]>
Commit | Line | Data |
---|---|---|
29d79486 | 1 | /* Internal declarations for malloc, for use within libc. |
bfff8b1b | 2 | Copyright (C) 2016-2017 Free Software Foundation, Inc. |
29d79486 FW |
3 | This file is part of the GNU C Library. |
4 | ||
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 License as | |
7 | published by the Free Software Foundation; either version 2.1 of the | |
8 | License, or (at your option) any later version. | |
9 | ||
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. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library; see the file COPYING.LIB. If | |
17 | not, see <http://www.gnu.org/licenses/>. */ | |
18 | ||
66355680 FW |
19 | #ifndef _MALLOC_INTERNAL_H |
20 | #define _MALLOC_INTERNAL_H | |
29d79486 | 21 | |
5bc17330 FW |
22 | #include <malloc-machine.h> |
23 | #include <malloc-sysdep.h> | |
24 | ||
25 | /* INTERNAL_SIZE_T is the word-size used for internal bookkeeping of | |
26 | chunk sizes. | |
27 | ||
28 | The default version is the same as size_t. | |
29 | ||
30 | While not strictly necessary, it is best to define this as an | |
31 | unsigned type, even if size_t is a signed type. This may avoid some | |
32 | artificial size limitations on some systems. | |
33 | ||
34 | On a 64-bit machine, you may be able to reduce malloc overhead by | |
35 | defining INTERNAL_SIZE_T to be a 32 bit `unsigned int' at the | |
36 | expense of not being able to handle more than 2^32 of malloced | |
37 | space. If this limitation is acceptable, you are encouraged to set | |
38 | this unless you are on a platform requiring 16byte alignments. In | |
39 | this case the alignment requirements turn out to negate any | |
40 | potential advantages of decreasing size_t word size. | |
41 | ||
42 | Implementors: Beware of the possible combinations of: | |
43 | - INTERNAL_SIZE_T might be signed or unsigned, might be 32 or 64 bits, | |
44 | and might be the same width as int or as long | |
45 | - size_t might have different width and signedness as INTERNAL_SIZE_T | |
46 | - int and long might be 32 or 64 bits, and might be the same width | |
47 | ||
48 | To deal with this, most comparisons and difference computations | |
49 | among INTERNAL_SIZE_Ts should cast them to unsigned long, being | |
50 | aware of the fact that casting an unsigned int to a wider long does | |
51 | not sign-extend. (This also makes checking for negative numbers | |
52 | awkward.) Some of these casts result in harmless compiler warnings | |
53 | on some systems. */ | |
54 | #ifndef INTERNAL_SIZE_T | |
55 | # define INTERNAL_SIZE_T size_t | |
56 | #endif | |
57 | ||
58 | /* The corresponding word size. */ | |
59 | #define SIZE_SZ (sizeof (INTERNAL_SIZE_T)) | |
60 | ||
61 | /* MALLOC_ALIGNMENT is the minimum alignment for malloc'ed chunks. It | |
62 | must be a power of two at least 2 * SIZE_SZ, even on machines for | |
63 | which smaller alignments would suffice. It may be defined as larger | |
64 | than this though. Note however that code and data structures are | |
65 | optimized for the case of 8-byte alignment. */ | |
66 | #ifndef MALLOC_ALIGNMENT | |
67 | # define MALLOC_ALIGNMENT (2 * SIZE_SZ < __alignof__ (long double) \ | |
68 | ? __alignof__ (long double) : 2 * SIZE_SZ) | |
69 | #endif | |
70 | ||
71 | /* The corresponding bit mask value. */ | |
72 | #define MALLOC_ALIGN_MASK (MALLOC_ALIGNMENT - 1) | |
73 | ||
74 | ||
29d79486 FW |
75 | /* Called in the parent process before a fork. */ |
76 | void __malloc_fork_lock_parent (void) internal_function attribute_hidden; | |
77 | ||
78 | /* Called in the parent process after a fork. */ | |
79 | void __malloc_fork_unlock_parent (void) internal_function attribute_hidden; | |
80 | ||
81 | /* Called in the child process after a fork. */ | |
82 | void __malloc_fork_unlock_child (void) internal_function attribute_hidden; | |
83 | ||
84 | ||
66355680 | 85 | #endif /* _MALLOC_INTERNAL_H */ |