munmap(2) [mojave man page]

MUNMAP(2)						      BSD System Calls Manual							 MUNMAP(2)

NAME

     munmap -- remove a mapping

SYNOPSIS

     #include <sys/mman.h>

     int
     munmap(void *addr, size_t len);

DESCRIPTION

     The munmap() system call deletes the mappings for the specified address range, causing further references to addresses within the range to
     generate invalid memory references.

DIRTY PAGE HANDLING

     How munmap() handles a dirty page, depends on what type of memory is being unmapped:

     [Anonymous]	If the memory is anonymous memory and if the last reference is going away, then the contents are discarded by definition
			of anonymous memory.

     [System V Shared]	If the memory mapping was created using System V shared memory, then the contents persist until the System V memory region
			is destroyed or the system is rebooted.

     [File mapping]	If the mapping maps data from a file (MAP_SHARED), then the memory will eventually be written back to disk if it's dirty.
			This will happen automatically at some point in the future (implementation dependent).	Note: to force the memory to be
			written back to the disk, use msync(2).

     If there are still other references to the memory when the munmap is done, then nothing is done to the memory itself and it may be swapped
     out if need be. The memory will continue to persist until the last reference goes away (except for System V shared memory in which case, see
     above).

RETURN VALUES

     Upon successful completion, munmap returns zero.  Otherwise, a value of -1 is returned and errno is set to indicate the error.

ERRORS

     munmap() will fail if:

     [EINVAL]		The addr parameter was not page aligned (i.e., a multiple of the page size).

     [EINVAL]		The len parameter was negative or zero.

     [EINVAL]		Some part of the region being unmapped is not part of the currently valid address space.

LEGACY SYNOPSIS

     #include <sys/types.h>
     #include <sys/mman.h>

     The include file <sys/types.h> is necessary.

     int
     munmap(caddr_t addr, size_t len);

     The type of addr has changed.

SEE ALSO

     getpagesize(3), msync(2), munmap(2), mprotect(2), madvise(2), mincore(2), compat(5)

HISTORY

     The munmap() function first appeared in 4.4BSD.

BSD
								 October 16, 2008							       BSD

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 correspond-
       ing 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 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_ALLOCAT-
       ABLE  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  avail-
       ability 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 Technol-
       ogy -- 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 .

IEEE
/The Open Group						       2003								MUNMAP(3P)