[libc++][CMake] Allow merging libc++abi.a into libc++ even on Apple platforms

Summary:
I can't see a good reason to disallow this, even though it isn't the
standard way we build libc++ for Apple platforms.

Making this work on Apple platforms requires using different flags for
--whole-archive and removing the -D flag when running `ar` to merge
archives because that flag isn't supported by the `ar` shipped on Apple
platforms. This shouldn't be an issue since the -D option appears to be
enabled by default in GNU `ar`.

Reviewers: phosek, EricWF, serge-sans-paille

Subscribers: mgorny, christof, jkorous, dexonsmith, libcxx-commits

Differential Revision: https://reviews.llvm.org/D59513

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@356903 91177308-0d34-0410-b5e6-96231b3b80d8

CMakeLists.txt

@@ -359,13 +359,9 @@ elseif(LIBCXX_BUILD_32_BITS)
   message(FATAL_ERROR "LIBCXX_BUILD_32_BITS=ON is not supported on this platform.")
 endif()
 
-# Check that this option is not enabled on Apple and emit a usage warning.
+# Warn users that LIBCXX_ENABLE_STATIC_ABI_LIBRARY is an experimental option.
 if (LIBCXX_ENABLE_STATIC_ABI_LIBRARY)
-  if (APPLE)
-    message(FATAL_ERROR "LIBCXX_ENABLE_STATIC_ABI_LIBRARY is not supported on OS X")
-  else()
-    message(WARNING "LIBCXX_ENABLE_STATIC_ABI_LIBRARY is an experimental option")
-  endif()
+  message(WARNING "LIBCXX_ENABLE_STATIC_ABI_LIBRARY is an experimental option")
   if (LIBCXX_ENABLE_STATIC AND NOT PYTHONINTERP_FOUND)
     message(FATAL_ERROR "LIBCXX_ENABLE_STATIC_ABI_LIBRARY requires python but it was not found.")
   endif()

lib/CMakeLists.txt

@@ -52,14 +52,19 @@ endif()
 add_library_flags_if(LIBCXX_COVERAGE_LIBRARY "${LIBCXX_COVERAGE_LIBRARY}")
 
 if (APPLE AND (LIBCXX_CXX_ABI_LIBNAME STREQUAL "libcxxabi" OR
-               LIBCXX_CXX_ABI_LIBNAME STREQUAL "default"))
+               LIBCXX_CXX_ABI_LIBNAME STREQUAL "default")
+          AND NOT DEFINED LIBCXX_OSX_REEXPORT_LIBCXXABI_SYMBOLS)
   set(LIBCXX_OSX_REEXPORT_LIBCXXABI_SYMBOLS ON)
 endif()
 
 if (LIBCXX_STATICALLY_LINK_ABI_IN_SHARED_LIBRARY)
-  add_library_flags("-Wl,--whole-archive" "-Wl,-Bstatic")
-  add_library_flags("${LIBCXX_CXX_ABI_LIBRARY}")
-  add_library_flags("-Wl,-Bdynamic" "-Wl,--no-whole-archive")
+  if (APPLE)
+    add_library_flags("-Wl,-force_load" "${LIBCXX_CXX_ABI_LIBRARY}")
+  else()
+    add_library_flags("-Wl,--whole-archive" "-Wl,-Bstatic")
+    add_library_flags("${LIBCXX_CXX_ABI_LIBRARY}")
+    add_library_flags("-Wl,-Bdynamic" "-Wl,--no-whole-archive")
+  endif()
 elseif (LIBCXX_OSX_REEXPORT_LIBCXXABI_SYMBOLS)
   add_library_flags("${LIBCXX_CXX_ABI_LIBRARY}")
 else ()

utils/merge_archives.py

@@ -127,7 +127,7 @@ def main():
         out = execute_command_verbose([ar_exe, 't', arc])
         files.extend(out.splitlines())
 
-    execute_command_verbose([ar_exe, 'rcsD', args.output] + files,
+    execute_command_verbose([ar_exe, 'rcs', args.output] + files,
                             cwd=temp_directory_root, verbose=args.verbose)