munmap(3p) — Linux manual page

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

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(3p) and mlockall(3p)) 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(3p), mlockall(3p), mmap(3p), posix_typed_mem_open(3p),
       sysconf(3p)

       The Base Definitions volume of POSIX.1‐2017, sys_mman.h(0p)

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(3P)

Pages that refer to this page: sys_mman.h(0p), _Exit(3p), mlock(3p), mlockall(3p), mmap(3p), shm_unlink(3p)

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