[CMake] Support CMake variables for setting target, sysroot and toolchain

[phosek]

Summary

CMake has a standard way of setting target triple, sysroot and external
toolchain through CMAKE_<LANG>_COMPILER_TARGET, CMAKE_SYSROOT and
CMAKE_<LANG>_COMPILER_EXTERNAL_TOOLCHAIN. These are turned into
corresponding --target=, --sysroot= and --gcc-toolchain= variables add
included appended to CMAKE_<LANG>_FLAGS.

libunwind, libc++abi, libc++ provides their own mechanism through
<PROJECT>_TARGET_TRIPLE, <PROJECT>_SYSROOT and <PROJECT>_GCC_TOOLCHAIN
variables. These are also passed to lit via lit.site.cfg, and lit config
uses these to set the corresponding compiler flags when building tessts.

This means that there are two different ways of setting target, sysroot
and toolchain, but only one is properly supported in lit. This change
extends CMake build for libunwind, libc++abi and libc++ to also support
the CMake variables in addition to project specific ones in lit.

[ldionne]

libcxx/test/lit.site.cfg.in

20

This could instead be len("@TARGET_TRIPLE@") > 0 and we would avoid introducing LIBCXX_USE_TARGET.

[phosek]

libcxx/test/lit.site.cfg.in

20

I think converting that string to bool is even easier (since empty string is falsy).

[ldionne]

libcxx/CMakeLists.txt

484

Not needed anymore.

[arichardson]

I believe this broke building libunwind standalone for me since it complains about add_target_flags() not being defined. I guess it also needs to be copied to the libunwind cmake files?

[ldionne]

In D57670#1406075, @arichardson wrote:

I believe this broke building libunwind standalone for me since it complains about add_target_flags() not being defined. I guess it also needs to be copied to the libunwind cmake files?

That looks right. @phosek can you submit a patch?

[phosek]

Done in D58745.

libcxx/CMakeLists.txt

 
 # Build libc++abi with libunwind. We need this option to determine whether to
 # link with libunwind or libgcc_s while running the test cases.
 option(LIBCXXABI_USE_LLVM_UNWINDER "Build and use the LLVM unwinder." OFF)
 option(LIBCXXABI_ENABLE_STATIC_UNWINDER "Statically link the LLVM unwinder." OFF)
 
 # Target options --------------------------------------------------------------
 option(LIBCXX_BUILD_32_BITS "Build 32 bit libc++." ${LLVM_BUILD_32_BITS})
+set(LIBCXX_TARGET_TRIPLE "" CACHE STRING "Use alternate target triple.")
 set(LIBCXX_SYSROOT "" CACHE STRING "Use alternate sysroot.")
 set(LIBCXX_GCC_TOOLCHAIN "" CACHE STRING "Use alternate GCC toolchain.")
 
 # Feature options -------------------------------------------------------------
 option(LIBCXX_ENABLE_EXCEPTIONS "Use exceptions." ON)
 option(LIBCXX_ENABLE_RTTI "Use run time type information." ON)
 option(LIBCXX_ENABLE_GLOBAL_FILESYSTEM_NAMESPACE "Build libc++ with support for the global filesystem namespace." ON)
 option(LIBCXX_ENABLE_STDIN "Build libc++ with support for stdin/std::cin." ON)

 # Include macros for adding and removing libc++ flags.
 include(HandleLibcxxFlags)
 
 # Target flags ================================================================
 # These flags get added to CMAKE_CXX_FLAGS and CMAKE_C_FLAGS so that
 # 'config-ix' use them during feature checks. It also adds them to both
 # 'LIBCXX_COMPILE_FLAGS' and 'LIBCXX_LINK_FLAGS'
 add_target_flags_if(LIBCXX_BUILD_32_BITS "-m32")
-add_target_flags_if(LIBCXX_TARGET_TRIPLE "--target=${LIBCXX_TARGET_TRIPLE}")
-add_target_flags_if(LIBCXX_SYSROOT "--sysroot=${LIBCXX_SYSROOT}")
-add_target_flags_if(LIBCXX_GCC_TOOLCHAIN "--gcc-toolchain=${LIBCXX_GCC_TOOLCHAIN}")
-if (LIBCXX_TARGET_TRIPLE)
+
+if(LIBCXX_TARGET_TRIPLE)
+  add_target_flags("--target=${LIBCXX_TARGET_TRIPLE}")
+elseif(CMAKE_CXX_COMPILER_TARGET)
+  set(LIBCXX_TARGET_TRIPLE "${CMAKE_CXX_COMPILER_TARGET}")
+endif()
+if(LIBCXX_SYSROOT)
+  add_target_flags("--sysroot=${LIBCXX_SYSROOT}")
+elseif(CMAKE_SYSROOT)
+  set(LIBCXX_SYSROOT "${CMAKE_SYSROOT}")
+endif()
+message("TOOLCHAIN ${CMAKE_CXX_COMPILE_OPTIONS_EXTERNAL_TOOLCHAIN}")
+if(LIBCXX_GCC_TOOLCHAIN)
+  add_target_flags("--gcc-toolchain=${LIBCXX_GCC_TOOLCHAIN}")
+elseif(CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN)
+  set(LIBCXX_GCC_TOOLCHAIN "${CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN}")
+endif()
+
+if(LIBCXX_TARGET_TRIPLE)
   set(TARGET_TRIPLE "${LIBCXX_TARGET_TRIPLE}")
+  set(LIBCXX_USE_TARGET ON)
 endif()
 
