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 .