我知道如何获取某些路径的根名称，并且有std：：filesystem：:d irectory_itirator用于遍历目录。
但是如何获取带有根名称的列表，如果不可能，那为什么？
看看最近开源的Microsoft实现std::filesystem，更具体地说是辅助函数_Find_root_name_end：
// This is the place in the generic grammar where library implementations have the most freedom.
// Below are example Windows paths, and what we've decided to do with them:
// * X:DriveRelative, X:DosAbsolute
// We parse X: as root-name, if and only if is present we consider that root-directory
// * RootRelative
// We parse no root-name, and as root-directory
// * \servershare
// We parse \server as root-name, as root-directory, and share as the first element in relative-path.
// Technically, Windows considers all of \servershare the logical "root", but for purposes
// of decomposition we want those split, so that path(R"(\servershare)").replace_filename("other_share")
// is \serverother_share
// * \?device
// * ??device
// * \.device
// CreateFile appears to treat these as the same thing; we will set the first three characters as root-name
// and the first as root-directory. Support for these prefixes varies by particular Windows version, but
// for the purposes of path decomposition we don't need to worry about that.
// * \?UNCservershare
// MSDN explicitly documents the \?UNC syntax as a special case. What actually happens is that the device
// Mup, or "Multiple UNC provider", owns the path \?UNC in the NT namespace, and is responsible for the
// network file access. When the user says \servershare, CreateFile translates that into
// \?UNCservershare to get the remote server access behavior. Because NT treats this like any other
// device, we have chosen to treat this as the \? case above.
这突出了一些问题：
- Windows 中的驱动器号可以来来去去，因此"有效根列表"将因调用而异
\servershare的情况需要"有效根列表"来枚举基本上整个互联网，因为\1.2.3.4是一个有效的主机。