 # Configure compiler.
 include(config-ix)
 
 if (LIBCXX_USE_COMPILER_RT)
   list(APPEND LIBCXX_LINK_FLAGS "-rtlib=compiler-rt")
 endif()

libcxx/test/lit.site.cfg.in

 config.enable_32bit             = "@LIBCXX_BUILD_32_BITS@"
 config.cxx_abi                  = "@LIBCXX_CXX_ABI_LIBNAME@"
 config.use_sanitizer            = "@LLVM_USE_SANITIZER@"
 config.sanitizer_library        = "@LIBCXX_SANITIZER_LIBRARY@"
 config.abi_library_path         = "@LIBCXX_CXX_ABI_LIBRARY_PATH@"
 config.configuration_variant    = "@LIBCXX_LIT_VARIANT@"
 config.host_triple              = "@LLVM_HOST_TRIPLE@"
 config.target_triple            = "@TARGET_TRIPLE@"
-config.use_target               = len("@LIBCXX_TARGET_TRIPLE@") > 0
+config.use_target               = bool("@LIBCXX_TARGET_TRIPLE@")
 config.sysroot                  = "@LIBCXX_SYSROOT@"
 config.gcc_toolchain            = "@LIBCXX_GCC_TOOLCHAIN@"
 config.generate_coverage        = "@LIBCXX_GENERATE_COVERAGE@"
 config.target_info              = "@LIBCXX_TARGET_INFO@"
 config.test_linker_flags        = "@LIBCXX_TEST_LINKER_FLAGS@"
 config.test_compiler_flags      = "@LIBCXX_TEST_COMPILER_FLAGS@"
 
 config.executor                 = "@LIBCXX_EXECUTOR@"

libcxxabi/CMakeLists.txt

 include(HandleLibcxxabiFlags)
 
 #===============================================================================
 # Setup Compiler Flags
 #===============================================================================
 
 # Configure target flags
 add_target_flags_if(LIBCXXABI_BUILD_32_BITS "-m32")
-add_target_flags_if(LIBCXXABI_TARGET_TRIPLE
-          "--target=${LIBCXXABI_TARGET_TRIPLE}")
-add_target_flags_if(LIBCXXABI_GCC_TOOLCHAIN
-         "--gcc-toolchain=${LIBCXXABI_GCC_TOOLCHAIN}")
-add_target_flags_if(LIBCXXABI_SYSROOT
-          "--sysroot=${LIBCXXABI_SYSROOT}")
+
+if(LIBCXXABI_TARGET_TRIPLE)
+  add_target_flags("--target=${LIBCXXABI_TARGET_TRIPLE}")
+elseif(CMAKE_CXX_COMPILER_TARGET)
+  set(LIBCXXABI_TARGET_TRIPLE "${CMAKE_CXX_COMPILER_TARGET}")
+endif()
+if(LIBCXX_GCC_TOOLCHAIN)
+  add_target_flags("--gcc-toolchain=${LIBCXXABI_GCC_TOOLCHAIN}")
+elseif(CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN)
+  set(LIBCXXABI_GCC_TOOLCHAIN "${CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN}")
+endif()
+if(LIBCXXABI_SYSROOT)
+  add_target_flags("--sysroot=${LIBCXXABI_SYSROOT}")
+elseif(CMAKE_SYSROOT)
+  set(LIBCXXABI_SYSROOT "${CMAKE_SYSROOT}")
+endif()
 
 if (LIBCXXABI_TARGET_TRIPLE)
   set(TARGET_TRIPLE "${LIBCXXABI_TARGET_TRIPLE}")
+  set(LIBCXXABI_USE_TARGET ON)
 endif()
 
 # Configure compiler. Must happen after setting the target flags.
 include(config-ix)
 
 if (LIBCXXABI_HAS_NOSTDINCXX_FLAG)
   list(APPEND LIBCXXABI_COMPILE_FLAGS -nostdinc++)
   # Remove -stdlib flags to prevent them from causing an unused flag warning.

