Why std::filesystem::exists returns false for c:\hiberfil.sys

[s-kipnis]

This behavior is at least strange. The file does exist, but has quite limited permissions.
Is it bug or side effect of Win32 API?

[viccpp]

May be because you write "c:\hiberfil.sys" instead of "c:\\hiberfil.sys"?

[s-kipnis]

Nope. You may try.

Approximately:

#include <filesystem>
#include <iostream>
#include <system_error>

int main(){
   std::error_code ec;
   std::cout << std::filesystem::exists("c:\\hiberfil.sys", ec );
   return 0;
}

error_code is set to 32 with message() ~ "no permission ... the file in use"

[viccpp]

Confirm. Looks like a bug

[viccpp]

Interestingly. GetFileAttributesW() returns ERROR_SHARING_VIOLATION. We can treat this result as path existence but we cannot distinguish regular files from directories. But file attributes can be obtained without such error using FindFirstFile()

[s-kipnis]

Yes, you are right: we can treat ERROR_SHARING_VIOLATION as path existence.
We must use next workaround:

for (auto const &dir_entry : fs::directory_iterator{file_path.parent_path()}) {
//everything is ok also for files with ERROR_SHARING_VIOLATION
}

[viccpp]

Anyways std::filesystem::exists() must work as user expects - just return true without any error

[StephanTLavavej]

Thanks - this sounds like a bug, so we'll convert this into an issue!

[StephanTLavavej]

@strega-nil-ms fixed this with #2715 in VS 2022 17.3 Preview 3.