diff -Nrup a/m4/fault.m4 b/m4/fault.m4
--- a/m4/fault.m4	2014-01-02 15:26:46.000000000 -0700
+++ b/m4/fault.m4	2020-01-17 15:40:41.420148995 -0700
@@ -49,7 +49,7 @@ static int zero_fd;
 # define SIGSEGV_FAULT_ADDRESS_ROUNDOFF_BITS 0UL
 #endif
 unsigned long page;
-int handler_called = 0;
+volatile int handler_called = 0;
 void sigsegv_handler ($5)
 {
   void *fault_address = (void *) ($6);