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_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.

       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 Technology -- 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(P)