1/* Copyright (C) 1991-2016 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, see
16 <http://www.gnu.org/licenses/>. */
17
18#include <errno.h>
19#include <stdint.h>
20#include <unistd.h>
21
22/* Defined in brk.c. */
23extern void *__curbrk;
24extern int __brk (void *addr);
25
26/* Defined in init-first.c. */
27extern 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. */
32void *
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 (increment > 0
51 ? ((uintptr_t) oldbrk + (uintptr_t) increment < (uintptr_t) oldbrk)
52 : ((uintptr_t) oldbrk < (uintptr_t) -increment))
53 {
54 __set_errno (ENOMEM);
55 return (void *) -1;
56 }
57
58 if (__brk (oldbrk + increment) < 0)
59 return (void *) -1;
60
61 return oldbrk;
62}
63libc_hidden_def (__sbrk)
64weak_alias (__sbrk, sbrk)
65