1/* Copyright (C) 1991-2020 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 <https://www.gnu.org/licenses/>. */
17
18#include <errno.h>
19#include <stdint.h>
20#include <unistd.h>
21#include <libc-internal.h>
22
23/* Defined in brk.c. */
24extern void *__curbrk;
25extern int __brk (void *addr);
26
27/* Extend the process's data space by INCREMENT.
28 If INCREMENT is negative, shrink data space by - INCREMENT.
29 Return start of new space allocated, or -1 for errors. */
30void *
31__sbrk (intptr_t increment)
32{
33 void *oldbrk;
34
35 /* If this is not part of the dynamic library or the library is used
36 via dynamic loading in a statically linked program update
37 __curbrk from the kernel's brk value. That way two separate
38 instances of __brk and __sbrk can share the heap, returning
39 interleaved pieces of it. */
40 if (__curbrk == NULL || __libc_multiple_libcs)
41 if (__brk (0) < 0) /* Initialize the break. */
42 return (void *) -1;
43
44 if (increment == 0)
45 return __curbrk;
46
47 oldbrk = __curbrk;
48 if (increment > 0
49 ? ((uintptr_t) oldbrk + (uintptr_t) increment < (uintptr_t) oldbrk)
50 : ((uintptr_t) oldbrk < (uintptr_t) -increment))
51 {
52 __set_errno (ENOMEM);
53 return (void *) -1;
54 }
55
56 if (__brk (oldbrk + increment) < 0)
57 return (void *) -1;
58
59 return oldbrk;
60}
61libc_hidden_def (__sbrk)
62weak_alias (__sbrk, sbrk)
63