libcxxabi/test/lit.site.cfg.in

 config.enable_32bit             = "@LIBCXXABI_BUILD_32_BITS@"
 config.target_info              = "@LIBCXXABI_TARGET_INFO@"
 config.executor                 = "@LIBCXXABI_EXECUTOR@"
 config.libcxxabi_shared         = "@LIBCXXABI_ENABLE_SHARED@"
 config.enable_shared            = "@LIBCXX_ENABLE_SHARED@"
 config.enable_exceptions        = "@LIBCXXABI_ENABLE_EXCEPTIONS@"
 config.host_triple              = "@LLVM_HOST_TRIPLE@"
 config.target_triple            = "@TARGET_TRIPLE@"
-config.use_target               = len("@LIBCXXABI_TARGET_TRIPLE@") > 0
+config.use_target               = bool("@LIBCXXABI_TARGET_TRIPLE@")
 config.sysroot                  = "@LIBCXXABI_SYSROOT@"
 config.gcc_toolchain            = "@LIBCXXABI_GCC_TOOLCHAIN@"
 config.cxx_ext_threads          = "@LIBCXXABI_BUILD_EXTERNAL_THREAD_LIBRARY@"
 
 # Let the main config do the real work.
 lit_config.load_config(config, "@LIBCXXABI_SOURCE_DIR@/test/lit.cfg")

libunwind/CMakeLists.txt

if (${condition})
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${var}")
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${var}")
     list(APPEND LIBUNWIND_COMPILE_FLAGS ${var})
     list(APPEND LIBUNWIND_LINK_FLAGS ${var})
   endif()
 endmacro()
 
 add_target_flags_if(LIBUNWIND_BUILD_32_BITS "-m32")
-add_target_flags_if(LIBUNWIND_TARGET_TRIPLE
-          "--target=${LIBUNWIND_TARGET_TRIPLE}")
-add_target_flags_if(LIBUNWIND_GCC_TOOLCHAIN
-          "--gcc-toolchain=${LIBUNWIND_GCC_TOOLCHAIN}")
-add_target_flags_if(LIBUNWIND_SYSROOT
-          "--sysroot=${LIBUNWIND_SYSROOT}")
+
+if(LIBUNWIND_TARGET_TRIPLE)
+  add_target_flags("--target=${LIBUNWIND_TARGET_TRIPLE}")
+elseif(CMAKE_CXX_COMPILER_TARGET)
+  set(LIBUNWIND_TARGET_TRIPLE "${CMAKE_CXX_COMPILER_TARGET}")
+endif()
+if(LIBUNWIND_GCC_TOOLCHAIN)
+  add_target_flags("--gcc-toolchain=${LIBUNWIND_GCC_TOOLCHAIN}")
+elseif(CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN)
+  set(LIBUNWIND_GCC_TOOLCHAIN "${CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN}")
+endif()
+if(LIBUNWIND_SYSROOT)
+  add_target_flags("--sysroot=${LIBUNWIND_SYSROOT}")
+elseif(CMAKE_SYSROOT)
+  set(LIBUNWIND_SYSROOT "${CMAKE_SYSROOT}")
+endif()
 
 if (LIBUNWIND_TARGET_TRIPLE)
   set(TARGET_TRIPLE "${LIBUNWIND_TARGET_TRIPLE}")
+  set(LIBUNWIND_USE_TARGET ON)
 endif()
 
 # Configure compiler.
 include(config-ix)
 
 if (LIBUNWIND_USE_COMPILER_RT AND NOT LIBUNWIND_HAS_NODEFAULTLIBS_FLAG)
   list(APPEND LIBUNWIND_LINK_FLAGS "-rtlib=compiler-rt")
 endif()

libunwind/test/lit.site.cfg.in

 config.test_linker_flags        = "@LIBUNWIND_TEST_LINKER_FLAGS@"
 config.test_compiler_flags      = "@LIBUNWIND_TEST_COMPILER_FLAGS@"
 config.executor                 = "@LIBUNWIND_EXECUTOR@"
 config.libunwind_shared         = "@LIBUNWIND_ENABLE_SHARED@"
 config.enable_shared            = "@LIBCXX_ENABLE_SHARED@"
 config.enable_exceptions        = "@LIBUNWIND_ENABLE_EXCEPTIONS@"
 config.host_triple              = "@LLVM_HOST_TRIPLE@"
 config.target_triple            = "@TARGET_TRIPLE@"
-config.use_target               = len("@LIBUNWIND_TARGET_TRIPLE@") > 0
+config.use_target               = bool("@LIBUNWIND_TARGET_TRIPLE@")
 config.sysroot                  = "@LIBUNWIND_SYSROOT@"
 config.gcc_toolchain            = "@LIBUNWIND_GCC_TOOLCHAIN@"
 config.cxx_ext_threads          = "@LIBUNWIND_BUILD_EXTERNAL_THREAD_LIBRARY@"
 
 # Let the main config do the real work.
 lit_config.load_config(config, "@LIBUNWIND_SOURCE_DIR@/test/lit.cfg")