simplify mgetgroups() and avoid -Wsign-compare warnings

* gl/lib/mgetgroups.c: Avoid -Wsign-compare warning by using unsigned
types for the parameters of the new function realloc_groupbuf().
mgetgroups() was refactored to use this function rather than
explicitly allocating and copying from automatic storage itself.
* src/group-list.c: Use int rather than size_t as variable is
used in signed comparisons.
* src/id.c: ditto.

3 files changed, 21 insertions, 33 deletions

diff --git a/gl/lib/mgetgroups.c b/gl/lib/mgetgroups.c
index ad1fd4f3b..e697013ef 100644
--- a/gl/lib/mgetgroups.c
+++ b/gl/lib/mgetgroups.c
@@ -1,6 +1,6 @@
 /* mgetgroups.c -- return a list of the groups a user is in
 
-   Copyright (C) 2007-2008 Free Software Foundation, Inc.
+   Copyright (C) 2007-2009 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -33,16 +33,16 @@
 #include "xalloc.h"
 
 
-static void *
-allocate_groupbuf (int size)
+static GETGROUPS_T *
+realloc_groupbuf (GETGROUPS_T *g, size_t num)
 {
-  if (xalloc_oversized (size, sizeof (GETGROUPS_T)))
+  if (xalloc_oversized (num, sizeof (*g)))
     {
       errno = ENOMEM;
       return NULL;
     }
 
-  return malloc (size * sizeof (GETGROUPS_T));
+  return realloc (g, num * sizeof (*g));
 }
 
 /* Like getugroups, but store the result in malloc'd storage.
@@ -65,45 +65,27 @@ mgetgroups (char const *username, gid_t gid, GETGROUPS_T **groups)
      performance characteristics.
 
      In glibc 2.3.2, getgrouplist is buggy.  If you pass a zero as the
-     size of the output buffer, getgrouplist will still write to the
+     length of the output buffer, getgrouplist will still write to the
      buffer.  Contrary to what some versions of the getgrouplist
      manpage say, this doesn't happen with nonzero buffer sizes.
      Therefore our usage here just avoids a zero sized buffer.  */
   if (username)
     {
       enum { N_GROUPS_INIT = 10 };
-      GETGROUPS_T smallbuf[N_GROUPS_INIT];
-
       max_n_groups = N_GROUPS_INIT;
-      ng = getgrouplist (username, gid, smallbuf, &max_n_groups);
 
-      g = allocate_groupbuf (max_n_groups);
+      g = realloc_groupbuf (NULL, max_n_groups);
       if (g == NULL)
 	return -1;
 
-      if (max_n_groups <= N_GROUPS_INIT)
-	{
-	  /* smallbuf was big enough, so we already have our data */
-	  memcpy (g, smallbuf, max_n_groups * sizeof *g);
-	  *groups = g;
-	  return max_n_groups;
-	}
-
       while (1)
 	{
 	  GETGROUPS_T *h;
-	  ng = getgrouplist (username, gid, g, &max_n_groups);
-	  if (0 <= ng)
-	    {
-	      *groups = g;
-	      return ng;
-	    }
 
-	  /* When getgrouplist fails, it guarantees that
-	     max_n_groups reflects the new number of groups.  */
+	  /* getgrouplist updates max_n_groups to num required.  */
+	  ng = getgrouplist (username, gid, g, &max_n_groups);
 
-	  if (xalloc_oversized (max_n_groups, sizeof *h)
-	      || (h = realloc (g, max_n_groups * sizeof *h)) == NULL)
+	  if ((h = realloc_groupbuf (g, max_n_groups)) == NULL)
 	    {
 	      int saved_errno = errno;
 	      free (g);
@@ -111,6 +93,12 @@ mgetgroups (char const *username, gid_t gid, GETGROUPS_T **groups)
 	      return -1;
 	    }
 	  g = h;
+
+	  if (0 <= ng)
+	    {
+	      *groups = g;
+	      return ng;
+	    }
 	}
     }
   /* else no username, so fall through and use getgroups. */
@@ -125,7 +113,7 @@ mgetgroups (char const *username, gid_t gid, GETGROUPS_T **groups)
   if (max_n_groups < 0)
       max_n_groups = 5;
 
-  g = allocate_groupbuf (max_n_groups);
+  g = realloc_groupbuf (NULL, max_n_groups);
   if (g == NULL)
     return -1;
 
diff --git a/src/group-list.c b/src/group-list.c
index 3547ed669..46895b474 100644
--- a/src/group-list.c
+++ b/src/group-list.c
@@ -1,5 +1,5 @@
 /* group-list.c --Print a list of group IDs or names.
-   Copyright (C) 1989-2008 Free Software Foundation, Inc.
+   Copyright (C) 1989-2009 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -57,7 +57,7 @@ print_group_list (const char *username,
 #if HAVE_GETGROUPS
   {
     GETGROUPS_T *groups;
-    size_t i;
+    int i;
 
     int n_groups = mgetgroups (username, (pwd ? pwd->pw_gid : (gid_t) -1),
                                &groups);
diff --git a/src/id.c b/src/id.c
index 156b066dd..05ad2d86b 100644
--- a/src/id.c
+++ b/src/id.c
@@ -1,5 +1,5 @@
 /* id -- print real and effective UIDs and GIDs
-   Copyright (C) 1989-2008 Free Software Foundation, Inc.
+   Copyright (C) 1989-2009 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -294,7 +294,7 @@ print_full_info (const char *username)
 #if HAVE_GETGROUPS
   {
     GETGROUPS_T *groups;
-    size_t i;
+    int i;
 
     int n_groups = mgetgroups (username, (pwd ? pwd->pw_gid : (gid_t) -1),
 			       &groups);