toolchain/download_ios_toolchain.bzl - skia - Git at Google

 """
 This file assembles a toolchain for cross compiling on a Mac host for iOS using the Clang Compiler
 and a locally-installed XCode.

 It downloads the necessary executables and creates symlinks in the external subfolder of the Bazel
 cache (the same place third party deps are downloaded with http_archive or similar functions in
 WORKSPACE.bazel). These will be able to be used via our
 custom c++ toolchain configuration (see //toolchain/ios_toolchain_config.bzl)

 The destination folder for these files and symlinks are:
   [outputRoot (aka Bazel cache)]/[outputUserRoot]/[outputBase]/external/clang_ios
   (See https://bazel.build/docs/output_directories#layout-diagram)
 """

 load(":clang_layering_check.bzl", "generate_system_module_map")
 load(":utils.bzl", "gcs_mirror_url")

 # From https://github.com/llvm/llvm-project/releases/tag/llvmorg-15.0.1
 # When updating this, don't forget to use //bazel/gcs_mirror to upload a new version.
 # go run bazel/gcs_mirror/gcs_mirror.go --url [clang_url] --sha256 [clang_sha256]
 clang_prefix_arm64 = "clang+llvm-15.0.1-arm64-apple-darwin21.0"
 clang_sha256_arm64 = "858f86d96b5e4880f69f7a583daddbf97ee94e7cffce0d53aa05cba6967f13b8"
 clang_url_arm64 = "https://github.com/llvm/llvm-project/releases/download/llvmorg-15.0.1/clang+llvm-15.0.1-arm64-apple-darwin21.0.tar.xz"

 ios_sdk_root = "/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/"

 def _get_system_xcode_path(ctx):
     # https://developer.apple.com/library/archive/technotes/tn2339/_index.html
     res = ctx.execute(["xcode-select", "--print-path"])
     if res.return_code != 0:
         fail("Error Getting XCode path: " + res.stderr)
     return res.stdout.rstrip()

 def _delete_ios_sdk_symlinks(ctx):
     ctx.delete("./symlinks/xcode/iOSSDK/usr")
     ctx.delete("./symlinks/xcode/iOSSDK/System/Library/Frameworks")

 def _create_ios_sdk_symlinks(ctx):
     system_xcode_path = _get_system_xcode_path(ctx)

     # https://bazel.build/rules/lib/actions#symlink
     ctx.symlink(
         # from =
         system_xcode_path + ios_sdk_root + "usr",
         # to =
         "./symlinks/xcode/iOSSDK/usr",
     )

     # It is very important to symlink the frameworks directory to [sysroot]/System/Library/Frameworks
     # because some Frameworks "re-export" other frameworks. These framework paths are relative to
     # the sysroot (which on a typical machine is /), and it is difficult to change these paths.
     # By making the symlinks emulate the original path structure, we can keep those re-exports
     # from breaking.
     ctx.symlink(
         # from =
         system_xcode_path + ios_sdk_root + "System/Library/Frameworks",
         # to =
         "./symlinks/xcode/iOSSDK/System/Library/Frameworks",
     )

 def _download_ios_toolchain_impl(ctx):
     # Download the clang toolchain (the extraction can take a while)
     # https://bazel.build/rules/lib/repository_ctx#download_and_extract
     ctx.download_and_extract(
         url = gcs_mirror_url(clang_url_arm64, clang_sha256_arm64),
         output = "",
         stripPrefix = clang_prefix_arm64,
         sha256 = clang_sha256_arm64,
     )

     # Some std library headers use #include_next to include system specific headers, and
     # some skia source files require Xcode headers when compiling, (see SkTypes.h and look
     # for TargetedConditionals.h)) All of these are located in Xcode, stopping the Mac
     # builds from being purely hermetic.
     # For now, we can grab the user's Xcode path by calling xcode-select and create a symlink in
     # our toolchain directory to refer to during compilation.

     _delete_ios_sdk_symlinks(ctx)
     _create_ios_sdk_symlinks(ctx)

     # This list of files lines up with _make_default_flags() in ios_toolchain_config.bzl
     # It is all locations that our toolchain could find a system header.
     builtin_include_directories = [
         "include/c++/v1",
         "lib/clang/15.0.1/include",
         "symlinks/xcode/iOSSDK/System/Library/Frameworks",
         "symlinks/xcode/iOSSDK/usr/include",
     ]

     generate_system_module_map(
         ctx,
         module_file = "toolchain_system_headers.modulemap",
         folders = builtin_include_directories,
     )

