1 | /* Copyright (C) 1991-2017 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. */ |
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 (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 | } |
63 | libc_hidden_def (__sbrk) |
64 | weak_alias (__sbrk, sbrk) |
65 | |