id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
9824	boost::filesystem::is_empty() doesn't work with symlinks on Windows	michael.burr@…	Beman Dawes	"See the original information on this problem in this Stackoverflow question:

    hxxp://stackoverflow.com/questions/22668337/boostfilesystemis-empty-returns-false-for-symlinks

The person who reported that problem/asked the question on Stackoverflow also set up a github project that demonstrates the problem:

    hxxps://github.com/monsdar/BoostSymLinkError

Basically, the `filesystem::is_empty()` function doesn't follow a symlink, so it will return false even if the target of the symlink has a length greater than 0.

The V2 filesystem library worked for this situation.  The difference is that V2 used the `stat()` function in the VC++ library, while the V3 filesystem library uses the Win32 `GetFileAttributesExW()` API.  The latter does not follow symlinks and returns a file size of 0 regardless of the size of the symlink target.

Attached is a diff for libs/filesystem/src/operations.cpp which uses the `stat()` technique very similar to what was used in filesystem V2.  A few differences:

  - `_wstat()` is used instead of `stat()` to accommodate UNICODE filenames
  - a bit test using `_S_IFDIR` is used to determine if the path is a directory instead of `S_ISDIR()` because the VC++ library doesn't include a `S_ISDIR()` or `_S_ISDIR()` macro.

This patch is only lightly tested (MSVC++ 12.0, 32-bit, on Win7 x64, filenames with ASCII characters only).  I'm not sure what the motivations for changing to the `GetFileAttributesExW()` API in filesystem V3 were, so I'm not sure if there's a fundamental flaw in using `_wstat()` that would prevent using it in V3.

"	Bugs	assigned	To Be Determined	filesystem	Boost 1.56.0	Regression