__getgrps.s

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/* Copyright (C) 1994 Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library 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
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <sysdep.h>
#include <limits.h>

/* Dynix erroneously reports `getgroups (0, 0)' as an error.
   We fix up for that case.  */

#define syscall_error myerror
SYSCALL__ (getgroups, 2)
#undef syscall_error
	ret
myerror:
	tstl 4(%esp)		/* Was the first arg 0?  */
	jnz syscall_error	/* If not, go to the normal error case.  */
	/* When called with (0, 0), we want to return the number of groups
	   without storing anything.  The Dynix system call gives an error
	   for this case, so we fix up by calling it with a local array we
	   never use, and just use the return value.  */
	subl %esp, $(NGROUPS_MAX * 4) /* Allocate a local array.  */
	movl $NGROUPS_MAX, %ecx	/* Pass NGROUPS_MAX for first arg.  */
	movl %esp, %edx		/* Pass local array for second arg.  */
	DO_CALL (getgroups, 2)	/* Do the system call.  */
	addl %esp, $(NGROUPS_MAX * 4) /* Pop the local array.  */
	jb syscall_error	/* Check for error from the system call.  */
	ret			/* Return its value.  */