diff -Naur varnish-6.3.0.orig/bin/varnishd/http1/cache_http1_deliver.c varnish-6.3.0/bin/varnishd/http1/cache_http1_deliver.c
--- varnish-6.3.0.orig/bin/varnishd/http1/cache_http1_deliver.c	2019-09-16 10:24:15.000000000 +0200
+++ varnish-6.3.0/bin/varnishd/http1/cache_http1_deliver.c	2019-09-20 08:59:52.609482627 +0200
@@ -74,7 +74,7 @@
 	VSLb(req->vsl, SLT_RespReason, "Internal Server Error");
 
 	req->wrk->stats->client_resp_500++;
-	(void)write(req->sp->fd, r_500, sizeof r_500 - 1);
+	if (write(req->sp->fd, r_500, sizeof r_500 - 1)) 0;
 	req->doclose = SC_TX_EOF;
 }
 
diff -Naur varnish-6.3.0.orig/bin/varnishd/mgt/mgt_param.c varnish-6.3.0/bin/varnishd/mgt/mgt_param.c
--- varnish-6.3.0.orig/bin/varnishd/mgt/mgt_param.c	2019-09-16 10:24:15.000000000 +0200
+++ varnish-6.3.0/bin/varnishd/mgt/mgt_param.c	2019-09-20 09:01:38.866609297 +0200
@@ -805,11 +805,11 @@
 				t2 = strchr(t1 + 1, '\t');
 				AN(t2);
 				printf("\n\t*");
-				(void)fwrite(t1 + 1, (t2 - 1) - t1, 1, stdout);
+				if (fwrite(t1 + 1, (t2 - 1) - t1, 1, stdout)) 1;
 				printf("*\n\t\t");
 				p = t2 + 1;
 			}
-			(void)fwrite(p, q - p, 1, stdout);
+			if(fwrite(p, q - p, 1, stdout)) 1;
 			p = q;
 			if (*p == '\n') {
 				printf("\n");
diff -Naur varnish-6.3.0.orig/bin/varnishtest/vtc_main.c varnish-6.3.0/bin/varnishtest/vtc_main.c
--- varnish-6.3.0.orig/bin/varnishtest/vtc_main.c	2019-09-16 10:24:15.000000000 +0200
+++ varnish-6.3.0/bin/varnishtest/vtc_main.c	2019-09-20 08:56:45.639506046 +0200
@@ -230,7 +230,7 @@
 	assert(cleaner_pid >= 0);
 	if (cleaner_pid == 0) {
 		closefd(&p[1]);
-		(void)nice(1);		/* Not important */
+		if (nice(1)) 1;
 		setbuf(stdin, NULL);
 		AZ(dup2(p[0], STDIN_FILENO));
 		while (fgets(buf, sizeof buf, stdin)) {
diff -Naur varnish-6.3.0.orig/lib/libvarnishapi/vsm.c varnish-6.3.0/lib/libvarnishapi/vsm.c
--- varnish-6.3.0.orig/lib/libvarnishapi/vsm.c	2019-09-16 10:24:19.000000000 +0200
+++ varnish-6.3.0/lib/libvarnishapi/vsm.c	2019-09-20 10:36:02.434763755 +0200
@@ -763,18 +763,18 @@
 		VSM_ResetError(vd);
 		if (u & VSM_MGT_RUNNING) {
 			if (progress >= 0 && n > 4)
-				(void)write(progress, "\n", 1);
+			  if (!write(progress, "\n", 1)) return (vsm_diag(vd, "Unable to write progress"));
 			vd->attached = 1;
 			return (0);
 		}
 		if (t0 < VTIM_mono()) {
 			if (progress >= 0 && n > 4)
-				(void)write(progress, "\n", 1);
+				if (!write(progress, "\n", 1)) return (vsm_diag(vd, "Unable to write progress"));
 			return (vsm_diag(vd,
 			    "Could not get hold of varnishd, is it running?"));
 		}
 		if (progress >= 0 && !(++n % 4))
-			(void)write(progress, ".", 1);
+			if (!write(progress, ".", 1)) return (vsm_diag(vd, "Unable to write progress"));
 		VTIM_sleep(.25);
 	}
 	return (vsm_diag(vd, "Attach interrupted"));