syscall: Windows Errno constants invalid

[networkimprov]

These constants: https://golang.org/src/syscall/types_windows.go#L7

Should appear in these constants: https://golang.org/src/syscall/zerrors_windows.go#L16

... because the latter are currently useless for comparison with Errno values, unlike other supported OSes. For example err.(*os.PathError).Err == syscall.ENOTEMPTY is never true on Windows.

Filed at request of @rsc

@gopherbot add OS-Windows

[rsc]

There do exist fake windows syscall Errnos. They won't go away entirely. But the fakes should only be used for traditional Unix errors that don't exist in Windows world. For example ENOENT and ENOTDIR already map to real windows errors instead of being provided by fakes. In the same way, ENOTEMPTY should map to ERROR_DIR_NOT_EMPTY. Perhaps there are others too. But to be clear, some (many) of the fakes will remain.

[networkimprov]

I'm unclear why each Errno that cannot appear on windows has a unique value. I would expect them to share a value, e.g. 0xbad5eed.

[networkimprov]

I think we're at NeedsFix here... Should this be assigned to someone?

[odeke-em]

Kindly pinging @jordanrh1 @alexbrainman

[alexbrainman]

Sure, I am happy to investigate. But I don't understand what the problem is. @networkimprov, please, try again.

Thank you.

Alex

[networkimprov]

@rsc or @ianlancetaylor, could you suggest a course of action?

[ianlancetaylor]

In zerrors_windows.go ENOENT and ENOTDIR are set to the values of Windows errors defined in types_windows.go. Then zerrors_windows.go has a list of other invented error values. For each invented error value in zerrors_windows.go we should check whether there is a defined Windows error value in types_windows.go with the same meaning. If there is, we should move that entry in zerrors_windows.go up to the ENOENT and ENOTDIR group, and set it to the appropriate value in types_windows.go.

[networkimprov]

Also the top comment re "mkerrors_windows.sh" should be removed, and maybe the file renamed, since it's no longer script-generated.

Any takers? This is tagged for 1.13.
cc @mattn

[mattn]

I know some error constants or signal types are fake on Windows. IMO, the fake errors on Windows is required to implement using runtime.GOOS.

if runtime.GOOS == "windows" {
  // do windows specific
} else {
  if err == syscall.ENOTEMPTY {
  }
}

As you know, we can separate this code to per OS's files with build constraints. However, we should provide simple way to write code.

[networkimprov]

I don't follow you. Did you see Ian's request? #32309 (comment)

This set: https://golang.org/src/syscall/zerrors_windows.go#L6
needs more of these: https://golang.org/src/syscall/types_windows.go#L7
For example ENOTEMPTY.

[mattn]

I just meant that it must not be removed. For about values of the UNIXish constaint, because it is OS specific valuse, that should be set same value defined in header file of mingw compiler.

Additional

I'm not sure, I don't think that all of UNIX constaint values can be mapped to Windows constaint.

[networkimprov]

@ianlancetaylor any thoughts on others to ping for this?