND COMPILER_RT_COMMON_LINK_FLAGS ${stdlib_flag})
-
-macro(append_libcxx_libs var)
-  if (${var}_INTREE)
-    if (SANITIZER_USE_STATIC_LLVM_UNWINDER AND (TARGET unwind_static OR HAVE_LIBUNWIND))
-      list(APPEND ${var}_LIBRARIES unwind_static)
-    elseif (TARGET unwind_shared OR HAVE_LIBUNWIND)
-      list(APPEND ${var}_LIBRARIES unwind_shared)
-    endif()
-
-    if (SANITIZER_USE_STATIC_CXX_ABI AND (TARGET cxxabi_static OR HAVE_LIBCXXABI))
-      list(APPEND ${var}_LIBRARIES cxxabi_static)
-    elseif (TARGET cxxabi_shared OR HAVE_LIBCXXABI)
-      list(APPEND ${var}_LIBRARIES cxxabi_shared)
-    endif()
-  else()
-    append_list_if(COMPILER_RT_HAS_LIBCXX c++ ${var}_LIBRARIES)
-  endif()
-endmacro()
-
-if (SANITIZER_CXX_ABI_LIBNAME STREQUAL "libc++")
-  append_libcxx_libs(SANITIZER_CXX_ABI)
-elseif (SANITIZER_CXX_ABI_LIBNAME STREQUAL "libcxxabi")
-  list(APPEND SANITIZER_CXX_ABI_LIBRARIES "c++abi")
-elseif (SANITIZER_CXX_ABI_LIBNAME STREQUAL "libstdc++")
-  append_list_if(COMPILER_RT_HAS_LIBSTDCXX stdc++ SANITIZER_CXX_ABI_LIBRARIES)
-endif()
+# Warnings to turn off for all libraries, not just sanitizers.
+append_string_if(COMPILER_RT_HAS_WUNUSED_PARAMETER_FLAG -Wno-unused-parameter CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
 
-if (SANITIZER_TEST_CXX_LIBNAME STREQUAL "libc++")
-  if (SANITIZER_TEST_CXX_INTREE)
-    if (SANITIZER_USE_STATIC_TEST_CXX)
-      set(cxx_target cxx_static)
-    else()
-      set(cxx_target cxx_shared)
-    endif()
-    list(APPEND SANITIZER_TEST_CXX_LIBRARIES "$<$<BOOL:$<TARGET_NAME_IF_EXISTS:${cxx_target}>>:$<TARGET_LINKER_FILE:${cxx_target}>>")
-  else()
-    append_list_if(COMPILER_RT_HAS_LIBCXX -lc++ SANITIZER_TEST_CXX_LIBRARIES)
-  endif()
-elseif (SANITIZER_TEST_CXX_LIBNAME STREQUAL "libstdc++")
-  append_list_if(COMPILER_RT_HAS_LIBSTDCXX -lstdc++ SANITIZER_TEST_CXX_LIBRARIES)
+if (CMAKE_LINKER MATCHES "link.exe$")
+  # Silence MSVC linker warnings caused by empty object files. The
+  # sanitizer libraries intentionally use ifdefs that result in empty
+  # files, rather than skipping these files in the build system.
+  # Ideally, we would pass this flag only for the libraries that need
+  # it, but CMake doesn't seem to have a way to set linker flags for
+  # individual static libraries, so we enable the suppression flag for
+  # the whole compiler-rt project.
+  set(CMAKE_STATIC_LINKER_FLAGS "${CMAKE_STATIC_LINKER_FLAGS} /IGNORE:4221")
 endif()
 
 # TODO: There's a lot of duplication across lib/*/tests/CMakeLists.txt files,
 # move some of the common flags to COMPILER_RT_UNITTEST_CFLAGS.
 
