POSIX_MEMALIGN
Section: POSIX Programmer's Manual (3P)
Updated: 2017
Page Index
PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
NAME
posix_memalign
--- aligned memory allocation
(
ADVANCED REALTIME)
SYNOPSIS
#include <stdlib.h>
int posix_memalign(void **memptr, size_t alignment, size_t size);
DESCRIPTION
The
posix_memalign()
function shall allocate
size
bytes aligned on a boundary specified by
alignment,
and shall return a pointer to the allocated memory in
memptr.
The value of
alignment
shall be a power of two multiple of
sizeof(
void *).
Upon successful completion, the value pointed to by
memptr
shall be a multiple of
alignment.
If the size of the space requested is 0, the behavior is
implementation-defined: either a null pointer shall be returned in
memptr,
or the behavior shall be as if the size were some non-zero value,
except that the behavior is undefined if the the value returned in
memptr
is used to access an object.
The
free()
function shall deallocate memory that has previously been allocated by
posix_memalign().
RETURN VALUE
Upon successful completion,
posix_memalign()
shall return zero; otherwise, an error number shall be returned to
indicate the error and the contents of
memptr
shall either be left unmodified or be set to a null pointer.
If
size
is 0, either:
- *
-
posix_memalign()
shall not attempt to allocate any space, in which case either an
implementation-defined error number shall be returned, or zero shall
be returned with a null pointer returned in
memptr,
or
- *
-
posix_memalign()
shall attempt to allocate some space and, if the allocation succeeds,
zero shall be returned and a pointer to the allocated space shall be
returned in
memptr.
The application shall ensure that the pointer is not used to access
an object.
ERRORS
The
posix_memalign()
function shall fail if:
- EINVAL
-
The value of the alignment parameter is not a power of two multiple of
sizeof(void *).
- ENOMEM
-
There is insufficient memory available with the requested alignment.
The following sections are informative.
EXAMPLES
The following example shows how applications can obtain consistent
behavior on error by setting *
memptr
to be a null pointer before calling
posix_memalign().
-
void *ptr = NULL;
...
//do some work, which might goto error
if (posix_memalign(&ptr, align, size))
goto error;
//do some more work, which might goto error
...
error:
free(ptr);
//more cleanup;
APPLICATION USAGE
The
posix_memalign()
function is part of the Advisory Information option and need not be
provided on all implementations.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
free(),
malloc()
The Base Definitions volume of POSIX.1-2017,
<stdlib.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .