[Boost-bugs] [Boost C++ Libraries] #4930: filesystem::copy_file() has inconsistent behavior when copy_option::overwrite_if_exists is used

Subject: [Boost-bugs] [Boost C++ Libraries] #4930: filesystem::copy_file() has inconsistent behavior when copy_option::overwrite_if_exists is used
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2010-12-04 17:04:34

#4930: filesystem::copy_file() has inconsistent behavior when
copy_option::overwrite_if_exists is used
------------------------------------+---------------------------------------
 Reporter:  postoronnimv77@…        |       Owner:  bemandawes
     Type:  Bugs                    |      Status:  new       
Milestone:  To Be Determined        |   Component:  filesystem
  Version:  Boost 1.44.0            |    Severity:  Problem   
 Keywords:                          |  
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 The behavior of filesystem::copy_file() function with
 copy_option::overwrite_if_exists option set is misleading and differs on
 Windows and on the rest (POSIX) systems.

 On Windows CopyFile() API is used for this which correctly overwrites the
 target file if it exists.

 On non-Windows systems open(2) is used with O_CREAT|O_WRONLY which causes
 only the first size(from_file) bytes of the destination file tp be
 overwritten with the source leaving the rest tail intact. So if the source
 file initially contains 'ABCD' and the destination contains 'abcde' the
 result of copy_file() with 'overwrite_if_exists option' set results the
 destination to contain 'ABCDe'.

 The fix seems trivial: add O_TRUNC option when opening the destination
 file.

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Ticket URL: <https://svn.boost.org/trac/boost/ticket/4930>
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