MUNMAP(3P) POSIX Programmer's Manual MUNMAP(3P)
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
munmap -- unmap pages of memory
SYNOPSIS
#include <sys/mman.h>
int munmap(void *addr, size_t len);
DESCRIPTION
The munmap() function shall remove any mappings for those entire pages
containing any part of the address space of the process starting at
addr and continuing for len bytes. Further references to these pages
shall result in the generation of a SIGSEGV signal to the process. If
there are no mappings in the specified address range, then munmap() has
no effect.
The implementation may require that addr be a multiple of the page size
as returned by sysconf().
If a mapping to be removed was private, any modifications made in this
address range shall be discarded.
Any memory locks (see mlock() and mlockall()) associated with this
address range shall be removed, as if by an appropriate call to
munlock().
If a mapping removed from a typed memory object causes the correspond-
ing address range of the memory pool to be inaccessible by any process
in the system except through allocatable mappings (that is, mappings of
typed memory objects opened with the POSIX_TYPED_MEM_MAP_ALLOCATABLE
flag), then that range of the memory pool shall become deallocated and
may become available to satisfy future typed memory allocation
requests.
A mapping removed from a typed memory object opened with the
POSIX_TYPED_MEM_MAP_ALLOCATABLE flag shall not affect in any way the
availability of that typed memory for allocation.
The behavior of this function is unspecified if the mapping was not
established by a call to mmap().
RETURN VALUE
Upon successful completion, munmap() shall return 0; otherwise, it
shall return -1 and set errno to indicate the error.
ERRORS
The munmap() function shall fail if:
EINVAL Addresses in the range [addr,addr+len) are outside the valid
range for the address space of a process.
EINVAL The len argument is 0.
The munmap() function may fail if:
EINVAL The addr argument is not a multiple of the page size as returned
by sysconf().
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
The munmap() function corresponds to SVR4, just as the mmap() function
does.
It is possible that an application has applied process memory locking
to a region that contains shared memory. If this has occurred, the mun-
map() call ignores those locks and, if necessary, causes those locks to
be removed.
Most implementations require that addr is a multiple of the page size
as returned by sysconf().
FUTURE DIRECTIONS
None.
SEE ALSO
mlock(), mlockall(), mmap(), posix_typed_mem_open(), sysconf()
The Base Definitions volume of POSIX.1-2008, <sys_mman.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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.ker-
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 MUNMAP(3P)