[libc++abi] Refactor CMake build to avoid object libraries

[ldionne]

Summary

Object libraries don't respect the default choice of PIC for shared
libraries. The change also makes the CMake code more localized and simpler.

[ldionne]

libcxxabi/src/CMakeLists.txt

205

I want to mention that assuming that LIBUNWIND_XXX is defined here is pretty bad, as it means none of this works unless libc++abi and libunwind are actually subprojects of the same CMake project. This is a pre-existing condition, but it's not great.

[smeenai]

LGTM

libcxxabi/src/CMakeLists.txt

206

Will you want to do something similar with libunwind (where it's not build as an object library anymore), at which point this logic will change too?

[ldionne]

libcxxabi/src/CMakeLists.txt

206

If we don't build object libraries for libunwind, then this would change to $<TARGET_OBJECTS:unwind_static> and $<TARGET_OBJECTS:unwind> respectively, IIUC.

[smeenai]

libcxxabi/src/CMakeLists.txt

206

$<TARGET_OBJECTS:...> only works with object libraries (https://cmake.org/cmake/help/v3.4/manual/cmake-generator-expressions.7.html), so it'd need a bit more tweaking, but yeah, that's kinda independent of this patch :)

I did realize a problem with this though. In our minimum supported CMake version (3.4.3), you can only use TARGET_SOURCES inside the sources list of add_library and add_executable. Later versions lift this restriction, but we need to adhere to it.

[smeenai]

libcxxabi/src/CMakeLists.txt

206

I meant TARGET_OBJECTS, not TARGET_SOURCES.

[smeenai]

libcxxabi/src/CMakeLists.txt

206

Although I guess it's unclear if passing the generator expression to target_sources will end up having the same effect as listing it in the sources list directly in the add_library call (and would therefore be okay on older CMake versions). Can you test this with a CMake version below 3.9 (which lifted the restriction)?

[ldionne]

Superseded by https://reviews.llvm.org/D60173.

libcxxabi/src/CMakeLists.txt

 split_list(LIBCXXABI_SHARED_LINK_FLAGS)
 
 # FIXME: libc++abi.so will not link when modules are enabled because it depends
 # on symbols defined in libc++.so which has not yet been built.
 if (LLVM_ENABLE_MODULES)
   string(REPLACE "-Wl,-z,defs" "" CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS}")
 endif()
 
-macro(cxxabi_object_library name)
-  cmake_parse_arguments(ARGS "" "" "DEFINES;FLAGS" ${ARGN})
-
-  # Add a object library that contains the compiled source files.
-  add_library(${name} OBJECT ${LIBCXXABI_SOURCES} ${LIBCXXABI_HEADERS})
-  set_target_properties(${name}
-                        PROPERTIES
-                          CXX_EXTENSIONS
-                            OFF
-                          CXX_STANDARD
-                            11
-                          CXX_STANDARD_REQUIRED
-                            ON
-                          COMPILE_FLAGS
-                            "${LIBCXXABI_COMPILE_FLAGS}")
-
-  if(ARGS_DEFINES)
-    target_compile_definitions(${name} PRIVATE ${ARGS_DEFINES})
-  endif()
-
-  if(ARGS_FLAGS)
-    target_compile_options(${name} PRIVATE ${ARGS_FLAGS})
-  endif()
-endmacro()
-
-if(LIBCXXABI_HERMETIC_STATIC_LIBRARY)
-  append_flags_if_supported(CXXABI_STATIC_OBJECTS_FLAGS -fvisibility=hidden)
-  append_flags_if_supported(CXXABI_STATIC_OBJECTS_FLAGS -fvisibility-global-new-delete-hidden)
-  cxxabi_object_library(cxxabi_static_objects
-    DEFINES
-      _LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS
-      _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS
-    FLAGS ${CXXABI_STATIC_OBJECTS_FLAGS})
-else()
-  cxxabi_object_library(cxxabi_static_objects)
-endif()
-
-cxxabi_object_library(cxxabi_shared_objects POSITION_INDEPENDENT_CODE ON)
-set(cxxabi_static_sources $<TARGET_OBJECTS:cxxabi_static_objects>)
-set(cxxabi_shared_sources $<TARGET_OBJECTS:cxxabi_shared_objects>)
-
 # Build the shared library.
 if (LIBCXXABI_ENABLE_SHARED)
-  add_library(cxxabi_shared SHARED ${cxxabi_shared_sources})
+  add_library(cxxabi_shared SHARED ${LIBCXXABI_SOURCES} ${LIBCXXABI_HEADERS})
   if(COMMAND llvm_setup_rpath)
     llvm_setup_rpath(cxxabi_shared)
   endif()
   target_link_libraries(cxxabi_shared PRIVATE ${LIBCXXABI_SHARED_LIBRARIES} ${LIBCXXABI_LIBRARIES})
   set_target_properties(cxxabi_shared
                         PROPERTIES
                           CXX_EXTENSIONS
                             OFF
                           CXX_STANDARD
                             11
                           CXX_STANDARD_REQUIRED
                             ON
+                          COMPILE_FLAGS
+                            "${LIBCXXABI_COMPILE_FLAGS}"
                           LINK_FLAGS
                             "${LIBCXXABI_LINK_FLAGS} ${LIBCXXABI_SHARED_LINK_FLAGS}"
                           OUTPUT_NAME
                             "c++abi"
                           POSITION_INDEPENDENT_CODE
                             ON
                           SOVERSION
                             "1"
                           VERSION
                             "1.0")
   list(APPEND LIBCXXABI_BUILD_TARGETS "cxxabi_shared")
   if (LIBCXXABI_INSTALL_SHARED_LIBRARY)
     list(APPEND LIBCXXABI_INSTALL_TARGETS "cxxabi_shared")
   endif()
 endif()
 
