[libunwind] Allow target flags to affect CMake configuration tests

[EricWF]

Summary

This patch changes the libunwind CMake so that it adds certain target flags like '-m32' or '--gcc-toolchain' before including config-ix.cmake.
Since these flags can affect things like check_library_exists([...]) they needed to be added before the tests are performed.

Additionally this patch adds LIBUNWIND_BUILD_32_BITS which defaults to LLVM_BUILD_32_BITS.

This patch fixes:

https://llvm.org/bugs/show_bug.cgi?id=27950
https://llvm.org/bugs/show_bug.cgi?id=27959

[EricWF]

Add missing declaration for "LIBUNWIND_TARGET_TRIPLE".

CMakeLists.txt

else()
   set(LLVM_LIT "${CMAKE_SOURCE_DIR}/utils/lit/lit.py")
 endif()
 
 #===============================================================================
 # Setup CMake Options
 #===============================================================================
 
 # 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_CROSS_UNWINDING "Enable cross-platform unwinding support." OFF)
 
-set(LIBUNWIND_GCC_TOOLCHAIN "" CACHE STRING "GCC toolchain for cross compiling.")
-set(LIBUNWIND_SYSROOT "" CACHE STRING "Sysroot for cross compiling.")
+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.")
 
 #===============================================================================
 # Configure System
 #===============================================================================
 
 # Add path for custom modules
 set(CMAKE_MODULE_PATH
     "${CMAKE_CURRENT_SOURCE_DIR}/cmake"
     ${CMAKE_MODULE_PATH})
 
-# Configure compiler.
-include(config-ix)
-
 set(LIBUNWIND_COMPILER    ${CMAKE_CXX_COMPILER})
 set(LIBUNWIND_SOURCE_DIR  ${CMAKE_CURRENT_SOURCE_DIR})
 set(LIBUNWIND_BINARY_DIR  ${CMAKE_CURRENT_BINARY_DIR})
 set(LIBUNWIND_LIBRARY_DIR ${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX})
 
-#===============================================================================
-# Setup Compiler Flags
-#===============================================================================
+set(LIBUNWIND_C_FLAGS "")
+set(LIBUNWIND_CXX_FLAGS "")
+set(LIBUNWIND_COMPILE_FLAGS "")
+set(LIBUNWIND_LINK_FLAGS "")
 
 # Get required flags.
 macro(append_if list condition var)
   if (${condition})
     list(APPEND ${list} ${var})
   endif()
 endmacro()
 
-set(LIBUNWIND_C_FLAGS "")
-set(LIBUNWIND_CXX_FLAGS "")
-set(LIBUNWIND_COMPILE_FLAGS "")
-set(LIBUNWIND_LINK_FLAGS "")
+macro(add_target_flags_if condition var)
+  if (${condition})
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${var}")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${var}")
+    list(APPEND LINUNWIND_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}")
+
+# Configure compiler.
+include(config-ix)
+
+#===============================================================================
+# 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)
 append_if(LIBUNWIND_COMPILE_FLAGS LIBUNWIND_HAS_WALL_FLAG -Wall)
 append_if(LIBUNWIND_COMPILE_FLAGS LIBUNWIND_HAS_WCHAR_SUBSCRIPTS_FLAG -Wchar-subscripts)
 append_if(LIBUNWIND_COMPILE_FLAGS LIBUNWIND_HAS_WCONVERSION_FLAG -Wconversion)
if (NOT LIBUNWIND_ENABLE_CROSS_UNWINDING)
   list(APPEND LIBUNWIND_COMPILE_FLAGS -D_LIBUNWIND_IS_NATIVE_ONLY)
 endif ()
 
 # This is the _ONLY_ place where add_definitions is called.
 if (MSVC)
   add_definitions(-D_CRT_SECURE_NO_WARNINGS)
 endif ()
 
-append_if(LIBUNWIND_COMPILE_FLAGS LIBUNWIND_TARGET_TRIPLE
-          "-target ${LIBUNWIND_TARGET_TRIPLE}")
-append_if(LIBUNWIND_COMPILE_FLAGS LIBUNWIND_GCC_TOOLCHAIN
-          "-gcc-toolchain ${LIBUNWIND_GCC_TOOLCHAIN}")
-append_if(LIBUNWIND_COMPILE_FLAGS LIBUNWIND_SYSROOT
-          "--sysroot=${LIBUNWIND_SYSROOT}")
-
 #===============================================================================
 # Setup Source Code
 #===============================================================================
 
 include_directories(include)
 
 add_subdirectory(src)

src/CMakeLists.txt

if (CMAKE_OSX_DEPLOYMENT_TARGET STREQUAL "10.6")
     list(APPEND LIBUNWIND_LINK_FLAGS
          "-current_version ${LIBUNWIND_VERSION}"
          "/usr/lib/libSystem.B.dylib")
   endif ()
 endif ()
 
 string(REPLACE ";" " " LIBUNWIND_COMPILE_FLAGS "${LIBUNWIND_COMPILE_FLAGS}")
 string(REPLACE ";" " " LIBUNWIND_CXX_FLAGS "${LIBUNWIND_CXX_FLAGS}")
+string(REPLACE ";" " " LIBUNWIND_C_FLAGS "${LIBUNWIND_C_FLAGS}")
 string(REPLACE ";" " " LIBUNWIND_LINK_FLAGS "${LIBUNWIND_LINK_FLAGS}")
 
 set_target_properties(unwind
                       PROPERTIES
-                        COMPILE_FLAGS "${CMAKE_COMPILE_FLAGS} ${LIBUNWIND_COMPILE_FLAGS}"
-                        LINK_FLAGS    "${CMAKE_LINK_FLAGS} ${LIBUNWIND_LINK_FLAGS}"
+                        COMPILE_FLAGS "${LIBUNWIND_COMPILE_FLAGS}"
+                        LINK_FLAGS    "${LIBUNWIND_LINK_FLAGS}"
                         OUTPUT_NAME   "unwind"
                         VERSION       "1.0"
                         SOVERSION     "1")
 set_property(SOURCE ${LIBUNWIND_CXX_SOURCES}
-             APPEND_STRING PROPERTY COMPILE_FLAGS "${LIBUNWIND_CXX_FLAGS}")
+             APPEND_STRING PROPERTY COMPILE_FLAGS "${CMAKE_CXX_FLAGS} ${LIBUNWIND_CXX_FLAGS}")
+set_property(SOURCE ${LIBUNWIND_C_SOURCES}
+             APPEND_STRING PROPERTY COMPILE_FLAGS "${CMAKE_C_FLAGS} ${LIBUNWIND_C_FLAGS}")
 
 install(TARGETS unwind
         LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX}
         ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX})