misc/sbrk.c

   1 /* Copyright (C) 1991,1995,1996,1997,2000,2002 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 Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    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 /* Defined in init-first.c.  */
  27 extern int __libc_multiple_libcs attribute_hidden;
  28
  29 /* Extend the process's data space by INCREMENT.
  30    If INCREMENT is negative, shrink data space by - INCREMENT.
  31    Return start of new space allocated, or -1 for errors.  */
  32 void *
  33 __sbrk (intptr_t increment)
  34 {
  35   void *oldbrk;
  36
  37   /* If this is not part of the dynamic library or the library is used
  38      via dynamic loading in a statically linked program update
  39      __curbrk from the kernel's brk value.  That way two separate
  40      instances of __brk and __sbrk can share the heap, returning
  41      interleaved pieces of it.  */
  42   if (__curbrk == NULL || __libc_multiple_libcs)
  43     if (__brk (0) < 0)          /* Initialize the break.  */
  44       return (void *) -1;
  45
  46   if (increment == 0)
  47     return __curbrk;
  48
  49   oldbrk = __curbrk;
  50   if (__brk (oldbrk + increment) < 0)
  51     return (void *) -1;
  52
  53   return oldbrk;
  54 }
  55 libc_hidden_def (__sbrk)
  56 weak_alias (__sbrk, sbrk)