build system: fix compiler warnings

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/scripts/kconfig/conf.c b/scripts/kconfig/conf.c
index 57734b5..866a7c5 100644
--- a/scripts/kconfig/conf.c
+++ b/scripts/kconfig/conf.c
@@ -142,7 +142,8 @@
 		check_stdin();
 	case ask_all:
 		fflush(stdout);
-		fgets(line, 128, stdin);
+		if (!fgets(line, 128, stdin))
+			exit(1);
 		return;
 	case set_default:
 		printf("%s\n", def);
@@ -390,7 +391,8 @@
 			check_stdin();
 		case ask_all:
 			fflush(stdout);
-			fgets(line, 128, stdin);
+			if (!fgets(line, 128, stdin))
+				exit(1);
 			strip(line);
 			if (line[0] == '?') {
 				printf("\n%s\n", menu->sym->help ?
diff --git a/scripts/kconfig/lxdialog/lxdialog.c b/scripts/kconfig/lxdialog/lxdialog.c
index 79f6c5f..5b8e3e9 100644
--- a/scripts/kconfig/lxdialog/lxdialog.c
+++ b/scripts/kconfig/lxdialog/lxdialog.c
@@ -189,7 +189,7 @@
 	int ret = dialog_inputbox(t, av[2], atoi(av[3]), atoi(av[4]),
 				  ac == 6 ? av[5] : (char *)NULL);
 	if (ret == 0)
-		fprintf(stderr, dialog_input_result);
+		fprintf(stderr, "%s", dialog_input_result);
 	return ret;
 }
 
diff --git a/scripts/kconfig/mconf.c b/scripts/kconfig/mconf.c
index adba114..c3a837a 100644
--- a/scripts/kconfig/mconf.c
+++ b/scripts/kconfig/mconf.c
@@ -482,7 +482,8 @@
 
 	*argptr++ = NULL;
 
-	pipe(pipefd);
+	if (pipe(pipefd))
+		_exit(EXIT_FAILURE);
 	pid = fork();
 	if (pid == 0) {
 		sigprocmask(SIG_SETMASK, &osset, NULL);
@@ -846,9 +847,11 @@
 static void show_textbox(const char *title, const char *text, int r, int c)
 {
 	int fd;
+	int len = strlen(text);
 
 	fd = creat(".help.tmp", 0777);
-	write(fd, text, strlen(text));
+	if (write(fd, text, len) != len)
+		exit(1);
 	close(fd);
 	show_file(".help.tmp", title, r, c);
 	unlink(".help.tmp");