Reland "[CMake][libunwind] Use -nodefaultlibs for CMake checks"

[phosek]

Summary

This is a reland of commit r299796.

Turned out that we need gcc_s or compiler-rt on ARM when checking the support for -funwind-tables which creates a dependency on __aeabi_unwind_cpp_pr0 symbol that's provided by the compiler runtime.

[phosek]

Ping, can someone please take a look?

[beanz]

This looks good to me!

CMakeLists.txt

 #===============================================================================
 # Setup Project
 #===============================================================================
 
 cmake_minimum_required(VERSION 3.4.3)
 
 if (POLICY CMP0042)
   cmake_policy(SET CMP0042 NEW) # Set MACOSX_RPATH=YES by default
 endif()
 
+# Add path for custom modules
+set(CMAKE_MODULE_PATH
+  "${CMAKE_CURRENT_SOURCE_DIR}/cmake"
+  "${CMAKE_CURRENT_SOURCE_DIR}/cmake/Modules"
+  ${CMAKE_MODULE_PATH}
+  )
+
 if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   project(libunwind)
 
   # Rely on llvm-config.
   set(CONFIG_OUTPUT)
   if(NOT LLVM_CONFIG_PATH)
     find_program(LLVM_CONFIG_PATH "llvm-config")
   endif()

 else()
   set(LLVM_MAIN_SRC_DIR "${CMAKE_SOURCE_DIR}" CACHE PATH "Path to LLVM source tree")
   set(LLVM_LIT "${CMAKE_SOURCE_DIR}/utils/lit/lit.py")
 endif()
 
 #===============================================================================
 # Setup CMake Options
 #===============================================================================
+include(HandleCompilerRT)
 
 # Define options.
 option(LIBUNWIND_BUILD_32_BITS "Build 32 bit libunwind" ${LLVM_BUILD_32_BITS})
 option(LIBUNWIND_ENABLE_ASSERTIONS "Enable assertions independent of build mode." ON)
 option(LIBUNWIND_ENABLE_PEDANTIC "Compile with pedantic enabled." ON)
 option(LIBUNWIND_ENABLE_WERROR "Fail and stop if a warning is triggered." OFF)
 option(LIBUNWIND_ENABLE_SHARED "Build libunwind as a shared library." ON)
 option(LIBUNWIND_ENABLE_STATIC "Build libunwind as a static library." ON)
 option(LIBUNWIND_ENABLE_CROSS_UNWINDING "Enable cross-platform unwinding support." OFF)
 option(LIBUNWIND_ENABLE_ARM_WMMX "Enable unwinding support for ARM WMMX registers." OFF)
 option(LIBUNWIND_ENABLE_THREADS "Build libunwind with threading support." ON)
+option(LIBUNWIND_USE_COMPILER_RT "Use compiler-rt instead of libgcc" OFF)
 option(LIBUNWIND_INCLUDE_DOCS "Build the libunwind documentation." ${LLVM_INCLUDE_DOCS})
 
 set(LIBUNWIND_TARGET_TRIPLE "" CACHE STRING "Target triple for cross compiling.")
 set(LIBUNWIND_GCC_TOOLCHAIN "" CACHE PATH "GCC toolchain for cross compiling.")
 set(LIBUNWIND_SYSROOT "" CACHE PATH "Sysroot for cross compiling.")
 
 if (NOT LIBUNWIND_ENABLE_SHARED AND NOT LIBUNWIND_ENABLE_STATIC)
   message(FATAL_ERROR "libunwind must be built as either a shared or static library.")

 add_target_flags_if(LIBUNWIND_GCC_TOOLCHAIN
           "-gcc-toolchain ${LIBUNWIND_GCC_TOOLCHAIN}")
 add_target_flags_if(LIBUNWIND_SYSROOT
           "--sysroot=${LIBUNWIND_SYSROOT}")
 
 # Configure compiler.
 include(config-ix)
 
+if (LIBUNWIND_USE_COMPILER_RT)
+  list(APPEND LIBUNWIND_LINK_FLAGS "-rtlib=compiler-rt")
+endif()
+
 #===============================================================================
 # Setup Compiler Flags
 #===============================================================================
 
 append_if(LIBUNWIND_COMPILE_FLAGS LIBUNWIND_HAS_WERROR_FLAG -Werror=return-type)
 
