third_party/mesa: turn off ubsan_vptr, since it's compiled without rtti.

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 109 matching lines @@
   cflags = []
   if (is_clang) {
     cflags += [
       "-Wno-tautological-constant-out-of-range-compare",
       "-Wno-mismatched-tags",  # Fixed upstream.
 
       # mesa's STATIC_ASSERT() macro expands to an ununused typedef.
       "-Wno-unused-local-typedef",
     ]
   }
+  if (is_ubsan_vptr) {
+    # UBsan's vptr is not compatible with -fno-rtti,
+    # which is used by gallium/auxiliary/Makefile.
+    cflags += [ "-fno-sanitize=vptr" ]

[Dirk Pranke, 2016/04/22 23:04:56]

This is dangerous, because this is likely sensitive tot he order in which the
flags appear on the command line.

The right way to do this is to define a config that sets this flag, have that
config get included when is_ubsan_vptr is set to true, and then *remove* that
config from this target if need be (so you need to mess with the settings in
//build/config/sanitzers/BUILD.gn a bit).

+  }
   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.
       "/wd4018",  # Signed/unsigned mismatch in comparison.
       "/wd4065",  # Switch statement contains 'default' but no 'case' labels.
       "/wd4090",  # 'Operation' : different 'modifier' qualifiers
       "/wd4099",  # Type name struct-vs-class doesn't match.
       "/wd4273",  # Inconsistent DLL linkage.
@@ skipping 614 matching lines @@
     deps = [
       "//third_party/wayland:wayland_util",
     ]
 
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
 
     public_configs = [ ":wayland_drm_protocol_config" ]
   }
 }