Build libvpx with -Wno-unused-function.

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("//build/config/chrome_build.gni")
 import("//third_party/libvpx/libvpx_srcs.gni")
 import("//third_party/yasm/yasm_assemble.gni")
 
@@ skipping 24 matching lines @@
   cpu_arch_full = current_cpu
 }
 
 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.
   ]
-  if (!is_win) {
-    cflags = [ "-Wno-unused-function", "-Wno-sign-compare" ]
+}
+
+# gn orders flags on a target before flags from configs. The default config
+# adds -Wall, and these flags have to be after -Wall -- so they need to come
+# from a config and can't be on the target directly.
+config("libvpx_warnings") {
+  if (is_clang) {
+    cflags = [
+      # libvpx heavily relies on implicit enum casting.
+      "-Wno-conversion",
+      # libvpx does `if ((a == b))` in some places.
+      "-Wno-parentheses-equality",
+      # libvpx has many static functions in header, which trigger this warning.
+      "-Wno-unused-function",
+    ]
   }
 }
 
 # This config is applied to targets that depend on libvpx.
 config("libvpx_external_config") {
   include_dirs = [
     "//third_party/libvpx/source/libvpx",
   ]
 }
 
@@ skipping 12 matching lines @@
      "//third_party/libvpx/source/libvpx",
       target_gen_dir
     ]
   }
 }
 
 static_library("libvpx_intrinsics_mmx") {
   configs += [ ":libvpx_config" ]
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
+  configs += [ ":libvpx_warnings" ]
   if (!is_win) {
     cflags = [ "-mmmx" ]
   }
   if (current_cpu == "x86") {
     sources = libvpx_srcs_x86_mmx
   } else if (current_cpu == "x64") {
     sources = libvpx_srcs_x86_64_mmx
   }
 }
 
 static_library("libvpx_intrinsics_sse2") {
   configs += [ ":libvpx_config" ]
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
+  configs += [ ":libvpx_warnings" ]
   if (!is_win || is_clang) {
     cflags = [ "-msse2" ]
   }
   if (current_cpu == "x86") {
     sources = libvpx_srcs_x86_sse2
   } else if (current_cpu == "x64") {
     sources = libvpx_srcs_x86_64_sse2
   }
 }
 
 static_library("libvpx_intrinsics_ssse3") {
   configs += [ ":libvpx_config" ]
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
+  configs += [ ":libvpx_warnings" ]
   if (!is_win || is_clang) {
     cflags = [ "-mssse3" ]
   }
   if (current_cpu == "x86") {
     sources = libvpx_srcs_x86_ssse3
   } else if (current_cpu == "x64") {
     sources = libvpx_srcs_x86_64_ssse3
   }
 }
 
 static_library("libvpx_intrinsics_sse4_1") {
   configs += [ ":libvpx_config" ]
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
+  configs += [ ":libvpx_warnings" ]
   if (!is_win || is_clang) {
     cflags = [ "-msse4.1" ]
   }
   if (current_cpu == "x86") {
     sources = libvpx_srcs_x86_sse4_1
   } else if (current_cpu == "x64") {
     sources = libvpx_srcs_x86_64_sse4_1
   }
 }
 
 static_library("libvpx_intrinsics_avx2") {
   configs += [ ":libvpx_config" ]
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
+  configs += [ ":libvpx_warnings" ]
   if (is_win) {
     cflags = [ "/arch:AVX2" ]
   } else {
     cflags = [ "-mavx2" ]
   }
   if (current_cpu == "x86") {
     sources = libvpx_srcs_x86_avx2
   } else if (current_cpu == "x64") {
     sources = libvpx_srcs_x86_64_avx2
   }
 }
 
 if (cpu_arch_full == "arm-neon-cpu-detect") {
   static_library("libvpx_intrinsics_neon") {
     configs -= [ "//build/config/compiler:compiler_arm_fpu" ]
     configs += [ ":libvpx_config" ]
+    configs += [ ":libvpx_warnings" ]
     cflags = [ "-mfpu=neon" ]
     sources = libvpx_srcs_arm_neon_cpu_detect_neon
   }
 }
 
 # Converts ARM assembly files to GAS style.
 if (current_cpu == "arm") {
   action_foreach("convert_arm_assembly") {
     script = "//third_party/libvpx/run_perl.py"
     if (cpu_arch_full == "arm-neon") {
@@ skipping 10 matching lines @@
                   root_build_dir),
       "-i", "{{source}}",
       "-o", rebase_path("$target_gen_dir/{{source_name_part}}.S")
     ]
   }
 
   static_library("libvpx_assembly_arm") {
     sources = get_target_outputs(":convert_arm_assembly")
     configs -= [ "//build/config/compiler:compiler_arm_fpu" ]
     configs += [ ":libvpx_config" ]
+    configs += [ ":libvpx_warnings" ]
     if (cpu_arch_full == "arm-neon" ||
         cpu_arch_full == "arm-neon-cpu-detect") {
       cflags = [ "-mfpu=neon" ]
     }
     deps = [
       ":convert_arm_assembly",
     ]
   }
 }
 
-# gn orders flags on a target before flags from configs. The default config
-# adds -Wall, and these flags have to be after -Wall -- so they need to come
-# from a config and can't be on the target directly.
-config("libvpx_warnings") {
-  if (is_clang) {
-     cflags = [ "-Wno-conversion" ]
-   }
-}
-
 static_library("libvpx") {
   if (!is_debug && is_win && is_official_build) {
     configs -= [ "//build/config/compiler:optimize" ]
     configs += [ "//build/config/compiler:optimize_max" ]
   }
 
   if (current_cpu == "x86") {
     sources = libvpx_srcs_x86
   } else if (current_cpu == "x64") {
     if (is_msan) {
@@ skipping 35 matching lines @@
   }
   if (is_android) {
     deps += [ "//third_party/android_tools:cpu_features" ]
   }
   if (current_cpu == "arm") {
     deps += [ ":libvpx_assembly_arm" ]
   }
 
   public_configs = [ ":libvpx_external_config" ]
 }