Section: POSIX Programmer's Manual (3P)
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.
--- unmap pages of memory
int munmap(void *addr, size_t len);
function shall remove any mappings for those entire pages containing
any part of the address space of the process starting at
and continuing for
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
has no effect.
The implementation may require that
be a multiple of the page size as returned by
If a mapping to be removed was private, any modifications made in this
address range shall be discarded.
Any memory locks (see
associated with this address range shall be removed, as if by an
appropriate call to
If a mapping removed from a typed memory object causes the
corresponding 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
Upon successful completion,
shall return 0; otherwise, it shall return -1 and set
to indicate the error.
function shall fail if:
Addresses in the range [addr,addr+len) are outside
the valid range for the address space of a process.
argument is 0.
function may fail if:
argument is not a multiple of the page size as returned by
The following sections are informative.
function corresponds to SVR4, just as the
It is possible that an application has applied process memory locking
to a region that contains shared memory. If this has occurred, the
call ignores those locks and, if necessary, causes those locks to be
Most implementations require that
is a multiple of the page size as returned by
The Base Definitions volume of POSIX.1-2008,
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
Electrical 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
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