[libcxxabi] Support building hermetic static library

[phosek]

Summary

This is useful when the static libc++abi library is being linked into
shared libraries that may be used in with other shared libraries that
use different C++ library. We want to avoid avoid exporting libc++abi
or libc++ symbols in those cases. This achieved by a new CMake option
which can be enabled by libc++abi vendors as needed.

[phosek]

This is a libc++abi counterpart of D55404. We combine both libc++abi and libc++ into a single static archive and for it to be hermetic, we need to make sure that both libc++abi and libc++ were built as such.

[ldionne]

libcxxabi/src/CMakeLists.txt

185 ↗

(On Diff #179359)

Does it make any sense to have LIBCXXABI_HERMETIC_STATIC_LIBRARY and LIBCXXABI_ENABLE_SHARED at the same time? I don't understand why we're creating a target named cxxabi_shared when LIBCXXABI_HERMETIC_STATIC_LIBRARY is true.

[phosek]

libcxxabi/src/CMakeLists.txt

185 ↗

(On Diff #179359)

When not building hermetic static library, we share objects between static and shared library, but when building the hermetic static library we cannot do that because those objects are build with different flags, hence this check. I've modified the code to follow the same pattern I used in libc++ build which hopefully makes it less confusing.

[phosek]

Ping?

libcxxabi/trunk/CMakeLists.txt

 if (LIBCXXABI_LIBCXX_PATH STREQUAL "LIBCXXABI_LIBCXX_PATH-NOTFOUND")
   message(WARNING "LIBCXXABI_LIBCXX_PATH was not specified and couldn't be infered.")
   set(LIBCXXABI_LIBCXX_PATH "")
 endif()
 
 set(LIBCXXABI_LIBCXX_PATH "${LIBCXXABI_LIBCXX_PATH}" CACHE PATH
     "Specify path to libc++ source." FORCE)
 
+option(LIBCXXABI_HERMETIC_STATIC_LIBRARY
+  "Do not export any symbols from the static library." OFF)
+
 #===============================================================================
 # Configure System
 #===============================================================================
 
 # Add path for custom modules
 set(CMAKE_MODULE_PATH
   "${CMAKE_CURRENT_SOURCE_DIR}/cmake"
   "${CMAKE_CURRENT_SOURCE_DIR}/cmake/Modules"

libcxxabi/trunk/cmake/Modules/HandleLibcxxabiFlags.cmake

macro(remove_flags)
   endforeach()
 endmacro(remove_flags)
 
 macro(check_flag_supported flag)
     mangle_name("${flag}" flagname)
     check_cxx_compiler_flag("${flag}" "LIBCXXABI_SUPPORTS_${flagname}_FLAG")
 endmacro()
 
+macro(append_flags DEST)
+  foreach(value ${ARGN})
+    list(APPEND ${DEST} ${value})
+    list(APPEND ${DEST} ${value})
+  endforeach()
+endmacro()
+
+# If the specified 'condition' is true then append the specified list of flags to DEST
+macro(append_flags_if condition DEST)
+  if (${condition})
+    list(APPEND ${DEST} ${ARGN})
+  endif()
+endmacro()
+
+# Add each flag in the list specified by DEST if that flag is supported by the current compiler.
+macro(append_flags_if_supported DEST)
+  foreach(flag ${ARGN})
+    mangle_name("${flag}" flagname)
+    check_cxx_compiler_flag("${flag}" "LIBCXXABI_SUPPORTS_${flagname}_FLAG")
+    append_flags_if(LIBCXXABI_SUPPORTS_${flagname}_FLAG ${DEST} ${flag})
+  endforeach()
+endmacro()
+
 # Add a macro definition if condition is true.
 macro(define_if condition def)
   if (${condition})
     add_definitions(${def})
   endif()
 endmacro()
 
 # Add a macro definition if condition is not true.

libcxxabi/trunk/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(cxxabi_objects OBJECT ${LIBCXXABI_SOURCES} ${LIBCXXABI_HEADERS})
-set_target_properties(cxxabi_objects
+  add_library(${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}"
                           POSITION_INDEPENDENT_CODE
                             ON)
 
+  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})
+  cxxabi_object_library(cxxabi_shared_objects)
+  set(cxxabi_static_sources $<TARGET_OBJECTS:cxxabi_static_objects>)
+  set(cxxabi_shared_sources $<TARGET_OBJECTS:cxxabi_shared_objects>)
+else()
+  cxxabi_object_library(cxxabi_objects)
+  set(cxxabi_static_sources $<TARGET_OBJECTS:cxxabi_objects>)
+  set(cxxabi_shared_sources $<TARGET_OBJECTS:cxxabi_objects>)
+endif()
+
 # Build the shared library.
 if (LIBCXXABI_ENABLE_SHARED)
-  add_library(cxxabi_shared SHARED $<TARGET_OBJECTS:cxxabi_objects>)
+  add_library(cxxabi_shared SHARED ${cxxabi_shared_sources})
   if(COMMAND llvm_setup_rpath)
     llvm_setup_rpath(cxxabi_shared)
   endif()
   target_link_libraries(cxxabi_shared ${LIBCXXABI_LIBRARIES} ${LIBCXXABI_SHARED_LIBRARIES})
   set_target_properties(cxxabi_shared
                         PROPERTIES
                           CXX_EXTENSIONS
                             OFF
if (LIBCXXABI_ENABLE_SHARED)
   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)
-  set(cxxabi_static_sources $<TARGET_OBJECTS:cxxabi_objects>)
   if (LIBCXXABI_USE_LLVM_UNWINDER AND LIBCXXABI_STATICALLY_LINK_UNWINDER_IN_STATIC_LIBRARY)
     if (TARGET unwind_static OR HAVE_LIBUNWIND)
       list(APPEND cxxabi_static_sources $<TARGET_OBJECTS:unwind_objects>)
     endif()
   endif()
   add_library(cxxabi_static STATIC ${cxxabi_static_sources})
   target_link_libraries(cxxabi_static ${LIBCXXABI_LIBRARIES} ${LIBCXXABI_STATIC_LIBRARIES})
   set_target_properties(cxxabi_static