PROTON-2268: Fix Threadercizer warning which fails to build on FreeBSD
diff --git a/c/tests/threaderciser.c b/c/tests/threaderciser.c
index 038d4b8..5f2bb62 100644
--- a/c/tests/threaderciser.c
+++ b/c/tests/threaderciser.c
@@ -94,7 +94,7 @@
   char msg[256];
   char *i = msg;
   char *end = i + sizeof(msg);
-  i += assert_no_err(snprintf(i, end-i, "(%lx) ", pthread_self()));
+  i += assert_no_err(snprintf(i, end-i, "(%lx) ", (uintptr_t) pthread_self()));
   if (i < end) {
     va_list ap;
     va_start(ap, fmt);