     # Create a BUILD.bazel file that makes the files necessary for compiling,
     # linking and creating archive files visible to Bazel.
     # The smaller the globs are, the more performant the sandboxed builds will be.
     # Additionally, globs that are too wide can pick up infinite symlink loops,
     # and be difficult to quash: https://github.com/bazelbuild/bazel/issues/13950
     # https://bazel.build/rules/lib/repository_ctx#file
     ctx.file(
         "BUILD.bazel",
         content = """
 # DO NOT EDIT THIS BAZEL FILE DIRECTLY
 # Generated from ctx.file action in download_ios_toolchain.bzl
 filegroup(
     name = "generated_module_map",
     srcs = ["toolchain_system_headers.modulemap"],
     visibility = ["//visibility:public"],
 )

 filegroup(
     name = "archive_files",
     srcs = [
         "bin/llvm-ar",
     ],
     visibility = ["//visibility:public"],
 )

 # Any framework that Skia depends on directly or indirectly needs to be listed here.
 FRAMEWORK_GLOB = [
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/CFNetwork.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/CloudKit.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/ColorSync.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreData.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreFoundation.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreGraphics.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreImage.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreLocation.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreServices.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreText.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreVideo.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/Foundation.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/ImageIO.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/IOKit.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/IOSurface.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/Metal.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/MetalKit.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/MobileCoreServices.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/ModelIO.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/OpenGLES.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/QuartzCore.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/Security.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/Symbols.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/UIKit.Framework/**",
     "symlinks/xcode/iOSSDK/System/Library/Frameworks/UserNotifications.Framework/**",
 ]

 filegroup(
     name = "compile_files",
     srcs = [
         "bin/clang",
     ] + glob(
         include = [
             "include/c++/v1/**",
             "lib/clang/15.0.1/include/**",
             "symlinks/xcode/iOSSDK/usr/include/**",
         ] + FRAMEWORK_GLOB,
         allow_empty = False,
     ),
     visibility = ["//visibility:public"],
 )

 filegroup(
     name = "link_files",
     srcs = [
         "bin/clang",
         "bin/ld.lld",
         "bin/lld",
         "lib/libc++.a",
         "lib/libc++abi.a",
         "lib/libunwind.a",
     ] + glob(
         include = [
             # libc++.tbd and libSystem.tbd live here.
             "symlinks/xcode/iOSSDK/usr/lib/*",
         ] + FRAMEWORK_GLOB,
         allow_empty = False,
     ),
     visibility = ["//visibility:public"],
 )
 """,
         executable = False,
     )

 # https://bazel.build/rules/repository_rules
 download_ios_toolchain = repository_rule(
     implementation = _download_ios_toolchain_impl,
     attrs = {},
     doc = "Downloads clang to build Skia with." +
           "Assumes you have xcode located on your device and have" +
           "xcode-select in your $PATH.",
 )
	"""
	This file assembles a toolchain for cross compiling on a Mac host for iOS using the Clang Compiler
	and a locally-installed XCode.

	It downloads the necessary executables and creates symlinks in the external subfolder of the Bazel
	cache (the same place third party deps are downloaded with http_archive or similar functions in
	WORKSPACE.bazel). These will be able to be used via our
	custom c++ toolchain configuration (see //toolchain/ios_toolchain_config.bzl)

	The destination folder for these files and symlinks are:
	[outputRoot (aka Bazel cache)]/[outputUserRoot]/[outputBase]/external/clang_ios
	(See https://bazel.build/docs/output_directories#layout-diagram)
	"""

	load(":clang_layering_check.bzl", "generate_system_module_map")
	load(":utils.bzl", "gcs_mirror_url")

	# From https://github.com/llvm/llvm-project/releases/tag/llvmorg-15.0.1
	# When updating this, don't forget to use //bazel/gcs_mirror to upload a new version.
	# go run bazel/gcs_mirror/gcs_mirror.go --url [clang_url] --sha256 [clang_sha256]
	clang_prefix_arm64 = "clang+llvm-15.0.1-arm64-apple-darwin21.0"
	clang_sha256_arm64 = "858f86d96b5e4880f69f7a583daddbf97ee94e7cffce0d53aa05cba6967f13b8"
	clang_url_arm64 = "https://github.com/llvm/llvm-project/releases/download/llvmorg-15.0.1/clang+llvm-15.0.1-arm64-apple-darwin21.0.tar.xz"

	ios_sdk_root = "/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/"

	def _get_system_xcode_path(ctx):
	# https://developer.apple.com/library/archive/technotes/tn2339/_index.html
	res = ctx.execute(["xcode-select", "--print-path"])
	if res.return_code != 0:
	fail("Error Getting XCode path: " + res.stderr)
	return res.stdout.rstrip()

	def _delete_ios_sdk_symlinks(ctx):
	ctx.delete("./symlinks/xcode/iOSSDK/usr")
	ctx.delete("./symlinks/xcode/iOSSDK/System/Library/Frameworks")

	def _create_ios_sdk_symlinks(ctx):
	system_xcode_path = _get_system_xcode_path(ctx)

	# https://bazel.build/rules/lib/actions#symlink
	ctx.symlink(
	# from =
	system_xcode_path + ios_sdk_root + "usr",
	# to =
	"./symlinks/xcode/iOSSDK/usr",
	)

