https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99430
Bug ID: 99430
Summary: std::filesystem::path: UNC device paths with \\?\… not
supported properly
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: moritz at bunkus dot org
Target Milestone: ---
Created attachment 50317
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50317&action=edit
test case highlighting the issue
Paths such as \\?\C:\WINDOWS or \\?\UNC\LOCALHOST\c$\WINDOWS don't work
properly with std::filesystem::path (e.g. exists() & is_directory() return
false).
According to Microsoft's documentation those are valid.[1]
The corresponding variants starting with \\.\ seem to fare better (safe for the
root name & absolute issues, but I've filed 99333 for that already).
boost::filesystem works fine with all of these paths.
The attached sample program outputs the following, showing how Boost's & std's
implementation differ:
-----------------------------------------
std::filesystem::path for \\?\C:\WINDOWS
is_aboslute 0
has_root_path 1
has_root_name 0
exists 0
is_directory 0
boost::filesystem::path for \\?\C:\WINDOWS
is_aboslute 1
has_root_path 1
has_root_name 1
exists 1
is_directory 1
std::filesystem::path for \\?\UNC\localhost\c$\WINDOWS
is_aboslute 0
has_root_path 1
has_root_name 0
exists 0
is_directory 0
boost::filesystem::path for \\?\UNC\localhost\c$\WINDOWS
is_aboslute 1
has_root_path 1
has_root_name 1
exists 1
is_directory 1
std::filesystem::path for \\.\C:\WINDOWS
is_aboslute 0
has_root_path 1
has_root_name 0
exists 1
is_directory 1
boost::filesystem::path for \\.\C:\WINDOWS
is_aboslute 1
has_root_path 1
has_root_name 1
exists 1
is_directory 1
std::filesystem::path for \\.\UNC\localhost\c$\WINDOWS
is_aboslute 0
has_root_path 1
has_root_name 0
exists 1
is_directory 1
boost::filesystem::path for \\.\UNC\localhost\c$\WINDOWS
is_aboslute 1
has_root_path 1
has_root_name 1
exists 1
is_directory 1
-----------------------------------------
gcc mingw 10.2.0 from MXE (cross-compiling from Linux to Windows), Boost 1.74.0
[1] https://docs.microsoft.com/en-us/dotnet/standard/io/file-path-formats
