getgroups: avoid calling exit

[gnulib.git] / lib / getgroups.c

diff --git a/lib/getgroups.c b/lib/getgroups.c
index 717f90e..e764d73 100644 (file)
--- a/lib/getgroups.c
+++ b/lib/getgroups.c
@@ -1,10 +1,12 @@
 /* provide consistent interface to getgroups for systems that don't allow N==0
-   Copyright (C) 1996 Free Software Foundation, Inc.
 
-   This program is free software; you can redistribute it and/or modify
+   Copyright (C) 1996, 1999, 2003, 2006, 2007, 2008, 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
-   the Free Software Foundation; either version 2, or (at your option)
-   any later version.
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
 
    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ -12,46 +14,55 @@
    GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with this program; if not, write to the Free Software Foundation,
-   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 /* written by Jim Meyering */
 
 #include <config.h>
-#include <stdio.h>
-#include <sys/types.h>
 
-char *xmalloc ();
+#include <unistd.h>
+
+#include <errno.h>
+#include <stdlib.h>
+
+#undef getgroups
 
-/* On Ultrix 4.3, getgroups (0, 0) always fails.
-   This function handles that special case and lets the system-
-   provided function handle all others.  */
+/* On at least Ultrix 4.3 and NextStep 3.2, getgroups (0, NULL) always
+   fails.  On other systems, it returns the number of supplemental
+   groups for the process.  This function handles that special case
+   and lets the system-provided function handle all others.  However,
+   it can fail with ENOMEM if memory is tight.  It is unspecified
+   whether the effective group id is included in the list.  */
 
 int
-getgroups (n, group)
-     size_t n;
-     GETGROUPS_T *group;
+rpl_getgroups (int n, GETGROUPS_T *group)
 {
-  int ng;
+  int n_groups;
   GETGROUPS_T *gbuf;
-
-#undef getgroups
+  int saved_errno;
 
   if (n != 0)
     return getgroups (n, group);
 
   n = 20;
-  gbuf = NULL;
   while (1)
     {
-      gbuf = (GETGROUPS_T *) xrealloc (gbuf, n * sizeof (GETGROUPS_T));
-      ng = getgroups (n, gbuf);
-      if (ng < n)
-       break;
-      n += 10;
+      /* No need to worry about address arithmetic overflow here,
+         since the ancient systems that we're running on have low
+         limits on the number of secondary groups.  */
+      gbuf = malloc (n * sizeof *gbuf);
+      if (!gbuf)
+        return -1;
+      n_groups = getgroups (n, gbuf);
+      if (n_groups == -1 ? errno != EINVAL : n_groups < n)
+        break;
+      free (gbuf);
+      n *= 2;
     }
 
+  saved_errno = errno;
   free (gbuf);
+  errno = saved_errno;
 
-  return ng;
+  return n_groups;
 }