	# It is very important to symlink the frameworks directory to [sysroot]/System/Library/Frameworks
	# because some Frameworks "re-export" other frameworks. These framework paths are relative to
	# the sysroot (which on a typical machine is /), and it is difficult to change these paths.
	# By making the symlinks emulate the original path structure, we can keep those re-exports
	# from breaking.
	ctx.symlink(
	# from =
	system_xcode_path + ios_sdk_root + "System/Library/Frameworks",
	# to =
	"./symlinks/xcode/iOSSDK/System/Library/Frameworks",
	)

	def _download_ios_toolchain_impl(ctx):
	# Download the clang toolchain (the extraction can take a while)
	# https://bazel.build/rules/lib/repository_ctx#download_and_extract
	ctx.download_and_extract(
	url = gcs_mirror_url(clang_url_arm64, clang_sha256_arm64),
	output = "",
	stripPrefix = clang_prefix_arm64,
	sha256 = clang_sha256_arm64,
	)

	# Some std library headers use #include_next to include system specific headers, and
	# some skia source files require Xcode headers when compiling, (see SkTypes.h and look
	# for TargetedConditionals.h)) All of these are located in Xcode, stopping the Mac
	# builds from being purely hermetic.
	# For now, we can grab the user's Xcode path by calling xcode-select and create a symlink in
	# our toolchain directory to refer to during compilation.

	_delete_ios_sdk_symlinks(ctx)
	_create_ios_sdk_symlinks(ctx)

	# This list of files lines up with _make_default_flags() in ios_toolchain_config.bzl
	# It is all locations that our toolchain could find a system header.
	builtin_include_directories = [
	"include/c++/v1",
	"lib/clang/15.0.1/include",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks",
	"symlinks/xcode/iOSSDK/usr/include",
	]

	generate_system_module_map(
	ctx,
	module_file = "toolchain_system_headers.modulemap",
	folders = builtin_include_directories,
	)

	# Create a BUILD.bazel file that makes the files necessary for compiling,
	# linking and creating archive files visible to Bazel.
	# The smaller the globs are, the more performant the sandboxed builds will be.
	# Additionally, globs that are too wide can pick up infinite symlink loops,
	# and be difficult to quash: https://github.com/bazelbuild/bazel/issues/13950
	# https://bazel.build/rules/lib/repository_ctx#file
	ctx.file(
	"BUILD.bazel",
	content = """
	# DO NOT EDIT THIS BAZEL FILE DIRECTLY
	# Generated from ctx.file action in download_ios_toolchain.bzl
	filegroup(
	name = "generated_module_map",
	srcs = ["toolchain_system_headers.modulemap"],
	visibility = ["//visibility:public"],
	)

	filegroup(
	name = "archive_files",
	srcs = [
	"bin/llvm-ar",
	],
	visibility = ["//visibility:public"],
	)

	# Any framework that Skia depends on directly or indirectly needs to be listed here.
	FRAMEWORK_GLOB = [
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/CFNetwork.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/CloudKit.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/ColorSync.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreData.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreFoundation.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreGraphics.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreImage.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreLocation.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreServices.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreText.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/CoreVideo.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/Foundation.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/ImageIO.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/IOKit.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/IOSurface.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/Metal.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/MetalKit.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/MobileCoreServices.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/ModelIO.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/OpenGLES.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/QuartzCore.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/Security.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/Symbols.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/UIKit.Framework/**",
	"symlinks/xcode/iOSSDK/System/Library/Frameworks/UserNotifications.Framework/**",
	]

	filegroup(
	name = "compile_files",
	srcs = [
	"bin/clang",
	] + glob(
	include = [
	"include/c++/v1/**",
	"lib/clang/15.0.1/include/**",
	"symlinks/xcode/iOSSDK/usr/include/**",
	] + FRAMEWORK_GLOB,
	allow_empty = False,
	),
	visibility = ["//visibility:public"],
	)

	filegroup(
	name = "link_files",
	srcs = [
	"bin/clang",
	"bin/ld.lld",
	"bin/lld",
	"lib/libc++.a",
	"lib/libc++abi.a",
	"lib/libunwind.a",
	] + glob(
	include = [
	# libc++.tbd and libSystem.tbd live here.
	"symlinks/xcode/iOSSDK/usr/lib/*",
	] + FRAMEWORK_GLOB,
	allow_empty = False,
	),
	visibility = ["//visibility:public"],
	)
	""",
	executable = False,
	)

	# https://bazel.build/rules/repository_rules
	download_ios_toolchain = repository_rule(
	implementation = _download_ios_toolchain_impl,
	attrs = {},
	doc = "Downloads clang to build Skia with." +
	"Assumes you have xcode located on your device and have" +
	"xcode-select in your $PATH.",
	)