Config changes to support target_os="fuchsia"

build/config/BUILDCONFIG.gn

 # Copyright (c) 2013 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.
 
 # =============================================================================
 # WHAT IS THIS FILE?
 # =============================================================================
 #
 # This is the master GN build configuration. This file is loaded after the
 # build args (args.gn) for the build directory and after the toplevel ".gn"
@@ skipping 119 matching lines @@
   # separate flags.
   is_official_build = false
 
   # Whether we're a traditional desktop unix.
   is_desktop_linux = current_os == "linux"
 
   # Set to true when compiling with the Clang compiler. Typically this is used
   # to configure warnings.
   is_clang =
       current_os == "mac" || current_os == "ios" || current_os == "chromeos" ||
+      current_os == "fuchsia" ||
       (current_os == "linux" && current_cpu != "s390x" &&
        current_cpu != "s390" && current_cpu != "ppc64" && current_cpu != "ppc")
 
   # Allows the path to a custom target toolchain to be injected as a single
   # argument, and set as the default toolchain.
   custom_toolchain = ""
 
   # This should not normally be set as a build argument.  It's here so that
   # every toolchain can pass through the "global" value via toolchain_args().
   host_toolchain = ""
 
   # DON'T ADD MORE FLAGS HERE. Read the comment above.
 }
 
 declare_args() {
   # Debug build. Enabling official builds automatically sets is_debug to false.
   is_debug = !is_official_build
 }
 
 declare_args() {
   # Component build. Setting to true compiles targets declared as "components"
   # as shared libraries loaded dynamically. This speeds up development time.
   # When false, components will be linked statically.
   #
   # For more information see
   # https://chromium.googlesource.com/chromium/src/+/master/docs/component_build.md
-  is_component_build = is_debug && current_os != "ios"
+  is_component_build =
+      is_debug && current_os != "ios" && current_os != "fuchsia"
 }
 
 assert(!(is_debug && is_official_build), "Can't do official debug builds")
 
 # ==============================================================================
 # TOOLCHAIN SETUP
 # ==============================================================================
 #
 # Here we set the default toolchain, as well as the variable host_toolchain
 # which will identify the toolchain corresponding to the local system when
@@ skipping 49 matching lines @@
   } else {
     _default_toolchain = "//build/toolchain/android:android_$target_cpu"
   }
 } else if (target_os == "chromeos" || target_os == "linux") {
   # See comments in build/toolchain/cros/BUILD.gn about board compiles.
   if (is_clang) {
     _default_toolchain = "//build/toolchain/linux:clang_$target_cpu"
   } else {
     _default_toolchain = "//build/toolchain/linux:$target_cpu"
   }
+} else if (target_os == "fuchsia") {
+  _default_toolchain = "//build/toolchain/fuchsia:$target_cpu"
 } else if (target_os == "ios") {
   _default_toolchain = "//build/toolchain/mac:ios_clang_$target_cpu"
 } else if (target_os == "mac") {
   assert(host_os == "mac", "Mac cross-compiles are unsupported.")
   _default_toolchain = host_toolchain
 } else if (target_os == "win") {
   # On Windows we use the same toolchain for host and target by default.
   assert(target_os == host_os, "Win cross-compiles only work on win hosts.")
   if (is_clang) {
     _default_toolchain = "//build/toolchain/win:clang_$target_cpu"
@@ skipping 32 matching lines @@
 #   generally too different despite being based on the Linux kernel).
 #
 # Do not add more is_* variants here for random lesser-used Unix systems like
 # aix or one of the BSDs. If you need to check these, just check the
 # current_os value directly.
 
 if (current_os == "win" || current_os == "winrt_81" ||
     current_os == "winrt_81_phone" || current_os == "winrt_10") {
   is_android = false
   is_chromeos = false
+  is_fuchsia = false
   is_ios = false
   is_linux = false
   is_mac = false
   is_nacl = false
   is_posix = false
   is_win = true
 } else if (current_os == "mac") {
   is_android = false
   is_chromeos = false
+  is_fuchsia = false
   is_ios = false
   is_linux = false
   is_mac = true
   is_nacl = false
   is_posix = true
   is_win = false
 } else if (current_os == "android") {
   is_android = true
   is_chromeos = false
+  is_fuchsia = false
   is_ios = false
   is_linux = false
   is_mac = false
   is_nacl = false
   is_posix = true
   is_win = false
 } else if (current_os == "chromeos") {
   is_android = false
   is_chromeos = true
+  is_fuchsia = false
   is_ios = false
   is_linux = true
   is_mac = false
   is_nacl = false
   is_posix = true
   is_win = false
 } else if (current_os == "nacl") {
   # current_os == "nacl" will be passed by the nacl toolchain definition.
   # It is not set by default or on the command line. We treat is as a
   # Posix variant.
   is_android = false
   is_chromeos = false
+  is_fuchsia = false
   is_ios = false
   is_linux = false
   is_mac = false
   is_nacl = true
   is_posix = true
   is_win = false
+} else if (current_os == "fuchsia") {
+  is_android = false
+  is_chromeos = false
+  is_fuchsia = true
+  is_ios = false
+  is_linux = false
+  is_mac = false
+  is_nacl = false
+  is_posix = true
+  is_win = false
 } else if (current_os == "ios") {
   is_android = false
   is_chromeos = false
+  is_fuchsia = false
   is_ios = true
   is_linux = false
   is_mac = false
   is_nacl = false
   is_posix = true
   is_win = false
 } else if (current_os == "linux") {
   is_android = false
   is_chromeos = false
+  is_fuchsia = false
   is_ios = false
   is_linux = true
   is_mac = false
   is_nacl = false
   is_posix = true
   is_win = false
 } else if (current_os == "aix") {
   is_android = false
   is_chromeos = false
   is_ios = false
@@ skipping 13 matching lines @@
 # to each assignment or appending to the sources variable and matches are
 # automatically removed.
 #
 # Note that the patterns are NOT regular expressions. Only "*" and "\b" (path
 # boundary = end of string or slash) are supported, and the entire string
 # must match the pattern (so you need "*.cc" to match all .cc files, for
 # example).
 
 # DO NOT ADD MORE PATTERNS TO THIS LIST, see set_sources_assignment_filter call
 # below.
 sources_assignment_filter = []

[miu, 2017/05/11 21:18:11]

Given recent discussion in the "Fuchsia porting guide for Chromium" doc, can we
add fuchsia filters in this change too?

  if (is_fuchsia) {
    sources_assignment_filter += [
      "*_fuchsia.h",
      "*_fuchsia.cc",
      ...

[scottmg, 2017/05/11 21:24:53]

That might be pleasant, but per Brett's comment, we're trying to avoid that,
especially for niche OSs. Until we have more than a handful of Fuchsia files, I
think if (is_fuchsia) in the sources is fine.

 if (!is_posix) {
   sources_assignment_filter += [
     "*_posix.h",
     "*_posix.cc",
     "*_posix_unittest.h",
     "*_posix_unittest.cc",
     "*\bposix/*",
   ]
 }
 
@@ skipping 280 matching lines @@
 set_defaults("component") {
   if (is_component_build) {
     configs = default_shared_library_configs
     if (is_android) {
       configs -= [ "//build/config/android:hide_all_but_jni_onload" ]
     }
   } else {
     configs = default_compiler_configs
   }
 }