uclibc-ng/libc/sysdeps/linux/i386/sbrk.c

/* Copyright (C) 1991, 1995, 1996, 1997, 2000 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 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.

   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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <unistd.h>
#include <errno.h>

/* Defined in brk.c.  */
extern void *___brk_addr;
extern int brk (void *addr);

/* Extend the process's data space by INCREMENT.
   If INCREMENT is negative, shrink data space by - INCREMENT.
   Return start of new space allocated, or -1 for errors.  */
void * sbrk (intptr_t increment)
{
  void *oldbrk;

  if (___brk_addr == NULL)
    if (brk (0) < 0)		/* Initialize the break.  */
      return (void *) -1;

  if (increment == 0)
    return ___brk_addr;

  oldbrk = ___brk_addr;
  if (brk (oldbrk + increment) < 0)
    return (void *) -1;

  return oldbrk;
}