login: use system definitions to determine maxium login name length

Allocating stack for about 10x more than longest possible user name is
wasteful, even if it happens for reletively short period of time.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>

diff --git a/login-utils/login.c b/login-utils/login.c
index b03808a5c2e16acf1a736c09abb0af5d6a26af87..0e7629f20f1cb75d72b57c8cb2ddee288dae7b5e 100644 (file)
--- a/login-utils/login.c
+++ b/login-utils/login.c
@@ -91,10 +91,6 @@
 # define TTY_MODE 0600
 #endif
 
-#ifndef SPT_BUFSIZE
-# define SPT_BUFSIZE     2048
-#endif
-
 static char **argv0;
 static size_t argv_lth;
 
@@ -260,18 +256,19 @@ static void process_title_init (int argc, char **argv)
                argv0 = argv;
 }
 
-static void process_title_update (const char *prog, const char *txt)
+static void process_title_update(const char *username)
 {
         size_t i;
-        char buf[SPT_BUFSIZE];
+        const char prefix[] = "login -- ";
+        char buf[sizeof(prefix) + LOGIN_NAME_MAX];
 
         if (!argv0)
                 return;
 
-       if (strlen(prog) + strlen(txt) + 5 > SPT_BUFSIZE)
+       if (sizeof(buf) < (sizeof(prefix) + strlen(username) + 1))
                return;
 
-       sprintf(buf, "%s -- %s", prog, txt);
+       snprintf(buf, sizeof(buf), "%s%s", prefix, username);
 
         i = strlen(buf);
         if (i > argv_lth - 2) {
@@ -1452,7 +1449,7 @@ int main(int argc, char **argv)
 
        init_environ(&cxt);             /* init $HOME, $TERM ... */
 
-       process_title_update("login", cxt.username);
+       process_title_update(cxt.username);
 
        log_syslog(&cxt);