os: Stat never stops if the path is a circular symbolic link on windows

[hirochachacha]

Please answer these questions before submitting your issue. Thanks!

1. What version of Go are you using (go version)?
   go1.6.3
2. What operating system and processor architecture are you using (go env)?
   windows/amd64
3. What did you do?
   If possible, provide a recipe for reproducing the error.
   A complete runnable program is good.
   A link on play.golang.org is best.

package main

import (
  "os"
)

func main() {
  os.Symlink("a", "b")
  os.Symlink("b", "a")
  err := os.Stat("a")
  if err != nil {
    panic(err)
  }
}

1. What did you expect to see?
   stopped with some errors.
2. What did you see instead?
   No errors. busy loop

[minux]

A simple fix (as used by Unix) is to limit the maximum number of iterations the loop at https://tip.golang.org/src/os/stat_windows.go#L64 executes. However, determining that threshold seems tricky. For Linux, MAXSYMLINKS is defined to be 40.

[hirochachacha]

A simple fix ...

I agree with you.

MAXSYMLINKS is defined to be 40.

or _POSIX_SYMLOOP_MAX = 8

http://pubs.opengroup.org/onlinepubs/009695399/basedefs/limits.h.html

[alexbrainman]

A simple fix (as used by Unix) is to limit the maximum number
of iterations

Sure. We already do something like that here https://tip.golang.org/src/path/filepath/symlink.go#L36

@hirochachacha do you want to send change (with new test) after go1.7 is released?

Alex

[hirochachacha]

Yes, I will.

[gopherbot]

CL https://golang.org/cl/27580 mentions this issue.