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
The implementation shall require that addr be a multiple of the page size
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
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 mmap().
The munmap() function corresponds to SVR4, just as the mmap()
It is possible that an application has applied process memory locking to a
region that contains shared memory. If this has occurred, the munmap()
call ignores those locks and, if necessary, causes those locks to be removed.
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 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