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 .