-# Unittests need access to C++ standard library.
-string(APPEND COMPILER_RT_TEST_COMPILER_CFLAGS " ${stdlib_flag}")
-
 # When cross-compiling, COMPILER_RT_TEST_COMPILER_CFLAGS help in compilation
 # and linking of unittests.
 string(REPLACE " " ";" COMPILER_RT_UNITTEST_CFLAGS "${COMPILER_RT_TEST_COMPILER_CFLAGS}")
 set(COMPILER_RT_UNITTEST_LINK_FLAGS ${COMPILER_RT_UNITTEST_CFLAGS})
 
-# Unittests support.
-set(COMPILER_RT_GTEST_PATH ${LLVM_MAIN_SRC_DIR}/utils/unittest/googletest)
-set(COMPILER_RT_GTEST_SOURCE ${COMPILER_RT_GTEST_PATH}/src/gtest-all.cc)
-set(COMPILER_RT_GTEST_CFLAGS
-  -DGTEST_NO_LLVM_SUPPORT=1
-  -DGTEST_HAS_RTTI=0
-  -I${COMPILER_RT_GTEST_PATH}/include
-  -I${COMPILER_RT_GTEST_PATH}
-)
-
-# Mocking support.
-set(COMPILER_RT_GMOCK_PATH ${LLVM_MAIN_SRC_DIR}/utils/unittest/googlemock)
-set(COMPILER_RT_GMOCK_SOURCE ${COMPILER_RT_GMOCK_PATH}/src/gmock-all.cc)
-set(COMPILER_RT_GMOCK_CFLAGS
-  -DGTEST_NO_LLVM_SUPPORT=1
-  -DGTEST_HAS_RTTI=0
-  -I${COMPILER_RT_GMOCK_PATH}/include
-  -I${COMPILER_RT_GMOCK_PATH}
-)
-
-if(COMPILER_RT_HAS_G_FLAG)
-  list(APPEND COMPILER_RT_UNITTEST_CFLAGS -g)
-endif()
 append_list_if(COMPILER_RT_DEBUG -DSANITIZER_DEBUG=1 COMPILER_RT_UNITTEST_CFLAGS)
+append_list_if(COMPILER_RT_HAS_G_FLAG -g COMPILER_RT_UNITTEST_CFLAGS)
 append_list_if(COMPILER_RT_HAS_WCOVERED_SWITCH_DEFAULT_FLAG -Wno-covered-switch-default COMPILER_RT_UNITTEST_CFLAGS)
 append_list_if(COMPILER_RT_HAS_WSUGGEST_OVERRIDE_FLAG -Wno-suggest-override COMPILER_RT_UNITTEST_CFLAGS)
 
-if(MSVC)
-  # gtest use a lot of stuff marked as deprecated on Windows.
-  list(APPEND COMPILER_RT_GTEST_CFLAGS -Wno-deprecated-declarations)
+option(COMPILER_RT_USE_LIBCXX
+  "Enable compiler-rt to use libc++ from the source tree" ON)
+if(COMPILER_RT_USE_LIBCXX)
+  # Disable the use of default standard library.
+  append_list_if(COMPILER_RT_HAS_NOSTDINCXX_FLAG -nostdinc++ SANITIZER_COMMON_CFLAGS)
+  append_list_if(COMPILER_RT_HAS_NOSTDLIBXX_FLAG -nostdlib++ SANITIZER_COMMON_LINK_FLAGS)
+
+  # Remove -stdlib= which is unused when passing -nostdinc++.
+  string(REGEX MATCHALL "-stdlib=[a-zA-Z+]*" stdlib_flag "${CMAKE_CXX_FLAGS}")
+  string(REGEX REPLACE "-stdlib=[a-zA-Z+]*" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+
+  if (SANITIZER_USE_STATIC_LLVM_UNWINDER)
+    set(unwind_target unwind_static)
+  else()
+    set(unwind_target unwind_shared)
   endif()
+  list(APPEND SANITIZER_CXX_ABI_LIBRARIES "$<$<TARGET_EXISTS:${unwind_target}>:$<TARGET_LINKER_FILE:${unwind_target}>>")
 
-# Warnings to turn off for all libraries, not just sanitizers.
-append_string_if(COMPILER_RT_HAS_WUNUSED_PARAMETER_FLAG -Wno-unused-parameter CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+  if (SANITIZER_USE_STATIC_CXX_ABI)
+    set(cxxabi_target cxxabi_static)
+  else()
+    set(cxxabi_target cxxabi_shared)
+  endif()
+  list(APPEND SANITIZER_CXX_ABI_LIBRARIES "$<$<TARGET_EXISTS:${cxxabi_target}>:$<TARGET_LINKER_FILE:${cxxabi_target}>>")
 
