Avoid array-bounds warning for strncat on i586 (bug 20260)
[glibc.git] / malloc / scratch_buffer_set_array_size.c
blob9254c9ae7bf4a007eec6db16cb34e2b6a0581f3a
1 /* Variable-sized buffer with on-stack default allocation.
2 Copyright (C) 2015-2016 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
19 #include <scratch_buffer.h>
20 #include <errno.h>
21 #include <limits.h>
23 bool
24 __libc_scratch_buffer_set_array_size (struct scratch_buffer *buffer,
25 size_t nelem, size_t size)
27 size_t new_length = nelem * size;
29 /* Avoid overflow check if both values are small. */
30 if ((nelem | size) >> (sizeof (size_t) * CHAR_BIT / 2) != 0
31 && nelem != 0 && size != new_length / nelem)
33 /* Overflow. Discard the old buffer, but it must remain valid
34 to free. */
35 scratch_buffer_free (buffer);
36 scratch_buffer_init (buffer);
37 __set_errno (ENOMEM);
38 return false;
41 if (new_length <= buffer->length)
42 return true;
44 /* Discard old buffer. */
45 scratch_buffer_free (buffer);
47 char *new_ptr = malloc (new_length);
48 if (new_ptr == NULL)
50 /* Buffer must remain valid to free. */
51 scratch_buffer_init (buffer);
52 return false;
55 /* Install new heap-based buffer. */
56 buffer->data = new_ptr;
57 buffer->length = new_length;
58 return true;
60 libc_hidden_def (__libc_scratch_buffer_set_array_size);