 # Get warning flags
 append_if(LIBUNWIND_COMPILE_FLAGS LIBUNWIND_HAS_W_FLAG -W)

cmake/Modules/HandleCompilerRT.cmake

+function(find_compiler_rt_library name dest)
+  if (NOT DEFINED LIBUNWIND_COMPILE_FLAGS)
+    message(FATAL_ERROR "LIBUNWIND_COMPILE_FLAGS must be defined when using this function")
+  endif()
+  set(dest "" PARENT_SCOPE)
+  set(CLANG_COMMAND ${CMAKE_CXX_COMPILER} ${TARGET_TRIPLE} ${LIBUNWIND_COMPILE_FLAGS}
+      "--rtlib=compiler-rt" "--print-libgcc-file-name")
+  if (CMAKE_CXX_COMPILER_ID MATCHES Clang AND CMAKE_CXX_COMPILER_TARGET)
+    list(APPEND CLANG_COMMAND "--target=${CMAKE_CXX_COMPILER_TARGET}")
+  endif()
+  execute_process(
+      COMMAND ${CLANG_COMMAND}
+      RESULT_VARIABLE HAD_ERROR
+      OUTPUT_VARIABLE LIBRARY_FILE
+  )
+  string(STRIP "${LIBRARY_FILE}" LIBRARY_FILE)
+  string(REPLACE "builtins" "${name}" LIBRARY_FILE "${LIBRARY_FILE}")
+  if (NOT HAD_ERROR AND EXISTS "${LIBRARY_FILE}")
+    message(STATUS "Found compiler-rt library: ${LIBRARY_FILE}")
+    set(${dest} "${LIBRARY_FILE}" PARENT_SCOPE)
+  else()
+    message(STATUS "Failed to find compiler-rt library")
+  endif()
+endfunction()
+
+function(find_compiler_rt_dir dest)
+  if (NOT DEFINED LIBUNWIND_COMPILE_FLAGS)
+    message(FATAL_ERROR "LIBUNWIND_COMPILE_FLAGS must be defined when using this function")
+  endif()
+  set(dest "" PARENT_SCOPE)
+  if (APPLE)
+    set(CLANG_COMMAND ${CMAKE_CXX_COMPILER} ${LIBUNWIND_COMPILE_FLAGS}
+        "-print-file-name=lib")
+    execute_process(
+        COMMAND ${CLANG_COMMAND}
+        RESULT_VARIABLE HAD_ERROR
+        OUTPUT_VARIABLE LIBRARY_DIR
+    )
+    string(STRIP "${LIBRARY_DIR}" LIBRARY_DIR)
+    set(LIBRARY_DIR "${LIBRARY_DIR}/darwin")
+  else()
+    set(CLANG_COMMAND ${CMAKE_CXX_COMPILER} ${LIBUNWIND_COMPILE_FLAGS}
+        "--rtlib=compiler-rt" "--print-libgcc-file-name")
+    execute_process(
+        COMMAND ${CLANG_COMMAND}
+        RESULT_VARIABLE HAD_ERROR
+        OUTPUT_VARIABLE LIBRARY_FILE
+    )
+    string(STRIP "${LIBRARY_FILE}" LIBRARY_FILE)
+    get_filename_component(LIBRARY_DIR "${LIBRARY_FILE}" DIRECTORY)
+  endif()
+  if (NOT HAD_ERROR AND EXISTS "${LIBRARY_DIR}")
+    message(STATUS "Found compiler-rt directory: ${LIBRARY_DIR}")
+    set(${dest} "${LIBRARY_DIR}" PARENT_SCOPE)
+  else()
+    message(STATUS "Failed to find compiler-rt directory")
+  endif()
+endfunction()

cmake/config-ix.cmake

 
 include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
 include(CheckLibraryExists)
 
