1MUNMAP(3P)                 POSIX Programmer's Manual                MUNMAP(3P)
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PROLOG

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

12       munmap — unmap pages of memory
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SYNOPSIS

15       #include <sys/mman.h>
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17       int munmap(void *addr, size_t len);
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DESCRIPTION

20       The munmap() function shall remove any mappings for those entire  pages
21       containing  any  part  of  the address space of the process starting at
22       addr and continuing for len bytes. Further references  to  these  pages
23       shall  result in the generation of a SIGSEGV signal to the process.  If
24       there are no mappings in the specified address range, then munmap() has
25       no effect.
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27       The implementation may require that addr be a multiple of the page size
28       as returned by sysconf().
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30       If a mapping to be removed was private, any modifications made in  this
31       address range shall be discarded.
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33       Any  memory  locks  (see  mlock()  and mlockall()) associated with this
34       address range shall be  removed,  as  if  by  an  appropriate  call  to
35       munlock().
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37       If  a mapping removed from a typed memory object causes the correspond‐
38       ing address range of the memory pool to be inaccessible by any  process
39       in the system except through allocatable mappings (that is, mappings of
40       typed memory objects opened  with  the  POSIX_TYPED_MEM_MAP_ALLOCATABLE
41       flag),  then that range of the memory pool shall become deallocated and
42       may  become  available  to  satisfy  future  typed  memory   allocation
43       requests.
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45       A   mapping  removed  from  a  typed  memory  object  opened  with  the
46       POSIX_TYPED_MEM_MAP_ALLOCATABLE flag shall not affect in  any  way  the
47       availability of that typed memory for allocation.
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49       The  behavior  of  this  function is unspecified if the mapping was not
50       established by a call to mmap().
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RETURN VALUE

53       Upon successful completion, munmap()  shall  return  0;  otherwise,  it
54       shall return -1 and set errno to indicate the error.
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ERRORS

57       The munmap() function shall fail if:
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59       EINVAL Addresses  in  the  range  [addr,addr+len) are outside the valid
60              range for the address space of a process.
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62       EINVAL The len argument is 0.
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64       The munmap() function may fail if:
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66       EINVAL The addr argument is not a multiple of the page size as returned
67              by sysconf().
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69       The following sections are informative.
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EXAMPLES

72       None.
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APPLICATION USAGE

75       None.
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RATIONALE

78       The  munmap() function corresponds to SVR4, just as the mmap() function
79       does.
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81       It is possible that an application has applied process  memory  locking
82       to a region that contains shared memory. If this has occurred, the mun‐
83       map() call ignores those locks and, if necessary, causes those locks to
84       be removed.
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86       Most  implementations  require that addr is a multiple of the page size
87       as returned by sysconf().
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FUTURE DIRECTIONS

90       None.
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SEE ALSO

93       mlock(), mlockall(), mmap(), posix_typed_mem_open(), sysconf()
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95       The Base Definitions volume of POSIX.1‐2017, <sys_mman.h>
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98       Portions of this text are reprinted and reproduced in  electronic  form
99       from  IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
100       table Operating System Interface (POSIX), The Open Group Base  Specifi‐
101       cations  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of
102       Electrical and Electronics Engineers, Inc and The Open Group.   In  the
103       event of any discrepancy between this version and the original IEEE and
104       The Open Group Standard, the original IEEE and The Open Group  Standard
105       is  the  referee document. The original Standard can be obtained online
106       at http://www.opengroup.org/unix/online.html .
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108       Any typographical or formatting errors that appear  in  this  page  are
109       most likely to have been introduced during the conversion of the source
110       files to man page format. To report such errors,  see  https://www.ker
111       nel.org/doc/man-pages/reporting_bugs.html .
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115IEEE/The Open Group                  2017                           MUNMAP(3P)
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