This printf uses the wrong format specifier for `r`, which is a `size_t`.

--- a/pjdfstest.c.old	2019-11-20 12:49:15.579700605 +0900
+++ b/pjdfstest.c	2019-11-20 12:49:24.703715792 +0900
@@ -1161,7 +1161,7 @@
 		do {
 			r = pread(fd, buf + rval, sizeof(buf) - rval,
 			    off + rval);
-			fprintf(stderr, "read %ld bytes\n", r);
+			fprintf(stderr, "read %zd bytes\n", r);
 			if (r < 0) {
 				rval = r;
 				break;