Do not fail password check if shadow password does not exist -

fall back to ordinary one

Reduced usage of functions returning datain static buffers.
(mostly passwd/group/shadow related):

function                                             old     new   delta
correct_password                                     143     193     +50
sulogin_main                                         490     533     +43
adduser_main                                         732     774     +42
passwd_main                                         1875    1915     +40
addgroup_main                                        330     365     +35
bb_internal_getspnam                                  38       -     -38
bb_internal_fgetpwent                                 38       -     -38
bb_internal_fgetgrent                                 38       -     -38
static.resultbuf                                     168      88     -80
static.buffer                                       1872    1104    -768
------------------------------------------------------------------------------
(add/remove: 0/3 grow/shrink: 5/2 up/down: 210/-962)         Total: -752 bytes

1 files changed, 8 insertions, 5 deletions

diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index 16256f726..61b88fdc8 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -342,15 +342,18 @@ static void username_tab_completion(char *ud, char *with_shash_flg)
                 }
         } else {
                 /* "~[^/]*" */
-                setpwent();
+                /* Using _r function to avoid pulling in static buffers */
+                char line_buff[PWD_BUFFER_SIZE];
+                struct passwd pwd;
+                struct passwd *result;
 
-                while ((entry = getpwent()) != NULL) {
+                setpwent();
+                while (!getpwent_r(&pwd, line_buff, sizeof(line_buff), &result)) {
                         /* Null usernames should result in all users as possible completions. */
-                        if ( /*!userlen || */ !strncmp(ud, entry->pw_name, userlen)) {
-                                add_match(xasprintf("~%s/", entry->pw_name));
+                        if (/*!userlen || */ strncmp(ud, pwd.pw_name, userlen) == 0) {
+                                add_match(xasprintf("~%s/", pwd.pw_name));
                         }
                 }
-
                 endpwent();
         }
 }