libbb: introduce and use xrealloc_vector

function                                             old     new   delta
xrealloc_vector_helper                                 -      51     +51
create_list                                           84      99     +15
getopt_main                                          690     695      +5
passwd_main                                         1049    1053      +4
get_cached                                            85      89      +4
msh_main                                            1377    1380      +3
add_match                                             42      41      -1
read_lines                                           720     718      -2
grave                                               1068    1066      -2
fill_match_lines                                     143     141      -2
add_to_dirlist                                        67      65      -2
add_input_file                                        49      47      -2
act                                                  252     250      -2
fsck_main                                           2252    2246      -6
man_main                                             765     757      -8
bb_internal_initgroups                               228     220      -8
cut_main                                            1052    1041     -11
add_edge_to_node                                      55      43     -12
dpkg_main                                           3851    3835     -16
ifupdown_main                                       2202    2178     -24
sort_main                                            838     812     -26
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 5/15 up/down: 82/-124)          Total: -42 bytes

1 files changed, 1 insertions, 5 deletions

diff --git a/libpwdgrp/pwd_grp.c b/libpwdgrp/pwd_grp.c
index 3fe70f40c..867caf096 100644
--- a/libpwdgrp/pwd_grp.c
+++ b/libpwdgrp/pwd_grp.c
@@ -643,11 +643,7 @@ int initgroups(const char *user, gid_t gid)
                         if (group.gr_gid != gid) {
                                 for (m = group.gr_mem; *m; m++) {
                                         if (!strcmp(*m, user)) {
-                                                if (!(num_groups & 7)) {
-                                                        gid_t *tmp = xrealloc(group_list,
-                                                                        (num_groups+8) * sizeof(gid_t *));
-                                                        group_list = tmp;
-                                                }
+                                                group_list = xrealloc_vector(group_list, 3, num_groups);
                                                 group_list[num_groups++] = group.gr_gid;
                                                 break;
                                         }