Reland "Upgrade compiler to Clang 10." (#327)

This reverts commit 1c98a42.

Author: chinmaygarde

build/config/BUILDCONFIG.gn

@@ -283,6 +283,8 @@ if (!is_clang && (is_asan || is_lsan || is_tsan || is_msan)) {
   is_clang = true
 }
 
+use_flutter_cxx = is_clang && (is_linux || is_android)
+
 if (is_msan && !is_linux) {
   assert(false, "Memory sanitizer is only available on Linux.")
 }
@@ -529,7 +531,7 @@ if (custom_toolchain != "") {
 #
 # Variables
 #   no_default_deps: If true, no standard dependencies will be added.
-if (is_android || (is_linux && current_cpu != "x86")) {
+if (use_flutter_cxx) {
   foreach(_target_type,
           [
             "executable",

build/config/compiler/BUILD.gn

@@ -163,7 +163,6 @@ config("compiler") {
       common_mac_flags += [
         "-arch",
         "x86_64",
-        "-march=core2",
       ]
     } else if (current_cpu == "x86") {
       common_mac_flags += [
@@ -210,10 +209,6 @@ config("compiler") {
       ldflags += [ "-m32" ]
       if (is_clang) {
         cflags += [
-          # Else building libyuv gives clang's register allocator issues,
-          # see llvm.org/PR15798 / crbug.com/233709
-          "-momit-leaf-frame-pointer",
-
           # Align the stack on 16-byte boundaries, http://crbug.com/418554.
           "-mstack-alignment=16",
           "-mstackrealign",
@@ -500,6 +495,7 @@ config("compiler_arm_fpu") {
 config("runtime_library") {
   cflags = []
   cflags_cc = []
+  cflags_objcc = []
   defines = []
   ldflags = []
   lib_dirs = []
@@ -521,6 +517,20 @@ config("runtime_library") {
     ]
   }
 
+  if (use_flutter_cxx) {
+    cflags_cc += [ "-nostdinc++" ]
+    cflags_objcc += [ "-nostdinc++" ]
+
+    # Unwind seemes to be in these libraries in Linux.
+    if (!is_linux) {
+      ldflags += [ "-nostdlib++" ]
+    }
+    include_dirs = [
+      "//third_party/libcxx/include",
+      "//third_party/libcxxabi/include",
+    ]
+  }
+
   # Android standard library setup.
   if (is_android) {
     if (is_clang) {
@@ -531,8 +541,6 @@ config("runtime_library") {
       ]
     }
 
-    defines += [ "__GNU_SOURCE=1" ]  # Necessary for clone().
-
     # TODO(jdduke) Re-enable on mips after resolving linking
     # issues with libc++ (crbug.com/456380).
     if (current_cpu != "mipsel" && current_cpu != "mips64el") {
@@ -556,11 +564,6 @@ config("runtime_library") {
       "-D__ANDROID_API__=$android_api_level",
     ]
 
-    include_dirs = [
-      "//third_party/libcxx/include",
-      "//third_party/libcxxabi/include",
-    ]
-
     # libunwind and libandroid_support also live in $android_libcpp_root.
     lib_dirs += [ "$android_libcpp_root/libs/$android_app_abi" ]
 
@@ -589,13 +592,7 @@ config("runtime_library") {
   # We compile our own libc++ on all Linux targets except i386 (for
   # gen_snapshot) where this is not supported.
   if (is_linux) {
-    if (current_cpu != "x86") {
-      cflags_cc += [ "-nostdinc++" ]
-      include_dirs = [
-        "//third_party/libcxx/include",
-        "//third_party/libcxxabi/include",
-      ]
-    } else {
+    if (!use_flutter_cxx) {
       cflags_cc += [ "-stdlib=libstdc++" ]
       ldflags += [ "-stdlib=libstdc++" ]
       libs += [ "gcc" ]
@@ -638,6 +635,9 @@ if (is_win) {
     # Disables.
     "-Wno-missing-field-initializers",  # "struct foo f = {0};"
     "-Wno-unused-parameter",  # Unused function parameters.
+    "-Wno-implicit-int-float-conversion",
+    "-Wno-reorder-init-list",
+    "-Wno-c99-designator",
   ]
 
   if (is_mac || is_ios) {

build/config/ios/BUILD.gn

@@ -2,12 +2,21 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-import("//build/config/sysroot.gni")
 import("//build/config/ios/ios_sdk.gni")
+import("//build/config/sysroot.gni")
 
 config("sdk") {
   common_flags = [ "-stdlib=libc++" ]
 
   cflags = common_flags
   ldflags = common_flags
+
+  common_ccflags = [
+    "-nostdinc++",
+    "-isystem",
+    "$xcode_toolchain/usr/include/c++/v1",
+  ]
+
+  cflags_cc = common_ccflags
+  cflags_objcc = common_ccflags
 }

build/config/mac/BUILD.gn

@@ -9,6 +9,15 @@ config("sdk") {
 
   cflags = common_flags
   ldflags = common_flags
+
+  common_ccflags = [
+    "-nostdinc++",
+    "-isystem",
+    "$xcode_toolchain/usr/include/c++/v1",
+  ]
+
+  cflags_cc = common_ccflags
+  cflags_objcc = common_ccflags
 }
 
