diff -Nrup a/acinclude.m4 b/acinclude.m4
--- a/acinclude.m4	2006-02-12 02:26:40.000000000 -0700
+++ b/acinclude.m4	2020-01-16 08:53:45.111761351 -0700
@@ -53,7 +53,7 @@ AC_CACHE_VAL(q_cv_must_reinstall_sighand
 #include <unistd.h>
 #endif
 typedef RETSIGTYPE sigfunc();
-int nsigint;
+volatile int nsigint;
 #ifdef HAVE_POSIX_SIGNALS
 sigfunc *
 set_signal_handler(sig, handler)