Add support for libc++abi.

Extends C++ interop with autodetected support for libc++abi in addition to the existing support for libcxxrt and libsubc++.

Fixes #142.

CMake/CMakeLists.txt

@@ -4,6 +4,13 @@ project(test_cxx_runtime)
 add_executable(test_cxx_runtime typeinfo_test.cc)
 add_executable(test_cxx_stdlib typeinfo_test.cc)
 if (CXX_RUNTIME)
+	if (CXX_RUNTIME MATCHES ".*libc\\+\\+abi.*")
+		find_library(M_LIBRARY m)
+		if (M_LIBRARY)
+			target_link_libraries(test_cxx_runtime ${M_LIBRARY})
+		endif()
+	endif()
+	set(CMAKE_CXX_IMPLICIT_LINK_LIBRARIES "")
 	target_link_libraries(test_cxx_runtime ${CXX_RUNTIME})
 	set_target_properties(test_cxx_runtime PROPERTIES
 		LINKER_LANGUAGE C)

CMake/typeinfo_test.cc

@@ -49,6 +49,9 @@ class type_info2 : public std::type_info
 	virtual bool __do_catch(const type_info *thrown_type,
 	                        void **thrown_object,
 	                        unsigned outer) const { return true; }
+	virtual bool __do_upcast(
+					const __class_type_info *target,
+					void **thrown_object) const { return true; };
 };
 bool type_info2::__is_pointer_p() const { return true; }
 

CMakeLists.txt

@@ -291,9 +291,11 @@ if (ENABLE_OBJCXX)
 		if (NOT CXX_RUNTIME)
 			test_cxx(supc++ false)
 		endif (NOT CXX_RUNTIME)
-		# libc++abi does not currently work, don't try it.
 		if (NOT CXX_RUNTIME)
-			# test_cxx(c++abi false)
+			list (FIND CMAKE_CXX_IMPLICIT_LINK_LIBRARIES "c++" _libcxx_index)
+			if (${_libcxx_index} GREATER -1)
+				test_cxx(c++abi false)
+			endif()
 		endif (NOT CXX_RUNTIME)
 
 		# If we have a C++ ABI library, then we can produce a single libobjc that
@@ -325,6 +327,9 @@ if (ENABLE_OBJCXX)
 			MAIN_DEPENDENCY eh_trampoline.cc)
 		list(APPEND libobjc_ASM_SRCS eh_trampoline.s)
 		list(APPEND libobjc_CXX_SRCS objcxx_eh.cc)
+
+		# Find libm for linking, as some versions of libc++ don't link against it
+		find_library(M_LIBRARY m)
 	endif ()
 endif (ENABLE_OBJCXX)
 
@@ -377,6 +382,11 @@ if (LIBGC)
 	target_link_libraries(objc ${LIBGC})
 endif ()
 
+# Explicitly link libm, as an implicit dependency of the C++ runtime
+if (M_LIBRARY)
+	target_link_libraries(objc ${M_LIBRARY})
+endif ()
+
 # Make weak symbols work on OS X
 if (APPLE)
 	set(CMAKE_SHARED_LIBRARY_CREATE_C_FLAGS
@@ -459,8 +469,18 @@ include (CPack)
 if (BOEHM_GC)
 	set(PC_REQUIRES_PRIVATE_BOEHM_GC "Requires.private: bdw-gc")
 endif ()
-if (ENABLE_OBJCXX AND NOT CXXRT_IS_STDLIB)
-	set(PC_LIBS_PRIVATE "Libs.private: -l${CXX_RUNTIME}")
+if (ENABLE_OBJCXX)
+	if (CXXRT_IS_STDLIB)
+		set(PC_LIBS_PRIVATE ${CMAKE_CXX_IMPLICIT_LINK_LIBRARIES})
+	else()
+		list(APPEND PC_LIBS_PRIVATE ${CXX_RUNTIME})
+		if (M_LIBRARY)
+			list(APPEND PC_LIBS_PRIVATE ${M_LIBRARY})
+		endif ()
+	endif()
+	list(REMOVE_DUPLICATES PC_LIBS_PRIVATE)
+	string(REPLACE  ";" " -l" PC_LIBS_PRIVATE "${PC_LIBS_PRIVATE}")
+	set(PC_LIBS_PRIVATE "Libs.private: -l${PC_LIBS_PRIVATE}")
 endif()
 