+check_library_exists(c fopen "" LIBUNWIND_HAS_C_LIB)
+
+if (NOT LIBUNWIND_USE_COMPILER_RT)
+  check_library_exists(gcc_s __gcc_personality_v0 "" LIBUNWIND_HAS_GCC_S_LIB)
+endif()
+
+# libunwind is built with -nodefaultlibs, so we want all our checks to also
+# use this option, otherwise we may end up with an inconsistency between
+# the flags we think we require during configuration (if the checks are
+# performed without -nodefaultlibs) and the flags that are actually
+# required during compilation (which has the -nodefaultlibs). libc is
+# required for the link to go through. We remove sanitizers from the
+# configuration checks to avoid spurious link errors.
+check_c_compiler_flag(-nodefaultlibs LIBUNWIND_HAS_NODEFAULTLIBS_FLAG)
+if (LIBUNWIND_HAS_NODEFAULTLIBS_FLAG)
+  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nodefaultlibs")
+  if (LIBUNWIND_HAS_C_LIB)
+    list(APPEND CMAKE_REQUIRED_LIBRARIES c)
+  endif ()
+  if (LIBUNWIND_USE_COMPILER_RT)
+    list(APPEND CMAKE_REQUIRED_FLAGS -rtlib=compiler-rt)
+    find_compiler_rt_library(builtins LIBUNWIND_BUILTINS_LIBRARY)
+    list(APPEND CMAKE_REQUIRED_LIBRARIES "${LIBUNWIND_BUILTINS_LIBRARY}")
+  elseif (LIBUNWIND_HAS_GCC_S_LIB)
+    list(APPEND CMAKE_REQUIRED_LIBRARIES gcc_s)
+  endif ()
+  if (CMAKE_C_FLAGS MATCHES -fsanitize OR CMAKE_CXX_FLAGS MATCHES -fsanitize)
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fno-sanitize=all")
+  endif ()
+  if (CMAKE_C_FLAGS MATCHES -fsanitize-coverage OR CMAKE_CXX_FLAGS MATCHES -fsanitize-coverage)
+    set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fno-sanitize-coverage=edge,trace-cmp,indirect-calls,8bit-counters")
+  endif ()
+endif ()
+
 # Check compiler flags
 check_c_compiler_flag(-funwind-tables         LIBUNWIND_HAS_FUNWIND_TABLES)
 check_cxx_compiler_flag(-fPIC                 LIBUNWIND_HAS_FPIC_FLAG)
 check_cxx_compiler_flag(-fno-exceptions       LIBUNWIND_HAS_NO_EXCEPTIONS_FLAG)
 check_cxx_compiler_flag(-fno-rtti             LIBUNWIND_HAS_NO_RTTI_FLAG)
 check_cxx_compiler_flag(-fstrict-aliasing     LIBUNWIND_HAS_FSTRICT_ALIASING_FLAG)
-check_cxx_compiler_flag(-nodefaultlibs        LIBUNWIND_HAS_NODEFAULTLIBS_FLAG)
 check_cxx_compiler_flag(-nostdinc++           LIBUNWIND_HAS_NOSTDINCXX_FLAG)
 check_cxx_compiler_flag(-Wall                 LIBUNWIND_HAS_WALL_FLAG)
 check_cxx_compiler_flag(-W                    LIBUNWIND_HAS_W_FLAG)
 check_cxx_compiler_flag(-Wno-unused-function  LIBUNWIND_HAS_WNO_UNUSED_FUNCTION_FLAG)
 check_cxx_compiler_flag(-Wunused-variable     LIBUNWIND_HAS_WUNUSED_VARIABLE_FLAG)
 check_cxx_compiler_flag(-Wunused-parameter    LIBUNWIND_HAS_WUNUSED_PARAMETER_FLAG)
 check_cxx_compiler_flag(-Wstrict-aliasing     LIBUNWIND_HAS_WSTRICT_ALIASING_FLAG)
 check_cxx_compiler_flag(-Wstrict-overflow     LIBUNWIND_HAS_WSTRICT_OVERFLOW_FLAG)

 check_cxx_compiler_flag(/EHa-                 LIBUNWIND_HAS_NO_EHA_FLAG)
 check_cxx_compiler_flag(/GR-                  LIBUNWIND_HAS_NO_GR_FLAG)
 check_cxx_compiler_flag(-std=c++11            LIBUNWIND_HAS_STD_CXX11)
 
 if(LIBUNWIND_HAS_STD_CXX11)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
 endif()
 
-check_library_exists(c fopen "" LIBUNWIND_HAS_C_LIB)
 check_library_exists(dl dladdr "" LIBUNWIND_HAS_DL_LIB)
 check_library_exists(pthread pthread_once "" LIBUNWIND_HAS_PTHREAD_LIB)