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 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.

       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 munmap() 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  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 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.kernel.org/doc/man-pages/reporting_bugs.html .