 configure_file("libobjc.pc.in" "libobjc.pc" @ONLY)

azure-pipelines.yml

@@ -7,20 +7,36 @@ jobs:
       matrix:
         Debug:
           BuildType: Debug
+          StdLib: libstdc++
+          CxxFlags: ""
         Release:
           BuildType: Release
+          StdLib: libstdc++
+          CxxFlags: ""
+        Debug-libc++:
+          BuildType: Debug
+          StdLib: libc++
+          CxxFlags: "-stdlib=libc++"
+        Release-libc++:
+          BuildType: Release
+          StdLib: libc++
+          CxxFlags: "-stdlib=libc++"
     steps:
     - checkout: self
       submodules: true
     - script: |
         sudo add-apt-repository "deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-8 main"
         sudo apt-get update
-        sudo apt-get install -y ninja-build
-        sudo apt-get install -y clang-8
+        sudo apt-get install -y ninja-build clang-8
+        if [ "$(StdLib)" = "libc++" ]; then
+          sudo apt-get install -qy libc++-8-dev libc++abi-8-dev
+        fi
+      displayName: Install Dependencies
 
     - task: CMake@1
+      displayName: Generate Build Scripts
       inputs:
-        cmakeArgs: '.. -GNinja -DCMAKE_BUILD_TYPE=$(BuildType) -DTESTS=ON -DCMAKE_CXX_COMPILER=clang++-8 -DCMAKE_C_COMPILER=clang-8'
+        cmakeArgs: '.. -GNinja -DCMAKE_BUILD_TYPE=$(BuildType) -DTESTS=ON -DCMAKE_CXX_COMPILER=clang++-8 -DCMAKE_C_COMPILER=clang-8 -DCMAKE_CXX_FLAGS="$(CxxFlags)"'
 
     - script: |
         ninja
@@ -32,6 +48,7 @@ jobs:
     - script: |
         ctest -j 4 --output-on-failure -T test
 
+      displayName: 'Test'
       workingDirectory: build
       failOnStderr: false
     - task: PublishTestResults@2

objcxx_eh.cc

@@ -292,6 +292,16 @@ namespace gnustep
 			                        unsigned outer) const;
 		};
 	}
+
+	static inline id dereference_thrown_object_pointer(void** obj) {
+		/* libc++-abi does not have  __is_pointer_p and won't do the double dereference 
+		 * required to get the object pointer. We need to do it ourselves if we have
+		 * caught an exception with libc++'s exception class. */
+		 if (cxx_exception_class == llvm_cxx_exception_class) {
+			 return **(id**)obj;
+		 }
+		 return *(id*)obj;
+	 }
 };
 
 
@@ -316,7 +326,7 @@ bool gnustep::libobjc::__objc_class_type_info::__do_catch(const type_info *throw
 	    || (AppleCompatibleMode && 
 	        dynamic_cast<const __objc_class_type_info*>(thrownType)))
 	{
-		thrown = *(id*)obj;
+		thrown = dereference_thrown_object_pointer(obj);
 		// nil only matches id catch handlers in Apple-compatible mode, or when thrown as an id
 		if (0 == thrown)
 		{
@@ -328,7 +338,7 @@ bool gnustep::libobjc::__objc_class_type_info::__do_catch(const type_info *throw
 	}
 	else if (dynamic_cast<const __objc_class_type_info*>(thrownType))
 	{
-		thrown = *(id*)obj;
+		thrown = dereference_thrown_object_pointer(obj);
 		found = isKindOfClass((Class)objc_getClass(thrownType->name()),
 		                      (Class)objc_getClass(name()));
 	}