Volatilize the global store in DummyExport to defeat Clang's optimizer and avoid ICF

chrome/browser/safe_browsing/incident_reporting/verifier_test/verifier_test_dll.cc

Index: chrome/browser/safe_browsing/incident_reporting/verifier_test/verifier_test_dll.cc
diff --git a/chrome/browser/safe_browsing/incident_reporting/verifier_test/verifier_test_dll.cc b/chrome/browser/safe_browsing/incident_reporting/verifier_test/verifier_test_dll.cc
index 0c6f0756bea782b47e5936b10893227c2ecc7833..092c226908d042a2003047cbb760bd0ebe7da573 100644
--- a/chrome/browser/safe_browsing/incident_reporting/verifier_test/verifier_test_dll.cc
+++ b/chrome/browser/safe_browsing/incident_reporting/verifier_test/verifier_test_dll.cc
@@ -9,12 +9,16 @@
 namespace {
 
 void (*g_somestate)(int) = nullptr;
-int g_somevalue = 0;
+volatile int g_somevalue = 0;
 
 }  // namespace
 
 extern "C"
 void DummyExport(int foo) {
+  // The test will patch the code of this function. Do a volatile store to a
+  // global variable to defeat LLVM's dead store elimination and the linker's
+  // ICF. Otherwise the code patch affects code run during DLL unloading.
+  // http://crbug.com/636157
   g_somevalue = foo;
 }