Silence three GCC warnings.

* In cmd-new-session.c, dsx and dxy "may be used uninitialized", and it was difficult to tell if that can happen in practice.
* In format.c, strftime can do format checking if a string literal is given.
* In options.c, pr "may be used uninitialized", though that can't happen in practice.

The "diagnostic push/pop" pragma was added in GCC 4.6, and according
to protocolbuffers/protobuf#4156, there
would be warnings if we used them for older GCCs.

cmd-new-session.c

@@ -76,7 +76,7 @@ cmd_new_session_exec(struct cmd *self, struct cmdq_item *item)
 	const char		*errstr, *template, *group, *prefix, *tmp;
 	char			*cause, *cwd = NULL, *cp, *newname = NULL;
 	int			 detached, already_attached, is_control = 0;
-	u_int			 sx, sy, dsx, dsy;
+	u_int			 sx, sy, dsx = 80, dsy = 24;
 	struct spawn_context	 sc;
 	enum cmd_retval		 retval;
 	struct cmd_find_state    fs;
@@ -193,8 +193,6 @@ cmd_new_session_exec(struct cmd *self, struct cmdq_item *item)
 		if (strcmp(tmp, "-") == 0) {
 			if (c != NULL)
 				dsx = c->tty.sx;
-			else
-				dsx = 80;
 		} else {
 			dsx = strtonum(tmp, 1, USHRT_MAX, &errstr);
 			if (errstr != NULL) {
@@ -208,8 +206,6 @@ cmd_new_session_exec(struct cmd *self, struct cmdq_item *item)
 		if (strcmp(tmp, "-") == 0) {
 			if (c != NULL)
 				dsy = c->tty.sy;
-			else
-				dsy = 24;
 		} else {
 			dsy = strtonum(tmp, 1, USHRT_MAX, &errstr);
 			if (errstr != NULL) {

format.c

@@ -1876,7 +1876,14 @@ format_expand1(struct format_tree *ft, const char *fmt, int time)
 
 	if (time) {
 		tm = localtime(&ft->time);
+#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wformat-nonliteral"
+#endif  // __GNUC__
 		if (strftime(expanded, sizeof expanded, fmt, tm) == 0) {
+#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
+# pragma GCC diagnostic pop
+#endif  // __GNUC__
 			format_log(ft, "format is too long");
 			return (xstrdup(""));
 		}

options.c

@@ -359,7 +359,7 @@ options_array_set(struct options_entry *o, u_int idx, const char *value,
 {
 	struct options_array_item	*a;
 	char				*new;
-	struct cmd_parse_result		*pr;
+	struct cmd_parse_result		*pr = NULL;
 
 	if (!OPTIONS_IS_ARRAY(o)) {
 		if (cause != NULL)