 # Build the static library.
 if (LIBCXXABI_ENABLE_STATIC)
-  if (LIBCXXABI_USE_LLVM_UNWINDER AND LIBCXXABI_STATICALLY_LINK_UNWINDER_IN_STATIC_LIBRARY)
-    if (TARGET unwind_static OR HAVE_LIBUNWIND)
-      if(LIBUNWIND_HERMETIC_STATIC_LIBRARY)
-        list(APPEND cxxabi_static_sources $<TARGET_OBJECTS:unwind_static_objects>)
-      else()
-        list(APPEND cxxabi_static_sources $<TARGET_OBJECTS:unwind_objects>)
-      endif()
-    endif()
-  endif()
-  add_library(cxxabi_static STATIC ${cxxabi_static_sources})
+  add_library(cxxabi_static STATIC ${LIBCXXABI_SOURCES} ${LIBCXXABI_HEADERS})
   target_link_libraries(cxxabi_static PRIVATE ${LIBCXXABI_STATIC_LIBRARIES} ${LIBCXXABI_LIBRARIES})
   set_target_properties(cxxabi_static
                         PROPERTIES
                           CXX_EXTENSIONS
                             OFF
                           CXX_STANDARD
                             11
                           CXX_STANDARD_REQUIRED
                             ON
+                          COMPILE_FLAGS
+                            "${LIBCXXABI_COMPILE_FLAGS}"
                           LINK_FLAGS
                             "${LIBCXXABI_LINK_FLAGS}"
                           OUTPUT_NAME
                             "c++abi")
+
+  if (LIBCXXABI_HERMETIC_STATIC_LIBRARY)
+    append_flags_if_supported(CXXABI_STATIC_OBJECTS_FLAGS -fvisibility=hidden)
+    append_flags_if_supported(CXXABI_STATIC_OBJECTS_FLAGS -fvisibility-global-new-delete-hidden)
+    target_compile_options(cxxabi_static PRIVATE ${CXXABI_STATIC_OBJECTS_FLAGS})
+    target_compile_definitions(cxxabi_static PRIVATE _LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS
+                                                     _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS)
+  endif()
+
+  if (LIBCXXABI_USE_LLVM_UNWINDER AND
+      LIBCXXABI_STATICALLY_LINK_UNWINDER_IN_STATIC_LIBRARY AND
+      (TARGET unwind_static OR HAVE_LIBUNWIND))
+    if(LIBUNWIND_HERMETIC_STATIC_LIBRARY)
+      target_sources(cxxabi_static PRIVATE $<TARGET_OBJECTS:unwind_static_objects>)
+    else()
+      target_sources(cxxabi_static PRIVATE $<TARGET_OBJECTS:unwind_objects>)
+    endif()
+  endif()
+
   list(APPEND LIBCXXABI_BUILD_TARGETS "cxxabi_static")
   if (LIBCXXABI_INSTALL_STATIC_LIBRARY)
     list(APPEND LIBCXXABI_INSTALL_TARGETS "cxxabi_static")
   endif()
 endif()
 
 # Add a meta-target for both libraries.
 add_custom_target(cxxabi DEPENDS ${LIBCXXABI_BUILD_TARGETS})