Merge pull request #336 from weidmueller/feature/fix-poll-function-calls

Fix error detection of poll function calls

cangen.c

@@ -503,8 +503,11 @@ resend:
 				return 1;
 			}
 			if (polltimeout) {
+				int ret;
+
 				/* wait for the write socket (with timeout) */
-				if (poll(&fds, 1, polltimeout) < 0) {
+				ret = poll(&fds, 1, polltimeout);
+				if (ret == 0 || (ret == -1 && errno != -EINTR)) {
 					perror("poll");
 					return 1;
 				}

cansequence.c

@@ -216,7 +216,7 @@ static void do_send()
 				}
 
 				err = poll(fds, 1, 1000);
-				if (err == -1 && errno != -EINTR) {
+				if (err == 0 || (err == -1 && errno != -EINTR)) {
 					perror("poll()");
 					exit(EXIT_FAILURE);
 				}

j1939cat.c

@@ -368,10 +368,12 @@ static int j1939cat_send_loop(struct j1939cat_priv *priv, int out_fd, char *buf,
 			int ret;
 
 			ret = poll(&fds, 1, priv->polltimeout);
-			if (ret == -EINTR)
-				continue;
-			if (ret < 0)
-				return -errno;
+			if (ret == -1) {
+				if (errno == -EINTR)
+					continue;
+				else
+					return -errno;
+			}
 			if (!ret)
 				return -ETIME;
 			if (!(fds.revents & events)) {
@@ -572,10 +574,12 @@ static int j1939cat_recv(struct j1939cat_priv *priv)
 			int ret;
 
 			ret = poll(&fds, 1, priv->polltimeout);
-			if (ret == -EINTR)
-				continue;
-			if (ret < 0)
-				return -errno;
+			if (ret == -1) {
+				if (errno == -EINTR)
+					continue;
+				else
+					return -errno;
+			}
 			if (!ret)
 				continue;
 			if (!(fds.revents & events)) {