sysdeps/generic/sbrk.c

   1 /* Copyright (C) 1991, 1995, 1996, 1997 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <unistd.h>
  20 #include <errno.h>
  21
  22 /* Defined in brk.c.  */
  23 extern void *__curbrk;
  24 extern int __brk (void *addr);
  25
  26 extern int __libc_multiple_libcs;       /* Defined in init-first.c.  */
  27
  28 /* Extend the process's data space by INCREMENT.
  29    If INCREMENT is negative, shrink data space by - INCREMENT.
  30    Return start of new space allocated, or -1 for errors.  */
  31 void *
  32 __sbrk (ptrdiff_t increment)
  33 {
  34   void *oldbrk;
  35
  36   /* If this is not part of the dynamic library or the library is used
  37      via dynamic loading in a statically linked program update
  38      __curbrk from the kernel's brk value.  That way two separate
  39      instances of __brk and __sbrk can share the heap, returning
  40      interleaved pieces of it.  */
  41   if (__curbrk == NULL || __libc_multiple_libcs)
  42     if (__brk (0) < 0)          /* Initialize the break.  */
  43       return (void *) -1;
  44
  45   if (increment == 0)
  46     return __curbrk;
  47
  48   oldbrk = __curbrk;
  49   if (__brk (oldbrk + increment) < 0)
  50     return (void *) -1;
  51
  52   return oldbrk;
  53 }
  54
  55 weak_alias (__sbrk, sbrk)