mirror of
https://sourceware.org/git/glibc.git
synced 2024-09-19 16:10:01 +00:00
65 lines
2.7 KiB
C
65 lines
2.7 KiB
C
/* Define INTERNAL_SIZE_T, SIZE_SZ, MALLOC_ALIGNMENT and MALLOC_ALIGN_MASK
|
|
for malloc.
|
|
Copyright (C) 2021-2024 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Lesser General Public
|
|
License as published by the Free Software Foundation; either
|
|
version 2.1 of the License, or (at your option) any later version.
|
|
|
|
The GNU C Library 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
|
|
Lesser General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public
|
|
License along with the GNU C Library; if not, see
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#ifndef _GENERIC_MALLOC_SIZE_H
|
|
#define _GENERIC_MALLOC_SIZE_H
|
|
|
|
/* INTERNAL_SIZE_T is the word-size used for internal bookkeeping of
|
|
chunk sizes.
|
|
|
|
The default version is the same as size_t.
|
|
|
|
While not strictly necessary, it is best to define this as an
|
|
unsigned type, even if size_t is a signed type. This may avoid some
|
|
artificial size limitations on some systems.
|
|
|
|
On a 64-bit machine, you may be able to reduce malloc overhead by
|
|
defining INTERNAL_SIZE_T to be a 32 bit `unsigned int' at the
|
|
expense of not being able to handle more than 2^32 of malloced
|
|
space. If this limitation is acceptable, you are encouraged to set
|
|
this unless you are on a platform requiring 16byte alignments. In
|
|
this case the alignment requirements turn out to negate any
|
|
potential advantages of decreasing size_t word size.
|
|
|
|
Implementors: Beware of the possible combinations of:
|
|
- INTERNAL_SIZE_T might be signed or unsigned, might be 32 or 64 bits,
|
|
and might be the same width as int or as long
|
|
- size_t might have different width and signedness as INTERNAL_SIZE_T
|
|
- int and long might be 32 or 64 bits, and might be the same width
|
|
|
|
To deal with this, most comparisons and difference computations
|
|
among INTERNAL_SIZE_Ts should cast them to unsigned long, being
|
|
aware of the fact that casting an unsigned int to a wider long does
|
|
not sign-extend. (This also makes checking for negative numbers
|
|
awkward.) Some of these casts result in harmless compiler warnings
|
|
on some systems. */
|
|
#ifndef INTERNAL_SIZE_T
|
|
# define INTERNAL_SIZE_T size_t
|
|
#endif
|
|
|
|
/* The corresponding word size. */
|
|
#define SIZE_SZ (sizeof (INTERNAL_SIZE_T))
|
|
|
|
#include <malloc-alignment.h>
|
|
|
|
/* The corresponding bit mask value. */
|
|
#define MALLOC_ALIGN_MASK (MALLOC_ALIGNMENT - 1)
|
|
|
|
#endif /* _GENERIC_MALLOC_SIZE_H */
|