Rework C++ library detection.

macOS ships with libc++abi, which doesn't provide the hooks required
for interop, so this was causing all of the tests to fail to link in
the Travis macOS test.  We're now correctly detecting that it won't
work on macOS and disabling those tests.

CMake/CMakeLists.txt

@@ -2,6 +2,8 @@ cmake_minimum_required(VERSION 2.8)
 
 add_executable(test_cxx_runtime typeinfo_test.cc)
 set(CMAKE_CXX_IMPLICIT_LINK_LIBRARIES "")
+if (CXX_RUNTIME)
 	target_link_libraries(test_cxx_runtime ${CXX_RUNTIME})
 	set_target_properties(test_cxx_runtime PROPERTIES
 		LINKER_LANGUAGE C)
+endif()

CMake/typeinfo_test.cc

@@ -57,5 +57,6 @@ bool type_info2::__is_pointer_p() const { return true; }
 
 int main()
 {
-	return 0;
+	type_info2 s;
+	return s.__is_pointer_p();
 }

CMakeLists.txt

@@ -73,7 +73,7 @@ set(libobjc_HDRS
 	objc/slot.h
 )
 
-set(libobjc_CXX_SRCS objcxx_eh.cc)
+set(libobjcxx_CXX_SRCS objcxx_eh.cc)
 
 # For release builds, we disable spamming the terminal with warnings about
 # selector type mismatches
@@ -162,18 +162,43 @@ set_source_files_properties(
 # C++ Runtime interaction
 #
 
+
+function(test_cxx CXX_RUNTIME_NAME IS_STDLIB)
+	set(CXX_RUNTIME_NAME "${CMAKE_SHARED_LIBRARY_PREFIX}${CXX_RUNTIME_NAME}${CMAKE_SHARED_LIBRARY_SUFFIX}")
+	message(STATUS "Testing ${CXX_RUNTIME_NAME} as the C++ runtime library")
+	find_library(CXX_RUNTIME NAMES libsupc++.so)
+	if (CXX_RUNTIME)
+		message(STATUS "Testing ${CXX_RUNTIME} as the C++ runtime library")
+		try_compile(USERUNTIME 
+			"${CMAKE_BINARY_DIR}/CMake"
+			"${CMAKE_SOURCE_DIR}/CMake"
+			test_cxx_runtime
+			CMAKE_FLAGS "-DCXX_RUNTIME=${CXX_RUNTIME} -DTEST_LINKER_LANGUAGE=C")
+		if (${USERUNTIME})
+			set(CXX_RUNTIME ${CXX_RUNTIME} PARENT_SCOPE)
+		endif()
+	endif()
+endfunction()
+
 set(ENABLE_OBJCXX true CACHE BOOL
 	"Enable support for Objective-C++")
-set(FORCE_LIBOBJCXX false CACHE BOOL
-	"Force building a separate Objective-C++ runtime library")
+
+set(CXXRT_IS_STDLIB false)
+
+add_library(objc SHARED ${libobjc_C_SRCS} ${libobjc_ASM_SRCS} ${libobjc_OBJC_SRCS})
+
 if (ENABLE_OBJCXX)
+	message(STATUS "Testing C++ interop")
 	# Try to find libcxxrt.so.  We can link to this to provide the C++ ABI
 	# layer, if it exists.
-	find_library(CXX_RUNTIME NAMES libcxxrt.so)
+	test_cxx(cxxrt false)
 	# If it doesn't, then look for GNU libsupc++.so instead (either works,
 	# they're ABI compatible).
 	if (NOT CXX_RUNTIME)
-		find_library(CXX_RUNTIME NAMES libsupc++.so)
+		test_cxx(supc++ false)
+	endif (NOT CXX_RUNTIME)
+	if (NOT CXX_RUNTIME)
+		test_cxx(c++abi false)
 	endif (NOT CXX_RUNTIME)
 
 	# If we have a C++ ABI library, then we can produce a single libobjc that
@@ -181,25 +206,33 @@ if (ENABLE_OBJCXX)
 	# a separate libobjcxx.
 	if (CXX_RUNTIME)
 		message(STATUS "Using ${CXX_RUNTIME} as the C++ runtime library")
+	else()
+		message(STATUS "Testing C++ standard library")
 		try_compile(USERUNTIME 
 			"${CMAKE_BINARY_DIR}/CMake"
 			"${CMAKE_SOURCE_DIR}/CMake"
-			test_cxx_runtime
-			CMAKE_FLAGS "-DCXX_RUNTIME=${CXX_RUNTIME}")
-		message(STATUS "Is runtime useable? ${USERUNTIME}")
-		if (NOT ${USERUNTIME})
+			test_cxx_runtime)
+		if (${USERUNTIME})
 			message(STATUS "libobjc will depend on C++ standard library")
+			set(CXXRT_IS_STDLIB true)
 		else()
+			message(STATUS "No useable C++ runtime found")
+			set(ENABLE_OBJCXX false)
+		endif()
+	endif ()
+endif (ENABLE_OBJCXX)
+
+
+if (ENABLE_OBJCXX)
+	if (NOT CXXRT_IS_STDLIB)
 		# We don't want to link the STL implementation (e.g. libstdc++) if
 		# we have a separate C++ runtime.
 		set(CMAKE_CXX_IMPLICIT_LINK_LIBRARIES "")
 		target_link_libraries(objc ${CXX_RUNTIME})
 	endif()
-	else ()
-		message(STATUS "libobjc will depend on C++ standard library")
+	set(libobjc_CXX_SRCS ${libobjcxx_CXX_SRCS})
+	target_sources(objc ${libobjcxx_CXX_SRCS})
 endif()
-endif (ENABLE_OBJCXX)
-
 
 
 # Currently, we actually need pthreads, but we should use the platform's native
@@ -210,7 +243,6 @@ set(objc_LINK_FLAGS "${objc_LINK_FLAGS} ${CMAKE_THREAD_LIBS_INIT}")
 
 
 
-add_library(objc SHARED ${libobjc_C_SRCS} ${libobjc_ASM_SRCS} ${libobjc_OBJC_SRCS} ${libobjc_CXX_SRCS})
 
 set_target_properties(objc PROPERTIES
 	LINKER_LANGUAGE C

Test/CMakeLists.txt

@@ -70,5 +70,7 @@ endforeach()
 # Tests that are more than a single file.
 addtest_flags(CXXExceptions "-O0" "CXXException.m;CXXException.cc;Test.m")
 addtest_flags(CXXExceptions_optimised "-O3" "CXXException.m;CXXException.cc;Test.m")
+if (ENABLE_OBJCXX)
 addtest_flags(ObjCXXEHInterop "-O0" "ObjCXXEHInterop.mm;ObjCXXEHInterop.m;Test.m")
 addtest_flags(ObjCXXEHInterop_optimised "-O3" "ObjCXXEHInterop.mm;ObjCXXEHInterop.m;Test.m")
+endif()