[compiler-rt/mac]: use DARWIN_osx_SYSROOT to set OSX_SYSROOT_FLAG

[thakis]

Summary

No behavior change, and less code.

While here, also un-bitrot the libc++ header copy suggestion a bit.

[delcypher]

compiler-rt/cmake/base-config-ix.cmake

104

Can we actually remove this? This file is actually included in two places.

$ git grep base-config-ix
CMakeLists.txt:include(base-config-ix)
lib/builtins/CMakeLists.txt:  include(base-config-ix)

It seems the builtins directory can be used for a standalone build. I'm not entirely sure who is using this but I suspect if you remove this code you'd probably break the standalone builtin build because it doesn't include config-ix.cmake.

[kubamracek]

compiler-rt/cmake/config-ix.cmake

372

config-ix does a bunch of compilation attempts and flag detection above this point. I assume you've tested the change and it works fine, but I'm wondering how come that the these compilations don't need this option already set?

[kubamracek]

compiler-rt/cmake/base-config-ix.cmake

104

This is a good point. @steven_wu @arphaman ?

[steven_wu]

compiler-rt/cmake/base-config-ix.cmake

104

Sounds like a valid point. It is hard to reason about compiler_rt cmake. Might want to test all our build configurations to make sure this still works.

[thakis]

I tested this in a "normal" build. Should I test anything exotic? (I can't test the apple-internal things, obvsly.)

compiler-rt/cmake/config-ix.cmake

372

I guess none of them include c++ stdlib headers.

[kubamracek]

compiler-rt/cmake/config-ix.cmake

372

The -isysroot flag is needed even for C headers. And for example test_targets() about 200 lines above is test-compiling and using stdlib.h+stdio.h.

compiler-rt/cmake/Modules/CompilerRTCompile.cmake

set(CMD
       "  echo 'You should copy or symlink your system C++ headers into ${LLVM_BINARY_DIR}/include/c++'"
       "  if [ -d $(dirname $(dirname $(xcrun -f clang)))/include/c++ ]"
       "    then echo 'e.g. with:'"
       "    echo '  cp -r' $(dirname $(dirname $(xcrun -f clang)))/include/c++ '${LLVM_BINARY_DIR}/include/'"
       "  elif [ -d $(dirname $(dirname $(xcrun -f clang)))/lib/c++ ]"
       "    then echo 'e.g. with:'"
       "    echo '  cp -r' $(dirname $(dirname $(xcrun -f clang)))/lib/c++ '${LLVM_BINARY_DIR}/include/'"
       "  fi"
-      "  echo 'This can also be fixed by checking out the libcxx project from llvm.org and installing the headers'"
-      "  echo 'into your build directory:'"
-      "  echo '  cd ${LLVM_MAIN_SRC_DIR}/projects && svn co http://llvm.org/svn/llvm-project/libcxx/trunk libcxx'"
-      "  echo '  cd ${LLVM_BINARY_DIR} && make -C ${LLVM_MAIN_SRC_DIR}/projects/libcxx installheaders HEADER_DIR=${LLVM_BINARY_DIR}/include'"
+      "  echo 'This can also be fixed by adding libcxx to LLVM_ENABLE_PROJECTS and building the cxx-headers target.'"
       "  echo"
       "  false"
       "fi"
       )
     add_custom_target(CompilerRTUnitTestCheckCxx
       COMMAND bash -c "${CMD}"
       COMMENT "Checking that just-built clang can find C++ headers..."
       VERBATIM)
     if (NOT COMPILER_RT_STANDALONE_BUILD AND NOT RUNTIMES_BUILD)
       ADD_DEPENDENCIES(CompilerRTUnitTestCheckCxx clang)
     endif()
   endif()
 endmacro()

compiler-rt/cmake/base-config-ix.cmake

 else(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR)
   set(COMPILER_RT_LIBRARY_OUTPUT_DIR
     ${COMPILER_RT_OUTPUT_DIR}/lib/${COMPILER_RT_OS_DIR})
   set(COMPILER_RT_LIBRARY_INSTALL_DIR
     ${COMPILER_RT_INSTALL_PATH}/lib/${COMPILER_RT_OS_DIR})
 endif()
 
 if(APPLE)
-  # On Darwin if /usr/include/c++ doesn't exist, the user probably has Xcode but
-  # not the command line tools (or is using macOS 10.14 or newer). If this is
-  # the case, we need to find the OS X sysroot to pass to clang.
-  if(NOT EXISTS /usr/include/c++)
-    execute_process(COMMAND xcrun -sdk macosx --show-sdk-path
-       OUTPUT_VARIABLE OSX_SYSROOT
-       ERROR_QUIET
-       OUTPUT_STRIP_TRAILING_WHITESPACE)
-    if (NOT OSX_SYSROOT OR NOT EXISTS ${OSX_SYSROOT})
-      message(WARNING "Detected OSX_SYSROOT ${OSX_SYSROOT} does not exist")
-    else()
-      message(STATUS "Found OSX_SYSROOT: ${OSX_SYSROOT}")
-      set(OSX_SYSROOT_FLAG "-isysroot${OSX_SYSROOT}")
-    endif()
-  else()
-    set(OSX_SYSROOT_FLAG "")
-  endif()
-
   option(COMPILER_RT_ENABLE_IOS "Enable building for iOS" On)
   option(COMPILER_RT_ENABLE_WATCHOS "Enable building for watchOS - Experimental" Off)
   option(COMPILER_RT_ENABLE_TVOS "Enable building for tvOS - Experimental" Off)
 
 else()
   option(COMPILER_RT_DEFAULT_TARGET_ONLY "Build builtins only for the default target" Off)
 endif()
 

compiler-rt/cmake/config-ix.cmake

if(NOT DARWIN_osx_SYSROOT)
     message(WARNING "Could not determine OS X sysroot, trying /usr/include")
     if(EXISTS /usr/include)
       set(DARWIN_osx_SYSROOT /)
     else()
       message(ERROR "Could not detect OS X Sysroot. Either install Xcode or the Apple Command Line Tools")
     endif()
   endif()
 
+  # /usr/include/c++ doesn't exist on macOS 10.14 or newer.
+  # If this is the case, we need to find the OS X sysroot to pass to clang.
+  if(NOT EXISTS /usr/include/c++)
+    set(OSX_SYSROOT_FLAG "-isysroot${DARWIN_osx_SYSROOT}")
+  else()
+    set(OSX_SYSROOT_FLAG "")
+  endif()
+
   if(COMPILER_RT_ENABLE_IOS)
     list(APPEND DARWIN_EMBEDDED_PLATFORMS ios)
     set(DARWIN_ios_MIN_VER 9.0)
     set(DARWIN_ios_MIN_VER_FLAG -miphoneos-version-min)
     set(DARWIN_ios_SANITIZER_MIN_VER_FLAG
       ${DARWIN_ios_MIN_VER_FLAG}=${DARWIN_ios_MIN_VER})
     set(DARWIN_iossim_MIN_VER_FLAG -mios-simulator-version-min)
     set(DARWIN_iossim_SANITIZER_MIN_VER_FLAG