luajit.cmake: Attempt to port LUAJIT_UNWIND_EXTERNAL logic from luaji…

…t's src/Makefile

deps/luajit.cmake

@@ -73,7 +73,6 @@ ENDIF()
 if ( WIN32 AND NOT CYGWIN )
   set ( LJVM_MODE peobj )
 elseif ( APPLE )
-  set ( CMAKE_EXE_LINKER_FLAGS "-pagezero_size 10000 -image_base 100000000 ${CMAKE_EXE_LINKER_FLAGS}" )
   set ( LJVM_MODE machasm )
 else ()
   set ( LJVM_MODE elfasm )
@@ -213,6 +212,39 @@ IF(TARGET_LJARCH STREQUAL "ppc")
   ENDIF()
 ENDIF()
 
+IF(APPLE)
+  SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DLUAJIT_UNWIND_EXTERNAL")
+ELSEIF(NOT WIN32)
+  IF(NOT LJ_NO_UNWIND_1)
+    # Find out whether the target toolchain always generates unwind tables.
+    MESSAGE(STATUS "Checking if the toolchain always generates unwind tables")
+    SET(TOOLCHAIN_GENERATES_UNWIND_TABLES 0)
+    SET(TMPUNWIND_DIR "${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp")
+    file(WRITE "${TMPUNWIND_DIR}/tmpunwind.c" "extern void b(void);int a(void){b();return 0;}")
+    # This seems flimsy; it would be better to use something like CMake's try_compile but
+    # there doesn't seem to be a way to avoid linking when using try_compile so this particular
+    # code can't use it (at least without modifying the test code)
+    execute_process(COMMAND "${CMAKE_C_COMPILER}" -c -x c "${TMPUNWIND_DIR}/tmpunwind.c" -o "${TMPUNWIND_DIR}/tmpunwind.o"
+      RESULT_VARIABLE UNWIND_TEST_ERRORED)
+    IF(NOT UNWIND_TEST_ERRORED)
+      file(READ "${TMPUNWIND_DIR}/tmpunwind.o" TMPUNWIND_O)
+      string(FIND "${TMPUNWIND_O}" "eh_frame" EH_FRAME_FOUND)
+      string(FIND "${TMPUNWIND_O}" "__unwind_info" UNWIND_INFO_FOUND)
+      IF(EH_FRAME_FOUND OR UNWIND_INFO_FOUND)
+        SET(TOOLCHAIN_GENERATES_UNWIND_TABLES 1)
+      ENDIF()
+    ENDIF()
+
+    IF(TOOLCHAIN_GENERATES_UNWIND_TABLES)
+      SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DLUAJIT_UNWIND_EXTERNAL")
+      MESSAGE(STATUS "Toolchain does generate unwind tables")
+    ELSE()
+      MESSAGE(STATUS "Toolchain does not generate unwind tables")
+    ENDIF()
+  ENDIF()
+ENDIF()
+
+
 add_executable(minilua ${LUAJIT_DIR}/src/host/minilua.c)
 SET_TARGET_PROPERTIES(minilua PROPERTIES COMPILE_DEFINITIONS "${TARGET_ARCH}")
 CHECK_LIBRARY_EXISTS(m sin "" MINILUA_USE_LIBM)