From c1d0a95eea8a1e3f05d78f734f0c93ef97b6b7e5 Mon Sep 17 00:00:00 2001
From: Sami Kerola
Date: Sat, 7 May 2016 12:50:01 +0100
Subject: write: remove unnecessary utmp variables

glibc documentation tells getutent() calls are not thread safe, and
recommends to copy the context of the structures when information is wished
to be stored.  This leads to excessive copying, that in this case is not
relevant.  write(1) is single threaded program and there is no reason to
assume this would change in future.

Reference: http://www.gnu.org/software/libc/manual/html_node/Manipulating-the-Database.html
Signed-off-by: Sami Kerola <kerolasa@iki.fi>
---
 term-utils/write.c | 28 +++++++++++-----------------
 1 file changed, 11 insertions(+), 17 deletions(-)

(limited to 'term-utils/write.c')

diff --git a/term-utils/write.c b/term-utils/write.c
index 6bf15dd40..8288e9d32 100644
--- a/term-utils/write.c
+++ b/term-utils/write.c
@@ -126,17 +126,15 @@ static int check_tty(char *tty, int *tty_writeable, time_t *tty_atime, int showe
  */
 static int check_utmp(const struct write_control *ctl)
 {
-	struct utmp u;
-	struct utmp *uptr;
+	struct utmp *u;
 	int res = 1;
 
 	utmpname(_PATH_UTMP);
 	setutent();
 
-	while ((uptr = getutent())) {
-		memcpy(&u, uptr, sizeof(u));
-		if (strncmp(ctl->dst_login, u.ut_user, sizeof(u.ut_user)) == 0 &&
-		    strncmp(ctl->dst_tty, u.ut_line, sizeof(u.ut_line)) == 0) {
+	while ((u = getutent())) {
+		if (strncmp(ctl->dst_login, u->ut_user, sizeof(u->ut_user)) == 0 &&
+		    strncmp(ctl->dst_tty, u->ut_line, sizeof(u->ut_line)) == 0) {
 			res = 0;
 			break;
 		}
@@ -159,38 +157,34 @@ static int check_utmp(const struct write_control *ctl)
  */
 static void search_utmp(struct write_control *ctl)
 {
-	struct utmp u;
-	struct utmp *uptr;
+	struct utmp *u;
 	time_t best_atime = 0, tty_atime;
 	int num_ttys = 0, valid_ttys = 0, tty_writeable = 0, user_is_me = 0;
-	char atty[sizeof(u.ut_line) + 1];
 
 	utmpname(_PATH_UTMP);
 	setutent();
 
-	while ((uptr = getutent())) {
-		memcpy(&u, uptr, sizeof(u));
-		if (strncmp(ctl->dst_login, u.ut_user, sizeof(u.ut_user)) == 0) {
+	while ((u = getutent())) {
+		if (strncmp(ctl->dst_login, u->ut_user, sizeof(u->ut_user)) == 0) {
 			num_ttys++;
-			xstrncpy(atty, u.ut_line, sizeof(atty));
-			if (check_tty(atty, &tty_writeable, &tty_atime, 0))
+			if (check_tty(u->ut_line, &tty_writeable, &tty_atime, 0))
 				/* bad term? skip */
 				continue;
 			if (ctl->src_uid && !tty_writeable)
 				/* skip ttys with msgs off */
 				continue;
-			if (strcmp(atty, ctl->src_tty) == 0) {
+			if (strcmp(u->ut_line, ctl->src_tty) == 0) {
 				user_is_me = 1;
 				/* don't write to yourself */
 				continue;
 			}
-			if (u.ut_type != USER_PROCESS)
+			if (u->ut_type != USER_PROCESS)
 				/* it's not a valid entry */
 				continue;
 			valid_ttys++;
 			if (tty_atime > best_atime) {
 				best_atime = tty_atime;
-				xstrncpy(ctl->dst_tty, atty, sizeof(ctl->dst_tty));
+				xstrncpy(ctl->dst_tty, u->ut_line, sizeof(ctl->dst_tty));
 			}
 		}
 	}
-- 
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