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/* provide consistent interface to getgroups for systems that don't allow N==0
Copyright (C) 1996, 1999, 2003, 2006-2023 Free Software Foundation, Inc.
This file is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
This file is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* written by Jim Meyering */
#include <config.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <stdint.h>
#if !HAVE_GETGROUPS
/* Provide a stub that fails with ENOSYS, since there is no group
information available on mingw. */
int
getgroups (_GL_UNUSED int n, _GL_UNUSED GETGROUPS_T *groups)
{
errno = ENOSYS;
return -1;
}
#else /* HAVE_GETGROUPS */
# undef getgroups
# ifndef GETGROUPS_ZERO_BUG
# define GETGROUPS_ZERO_BUG 0
# endif
/* On OS X 10.6 and later, use the usual getgroups, not the one
supplied when _DARWIN_C_SOURCE is defined. _DARWIN_C_SOURCE is
normally defined, since it means "conform to POSIX, but add
non-POSIX extensions even if that violates the POSIX namespace
rules", which is what we normally want. But with getgroups there
is an inconsistency, and _DARWIN_C_SOURCE means "change getgroups()
so that it no longer works right". The BUGS section of compat(5)
says that the behavior is dubious if you compile different sections
of a program with different _DARWIN_C_SOURCE settings, so fix only
the offending symbol. */
# ifdef __APPLE__
int posix_getgroups (int, gid_t []) __asm ("_getgroups");
# define getgroups posix_getgroups
# endif
/* On at least 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
rpl_getgroups (int n, gid_t *group)
{
int n_groups;
GETGROUPS_T *gbuf;
if (n < 0)
{
errno = EINVAL;
return -1;
}
if (n != 0 || !GETGROUPS_ZERO_BUG)
{
int result;
if (sizeof *group == sizeof *gbuf)
return getgroups (n, (GETGROUPS_T *) group);
if (SIZE_MAX / sizeof *gbuf <= n)
{
errno = ENOMEM;
return -1;
}
gbuf = malloc (n * sizeof *gbuf);
if (!gbuf)
return -1;
result = getgroups (n, gbuf);
if (0 <= result)
{
n = result;
while (n--)
group[n] = gbuf[n];
}
free (gbuf);
return result;
}
n = 20;
while (1)
{
/* 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;
}
free (gbuf);
return n_groups;
}
#endif /* HAVE_GETGROUPS */
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