[libcxx] Allow building both shared and static library

[phosek]

Summary

This change allows building both shared and static version of libc++ in a single build, sharing object files between both versions.

[compnerd]

lib/CMakeLists.txt

188 ↗

(On Diff #67046)

Im not sure I understand this. Couldn't you build both static and shared versions, and therefore, need both branches?

[phosek]

lib/CMakeLists.txt

188 ↗

(On Diff #67046)

These are just link dependencies for libc++experimental.a, libc++.a and libc++.so` will get build in any case (see the cxx meta-target). Using both branches here imply lib/libc++.a -lc++ as link dependency which is most certainly incorrect. In fact, it seems that CMake ignores link dependencies for static libraries (which is a correct behavior) so this entire block can be safely removed.

[compnerd]

lib/CMakeLists.txt

188 ↗

(On Diff #67046)

Ah, missed the explicit static on the cxx_experimental.

libcxx/trunk/CMakeLists.txt

 
 #===============================================================================
 # Setup CMake Options
 #===============================================================================
 
 # Basic options ---------------------------------------------------------------
 option(LIBCXX_ENABLE_ASSERTIONS "Enable assertions independent of build mode." ON)
 option(LIBCXX_ENABLE_SHARED "Build libc++ as a shared library." ON)
+option(LIBCXX_ENABLE_STATIC "Build libc++ as a static library." ON)
 option(LIBCXX_ENABLE_EXPERIMENTAL_LIBRARY "Build libc++experimental.a" ON)
 option(LIBCXX_ENABLE_FILESYSTEM
         "Build filesystem as part of libc++experimental.a" ${LIBCXX_ENABLE_EXPERIMENTAL_LIBRARY})
 option(LIBCXX_INCLUDE_TESTS "Build the libc++ tests." ${LLVM_INCLUDE_TESTS})
 option(LIBCXX_INCLUDE_BENCHMARKS "Build the libc++ benchmarks and their dependancies" OFF)
 option(LIBCXX_BUILD_BENCHMARK_NATIVE_STDLIB "Build the benchmarks against the native STL" OFF)
 option(LIBCXX_INCLUDE_DOCS "Build the libc++ documentation." ${LLVM_INCLUDE_DOCS})
 set(LIBCXX_LIBDIR_SUFFIX "${LLVM_LIBDIR_SUFFIX}" CACHE STRING
     "Define suffix of library directory name (32/64)")
 option(LIBCXX_INSTALL_HEADERS "Install the libc++ headers." ON)
 option(LIBCXX_INSTALL_LIBRARY "Install the libc++ library." ON)
 option(LIBCXX_INSTALL_SUPPORT_HEADERS "Install libc++ support headers." ON)
 option(LIBCXX_INSTALL_EXPERIMENTAL_LIBRARY "Install libc++experimental.a" OFF)
 set(LIBCXX_ABI_VERSION 1 CACHE STRING "ABI version of libc++.")
 option(LIBCXX_ABI_UNSTABLE "Unstable ABI of libc++." OFF)
 
+if (NOT LIBCXX_ENABLE_SHARED AND NOT LIBCXX_ENABLE_STATIC)
+  message(FATAL_ERROR "libc++ must be built as either a shared or static library.")
+endif()
+
 # ABI Library options ---------------------------------------------------------
 set(LIBCXX_CXX_ABI "${LIBCXX_CXX_ABI}" CACHE STRING
     "Specify C++ ABI library to use." FORCE)
 set(CXXABIS none libcxxabi libcxxrt libstdc++ libsupc++)
 set_property(CACHE LIBCXX_CXX_ABI PROPERTY STRINGS ;${CXXABIS})
 
 # Setup the default options if LIBCXX_CXX_ABI is not specified.
 if (NOT LIBCXX_CXX_ABI)

libcxx/trunk/docs/BuildingLibcxx.rst

.. option:: LIBCXX_BUILD_32_BITS:BOOL
   **Default**: ``OFF``
 
   Build libc++ as a 32 bit library. Also see :option:`LLVM_BUILD_32_BITS`.
 
 .. option:: LIBCXX_ENABLE_SHARED:BOOL
 
   **Default**: ``ON``
 
-  Build libc++ as a shared library. If ``OFF`` is specified then libc++ is
-  built as a static library.
+  Build libc++ as a shared library. Either :option:`LIBCXX_ENABLE_SHARED` or
+  :option:`LIBCXX_ENABLE_STATIC` has to be enabled.
+
+.. option:: LIBCXX_ENABLE_STATIC:BOOL
+
+  **Default**: ``ON``
+
+  Build libc++ as a static library. Either :option:`LIBCXX_ENABLE_SHARED` or
+  :option:`LIBCXX_ENABLE_STATIC` has to be enabled.
 
