diff --git a/echo.c b/echo.c
index 168dec7..963d225 100644
--- a/echo.c
+++ b/echo.c
@@ -48,7 +48,10 @@ taskmain(int argc, char **argv)
 		fprintf(stderr, "cannot announce on tcp port %d: %s\n", atoi(argv[1]), strerror(errno));
 		taskexitall(1);
 	}
-	fdnoblock(fd);
+	if(fdnoblock(fd) < 0){
+		fprintf(stderr, "fdnoblock\n");
+		taskexitall(1);
+	}
 	while((cfd = netaccept(fd, remote, &rport)) >= 0){
 		if(verbose)
 			fprintf(stderr, "connection from %s:%d\n", remote, rport);
diff --git a/fd.c b/fd.c
index 5b4f579..4e0fdcc 100644
--- a/fd.c
+++ b/fd.c
@@ -220,6 +220,8 @@ fdwait(int fd, int rw)
 	if(r < 0 || errno == EEXIST){
 		duped = 1;
 		fd = dup(fd);
+		if(fd < 0)
+			abort();
 		r = epoll_ctl(epfd, EPOLL_CTL_ADD, fd, &ev);
 		if(r != 0)
 			abort();
diff --git a/net.c b/net.c
index e635518..f3ec128 100644
--- a/net.c
+++ b/net.c
@@ -62,7 +62,10 @@ netannounce(int istcp, char *server, int port)
 	sn = sizeof n;
 	if(istcp && getsockopt(fd, SOL_SOCKET, SO_TYPE, (void*)&n, &sn) >= 0){
 		n = 1;
-		setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char*)&n, sizeof n);
+		if(setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char*)&n, sizeof n) < 0){
+			close(fd);
+			return -1;
+		}
 	}
 
 	if(bind(fd, (struct sockaddr*)&ss, sizeof ss) < 0){
@@ -74,7 +77,10 @@ netannounce(int istcp, char *server, int port)
 	if(proto == SOCK_STREAM)
 		listen(fd, 16);
 
-	fdnoblock(fd);
+	if(fdnoblock(fd) < 0){
+		close(fd);
+		return -1;
+	}
 	taskstate("netannounce succeeded");
 	return fd;
 }
@@ -109,9 +115,15 @@ netaccept(int fd, char *server, int *port)
 			*port = nhgets(&((struct sockaddr_in6*)&ss)->sin6_port);
 		break;
 	}
-	fdnoblock(cfd);
+	if(fdnoblock(cfd) < 0){
+		close(cfd);
+		return -1;
+	}
 	one = 1;
-	setsockopt(cfd, IPPROTO_TCP, TCP_NODELAY, (char*)&one, sizeof one);
+	if(setsockopt(cfd, IPPROTO_TCP, TCP_NODELAY, (char*)&one, sizeof one) < 0){
+		close(cfd);
+		return -1;
+	}
 	taskstate("netaccept succeeded");
 	return cfd;
 }
@@ -136,10 +148,12 @@ netlookup(char *name, unsigned char *ip)
 			break;
 		}
 		taskstate("netlookup succeeded");
+		freeaddrinfo(result);
 		return 0;
 	}
 
 	taskstate("netlookup failed");
+	freeaddrinfo(result);
 	return -1;
 }
 
@@ -160,12 +174,18 @@ netdial(int istcp, char *server, int port)
 		taskstate("socket failed");
 		return -1;
 	}
-	fdnoblock(fd);
+	if(fdnoblock(fd) < 0){
+		close(fd);
+		return -1;
+	}
 
 	/* for udp */
 	if(!istcp){
 		n = 1;
-		setsockopt(fd, SOL_SOCKET, SO_BROADCAST, &n, sizeof n);
+		if(setsockopt(fd, SOL_SOCKET, SO_BROADCAST, &n, sizeof n) < 0){
+			close(fd);
+			return -1;
+		}
 	}
 
 	/* start connecting */
@@ -198,7 +218,10 @@ netdial(int istcp, char *server, int port)
 
 	/* report error */
 	sn = sizeof n;
-	getsockopt(fd, SOL_SOCKET, SO_ERROR, (void*)&n, &sn);
+	if(getsockopt(fd, SOL_SOCKET, SO_ERROR, (void*)&n, &sn) < 0){
+		close(fd);
+		return -1;
+	}
 	if(n == 0)
 		n = ECONNREFUSED;
 	close(fd);
diff --git a/task.c b/task.c
index 074b6bf..6360d31 100644
--- a/task.c
+++ b/task.c
@@ -46,7 +46,8 @@ taskdebug(char *fmt, ...)
 			p = argv0;
 		snprint(buf, sizeof buf, "/tmp/%s.tlog", p);
 		if((fd = open(buf, O_CREAT|O_WRONLY, 0666)) < 0)
-			fd = open("/dev/null", O_WRONLY);
+			if((fd = open("/dev/null", O_WRONLY)) < 0)
+				abort();
 	}
 
 	va_start(arg, fmt);
diff --git a/tcpload.c b/tcpload.c
index 9f6dfc8..d507a88 100644
--- a/tcpload.c
+++ b/tcpload.c
@@ -47,7 +47,6 @@ fetchtask(void *v)
 		}
 		snprintf(buf, sizeof buf, "xxxxxxxxxx");
 		fdwrite(fd, buf, strlen(buf));
-		fdread(fd, buf, sizeof buf);
 		close(fd);
 	}
 }
diff --git a/tcpproxy.c b/tcpproxy.c
index 349d6c2..5098ae3 100644
--- a/tcpproxy.c
+++ b/tcpproxy.c
@@ -51,7 +51,10 @@ taskmain(int argc, char **argv)
 		fprintf(stderr, "cannot announce on tcp port %d: %s\n", atoi(argv[1]), strerror(errno));
 		taskexitall(1);
 	}
-	fdnoblock(fd);
+	if(fdnoblock(fd) < 0){
+		fprintf(stderr, "fdnoblock\n");
+		taskexitall(1);
+	}
 	while((cfd = netaccept(fd, remote, &rport)) >= 0){
 		if(verbose)
 			fprintf(stderr, "connection from %s:%d\n", remote, rport);