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-'\" t
-.\" Copyright (c) 2001 by John Levon <moz@compsoc.man.ac.uk>
-.\" Based in part on GNU libc documentation.
-.\"
-.\" SPDX-License-Identifier: Linux-man-pages-copyleft
-.\"
-.\" 2001-10-11, 2003-08-22, aeb, added some details
-.\" 2012-03-23, Michael Kerrisk <mtk.manpages@mail.com>
-.\" Document pvalloc() and aligned_alloc()
-.TH posix_memalign 3 2023-11-24 "Linux man-pages 6.7"
-.SH NAME
-posix_memalign, aligned_alloc, memalign, valloc, pvalloc \-
-allocate aligned memory
-.SH LIBRARY
-Standard C library
-.RI ( libc ", " \-lc )
-.SH SYNOPSIS
-.nf
-.B #include <stdlib.h>
-.P
-.BI "int posix_memalign(void **" memptr ", size_t " alignment ", size_t " size );
-.BI "void *aligned_alloc(size_t " alignment ", size_t " size );
-.BI "[[deprecated]] void *valloc(size_t " size );
-.P
-.B #include <malloc.h>
-.P
-.BI "[[deprecated]] void *memalign(size_t " alignment ", size_t " size );
-.BI "[[deprecated]] void *pvalloc(size_t " size );
-.fi
-.P
-.RS -4
-Feature Test Macro Requirements for glibc (see
-.BR feature_test_macros (7)):
-.RE
-.P
-.BR posix_memalign ():
-.nf
- _POSIX_C_SOURCE >= 200112L
-.fi
-.P
-.BR aligned_alloc ():
-.nf
- _ISOC11_SOURCE
-.fi
-.P
-.BR valloc ():
-.nf
- Since glibc 2.12:
- (_XOPEN_SOURCE >= 500) && !(_POSIX_C_SOURCE >= 200112L)
- || /* glibc >= 2.19: */ _DEFAULT_SOURCE
- || /* glibc <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
- Before glibc 2.12:
- _BSD_SOURCE || _XOPEN_SOURCE >= 500
-.\" || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
-.fi
-.SH DESCRIPTION
-.BR posix_memalign ()
-allocates
-.I size
-bytes and places the address of the allocated memory in
-.IR "*memptr" .
-The address of the allocated memory will be a multiple of
-.IR "alignment" ,
-which must be a power of two and a multiple of
-.IR "sizeof(void\ *)" .
-This address can later be successfully passed to
-.BR free (3).
-If
-.I size
-is 0, then
-the value placed in
-.I *memptr
-is either NULL
-.\" glibc does this:
-or a unique pointer value.
-.P
-The obsolete function
-.BR memalign ()
-allocates
-.I size
-bytes and returns a pointer to the allocated memory.
-The memory address will be a multiple of
-.IR alignment ,
-which must be a power of two.
-.\" The behavior of memalign() for size==0 is as for posix_memalign()
-.\" but no standards govern this.
-.P
-.BR aligned_alloc ()
-is the same as
-.BR memalign (),
-except for the added restriction that
-.I alignment
-must be a power of two.
-.P
-The obsolete function
-.BR valloc ()
-allocates
-.I size
-bytes and returns a pointer to the allocated memory.
-The memory address will be a multiple of the page size.
-It is equivalent to
-.IR "memalign(sysconf(_SC_PAGESIZE),size)" .
-.P
-The obsolete function
-.BR pvalloc ()
-is similar to
-.BR valloc (),
-but rounds the size of the allocation up to
-the next multiple of the system page size.
-.P
-For all of these functions, the memory is not zeroed.
-.SH RETURN VALUE
-.BR aligned_alloc (),
-.BR memalign (),
-.BR valloc (),
-and
-.BR pvalloc ()
-return a pointer to the allocated memory on success.
-On error, NULL is returned, and \fIerrno\fP is set
-to indicate the error.
-.P
-.BR posix_memalign ()
-returns zero on success, or one of the error values listed in the
-next section on failure.