 .. option:: LIBCXX_LIBDIR_SUFFIX:STRING
 
   Extra suffix to append to the directory where libraries are to be installed.
   This option overrides :option:`LLVM_LIBDIR_SUFFIX`.
 
 
 .. _libc++experimental options:

libcxx/trunk/lib/CMakeLists.txt

if (MSVC_IDE)
     source_group("Header Files" FILES ${LIBCXX_HEADERS})
   endif()
 endif()
 
 if(NOT LIBCXX_INSTALL_LIBRARY)
   set(exclude_from_all EXCLUDE_FROM_ALL)
 endif()
 
-if (LIBCXX_ENABLE_SHARED)
-  add_library(cxx SHARED ${exclude_from_all} ${LIBCXX_SOURCES} ${LIBCXX_HEADERS})
-else()
-  add_library(cxx STATIC ${exclude_from_all} ${LIBCXX_SOURCES} ${LIBCXX_HEADERS})
-endif()
-
-if (DEFINED LIBCXX_CXX_ABI_DEPS)
-  add_dependencies(cxx LIBCXX_CXX_ABI_DEPS)
-endif()
-
 #if LIBCXX_CXX_ABI_LIBRARY_PATH is defined we want to add it to the search path.
 add_link_flags_if(LIBCXX_CXX_ABI_LIBRARY_PATH "-L${LIBCXX_CXX_ABI_LIBRARY_PATH}")
 
 add_library_flags_if(LIBCXX_COVERAGE_LIBRARY "${LIBCXX_COVERAGE_LIBRARY}")
 
 add_library_flags_if(LIBCXX_ENABLE_STATIC_ABI_LIBRARY "-Wl,--whole-archive" "-Wl,-Bstatic")
 add_library_flags("${LIBCXX_CXX_ABI_LIBRARY}")
 add_library_flags_if(LIBCXX_ENABLE_STATIC_ABI_LIBRARY "-Wl,-Bdynamic" "-Wl,--no-whole-archive")
add_link_flags(
       "-install_name /usr/lib/libc++.1.dylib"
       "-Wl,-unexported_symbols_list,${CMAKE_CURRENT_SOURCE_DIR}/libc++unexp.exp"
       "${OSX_RE_EXPORT_LINE}"
       "-Wl,-force_symbols_not_weak_list,${CMAKE_CURRENT_SOURCE_DIR}/notweak.exp"
       "-Wl,-force_symbols_weak_list,${CMAKE_CURRENT_SOURCE_DIR}/weak.exp")
   endif()
 endif()
 
-target_link_libraries(cxx ${LIBCXX_LIBRARIES})
 split_list(LIBCXX_COMPILE_FLAGS)
 split_list(LIBCXX_LINK_FLAGS)
 
-set_target_properties(cxx
+# Add a object library that contains the compiled source files.
+add_library(cxx_objects OBJECT ${exclude_from_all} ${LIBCXX_SOURCES} ${LIBCXX_HEADERS})
+
+set_target_properties(cxx_objects
   PROPERTIES
     COMPILE_FLAGS "${LIBCXX_COMPILE_FLAGS}"
+)
+
+set(LIBCXX_TARGETS)
+
+# Build the shared library.
+if (LIBCXX_ENABLE_SHARED)
+  add_library(cxx_shared SHARED $<TARGET_OBJECTS:cxx_objects>)
+  target_link_libraries(cxx_shared ${LIBCXX_LIBRARIES})
+  set_target_properties(cxx_shared
+    PROPERTIES
       LINK_FLAGS    "${LIBCXX_LINK_FLAGS}"
       OUTPUT_NAME   "c++"
       VERSION       "${LIBCXX_ABI_VERSION}.0"
       SOVERSION     "${LIBCXX_ABI_VERSION}"
   )
+  list(APPEND LIBCXX_TARGETS "cxx_shared")
+endif()
+
+# Build the static library.
+if (LIBCXX_ENABLE_STATIC)
+  add_library(cxx_static STATIC $<TARGET_OBJECTS:cxx_objects>)
+  target_link_libraries(cxx_static ${LIBCXX_LIBRARIES})
+  set_target_properties(cxx_static
+    PROPERTIES
+      LINK_FLAGS    "${LIBCXX_LINK_FLAGS}"
+      OUTPUT_NAME   "c++"
+  )
+  list(APPEND LIBCXX_TARGETS "cxx_static")
+endif()
+
+# Add a meta-target for both libraries.
+add_custom_target(cxx DEPENDS ${LIBCXX_TARGETS})
+
+if (DEFINED LIBCXX_CXX_ABI_DEPS)
+  add_dependencies(cxx LIBCXX_CXX_ABI_DEPS)
+endif()
 
 if (LIBCXX_ENABLE_EXPERIMENTAL_LIBRARY)
   file(GLOB LIBCXX_EXPERIMENTAL_SOURCES ../src/experimental/*.cpp)
   if (LIBCXX_ENABLE_FILESYSTEM)
     file(GLOB LIBCXX_FILESYSTEM_SOURCES ../src/experimental/filesystem/*.cpp)
   endif()
   add_library(cxx_experimental STATIC ${LIBCXX_EXPERIMENTAL_SOURCES} ${LIBCXX_FILESYSTEM_SOURCES})
-  target_link_libraries(cxx_experimental cxx)
+  if (LIBCXX_ENABLE_SHARED)
+    target_link_libraries(cxx_experimental cxx_shared)
+  else()
+    target_link_libraries(cxx_experimental cxx_static)
+  endif()
 
   set(experimental_flags "${LIBCXX_COMPILE_FLAGS}")
   check_flag_supported(-std=c++14)
   if (NOT MSVC AND LIBCXX_SUPPORTS_STD_EQ_CXX14_FLAG)
     string(REPLACE "-std=c++11" "-std=c++14" experimental_flags "${LIBCXX_COMPILE_FLAGS}")
   endif()
   set_target_properties(cxx_experimental
     PROPERTIES
       COMPILE_FLAGS "${experimental_flags}"
       OUTPUT_NAME   "c++experimental"
   )
 endif()
 
 # Generate a linker script inplace of a libc++.so symlink. Rerun this command
 # after cxx builds.
-if (LIBCXX_ENABLE_ABI_LINKER_SCRIPT)
+if (LIBCXX_ENABLE_SHARED AND LIBCXX_ENABLE_ABI_LINKER_SCRIPT)
   # Get the name of the ABI library and handle the case where CXXABI_LIBNAME
   # is a target name and not a library. Ex cxxabi_shared.
   set(SCRIPT_ABI_LIBNAME "${LIBCXX_CXX_ABI_LIBRARY}")
   if (SCRIPT_ABI_LIBNAME STREQUAL "cxxabi_shared")
     set(SCRIPT_ABI_LIBNAME "c++abi")
   endif()
   # Generate a linker script inplace of a libc++.so symlink. Rerun this command
   # after cxx builds.
-  add_custom_command(TARGET cxx POST_BUILD
+  add_custom_command(TARGET cxx_shared POST_BUILD
     COMMAND
       ${PYTHON_EXECUTABLE} ${LIBCXX_SOURCE_DIR}/utils/gen_link_script/gen_link_script.py
     ARGS
-      "$<TARGET_LINKER_FILE:cxx>"
+      "$<TARGET_LINKER_FILE:cxx_shared>"
       "${SCRIPT_ABI_LIBNAME}"
     WORKING_DIRECTORY ${LIBCXX_BUILD_DIR}
   )
 endif()
 
 if (LIBCXX_INSTALL_LIBRARY)
   if (LIBCXX_INSTALL_EXPERIMENTAL_LIBRARY)
     set(experimental_lib cxx_experimental)
   endif()
-  install(TARGETS cxx ${experimental_lib}
+  install(TARGETS ${LIBCXX_TARGETS} ${experimental_lib}
     LIBRARY DESTINATION lib${LIBCXX_LIBDIR_SUFFIX} COMPONENT libcxx
     ARCHIVE DESTINATION lib${LIBCXX_LIBDIR_SUFFIX} COMPONENT libcxx
     )
   # NOTE: This install command must go after the cxx install command otherwise
   # it will not be executed after the library symlinks are installed.
-  if (LIBCXX_ENABLE_ABI_LINKER_SCRIPT)
+  if (LIBCXX_ENABLE_SHARED AND LIBCXX_ENABLE_ABI_LINKER_SCRIPT)
     # Replace the libc++ filename with $<TARGET_LINKER_FILE:cxx>
     # after we required CMake 3.0.
     install(FILES "${LIBCXX_LIBRARY_DIR}/libc++${CMAKE_SHARED_LIBRARY_SUFFIX}"
       DESTINATION lib${LIBCXX_LIBDIR_SUFFIX}
       COMPONENT libcxx)
   endif()
 endif()