clang/win: Make everything work in a GN build.

third_party/mesa/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/ui.gni")
 
 config("mesa_headers_config") {
   include_dirs = [ "src/include" ]
   if (use_x11) {
     defines = [ "MESA_EGL_NO_X11_HEADERS" ]
@@ skipping 60 matching lines @@
     "src/src/mapi/glapi",
     "src/src/mesa",
     "src/src/mesa/main",
     "src/include",
     "$generated_src_dir/mesa/",
     "$generated_src_dir/mesa/main",
     "$generated_src_dir/mesa/program",
     "$generated_src_dir/mesa/glapi",
   ]
 
-  if (is_clang) {
-    cflags += [ "-Wno-tautological-constant-out-of-range-compare" ]
-  }
-
   if (is_android) {
     defines += [
       "__GLIBC__",
       "_GNU_SOURCE",
     ]
   }
 
   if (is_linux) {
     defines += [ "_GNU_SOURCE" ]
   }
 
   if (is_posix) {
     defines += [
       "HAVE_DLOPEN",
       "HAVE_PTHREAD=1",
       "HAVE_UNISTD_H=1",
     ]
 
     if (!is_android) {
       defines += [ "HAVE_POSIX_MEMALIGN" ]
     }
 
     if (!is_android && !is_mac) {
       cflags += [ "-fPIC" ]
     }
   }
+}
 
+# mesa_internal_config is prepended to the config lists.  Flags that
+# disable warnings need to be appended instead so that they show up
+# after flags like -Wall. (gn orders flags on a target before flags from
+# configs.)
+config("mesa_internal_warnings") {
+  cflags = []
+  if (is_clang) {
+    cflags += [
+      "-Wno-tautological-constant-out-of-range-compare",
+      "-Wno-mismatched-tags",  # Fixed upstream.
+    ]
+  }
   if (is_win) {
     # TODO(scottmg): http://crbug.com/143877 These should be removed if
     # Mesa is ever rolled and the warnings are fixed.
     cflags += [
       "/wd4005",  # Macro defined twice.
       "/wd4065",  # Switch statement contains 'default' but no 'case' labels.
       "/wd4090",  # 'Operation' : different 'modifier' qualifiers
       "/wd4099",  # Type name struct-vs-class doesn't match.
-      "/wd4267",  # size_t to type.
       "/wd4273",  # Inconsistent DLL linkage.
       "/wd4291",  # No matching operator delete found for placement new.
       "/wd4305",  # Truncation from int to float.
       "/wd4334",  # Result of 32-bit shift implicitly converted to 64 bits.
       "/wd4345",  # POD-type default initializers.
     ]
   }
 }
 
 static_library("mesa_libglslcommon") {
@@ skipping 97 matching lines @@
     #"src/src/glsl/standalone_scaffolding.cpp",
     #"src/src/glsl/standalone_scaffolding.h",
     "src/src/glsl/strtod.c",
     "src/src/glsl/strtod.h",
   ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   previous_configs = configs
   configs = []
-  configs = [ ":mesa_internal_config" ] + previous_configs
+  configs = [ ":mesa_internal_config" ] + previous_configs +
+            [ ":mesa_internal_warnings" ]
 
   if (is_clang) {
     # Mesa triggers some of these Clang warnings.
     configs -= [ "//build/config/clang:extra_warnings" ]
   }
 
   deps = [
     ":mesa_headers",
   ]
 }
@@ skipping 361 matching lines @@
     "src/src/mesa/vbo/vbo_split_copy.c",
     "src/src/mesa/vbo/vbo_split_inplace.c",
     "src/src/mesa/x86-64/x86-64.c",
     "src/src/mesa/x86-64/x86-64.h",
   ]
 
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [ "//build/config/compiler:no_chromium_code" ]
   previous_configs = configs
   configs = []
-  configs = [ ":mesa_internal_config" ] + previous_configs
+  configs = [ ":mesa_internal_config" ] + previous_configs +
+            [ ":mesa_internal_warnings" ]
 
   if (is_clang) {
     # Mesa triggers some of these Clang warnings.
     configs -= [ "//build/config/clang:extra_warnings" ]
   }
 
   cflags = []
 
   if (is_android && !is_clang) {
     # Disable sincos() optimization to avoid a linker error
@@ skipping 27 matching lines @@
       "src/src/mesa/drivers/osmesa/osmesa.def",
     ]
 
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [
       ":mesa_headers_config",
       "//build/config/compiler:no_chromium_code",
     ]
     previous_configs = configs
     configs = []
-    configs = [ ":mesa_internal_config" ] + previous_configs
+    configs = [ ":mesa_internal_config" ] + previous_configs +
+              [ ":mesa_internal_warnings" ]
 
     include_dirs = [ "src/src/mesa/drivers" ]
 
     if (is_clang) {
       # Mesa triggers some of these Clang warnings.
       configs -= [ "//build/config/clang:extra_warnings" ]
     }
 
     deps = [
       ":mesa_headers",
       ":mesa",
       ":mesa_libglslcommon",
     ]
 
     if (is_win) {
       defines = [
         "BUILD_GL32",
         "KEYWORD1=GLAPI",
         "KEYWORD2=GLAPIENTRY",
       ]
     }
   }
 } else {
   #  Placeholder to allow targets to unconditionally depend on this.
   group("osmesa") {
   }
 }  # !is_android
 # TODO(GYP) Android osmesa_in_lib_dir target.