path/filepath: IsAbs considers \\host\share as a relative path but should be recognized as an absolute path #47123

MichaelEischer · 2021-07-10T22:24:19Z

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

$ go version
go version go1.16.5 windows/amd64

Does this issue reproduce with the latest release?

1.16.5 is the latest release at the moment.

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

go env Output

$ go env
set GO111MODULE=
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\Michael\AppData\Local\go-build
set GOENV=C:\Users\Michael\AppData\Roaming\go\env
set GOEXE=.exe
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\Michael\go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\Michael\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=C:\Program Files\Go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLDIR=C:\Program Files\Go\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.16.5
set GCCGO=gccgo
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=NUL
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=C:\Users\Michael\AppData\Local\Temp\go-build1869960865=/tmp/go-build -gno-record-gcc-switches

What did you do?

package main

import (
        "fmt"
        "path/filepath"
)

func main() {
        fmt.Println(filepath.IsAbs(`\\host\share`))
        fmt.Println(filepath.IsAbs(`\\host\share\`))
}

What did you expect to see?

true
true

What did you see instead?

false
true

According to https://docs.microsoft.com/en-us/dotnet/standard/io/file-path-formats#unc-paths "UNC paths must always be fully qualified." which suggests that there are no relative UNC paths, and thus \\host\share should also be considered as absolute path.

The text was updated successfully, but these errors were encountered:

odeke-em · 2021-07-11T09:13:24Z

Thank you for the bug report @MichaelEischer! Kindly cc-ing @alexbrainman @zx2c4 for when y’all have some spare time/cycles.

gopherbot · 2021-07-12T13:42:36Z

Change https://golang.org/cl/333911 mentions this issue: path/filepath: fix IsAbs considers \\host\share as a relative path

alexbrainman · 2021-07-13T09:50:40Z

Thank you for bug report @MichaelEischer .

You might have a point with your reasoning, but I am not convinced we should change current behaviour.

Consider this: \\host\share\ refers to a root directory of that share. What does \\host\share reefer to? Same root directory? I am not convinced. \\host\share is more like C: - it is more like a drive letter.

Also, path/filepath.IsAbs(path/filepath.Volume(x)) currently always returns false regardless if path is UNC or not. This symmetry will break, if we change path/filepath.IsAbs behaviour.

Also let's hear what @mattn has to say about this. He, probably, wrote original code.

Alex

MichaelEischer · 2021-07-14T19:45:56Z

I'd say that \\host\share and \\host\share\ refer to the same directory, as there are no relative UNC paths. But I also agree that \\host\share conceptually seems to be more of a volume than a directory. Interestingly dir \\host\share\ on Windows prints that the directory listing is for volume and directory \\host\share, whereas for dir C:\ I get volume C: and directory C:\.

Doesn't the IsAbs/Volume asymmetry already apply to filepath.Rel after the changes in #41230?

filepath.Rel(`C:`, `C:\dir`)

doesn't work, whereas

filepath.Rel(`\\host\share`, `\\host\share\file.txt`)

does.

180909 · 2021-07-15T13:42:19Z

Maybe this can give some help.

mattn · 2021-07-15T14:37:43Z

I agree with this change. \\host\share is not like C:. IsAbs have not to return result depend on last backslash for UNC paths. The syntax that can represent a relative path is only available if the path is C:.

#include <stdio.h>
#include <stdlib.h>

int
main(int argc, char* argv[]) {
  char* paths[] = {
    "C:",
    "C:\\",
    "C:temp",
    "C:\\temp",
    "\\\\127.0.0.1",
    "\\\\127.0.0.1\\",
    "\\\\127.0.0.1\\C$",
    "\\\\127.0.0.1\\C$\\",
    NULL
  };
  for (char **p = paths; *p; p++) {
    char path[_MAX_PATH];
    char* res = _fullpath(path, *p, sizeof(path));
    printf("%s is %s\n", *p, res);
  }
  return 0;
}

C: is C:\temp
C:\ is C:\
C:temp is C:\temp\temp
C:\temp is C:\temp
\\127.0.0.1 is \\127.0.0.1
\\127.0.0.1\ is \\127.0.0.1\
\\127.0.0.1\C$ is \\127.0.0.1\C$
\\127.0.0.1\C$\ is \\127.0.0.1\C$\

(This is obviously thing)

mattn · 2021-07-15T14:43:05Z

~~But https://golang.org/cl/333911 seems wrong code. IsAbs should be separated for Windows.~~

Ah, it's wrong (fixing path not path/filepath)

gopherbot · 2021-07-15T14:55:02Z

Change https://golang.org/cl/334809 mentions this issue: path/filepath: fix IsAbs considers \\host\share as a relative path

alexbrainman · 2021-07-18T06:02:42Z

Doesn't the IsAbs/Volume asymmetry already apply to filepath.Rel after the changes in #41230?

Indeed.

Alex

MichaelEischer mentioned this issue Jul 10, 2021

Problem backuping - Fatal: unable to save snapshot: Lstat: CreateFile restic/restic#3339

Closed

odeke-em changed the title ~~filepath.IsAbs considers \\host\share as relative path~~ path/filepath: IsAbs considers \\host\share as a relative path but should be recognized as an absolute path Jul 11, 2021

odeke-em added NeedsInvestigation OS-Windows labels Jul 11, 2021

This was referenced Jul 12, 2021

path/filepath: fix IsAbs considers \\host\share as a relative path #47134

Closed

path/filepath: fix IsAbs considers \\host\share as a relative path #47137

Closed

gopherbot closed this as completed in 8b471db Aug 18, 2021

golang locked and limited conversation to collaborators Aug 18, 2022

gopherbot added the FrozenDueToAge label Aug 18, 2022

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path/filepath: IsAbs considers \\host\share as a relative path but should be recognized as an absolute path #47123

path/filepath: IsAbs considers \\host\share as a relative path but should be recognized as an absolute path #47123

MichaelEischer commented Jul 10, 2021

odeke-em commented Jul 11, 2021

gopherbot commented Jul 12, 2021

alexbrainman commented Jul 13, 2021

MichaelEischer commented Jul 14, 2021

180909 commented Jul 15, 2021

mattn commented Jul 15, 2021

mattn commented Jul 15, 2021 •

edited

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gopherbot commented Jul 15, 2021

alexbrainman commented Jul 18, 2021

path/filepath: IsAbs considers \\host\share as a relative path but should be recognized as an absolute path #47123

path/filepath: IsAbs considers \\host\share as a relative path but should be recognized as an absolute path #47123

Comments

MichaelEischer commented Jul 10, 2021

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

Does this issue reproduce with the latest release?

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

What did you do?

What did you expect to see?

What did you see instead?

odeke-em commented Jul 11, 2021

gopherbot commented Jul 12, 2021

alexbrainman commented Jul 13, 2021

MichaelEischer commented Jul 14, 2021

180909 commented Jul 15, 2021

mattn commented Jul 15, 2021

mattn commented Jul 15, 2021 • edited Loading

gopherbot commented Jul 15, 2021

alexbrainman commented Jul 18, 2021

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

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

mattn commented Jul 15, 2021 •

edited

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