[Bug c++/93244] New: std::filesystem::path::generic_string doesn't convert the first slash on Windows

[orgads at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93244

            Bug ID: 93244
           Summary: std::filesystem::path::generic_string doesn't convert
                    the first slash on Windows
           Product: gcc
           Version: 9.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: orgads at gmail dot com
  Target Milestone: ---

#include <filesystem>

int main()
{
    std::cout << std::filesystem::current_path().generic_string() << std::endl;
}

Prints F:\Projects/test/foo/bar/baz

I debugged it a bit, and from
https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/include/bits/fs_path.h#L1136
I saw that the elements are:
* _Root_name (F:) - __add_slash remains false
* _Root_dir (\) - It is appended as it is (that's the bug), and __add_slash
remains false
* From this point, the elements are all _Filename, and forward slashes are
appended.