This is what documentation on boost::filesystem::rename states:
http://www.boost.org/libs/filesystem/doc/tr2_proposal.html
template void rename(const Path1& from_p,
const Path2& to_p);
Requires: Path1::external_string_type and
Path2::external_string_type are the same type.
Effects: Renames from_p to to_p, as if by POSIX rename().
Postconditions: !exists(from_p) && exists(to_p), and the contents
and attributes of the file originally named from_p are otherwise unchanged.
[Note: If from_p and to_p resolve to the same file, no action is
taken. Otherwise, if to_p resolves to an existing file, it is removed. A
symbolic link is itself renamed, rather than the file it resolves to
being renamed. -- end note]
Actual effect is that an exception is thrown when renaming a file to an
existing file on the same fs. rename(2) performs an 'atomic' rename in
this case without problems, but in the boost code there is a specila
check against "too permissive" posix rename():
http://boost.cvs.sourceforge.net/boost/boost/libs/filesystem/src/operations.cpp?revision=1.23.2.4&view=markup
1126 rename_api( const std::string & from, const std::string & to)
1127 {
1128 // POSIX is too permissive so must check
1129 fs::system_error_type dummy;
1130 if ( fs::exists( status_api( to, dummy ) ) )
1131 return EEXIST;
1132 return std::rename( from.c_str(), to.c_str() ) != 0
1133 ? errno : 0;
1134 }
And rename testing code also checks for the above behavior.
I think that this is a huge difference between the docs and the code,
and this is very counter-intuitive too.
--
Andriy Gapon
