munmap(3p)

1MUNMAP(P)                  POSIX Programmer's Manual                 MUNMAP(P)
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NAME

6       munmap - unmap pages of memory
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SYNOPSIS

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

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

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

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

66       None.
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APPLICATION USAGE

69       The munmap() function is only supported  if  the  Memory  Mapped  Files
70       option or the Shared Memory Objects option is supported.
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RATIONALE

73       The  munmap() function corresponds to SVR4, just as the mmap() function
74       does.
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76       It is possible that an application has applied process  memory  locking
77       to a region that contains shared memory. If this has occurred, the mun‐
78       map() call ignores those locks and, if necessary, causes those locks to
79       be removed.
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FUTURE DIRECTIONS

82       None.
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COPYRIGHT

90       Portions  of  this text are reprinted and reproduced in electronic form
91       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
92       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
93       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
94       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
95       event of any discrepancy between this version and the original IEEE and
96       The  Open Group Standard, the original IEEE and The Open Group Standard
97       is the referee document. The original Standard can be  obtained  online
98       at http://www.opengroup.org/unix/online.html .
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102IEEE/The Open Group                  2003                            MUNMAP(P)