Merge "Fix typo."
diff --git a/runtime/fault_handler.cc b/runtime/fault_handler.cc
index 1304b04..283faa2 100644
--- a/runtime/fault_handler.cc
+++ b/runtime/fault_handler.cc
@@ -35,6 +35,13 @@
 // Static fault manger object accessed by signal handler.
 FaultManager fault_manager;
 
+extern "C" {
+void art_sigsegv_fault() {
+  // Set a breakpoint here to be informed when a SIGSEGV is unhandled by ART.
+  LOG(ERROR)<< "Caught unknown SIGSEGV in ART fault handler";
+}
+}
+
 // Signal handler called on SIGSEGV.
 static void art_fault_handler(int sig, siginfo_t* info, void* context) {
   fault_manager.HandleFault(sig, info, context);
@@ -75,7 +82,10 @@
       return;
     }
   }
-  LOG(ERROR)<< "Caught unknown SIGSEGV in ART fault handler";
+
+  // Allow the user to catch this problem with a simple breakpoint in art_sigsegv_fault.
+  art_sigsegv_fault();
+
   oldaction_.sa_sigaction(sig, info, context);
 }
 
diff --git a/runtime/parsed_options.cc b/runtime/parsed_options.cc
index f6a98e1..1562527 100644
--- a/runtime/parsed_options.cc
+++ b/runtime/parsed_options.cc
@@ -254,7 +254,7 @@
 #ifdef HAVE_ANDROID_OS
   {
     char buf[PROP_VALUE_MAX];
-    property_get("dalvik.vm.implicit_checks", buf, "none");
+    property_get("dalvik.vm.implicit_checks", buf, "null,stack");
     std::string checks(buf);
     std::vector<std::string> checkvec;
     Split(checks, ',', checkvec);
diff --git a/runtime/runtime.cc b/runtime/runtime.cc
index 027feee..cbd51d4 100644
--- a/runtime/runtime.cc
+++ b/runtime/runtime.cc
@@ -535,9 +535,20 @@
     GetInstrumentation()->ForceInterpretOnly();
   }
 
-  if (options->explicit_checks_ != (ParsedOptions::kExplicitSuspendCheck |
+  bool implicit_checks_supported = false;
+  switch (kRuntimeISA) {
+  case kArm:
+  case kThumb2:
+    implicit_checks_supported = true;
+    break;
+  default:
+    break;
+  }
+
+  if (implicit_checks_supported &&
+    (options->explicit_checks_ != (ParsedOptions::kExplicitSuspendCheck |
         ParsedOptions::kExplicitNullCheck |
-        ParsedOptions::kExplicitStackOverflowCheck) || kEnableJavaStackTraceHandler) {
+        ParsedOptions::kExplicitStackOverflowCheck) || kEnableJavaStackTraceHandler)) {
     fault_manager.Init();
 
     // These need to be in a specific order.  The null point check handler must be