<filesystem>: `directory_entry` does not work for paths on FAT32 filesystems

[e4lam]

From #232, we had this sample code:

// compile with: cl /std:c++17 /permissive- /EHsc /Od /Zi symlink.cpp
// run: .\symlink does_not_exist
//
#include <filesystem>
#include <iostream>
namespace fs = std::filesystem;

int main(int argc, const char* argv[])
{
  if (argc < 2)
  {
    std::cerr << "Missing file path argument\n";
    return -1;
  }
  fs::path dst(argv[1]);

  std::error_code err1;
  fs::directory_entry src(dst, err1);
  std::cout << "directory_entry(" << dst << ") = " << err1 << " " << err1.message() << "\n";

  std::error_code err2;
  src.refresh(err2);
  std::cout << "refresh(" << dst << ") = " << err2 << " " << err2.message() << "\n";

  return 0;
}

Running this on a FAT32 file system (e.g. on a USB key but I tested with just a RAMDISK formatted to FAT32) gives the following result. (src is a directory on the G: drive demonstrated here)

G:\> /path/to/symlink.exe src
directory_entry("src") = system:0 The operation completed successfully.
refresh("src") = system:87 The parameter is incorrect.

I tried to workaround this by calling std::directory_entry::status( std::error_code& ec ) and std::directory_entry::symlink_status( std::error_code& ec ) as well. But they both fail, giving no way to confirm if a path on a FAT32 filesystem is indeed a directory or not.

I tested this myself on Windows 7, but my colleague who had first encountered the problem narrowed down here I believe was on Windows 10.

[BillyONeal]

This problem also affects exFAT.