-if (CMAKE_LINKER MATCHES "link.exe$")
-  # Silence MSVC linker warnings caused by empty object files. The
-  # sanitizer libraries intentionally use ifdefs that result in empty
-  # files, rather than skipping these files in the build system.
-  # Ideally, we would pass this flag only for the libraries that need
-  # it, but CMake doesn't seem to have a way to set linker flags for
-  # individual static libraries, so we enable the suppression flag for
-  # the whole compiler-rt project.
-  set(CMAKE_STATIC_LINKER_FLAGS "${CMAKE_STATIC_LINKER_FLAGS} /IGNORE:4221")
+  # TODO: COMPILER_RT_COMMON_CFLAGS and COMPILER_RT_COMMON_LINK_FLAGS are
+  # intended for use in non-sanitizer runtimes such as libFuzzer, profile or XRay,
+  # move these higher to include common flags, then derive SANITIZER_COMMON_CFLAGS
+  # and SANITIZER_COMMON_LINK_FLAGS from those and append sanitizer-specific flags.
+  set(COMPILER_RT_COMMON_CFLAGS ${SANITIZER_COMMON_CFLAGS})
+  set(COMPILER_RT_COMMON_LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS})
+
+  if (COMPILER_RT_ENABLE_STATIC_LIBCXX)
+    set(cxx_target cxx_static)
+  else()
+    set(cxx_target cxx_shared)
   endif()
 
-add_subdirectory(include)
+  list(APPEND COMPILER_RT_COMMON_CFLAGS "$<$<TARGET_EXISTS:cxx-headers>:-isystem$<JOIN:$<TARGET_PROPERTY:cxx-headers,INTERFACE_INCLUDE_DIRECTORIES>,$<SEMICOLON>-isystem>>")
+  list(APPEND COMPILER_RT_COMMON_LINK_FLAGS "$<$<TARGET_EXISTS:${cxx_target}>:$<TARGET_LINKER_FILE:${cxx_target}>>")
+
+  # Use the in-tree libc++ for unit tests as well.
+  append_list_if(COMPILER_RT_HAS_NOSTDINCXX_FLAG -nostdinc++ COMPILER_RT_UNITTEST_CFLAGS)
+  append_list_if(COMPILER_RT_HAS_NOSTDLIBXX_FLAG -nostdlib++ COMPILER_RT_UNITTEST_LINK_FLAGS)
+
+  list(APPEND COMPILER_RT_UNITTEST_CFLAGS "$<$<TARGET_EXISTS:cxx-headers>:-isystem$<JOIN:$<TARGET_PROPERTY:cxx-headers,INTERFACE_INCLUDE_DIRECTORIES>,$<SEMICOLON>-isystem>>")
+  list(APPEND COMPILER_RT_UNITTEST_LINK_FLAGS "$<$<TARGET_EXISTS:${cxx_target}>:$<TARGET_LINKER_FILE:${cxx_target}>>")
 
-option(COMPILER_RT_USE_LIBCXX
-  "Enable compiler-rt to use libc++ from the source tree" ON)
-if(COMPILER_RT_USE_LIBCXX)
   if(LLVM_ENABLE_PROJECTS_USED)
     # Don't use libcxx if LLVM_ENABLE_PROJECTS does not enable it.
     set(COMPILER_RT_LIBCXX_PATH ${LLVM_EXTERNAL_LIBCXX_SOURCE_DIR})
     set(COMPILER_RT_LIBCXXABI_PATH ${LLVM_EXTERNAL_LIBCXXABI_SOURCE_DIR})
   else()
     foreach(path IN ITEMS ${LLVM_MAIN_SRC_DIR}/projects/libcxx
                           ${LLVM_MAIN_SRC_DIR}/runtimes/libcxx
                           ${LLVM_MAIN_SRC_DIR}/../libcxx
                           ${LLVM_EXTERNAL_LIBCXX_SOURCE_DIR})
       if(IS_DIRECTORY ${path})
         set(COMPILER_RT_LIBCXX_PATH ${path})
         break()
       endif()
     endforeach()
     foreach(path IN ITEMS ${LLVM_MAIN_SRC_DIR}/projects/libcxxabi
                           ${LLVM_MAIN_SRC_DIR}/runtimes/libcxxabi
                           ${LLVM_MAIN_SRC_DIR}/../libcxxabi
                           ${LLVM_EXTERNAL_LIBCXXABI_SOURCE_DIR})
       if(IS_DIRECTORY ${path})
         set(COMPILER_RT_LIBCXXABI_PATH ${path})
         break()
       endif()
     endforeach()
   endif()
+else()
+  set(COMPILER_RT_COMMON_CFLAGS ${SANITIZER_COMMON_CFLAGS})
+  set(COMPILER_RT_COMMON_LINK_FLAGS ${SANITIZER_COMMON_LINK_FLAGS})
+endif()
+
+# Unittests support.
+set(COMPILER_RT_GTEST_PATH ${LLVM_MAIN_SRC_DIR}/utils/unittest/googletest)
+set(COMPILER_RT_GTEST_SOURCE ${COMPILER_RT_GTEST_PATH}/src/gtest-all.cc)
+set(COMPILER_RT_GTEST_CFLAGS
+  -DGTEST_NO_LLVM_SUPPORT=1
+  -DGTEST_HAS_RTTI=0
+  -I${COMPILER_RT_GTEST_PATH}/include
+  -I${COMPILER_RT_GTEST_PATH}
+)
+
+# Mocking support.
+set(COMPILER_RT_GMOCK_PATH ${LLVM_MAIN_SRC_DIR}/utils/unittest/googlemock)
+set(COMPILER_RT_GMOCK_SOURCE ${COMPILER_RT_GMOCK_PATH}/src/gmock-all.cc)
+set(COMPILER_RT_GMOCK_CFLAGS
+  -DGTEST_NO_LLVM_SUPPORT=1
+  -DGTEST_HAS_RTTI=0
+  -I${COMPILER_RT_GMOCK_PATH}/include
+  -I${COMPILER_RT_GMOCK_PATH}
+)
+
+if(MSVC)
+  # gtest use a lot of stuff marked as deprecated on Windows.
+  list(APPEND COMPILER_RT_GTEST_CFLAGS -Wno-deprecated-declarations)
 endif()
 
