1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
|
/* This test file is part of GDB, the GNU debugger.
Copyright 2021-2024 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <stdlib.h>
#include <assert.h>
#include <string.h>
#include <stdint.h>
/* Return true if address P is ALIGNMENT-byte aligned. */
static int
is_aligned (void *p, size_t alignment)
{
size_t mask = (alignment - 1);
return ((uintptr_t)p & mask) == 0;
}
/* Allocate SIZE memory with ALIGNMENT, and return it. If FREE_POINTER,
return in it the corresponding pointer to be passed to free.
Do the alignment precisely, in other words, if an alignment of 4 is
requested, make sure the pointer is 4-byte aligned, but not 8-byte
aligned. In other words, make sure the pointer is not overaligned.
The benefit of using precise alignment is that accidentally specifying
a too low alignment will not be compensated by accidental
overalignment. */
static void *
precise_aligned_alloc (size_t alignment, size_t size, void **free_pointer)
{
/* Allocate extra to compensate for "p += alignment". */
size_t alloc_size = size + alignment;
/* Align extra, to be able to do precise align. */
void *p = aligned_alloc (alignment * 2, alloc_size);
assert (p != NULL);
void *p_orig = p;
void *p_end = p + alloc_size;
/* Make p precisely aligned. */
p += alignment;
/* Verify p is without bounds, and points to large enough area. */
assert (p >= p_orig);
assert (p + size <= p_end);
/* Verify required alignment. */
assert (is_aligned (p, alignment));
/* Verify required alignment is precise. */
assert (! is_aligned (p, 2 * alignment));
if (free_pointer != NULL)
*free_pointer = p_orig;
return p;
}
/* Duplicate data SRC of size SIZE to a newly allocated, precisely aligned
location with alignment ALIGNMENT. */
static void *
precise_aligned_dup (size_t alignment, size_t size, void **free_pointer,
void *src)
{
void *p = precise_aligned_alloc (alignment, size, free_pointer);
memcpy (p, src, size);
return p;
}
|
