go: os: RemoveAll fails for long file paths

What version of Go are you using (go version)?

go version go1.10.3 linux/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

Linux, amd64

What did you do?

Make a long file path (> 4096 chars). os.RemoveAll(path).

package main

import (
        "io/ioutil"
        "os"
        "path/filepath"
        "syscall"
        "fmt"
)

func main() {
        tmpDir, err := ioutil.TempDir("", "")
        if err != nil {
                panic(err)
        }
        err = createVeryLongFilePath(tmpDir)
        if err != nil {
                panic(err)
        }

        fmt.Println(tmpDir)
        err = os.RemoveAll(tmpDir)
        if err != nil {
                panic(err)
        }
}

func createVeryLongFilePath(startPath string) error {
        currentPath := startPath
        for i := 0; i < 41; i++ {
                name := ""
                for j := 0; j < 100; j++ {
                        name = name + "a"
                }
                if err := mkdirAt(currentPath, name); err != nil {
                        return err
                }
                currentPath = filepath.Join(currentPath, name)
        }

        return nil
}

func mkdirAt(atPath, path string) error {
        fd, err := syscall.Open(atPath, syscall.O_RDONLY, 0)
        if err != nil {
                return err
        }
        defer syscall.Close(fd)

        return syscall.Mkdirat(fd, path, 755)
}

What did you expect to see?

Success.

What did you see instead?

it fails with file name too long.

Suggested solutions

We have worked around this using unix.Openat and unix.Unlinkat in our code base, but this solution would only work on unix.

The problem really is with os.Remove, whose unix syscalls don’t accept long file paths. An alternate solution would be to alter os.Remove to split long path names on unix systems.

We’d be happy to submit pull requests for either approach. cc @callisto13