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 shall require that addr be a multiple of the page
size {PAGESIZE}.
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
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().
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.
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
The munmap() function is only supported if the Memory Mapped Files
option or the Shared Memory Objects option is supported.
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
munmap() call ignores those locks and, if necessary, causes those locks
to be removed.
FUTURE DIRECTIONS
None.
SEE ALSO
mlock() , mlockall() , mmap() , posix_typed_mem_open() , sysconf() ,
the Base Definitions volume of IEEE Std 1003.1-2001, <signal.h>,
<sys/mman.h>
COPYRIGHT
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 .