-The value of
-.I errno
-is not set.
-On Linux (and other systems),
-.BR posix_memalign ()
-does not modify
-.I memptr
-on failure.
-A requirement standardizing this behavior was added in POSIX.1-2008 TC2.
-.\" http://austingroupbugs.net/view.php?id=520
-.SH ERRORS
-.TP
-.B EINVAL
-The
-.I alignment
-argument was not a power of two, or was not a multiple of
-.IR "sizeof(void\ *)" .
-.TP
-.B ENOMEM
-Out of memory.
-.SH ATTRIBUTES
-For an explanation of the terms used in this section, see
-.BR attributes (7).
-.TS
-allbox;
-lbx lb lb
-l l l.
-Interface Attribute Value
-T{
-.na
-.nh
-.BR aligned_alloc (),
-.BR memalign (),
-.BR posix_memalign ()
-T} Thread safety MT-Safe
-T{
-.na
-.nh
-.BR valloc (),
-.BR pvalloc ()
-T} Thread safety MT-Unsafe init
-.TE
-.SH STANDARDS
-.TP
-.BR aligned_alloc ()
-C11.
-.TP
-.BR posix_memalign ()
-POSIX.1-2008.
-.TP
-.BR memalign ()
-.TQ
-.BR valloc ()
-None.
-.TP
-.BR pvalloc ()
-GNU.
-.SH HISTORY
-.TP
-.BR aligned_alloc ()
-glibc 2.16.
-C11.
-.TP
-.BR posix_memalign ()
-glibc 2.1.91.
-POSIX.1d, POSIX.1-2001.
-.TP
-.BR memalign ()
-glibc 2.0.
-SunOS 4.1.3.
-.TP
-.BR valloc ()
-glibc 2.0.
-3.0BSD.
-Documented as obsolete in 4.3BSD,
-and as legacy in SUSv2.
-.TP
-.BR pvalloc ()
-glibc 2.0.
-.\"
-.SS Headers
-Everybody agrees that
-.BR posix_memalign ()
-is declared in \fI<stdlib.h>\fP.
-.P
-On some systems
-.BR memalign ()
-is declared in \fI<stdlib.h>\fP instead of \fI<malloc.h>\fP.
-.P
-According to SUSv2,
-.BR valloc ()
-is declared in \fI<stdlib.h>\fP.
-.\" Libc4,5 and
-glibc declares it in \fI<malloc.h>\fP, and also in
-\fI<stdlib.h>\fP
-if suitable feature test macros are defined (see above).
-.SH NOTES
-On many systems there are alignment restrictions, for example, on buffers
-used for direct block device I/O.
-POSIX specifies the
-.I "pathconf(path,_PC_REC_XFER_ALIGN)"
-call that tells what alignment is needed.
-Now one can use
-.BR posix_memalign ()
-to satisfy this requirement.
-.P
-.BR posix_memalign ()
-verifies that
-.I alignment
-matches the requirements detailed above.
-.BR memalign ()
-may not check that the
-.I alignment
-argument is correct.
-.P
-POSIX requires that memory obtained from
-.BR posix_memalign ()
-can be freed using
-.BR free (3).
-Some systems provide no way to reclaim memory allocated with
-.BR memalign ()
-or
-.BR valloc ()
-(because one can pass to
-.BR free (3)
-only a pointer obtained from
-.BR malloc (3),
-while, for example,
-.BR memalign ()
-would call
-.BR malloc (3)
-and then align the obtained value).
-.\" Other systems allow passing the result of
-.\" .IR valloc ()
-.\" to
-.\" .IR free (3),
-.\" but not to
-.\" .IR realloc (3).
-The glibc implementation
-allows memory obtained from any of these functions to be
-reclaimed with
-.BR free (3).
-.P
-The glibc
-.BR malloc (3)
-always returns 8-byte aligned memory addresses, so these functions are
-needed only if you require larger alignment values.
-.SH SEE ALSO
-.BR brk (2),
-.BR getpagesize (2),
-.BR free (3),
-.BR malloc (3)