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/* Allocate memory with indefinite extent and specified alignment.
Copyright (C) 2020-2023 Free Software Foundation, Inc.
This file 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.
This file 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 this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Bruno Haible <bruno@clisp.org>, 2020. */
/* Before including this file, you need to define the following macro:
ALIGNMENT A constant expression that evaluates to the desired alignment
(a power of 2).
And you also need to #include <stdint.h> and <stdlib.h>. */
/* aligned_malloc allocates a block of memory of SIZE bytes, aligned on a
boundary of ALIGNMENT bytes.
The block can be freed through aligned_free(), NOT through free().
Upon failure, it returns NULL. */
/* This module exists instead of a posix_memalign(), aligned_alloc(), or
memalign() emulation, because we can't reasonably emulate posix_memalign(),
aligned_alloc(), or memalign():
If malloc() returned p, only free (p) is allowed, not free (p + 1),
free (p + 2), free (p + 4), free (p + 8), or similar.
We can use posix_memalign(), a POSIX function.
We can also use aligned_alloc(), an ISO C11 and POSIX function. But it's
a bit more awkward to use.
On older systems, we can alternatively use memalign() instead. In the
Solaris documentation of memalign() it is not specified how a memory block
returned by memalign() can be freed, but it actually can be freed with
free(). */
/* This file uses MALLOC_ALIGNMENT, HAVE_POSIX_MEMALIGN, HAVE_ALIGNED_ALLOC,
HAVE_MEMALIGN. */
#if !_GL_CONFIG_H_INCLUDED
#error "Please include config.h first."
#endif
#if !defined ALIGNMENT
# error "ALIGNMENT is not defined"
#endif
#if !((ALIGNMENT) > 0 && ((ALIGNMENT) & ((ALIGNMENT) - 1)) == 0)
# error "ALIGNMENT is not a power of 2"
#endif
#if ((ALIGNMENT) <= MALLOC_ALIGNMENT) || HAVE_POSIX_MEMALIGN || HAVE_ALIGNED_ALLOC || HAVE_MEMALIGN
# if defined aligned_free || __GNUC__ >= 11
/* The caller wants an inline function, not a macro,
or we can use GCC's -Wmismatched-dealloc warning. */
static inline void
aligned_free (void *q)
{
free (q);
}
# else
# define aligned_free free
# endif
# if (ALIGNMENT) <= MALLOC_ALIGNMENT
/* Simply use malloc. */
# if defined aligned_malloc || __GNUC__ >= 11
/* The caller wants an inline function, not a macro,
or GCC's -Wmismatched-dealloc warning might be in effect. */
static inline
/*_GL_ATTRIBUTE_DEALLOC (aligned_free, 1)*/
void *
aligned_malloc (size_t size)
{
return malloc (size);
}
# else
# define aligned_malloc malloc
# endif
# elif HAVE_POSIX_MEMALIGN
/* Use posix_memalign.
This is OK since ALIGNMENT > MALLOC_ALIGNMENT >= sizeof (void *). */
static inline
/*_GL_ATTRIBUTE_DEALLOC (aligned_free, 1)*/
void *
aligned_malloc (size_t size)
{
void *p;
int ret = posix_memalign (&p, (ALIGNMENT), size);
if (ret == 0)
return p;
else
return NULL;
}
# elif HAVE_ALIGNED_ALLOC
/* Use aligned_alloc. */
static inline
/*_GL_ATTRIBUTE_DEALLOC (aligned_free, 1)*/
void *
aligned_malloc (size_t size)
{
/* Round up SIZE to the next multiple of ALIGNMENT,
namely (SIZE + ALIGNMENT - 1) & ~(ALIGNMENT - 1). */
size += (ALIGNMENT) - 1;
if (size >= (ALIGNMENT) - 1) /* no overflow? */
{
size &= ~(size_t)((ALIGNMENT) - 1);
return aligned_alloc ((ALIGNMENT), size);
}
return NULL;
}
# elif HAVE_MEMALIGN /* HP-UX, IRIX, Solaris <= 10 */
/* Use memalign. */
static inline
/*_GL_ATTRIBUTE_DEALLOC (aligned_free, 1)*/
void *
aligned_malloc (size_t size)
{
return memalign ((ALIGNMENT), size);
}
# endif
#else
/* Use malloc and waste a bit of memory. */
static inline void
aligned_free (void *q)
{
if (q != NULL)
{
if ((uintptr_t) q & ((ALIGNMENT) - 1))
/* Argument not aligned as expected. */
abort ();
else
{
void *p = ((void **) q)[-1];
if (!((uintptr_t) p <= (uintptr_t) q
&& (uintptr_t) q - (uintptr_t) p >= MALLOC_ALIGNMENT
&& (uintptr_t) q - (uintptr_t) p <= (ALIGNMENT)))
abort ();
free (p);
}
}
}
static inline
/*_GL_ATTRIBUTE_DEALLOC (aligned_free, 1)*/
void *
aligned_malloc (size_t size)
{
size += (ALIGNMENT);
if (size >= (ALIGNMENT)) /* no overflow? */
{
void *p = malloc (size);
if (p != NULL)
{
/* Go to the next multiple of ALIGNMENT. */
void *q =
(void *) (((uintptr_t) p + (ALIGNMENT)) & -(intptr_t)(ALIGNMENT));
/* Now q - p <= ALIGNMENT and
q - p >= MALLOC_ALIGNMENT >= sizeof (void *).
This is enough to store a back pointer to p. */
((void **) q)[-1] = p;
return q;
}
}
return NULL;
}
#endif
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