 # On Mac, this is used for everything except static libraries.

build/config/mac/xcode_toolchain.py

@@ -0,0 +1,17 @@
+#!/usr/bin/python
+# Copyright (c) 2015 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import sys
+import os
+import subprocess
+
+def Main():
+  path = subprocess.check_output(['/usr/bin/env', 'xcode-select', '-p']).strip();
+  path = os.path.join(path, "Toolchains", "XcodeDefault.xctoolchain")
+  assert os.path.exists(path)
+  print path
+
+if __name__ == '__main__':
+  sys.exit(Main())

build/config/sysroot.gni

@@ -9,6 +9,10 @@ declare_args() {
   # The absolute path of the sysroot that is applied when compiling using
   # the target toolchain.
   target_sysroot = ""
+
+  # The absolute path to the Xcode toolchain. This is used to look for headers
+  # that usually ship with the toolchain like c++/v1.
+  xcode_toolchain = ""
 }
 
 if (current_toolchain == default_toolchain && target_sysroot != "") {
@@ -31,3 +35,10 @@ if (current_toolchain == default_toolchain && target_sysroot != "") {
 } else {
   sysroot = ""
 }
+
+if ((is_mac || is_ios) && xcode_toolchain == "") {
+  xcode_toolchain = exec_script("//build/config/mac/xcode_toolchain.py",
+                                [],
+                                "trim string",
+                                [])
+}

build/secondary/third_party/libcxxabi/BUILD.gn

@@ -5,21 +5,60 @@
 import("$flutter_root/common/config.gni")
 
 config("libcxxabi_config") {
+  common_cc_flags = [ "-nostdinc++" ]
+
+  cflags_cc = common_cc_flags
+  cflags_objcc = common_cc_flags
+
   include_dirs = [ "include" ]
 }
 
 source_set("libcxxabi") {
   visibility = [ "../libcxx:*" ]
 
-  sources = [
+  public_configs = [ ":libcxxabi_config" ]
+
+  defines = [
+    "_LIBCXXABI_NO_EXCEPTIONS",
+    "_LIBCXXABI_BUILDING_LIBRARY",
+    "LIBCXXABI_SILENT_TERMINATE",
+  ]
+
+  sources = []
+
+  # Compile libcxx ABI using C++11. This replicates the rule in the
+  # CMakeLists on the "cxx_abiobjects" target.
+  configs -= [ "//build/config/compiler:cxx_version_default" ]
+  configs += [ "//build/config/compiler:cxx_version_11" ]
+
+  configs += [ "../libcxx:libcxx_config" ]
+
+  # No translation units in the engine are built with exceptions. But, using
+  # Objective-C exceptions requires some infrastructure setup for exceptions.
+  # Build support for the same in cxxabi on Darwin.
+  if (is_mac || is_ios) {
+    configs -= [ "//build/config/gcc:no_exceptions" ]
+    sources += [
+      "src/cxa_exception.cpp",
+      "src/cxa_personality.cpp",
+    ]
+  } else {
+    sources += [ "src/cxa_noexception.cpp" ]
+  }
+
+  # Third party dependencies may depend on RTTI. Add support for the same in
+  # cxxabi.
+  configs -= [ "//build/config/compiler:no_rtti" ]
+  configs += [ "//build/config/compiler:rtti" ]
+
+  sources += [
     "src/abort_message.cpp",
     "src/cxa_aux_runtime.cpp",
     "src/cxa_default_handlers.cpp",
     "src/cxa_demangle.cpp",
     "src/cxa_exception_storage.cpp",
     "src/cxa_guard.cpp",
     "src/cxa_handlers.cpp",
-    "src/cxa_noexception.cpp",
     "src/cxa_unexpected.cpp",
     "src/cxa_vector.cpp",
     "src/cxa_virtual.cpp",
@@ -29,26 +68,4 @@ source_set("libcxxabi") {
     "src/stdlib_stdexcept.cpp",
     "src/stdlib_typeinfo.cpp",
   ]
-
-  public_configs = [ ":libcxxabi_config" ]
-
-  defines = [
-    "_LIBCXXABI_NO_EXCEPTIONS",
-    "_LIBCXXABI_BUILDING_LIBRARY",
-    "LIBCXXABI_SILENT_TERMINATE",
-  ]
-
-  # ICU uses RTTI, so we need to build libcxxabi with support for it,
-  # https://github.com/flutter/flutter/issues/24535.
-  configs -= [ "//build/config/compiler:no_rtti" ]
-
-  # Compile libcxx ABI using an older standard. This replicates the rule in the
-  # CMakeLists on the "cxx_abiobjects" target.
-  configs -= [ "//build/config/compiler:cxx_version_default" ]
-  configs += [ "//build/config/compiler:cxx_version_11" ]
-
-  configs += [
-    "//build/config/compiler:rtti",
-    "//third_party/libcxx:libcxx_config",
-  ]
 }