lib/utmp.c: strdup() to avoid strtcpy()

Technically, this is a memory leak, but since it's a static pointer, and
we only dup it once in the program life, it's a controlled memory leak.
That's fine.

This reduces arbitrary string truncation, removing one call to strtcpy().

The truncation probably didn't matter, because we were comparing to a
string that came from what I suspect was a buffer of size 32.
Nevertheless, it doesn't hurt to get rid of that arbitrary limitation.

Signed-off-by: Alejandro Colomar <alx@kernel.org>

1 files changed, 4 insertions, 7 deletions

diff --git a/lib/utmp.c b/lib/utmp.c
index 8bb76cf2..5fb49d06 100644
--- a/lib/utmp.c
+++ b/lib/utmp.c
@@ -37,22 +37,19 @@ static bool is_my_tty (const char tty[UT_LINESIZE])
 {
 	char         full_tty[STRLEN("/dev/") + UT_LINESIZE + 1];
 	/* tmptty shall be bigger than full_tty */
-	static char  tmptty[sizeof(full_tty) + 1];
+	static char  *tmptty;
 
 	full_tty[0] = '\0';
 	if (tty[0] != '/')
 		strcpy (full_tty, "/dev/");
 	strncat (full_tty, tty, UT_LINESIZE);
 
-	if ('\0' == tmptty[0]) {
-		const char *tname = ttyname (STDIN_FILENO);
-
-		if (NULL == tname) {
+	if (tmptty == NULL) {
+		tmptty = strdup0(ttyname(STDIN_FILENO));
+		if (tmptty == NULL) {
 			(void) puts (_("Unable to determine your tty name."));
 			exit (EXIT_FAILURE);
 		}
-
-		STRTCPY(tmptty, tname);
 	}
 
 	return strcmp (full_tty, tmptty) == 0;