MUNMAP(3)                  POSIX Programmer's Manual                 MUNMAP(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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.1-2017, <sys_mman.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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 .



IEEE/The Open Group                  2017                            MUNMAP(3)
