Mac: Add ARM64 configuration support (see issue #2981)

Requires Xcode 12.2 and the MacOS 11.0 SDK. To generate ARM64 builds set
the CEF_ENABLE_ARM64=1 environment variable and replace all usage of
--x64-build with --arm64-build in script command-line arguments.

tools/automate/automate-git.py

@@ -921,7 +921,8 @@ parser.add_option(
     '--distrib-subdir-suffix',
     dest='distribsubdirsuffix',
     default='',
-    help='CEF distrib dir name suffix, child of chromium/src/cef/binary_distrib')
+    help='CEF distrib dir name suffix, child of chromium/src/cef/binary_distrib'
+)
 
 (options, args) = parser.parse_args()
 
@@ -1032,16 +1033,11 @@ if options.armbuild:
     print('The ARM build option is only supported on Linux.')
     sys.exit()
 
-if options.arm64build:
-  if platform != 'linux' and platform != 'windows':
-    print('The ARM64 build option is only supported on Linux and Windows.')
-    sys.exit()
-
 deps_file = 'DEPS'
 
-if platform == 'mac' and not options.x64build:
+if platform == 'mac' and not (options.x64build or options.arm64build):
   print('32-bit MacOS builds are not supported. ' +
-        'Add --x64-build flag to generate a 64-bit build.')
+        'Add --x64-build or --arm64-build flag to generate a 64-bit build.')
   sys.exit()
 
 # Platforms that build a cef_sandbox library.

tools/cefbuilds/cef_json_builder.py

@@ -99,7 +99,7 @@ class cef_json_builder:
   @staticmethod
   def get_platforms():
     """ Returns the list of supported platforms. """
-    return ('linux32', 'linux64', 'linuxarm', 'linuxarm64', 'macosx64',
+    return ('linux32', 'linux64', 'linuxarm', 'linuxarm64', 'macosarm64', 'macosx64',
             'windows32', 'windows64')
 
   @staticmethod

tools/distrib/mac/README.redistrib.txt

@@ -26,7 +26,7 @@ cefclient.app/
           cef_extensions.pak <=====^
           devtools_resources.pak <=^
           icudtl.dat <= unicode support
-          snapshot_blob.bin, v8_context_snapshot.bin <= V8 initial snapshot
+          snapshot_blob.bin, v8_context_snapshot.[x86_64|arm64].bin <= V8 initial snapshot
           en.lproj/, ... <= locale-specific resources and strings
           Info.plist
       cefclient Helper.app/

tools/gn_args.py

@@ -327,11 +327,11 @@ def ValidateArgs(args):
     windows_sdk_path = GetArgValue(args, 'windows_sdk_path')
 
   # Target CPU architecture.
-  # - Windows supports "x86" and "x64".
-  # - Mac supports only "x64".
+  # - Windows supports "x86", "x64" and "arm64".
+  # - Mac supports "x64" and "arm64".
   # - Linux supports only "x64" unless using a sysroot environment.
   if platform == 'mac':
-    assert target_cpu == 'x64', 'target_cpu must be "x64"'
+    assert target_cpu in ('x64', 'arm64'), 'target_cpu must be "x64" or "arm64"'
   elif platform == 'windows':
     assert target_cpu in ('x86', 'x64',
                           'arm64'), 'target_cpu must be "x86", "x64" or "arm64"'
@@ -548,6 +548,8 @@ def GetAllPlatformConfigs(build_args):
       supported_cpus.append('arm64')
   elif platform == 'mac':
     supported_cpus = ['x64']
+    if os.environ.get('CEF_ENABLE_ARM64', '') == '1':
+      supported_cpus.append('arm64')
   else:
     raise Exception('Unsupported platform')
 

tools/make_distrib.py

@@ -381,7 +381,8 @@ def combine_libs(platform, build_dir, libs, dest_lib):
     # Create an intermediate object file that combines all other object files.
     # Symbols not identified above will be made private (local).
     intermediate_obj = os.path.splitext(dest_lib)[0] + '.o'
-    cmdline = 'ld -arch x86_64 -r -o "%s"' % intermediate_obj
+    arch = 'arm64' if options.arm64build else 'x86_64'
+    cmdline = 'ld -arch %s -r -o "%s"' % (arch, intermediate_obj)
     for symbol in symbols:
       cmdline += ' -exported_symbol %s' % symbol
 
@@ -410,6 +411,10 @@ def combine_libs(platform, build_dir, libs, dest_lib):
     # Verify that no C++ symbols are imported by the archive file. If the
     # archive imports C++ symbols and the client app links an incompatible C++
     # library, the result will be undefined behavior.
+    # For example, to avoid importing libc++ symbols the cef_sandbox target
+    # should have a dependency on libc++abi. This dependency can be verified
+    # with the following command:
+    # gn path out/[config] //cef:cef_sandbox //buildtools/third_party/libc++abi
     print('Verifying imported (undefined) symbols...')
     undefined_symbols = get_undefined_symbols(dest_lib)
     cpp_symbols = list(
@@ -565,10 +570,6 @@ if options.armbuild and platform != 'linux':
   print_error('--arm-build is only supported on Linux.')
   sys.exit()
 
-if options.arm64build and not platform in ('linux', 'windows'):
-  print_error('--arm64-build is only supported on Linux and Windows.')
-  sys.exit()
-
 if options.sandbox and not platform in ('mac', 'windows'):
   print_error('--sandbox is only supported on macOS and Windows.')
   sys.exit()
@@ -632,8 +633,11 @@ else:
 output_dir_base = 'cef_binary_' + cef_ver
 
 if options.distribsubdir == '':
-  # For backwards compatibility keep the old default directory name on mac.
-  platform_name = 'macosx' if platform == 'mac' else platform
+  if platform == 'mac':
+    # For backwards compatibility keep the old default directory name on mac.
+    platform_name = 'macos' + ('x' if platform_arch == '64' else '')
+  else:
+    platform_name = platform
 
   output_dir_name = output_dir_base + '_' + platform_name + platform_arch
   if options.distribsubdirsuffix != '':