[CMake] Support libc++ as Clang default stdlib in compiler-rt

[phosek]

Summary

Use libc++ when selected as default Clang stdlib and avoid checking
C++ compiler when using the in-tree version of libc++.

This is a partial alternative to D47094 that does not rely on compiler
runtime checks.

[vitalybuka]

compiler-rt/CMakeLists.txt

143 ↗

(On Diff #147692)

Is it possible to split the patch in parts and submit independently with some delay for easier debugging?

[phosek]

compiler-rt/CMakeLists.txt

143 ↗

(On Diff #147692)

Yes, totally. Do you have any preference? I could split the change to test_target_arch as one patch, change to options as a second one and change to llvm/runtimes as a third one?

[vitalybuka]

compiler-rt/CMakeLists.txt

143 ↗

(On Diff #147692)

sgtm

CMakeLists.txt

 endif()
 
 option(COMPILER_RT_DEBUG "Build runtimes with full debug info" OFF)
 option(COMPILER_RT_EXTERNALIZE_DEBUGINFO
   "Generate dSYM files and strip executables and libraries (Darwin Only)" OFF)
 # COMPILER_RT_DEBUG_PYBOOL is used by lit.common.configured.in.
 pythonize_bool(COMPILER_RT_DEBUG)
 
-include(HandleCompilerRT)
-include(config-ix)
-
 if(APPLE AND SANITIZER_MIN_OSX_VERSION AND SANITIZER_MIN_OSX_VERSION VERSION_LESS "10.9")
   # Mac OS X prior to 10.9 had problems with exporting symbols from
   # libc++/libc++abi.
   set(cxxabi_supported OFF)
 else()
   set(cxxabi_supported ON)
 endif()
 
 option(SANITIZER_ALLOW_CXXABI "Allow use of C++ ABI details in ubsan" ON)
 
 set(SANITIZE_CAN_USE_CXXABI OFF)
 if (cxxabi_supported AND SANITIZER_ALLOW_CXXABI)
   set(SANITIZER_CAN_USE_CXXABI ON)
 endif()
 pythonize_bool(SANITIZER_CAN_USE_CXXABI)
 
 set(SANITIZER_CXX_ABI "default" CACHE STRING
     "Specify C++ ABI library to use.")
-set(CXXABIS none default libcxxabi libstdc++ libc++)
+set(CXXABIS none default libstdc++ libc++)
 set_property(CACHE SANITIZER_CXX_ABI PROPERTY STRINGS ;${CXXABIS})
 
 if (SANITIZER_CXX_ABI STREQUAL "default")
-  if (HAVE_LIBCXXABI AND COMPILER_RT_DEFAULT_TARGET_ONLY)
-    set(SANITIZER_CXX_ABI_LIBNAME "libcxxabi")
+  if (CLANG_DEFAULT_CXX_STDLIB STREQUAL "libc++" AND (TARGET cxx OR HAVE_LIBCXX))
+    set(SANITIZER_CXX_ABI_LIBNAME "libc++")
     set(SANITIZER_CXX_ABI_INTREE 1)
   elseif (APPLE)
-    set(SANITIZER_CXX_ABI_LIBNAME "libcxxabi")
+    set(SANITIZER_CXX_ABI_LIBNAME "libc++")
     set(SANITIZER_CXX_ABI_SYSTEM 1)
+  elseif (FUCHSIA)
+    set(SANITIZER_CXX_ABI_LIBNAME "libc++")
+    set(SANITIZER_CXX_ABI_INTREE 1)
   else()
     set(SANITIZER_CXX_ABI_LIBNAME "libstdc++")
+    set(SANITIZER_CXX_ABI_SYSTEM 1)
   endif()
 else()
   set(SANITIZER_CXX_ABI_LIBNAME "${SANITIZER_CXX_ABI}")
-endif()
-
-if (SANITIZER_CXX_ABI_LIBNAME STREQUAL "libcxxabi")
-  if (SANITIZER_CXX_ABI_INTREE)
-    if (NOT LIBCXXABI_ENABLE_STATIC_UNWINDER AND (TARGET unwind_shared OR HAVE_LIBUNWIND))
-      list(APPEND SANITIZER_CXX_ABI_LIBRARY unwind_shared)
-    elseif (LIBCXXABI_ENABLE_STATIC_UNWINDER AND (TARGET unwind_static OR HAVE_LIBUNWIND))
-      list(APPEND SANITIZER_CXX_ABI_LIBRARY unwind_static)
-    endif()
-    if (NOT LIBCXX_ENABLE_STATIC_ABI_LIBRARY AND (TARGET cxxabi_shared OR HAVE_LIBCXXABI))
-      list(APPEND SANITIZER_CXX_ABI_LIBRARY cxxabi_shared)
-    elseif (LIBCXX_ENABLE_STATIC_ABI_LIBRARY AND (TARGET cxxabi_static OR HAVE_LIBCXXABI))
-      list(APPEND SANITIZER_CXX_ABI_LIBRARY cxxabi_static)
-    endif()
-  else()
-    list(APPEND SANITIZER_CXX_ABI_LIBRARY "c++abi")
-  endif()
-elseif (SANITIZER_CXX_ABI_LIBNAME STREQUAL "libc++")
-  list(APPEND SANITIZER_CXX_ABI_LIBRARY "c++")
-elseif (SANITIZER_CXX_ABI_LIBNAME STREQUAL "libstdc++")
-  append_list_if(COMPILER_RT_HAS_LIBSTDCXX stdc++ SANITIZER_CXX_ABI_LIBRARY)
+  set(SANITIZER_CXX_ABI_SYSTEM 1)
 endif()
 
