Implement use_cfi_cast to optionally enable cast checks.

build/config/sanitizers/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/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/clang/clang.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/toolchain/toolchain.gni")
 
@@ skipping 137 matching lines @@
       ldflags += [ "-fsanitize=undefined" ]
     }
     if (is_ubsan_null) {
       ldflags += [ "-fsanitize=null" ]
     }
     if (is_ubsan_vptr) {
       ldflags += [ "-fsanitize=vptr" ]
     }
 
     if (is_cfi && !is_nacl) {
-      ldflags += [
-        "-fsanitize=cfi-vcall",
-        "-fsanitize=cfi-derived-cast",
-        "-fsanitize=cfi-unrelated-cast",
-      ]
+      ldflags += [ "-fsanitize=cfi-vcall" ]
+      if (use_cfi_cast) {
+        ldflags += [
+          "-fsanitize=cfi-derived-cast",
+          "-fsanitize=cfi-unrelated-cast",
+        ]
+      }
       if (use_cfi_diag) {
         ldflags += [
           "-fno-sanitize-trap=cfi",
           "-fsanitize-recover=cfi",
         ]
       }
     }
   }
 }
 
@@ skipping 69 matching lines @@
       } else {
         # TODO(rnk): DLLs in the non-component build should link against
         # clang_rt.asan_dll_thunk-i386.lib instead.
         libs = [ "clang_rt.asan-i386.lib" ]
       }
     }
   }
 }
 
 config("cfi_flags") {
+  defines = []
   cflags = []
   if (is_cfi && !is_nacl) {
     cfi_blacklist_path =
         rebase_path("//tools/cfi/blacklist.txt", root_build_dir)
     cflags += [
       "-fsanitize=cfi-vcall",
-      "-fsanitize=cfi-derived-cast",
-      "-fsanitize=cfi-unrelated-cast",
       "-fsanitize-blacklist=$cfi_blacklist_path",
     ]
 
+    if (use_cfi_cast) {
+      cflags += [
+        "-fsanitize=cfi-derived-cast",
+        "-fsanitize=cfi-unrelated-cast",
+      ]
+
+      # TODO(krasin): remove CFI_CAST_CHECK, see https://crbug.com/626794.
+      defines += [ "CFI_CAST_CHECK" ]

[Nico, 2016/07/12 23:23:59]

likewise

[krasin1, 2016/07/13 00:02:51]

Done.

+    }
+
     if (use_cfi_diag) {
       cflags += [
         "-fno-sanitize-trap=cfi",
         "-fsanitize-recover=cfi",
         "-fno-inline-functions",
         "-fno-inline",
         "-fno-omit-frame-pointer",
         "-O1",
       ]
     } else {
-      defines = [ "CFI_ENFORCEMENT" ]
+      defines += [ "CFI_ENFORCEMENT" ]
     }
   }
 }
 
 config("coverage_flags") {
   cflags = []
 
   if (use_sanitizer_coverage) {
     cflags += [
       "-fsanitize-coverage=$sanitizer_coverage_flags",
@@ skipping 149 matching lines @@
 # This allows to selectively disable ubsan_vptr, when needed. In particular,
 # if some third_party code is required to be compiled without rtti, which
 # is a requirement for ubsan_vptr.
 config("default_sanitizer_flags_but_ubsan_vptr") {
   configs = all_sanitizer_configs - [ ":ubsan_vptr_flags" ]
 }
 
 config("default_sanitizer_flags_but_coverage") {
   configs = all_sanitizer_configs - [ ":coverage_flags" ]
 }