NAME
posix_memalign,
aligned_alloc —
aligned memory allocation
LIBRARY
library “libc”
SYNOPSIS
#include
<stdlib.h>
int
posix_memalign(void
**ptr, size_t
alignment, size_t
size);
void *
aligned_alloc(size_t
alignment, size_t
size);
DESCRIPTION
Theposix_memalign()
function allocates size bytes of memory such that the
allocation's base address is an even multiple of
alignment, and returns the allocation in the value
pointed to by ptr.
The requested alignment must be
a power of 2 at least as large as
sizeof(void
*).
Memory that is allocated via
posix_memalign()
can be used as an argument in subsequent calls to
realloc(3),
reallocf(3), and
free(3).
The
aligned_alloc()
is similar to posix_memalign(), but it does not have
the sizeof(void *)
restriction, takes just alignment and
size and the allocation pointer is returned.
IMPLEMENTATION NOTES
The posix_memalign() function is directly
supported by matching the requested alignment against a zone of the slab
allocator with a compatible chunking, and using the power-of-2 shortcut
whenever possible. Alignments beyond those supported by the zone mechanism
are still guaranteed using cute
mmap(2) tricks. Our posix_memalign() is thus
able to take advantage of the slab allocator to produce well-fitted results
when the requests are reasonable.
RETURN VALUES
The posix_memalign() function returns the
value 0 if successful; otherwise it returns an error value. The
aligned_alloc() returns a pointer to the allocated
memory if successful; otherwise a NULL pointer is
returned and errno is set.
ERRORS
The posix_memalign() and
aligned_alloc() functions will fail if:
- [
EINVAL] - The alignment parameter is not a power of 2 at least
as large as
sizeof(void *). - [
ENOMEM] - Memory allocation error.
SEE ALSO
STANDARDS
The posix_memalign() function conforms to
IEEE Std 1003.1-2008 (“POSIX.1”). The
aligned_alloc() function conforms to
ISO/IEC 9899:2011
(“ISO C11”).