 option(SANITIZER_USE_COMPILER_RT "Use compiler-rt builtins instead of libgcc" OFF)
 
+include(HandleCompilerRT)
+include(config-ix)
+
 #================================
 # Setup Compiler Flags
 #================================
 
 if(MSVC)
   # Override any existing /W flags with /W4. This is what LLVM does.  Failing to
   # remove other /W[0-4] flags will result in a warning about overriding a
   # previous flag.

 
 append_list_if(COMPILER_RT_HAS_LIBC c SANITIZER_COMMON_LINK_LIBS)
 
 if("${CMAKE_SYSTEM_NAME}" STREQUAL "Fuchsia")
   list(APPEND SANITIZER_COMMON_LINK_FLAGS -Wl,-z,defs,-z,now,-z,relro)
   list(APPEND SANITIZER_COMMON_LINK_LIBS zircon)
 endif()
 
+if (SANITIZER_CXX_ABI_LIBNAME STREQUAL "libc++")
+  if (SANITIZER_CXX_ABI_INTREE)
+    if (NOT LIBCXXABI_ENABLE_STATIC_UNWINDER AND (TARGET unwind_shared OR HAVE_LIBUNWIND))
+      list(APPEND SANITIZER_CXX_ABI_LIBRARY unwind_shared)
+    elseif (LIBCXXABI_ENABLE_STATIC_UNWINDER AND (TARGET unwind_static OR HAVE_LIBUNWIND))
+      list(APPEND SANITIZER_CXX_ABI_LIBRARY unwind_static)
+    endif()
+    if (NOT LIBCXX_ENABLE_STATIC_ABI_LIBRARY AND (TARGET cxxabi_shared OR HAVE_LIBCXXABI))
+      list(APPEND SANITIZER_CXX_ABI_LIBRARY cxxabi_shared)
+    elseif (LIBCXX_ENABLE_STATIC_ABI_LIBRARY AND (TARGET cxxabi_static OR HAVE_LIBCXXABI))
+      list(APPEND SANITIZER_CXX_ABI_LIBRARY cxxabi_static)
+    endif()
+  else()
+    append_list_if(COMPILER_RT_HAS_LIBCXX c++ SANITIZER_CXX_ABI_LIBRARY)
+  endif()
+elseif (SANITIZER_CXX_ABI_LIBNAME STREQUAL "libstdc++")
+  append_list_if(COMPILER_RT_HAS_LIBSTDCXX stdc++ SANITIZER_CXX_ABI_LIBRARY)
+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 (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

cmake/config-ix.cmake

 check_library_exists(dl dlopen "" COMPILER_RT_HAS_LIBDL)
 check_library_exists(rt shm_open "" COMPILER_RT_HAS_LIBRT)
 check_library_exists(m pow "" COMPILER_RT_HAS_LIBM)
 check_library_exists(pthread pthread_create "" COMPILER_RT_HAS_LIBPTHREAD)
 if (ANDROID AND COMPILER_RT_HAS_LIBDL)
   # Android's libstdc++ has a dependency on libdl.
   list(APPEND CMAKE_REQUIRED_LIBRARIES dl)
 endif()
+check_library_exists(c++ __cxa_throw "" COMPILER_RT_HAS_LIBCXX)
 check_library_exists(stdc++ __cxa_throw "" COMPILER_RT_HAS_LIBSTDCXX)
 
 # Linker flags.
 if(ANDROID)
   check_linker_flag("-Wl,-z,global" COMPILER_RT_HAS_Z_GLOBAL)
   check_library_exists(log __android_log_write "" COMPILER_RT_HAS_LIBLOG)
 endif()