Linux: Enable ODR violation detection.

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 9739093b64a7a1cbe4e287783288c24e3db8af00..1d996dfd8593cb4e7c4a9fb1bd6a332573633f4f 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -71,7 +71,7 @@ if (!is_win) {
 #
 # Base compiler configuration.
 #
-# See also "runtime_library" below for related stuff and a discusison about
+# See also "runtime_library" below for related stuff and a discussion about
 # where stuff should go. Put warning related stuff in the "warnings" config.
 
 config("compiler") {
@@ -382,6 +382,7 @@ config("compiler") {
       # linker might not be gold, but isn't used much anyway.
       "-Wl,--threads",
       "-Wl,--thread-count=4",
+      "-Wl,--detect-odr-violations",
     ]
   }
 
@@ -475,6 +476,15 @@ config("compiler_arm_fpu") {
   }
 }
 
+# //third_party/libphonenumber is the only existing code that needs this.
+# http://crbug.com/456021
+# New code should fix their ODR violations instead of ignoring them.
+config("compiler_allow_odr_violations") {
+  if (use_gold) {
+    ldflags = [ "-Wl,--no-detect-odr-violations" ]
+  }
+}

[Nico, 2015/02/06 15:46:04]

You can have a local config in the libphonenumber build file, like so:
https://codereview.chromium.org/722513003/diff/120001/third_party/libphonenum...
(…oh hey, the example is in libphonenumber too!)

[Lei Zhang, 2015/02/06 23:44:55]

Oh, I tried that, but I needed to duplicate the |use_gold| variable. Is there a
way to reference a variable in another .gn file?

+
 # runtime_library -------------------------------------------------------------
 #
 # Sets the runtime library and associated options.