gn: Fix build on Windows

BUILD.gn

 # Copyright 2014 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("//build/config/arm.gni")
 import("//build/config/android/config.gni")
 import("//third_party/libvpx/libvpx_srcs.gni")
 import("//third_party/yasm/yasm_assemble.gni")
 
 if (is_posix && !is_mac) {
@@ skipping 23 matching lines @@
   cpu_arch_full = cpu_arch
 }
 
 config("libvpx_config") {
   include_dirs = [
     "//third_party/libvpx/source/config",
     "//third_party/libvpx/source/config/$os_category/$cpu_arch_full",
     "//third_party/libvpx/source/libvpx",
     "$root_gen_dir/third_party/libvpx", # Provides vpx_rtcd.h.
   ]
-  cflags = [ "-Wno-unused-function", "-Wno-sign-compare" ]
+  if (is_win) {
+    cflags = [
+      "/wd4057",

[Johann, 2014/09/25 21:00:25]

We (try) to track Windows errors pretty carefully and have removed all the
warnings we're aware of in both our local builds and Chromium. Has something
changed in GN that warnings which were not enabled in GYP are now turned on?

+      "/wd4201",
+      "/wd4204",
+      "/wd4221",
+      "/wd4245",
+      "/wd4324",
+      "/wd4389",
+      "/wd4701",
+      "/wd4706",
+    ]
+  } else {
+    cflags = [ "-Wno-unused-function", "-Wno-sign-compare" ]
+  }
 }
 
 # This config is applied to targets that depend on libvpx.
 config("libvpx_external_config") {
   include_dirs = [
     "//third_party/libvpx/source/libvpx",
   ]
 }
 
 executable("libvpx_obj_int_extract") {
@@ skipping 31 matching lines @@
                          "/libvpx_obj_int_extract",
                          root_build_dir)
     ]
 
     if (cpu_arch == "arm") {
       args += [ "-f", "gas" ]
     } else {
       args += [ "-f", "rvds" ]
     }
 
+    if (is_win) {
+      obj_extension = "obj"
+    } else {
+      obj_extension = "o"
+    }
+
     args += [
       "-b",
       rebase_path(get_label_info(":libvpx_asm_offsets", "target_out_dir")) +
           "/" + invoker.src_dir + "/libvpx_asm_offsets." +
-          invoker.obj_file_root + ".o"
+          invoker.obj_file_root + ".${obj_extension}"
     ]
     out_file = "$target_gen_dir/" + invoker.obj_file_root + ".asm"
     args += [ "-o", rebase_path(out_file) ]
     outputs = [ out_file ]
     deps = [
       ":libvpx_asm_offsets",
       ":libvpx_obj_int_extract($host_toolchain)"
     ]
   }
 }
@@ skipping 25 matching lines @@
     ]
     deps = [
       ":gen_asm_offsets_vp8",
       ":gen_asm_offsets_scale",
     ]
   }
 }
 
 static_library("libvpx_intrinsics_mmx") {
   configs += [ ":libvpx_config" ]
-  cflags = [ "-mmmx" ]
+  if (!is_win) {
+    cflags = [ "-mmmx" ]
+  }
   if (cpu_arch == "x86") {
     sources = libvpx_srcs_x86_mmx
   } else if (cpu_arch == "x64") {
     sources = libvpx_srcs_x86_64_mmx
   }
 }
 
 static_library("libvpx_intrinsics_sse2") {
   configs += [ ":libvpx_config" ]
-  cflags = [ "-msse2" ]
+  if (!is_win) {
+    cflags = [ "-msse2" ]
+  }
   if (cpu_arch == "x86") {
     sources = libvpx_srcs_x86_sse2
   } else if (cpu_arch == "x64") {
     sources = libvpx_srcs_x86_64_sse2
   }
 }
 
 static_library("libvpx_intrinsics_ssse3") {
   configs += [ ":libvpx_config" ]
-  cflags = [ "-mssse3" ]
+  if (!is_win) {
+    cflags = [ "-mssse3" ]
+  }
   if (cpu_arch == "x86") {
     sources = libvpx_srcs_x86_ssse3
   } else if (cpu_arch == "x64") {
     sources = libvpx_srcs_x86_64_ssse3
   }
 }
 
 static_library("libvpx_intrinsics_sse4_1") {
   configs += [ ":libvpx_config" ]
-  cflags = [ "-msse4.1" ]
+  if (!is_win) {
+    cflags = [ "-msse4.1" ]
+  }
   if (cpu_arch == "x86") {
     sources = libvpx_srcs_x86_sse4_1
   } else if (cpu_arch == "x64") {
     sources = libvpx_srcs_x86_64_sse4_1
   }
 }
 
 if (cpu_arch_full == "arm-neon-cpu-detect") {
   static_library("libvpx_intrinsics_neon") {
     configs -= [ "//build/config/compiler:compiler_arm_fpu" ]
@@ skipping 83 matching lines @@
   }
   if (is_android) {
     deps += [ "//third_party/android_tools:cpu_features" ]
   }
   if (cpu_arch == "arm") {
     deps += [ ":libvpx_assembly_arm" ]
   }
 
   public_configs = [ ":libvpx_external_config" ]
 }