lib/utmp.c: Replace UT_LINESIZE by a NITEMS() calculation

A difference between 'struct utmp' and 'struct utmpx' is that
the former uses UT_LINESIZE for the size of its array members,
while the latter doesn't have a standard variable to get its
size.  Therefore, we need to get the number of elements in
the array with NITEMS().

Reviewed-by: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Cc: Firas Khalil Khana <firasuke@gmail.com>
Cc: "A. Wilfox" <https://github.com/awilfox>
Cherry-picked-from: 5ff6edf9f29e ("lib/utmp.c: Replace UT_LINESIZE by a NITEMS() calculation")
Signed-off-by: Alejandro Colomar <alx@kernel.org>

diff --git a/lib/utmp.c b/lib/utmp.c
index 95ff1dbbaa3551107b79a3b7b6c224489747f6aa..7c603e6cc272f21a0bebd15d098fb2ff77484f79 100644 (file)
--- a/lib/utmp.c
+++ b/lib/utmp.c
@@ -27,19 +27,23 @@
 #ident "$Id$"
 
 
+#define UTX_LINESIZE  NITEMS((struct utmpx){}.ut_line)
+
+
 /*
  * is_my_tty -- determine if "tty" is the same TTY stdin is using
  */
-static bool is_my_tty (const char tty[UT_LINESIZE])
+static bool
+is_my_tty(const char tty[UTX_LINESIZE])
 {
-       char         full_tty[STRLEN("/dev/") + UT_LINESIZE + 1];
+       char         full_tty[STRLEN("/dev/") + UTX_LINESIZE + 1];
        /* tmptty shall be bigger than full_tty */
        static char  tmptty[sizeof(full_tty) + 1];
 
        full_tty[0] = '\0';
        if (tty[0] != '/')
                strcpy (full_tty, "/dev/");
-       strncat (full_tty, tty, UT_LINESIZE);
+       strncat(full_tty, tty, UTX_LINESIZE);
 
        if ('\0' == tmptty[0]) {
                const char *tname = ttyname (STDIN_FILENO);

diff --git a/src/logoutd.c b/src/logoutd.c
index 9a5d11e8658e5c5b755ee045710e061c65f0eea1..3cfecaee0361d24526b43e0cf7f7d5b774640e7a 100644 (file)
--- a/src/logoutd.c
+++ b/src/logoutd.c
@@ -212,7 +212,7 @@ main(int argc, char **argv)
                                tty_name[0] = '\0';
                        }
 
-                       strncat (tty_name, ut->ut_line, UT_LINESIZE);
+                       strncat(tty_name, ut->ut_line, NITEMS(ut->ut_line));
 #ifndef O_NOCTTY
 #define O_NOCTTY 0
 #endif