[Boost-bugs] [Boost C++ Libraries] #1972: boost::filesystem::remove() throws on self referenced symlinks

Subject: [Boost-bugs] [Boost C++ Libraries] #1972: boost::filesystem::remove() throws on self referenced symlinks
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2008-05-30 12:23:52

#1972: boost::filesystem::remove() throws on self referenced symlinks
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 Reporter:  dizzy_at_[hidden]  |       Owner:  bemandawes
     Type:  Bugs             |      Status:  new       
Milestone:  Boost 1.36.0     |   Component:  filesystem
  Version:  Boost 1.35.0     |    Severity:  Problem   
 Keywords:                   |  
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 If one creates a symlink like this "ln -s sym sym" (to itself symlink),
 bfs::exists("sym") will throw because the documentation defines it to do
 so
 (and I have nothing against it doing so, although in my programs because
 of
 this I am forced to just use "lstat()" and I can't replace using "lstat()"
 to
 check if something exists with bfs::exists).

 However, I do think that bfs::remove("sym") throwing for the same reason
 (because it calls upon bfs::exists()) is the wrong thing to do. The source
 around bfs::remove() implementation even try to solve the issue of
 "dangling
 symlinks" as they call it by having an exception in case bfs::exists
 returns
 false and the target path points to a dangling symlink and still tries to
 remove it. Unfortunetly, exists will throw in my example of a symlink (not
 even dangling technically speaking :) ) even tho a remove on that kind of
 symlink should work just fine (it does work in shell or just doing
 std::remove()).

 If boost::exists is going to be left in place to throw for those "valid"
 symlinks (because exists is suposed to try to dereference symlinks and
 dereferencing such a recursive symlink is always an error) then the only
 solution I see is to not use exists at all. Because I also found that
 remove and remove_all are fairly inefficient regarding repetitive calls fo
 stat/lstat on the same path I've created the attached patch that fixes the
 reported problem and would be more efficient "system call" wise.

 I am using Linux and ext3 filesystem tho in theory it should perform the
 same on any symlink supporting platform (since symlinks are just
 containers of strings as defined by POSIX and if you try to dereference a
 self referencing symlink you should always get an error different than
 ENOENT and others for which exists() does not throw).

-- 
Ticket URL: <http://svn.boost.org/trac/boost/ticket/1972>
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