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>

diff --git a/term-utils/write.c b/term-utils/write.c
index 6bf15dd40136951cf2aa13e4241ec945d747ace1..8288e9d324ce174f74763c174744c8fba1738ee8 100644 (file)
--- 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));
                        }
                }
        }