If a folder doesn't have read/write access, if (!(permission & fs::perms::owner_read) == fs::perms::no_perms) will always return success.

[Rahool24]

If a folder doesn't have read/write access, if (!(permission & fs::perms::owner_read) == fs::perms::no_perms) will always return success.

[Lastique]

1. if (!(permission & fs::perms::owner_read) == fs::perms::no_perms) is likely incorrect. operator! has higher precedence than operator==, so the condition reads as if ( (!(permission & fs::perms::owner_read)) == fs::perms::no_perms ), i.e. the result of permission & fs::perms::owner_read is converted to bool, then an inverse of it is converted to fs::perms and compared to fs::perms::no_perms. This makes no sense at all. I think, you wanted to say if ((permission & fs::perms::owner_read) != fs::perms::no_perms) instead.
2. On Windows, read permission is always indicated as present because Windows doesn't really support POSIX permissions. Basically, if a file is marked with the "read-only" attribute, Boost.Filesystem will indicate the file as readable. If it is not marked, it will indicate it as both readable and writable.
3. Boost.Filesystem does not support or interpret ACLs, if that's how you define the file as "readable". There are no plans to support ACLs, and such support would not translate to POSIX-style permissions anyway.