 set(COMPILER_RT_LLD_PATH ${LLVM_MAIN_SRC_DIR}/tools/lld)
 if(EXISTS ${COMPILER_RT_LLD_PATH}/ AND LLVM_TOOL_LLD_BUILD)
   set(COMPILER_RT_HAS_LLD TRUE)
 else()
   set(COMPILER_RT_LLD_PATH ${LLVM_MAIN_SRC_DIR}/../lld)
   if(EXISTS ${COMPILER_RT_LLD_PATH}/ AND LLVM_TOOL_LLD_BUILD)
     set(COMPILER_RT_HAS_LLD TRUE)
   endif()
 endif()
 
 if(ANDROID)
   set(COMPILER_RT_HAS_LLD TRUE)
   set(COMPILER_RT_TEST_USE_LLD TRUE)
   append_list_if(COMPILER_RT_HAS_FUSE_LD_LLD_FLAG -fuse-ld=lld SANITIZER_COMMON_LINK_FLAGS)
   append_list_if(COMPILER_RT_HAS_LLD -fuse-ld=lld COMPILER_RT_UNITTEST_LINK_FLAGS)
 endif()
 pythonize_bool(COMPILER_RT_HAS_LLD)
 pythonize_bool(COMPILER_RT_TEST_USE_LLD)
 
+add_subdirectory(include)
 add_subdirectory(lib)
 
 if(COMPILER_RT_INCLUDE_TESTS)
   add_subdirectory(unittests)
   add_subdirectory(test)
   # Don't build llvm-lit for runtimes-build, it will clean up map_config.
   if (COMPILER_RT_STANDALONE_BUILD AND NOT LLVM_RUNTIMES_BUILD)
     # If we have a valid source tree, generate llvm-lit into the bin directory.

compiler-rt/lib/fuzzer/CMakeLists.txt

 
 CHECK_CXX_SOURCE_COMPILES("
   static thread_local int blah;
   int main() {
   return 0;
   }
   " HAS_THREAD_LOCAL)
 
-set(LIBFUZZER_CFLAGS ${COMPILER_RT_COMMON_CFLAGS})
+set(LIBFUZZER_CFLAGS ${SANITIZER_COMMON_CFLAGS})
 
 if(OS_NAME MATCHES "Linux|Fuchsia" AND
    COMPILER_RT_LIBCXX_PATH AND
    COMPILER_RT_LIBCXXABI_PATH)
   list(APPEND LIBFUZZER_CFLAGS -D_LIBCPP_ABI_VERSION=Fuzzer)
   append_list_if(COMPILER_RT_HAS_NOSTDINCXX_FLAG -nostdinc++ LIBFUZZER_CFLAGS)
 elseif(TARGET cxx-headers OR HAVE_LIBCXX)
   # libFuzzer uses C++ standard library headers.