os: go 1.25.x regression on RemoveAll for oldest Windows 10 build 10240

[vadimsht]

Go version

1.26.1, 1.25.8

Output of go env in your module/workspace:

AR='ar'
CC='gcc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='0'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='g++'
GCCGO='gccgo'
GO111MODULE='on'
GOAMD64='v1'
GOARCH='amd64'
GOAUTH='netrc'
GOBIN='/Users/vadimsh/infra/infra_internal/dep/infra.git/go/bin'
GOCACHE='/Users/vadimsh/infra/infra_internal/dep/infra.git/go/golang/gocache'
GOCACHEPROG=''
GODEBUG=''
GOENV='/Users/vadimsh/Library/Application Support/go/env'
GOEXE='.exe'
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-m64 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/s5/038psd6x11x2n172nwdpvk94005swt/T/go-build105125036=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMOD='/Users/vadimsh/infra/infra_internal/dep/infra.git/go/src/go.chromium.org/luci/go.mod'
GOMODCACHE='/Users/vadimsh/infra/infra_internal/dep/infra.git/go/golang/modcache'
GONOPROXY='*.googlesource.com,*.git.corp.google.com,google.com'
GONOSUMDB='*.googlesource.com,*.git.corp.google.com,google.com'
GOOS='windows'
GOPATH='/Users/vadimsh/go'
GOPRIVATE='*.googlesource.com,*.git.corp.google.com,google.com'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/Users/vadimsh/infra/infra_internal/dep/infra.git/go/golang/go'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/Users/vadimsh/Library/Application Support/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='local'
GOTOOLDIR='/Users/vadimsh/infra/infra_internal/dep/infra.git/go/golang/go/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.25.8'
GOWORK=''
PKG_CONFIG='pkg-config'

(note I'm cross-compiling to Win amd64, but it doesn't matter, native Windows build fail in the same way)

What did you do?

When build the below snippet with go1.26.1 and running it on Windows 10 build 10240 (aka Windows 10 v1507, aka Windows 10 first RTM release ever), it fails with

openfdat .\test: The parameter is incorrect

It succeeds when building it with go1.24.13.

It also succeeds when running it on Windows 10 build 19045 (aka Windows 10 version 22H2) and newer (I haven't tested any older versions, since I don't have access to them).

package main

import (
	"fmt"
	"os"
	"path/filepath"
)

func main() {
	if err := run(); err != nil {
		fmt.Printf("%s\n", err)
	} else {
		fmt.Printf("Done\n")
	}
}

func run() error {
	if err := os.MkdirAll(filepath.Join("test", "a"), 0777); err != nil {
		return err
	}
	return os.RemoveAll("test")
}

This matters for the Chrome CI since we use Golang tooling to run tests and Chrome still officially supports this version of Windows (and our tooling is now failing there). IIUC, Go also officially supports Windows 10, but does this support extend to this very first Win 10 version? :)

To be clear, windows build numbers here are the same as reported by https://pkg.go.dev/golang.org/x/sys/windows#RtlGetNtVersionNumbers

What did you see happen?

openfdat .\test: The parameter is incorrect

What did you expect to see?

Done

[vadimsht]

Note if you are a googler, I can help with getting a remote access to such older Windows 10 VM (or even set it up as Golang LUCI CI bot). Here are two Swarming tasks I used to test this: https://chromium-swarm-dev.appspot.com/task?id=76fc481ed588b310 and https://chromium-swarm-dev.appspot.com/task?id=76fc478dbaeea810

[randall77]

It would be good if someone could bisect this to a CL.
@golang/windows

[BasavarajBankolli]

It would be good if someone could bisect this to a CL. @golang/windows

Using git bisect, the regression appears to point to:

https://go-review.googlesource.com/c/go/+/684515
"os: use minimal file permissions when opening parent directory in RemoveAll"

This change modified how the parent directory is opened on Windows:

Before:
parent, err := Open(parentDir)

After:
flag := O_RDONLY
if runtime.GOOS == "windows" {
flag = O_WRONLY | O_RDWR
}
parent, err := OpenFile(parentDir, flag, 0)

After this change, RemoveAll fails on Windows 10 build 10240 with:

openfdat .\test: The parameter is incorrect

It seems the flag combination used when opening the directory may not be accepted on this older Windows build.

If this analysis looks correct, I'd be happy to try working on a fix.

[gabyhelp]

Related Issues

• os: Go 1.25.x regression on RemoveAll for windows #77402 (closed)
• os: on windows RemoveAll removing directories containing read-only files errors with `unlinkat ... Access is denied` #75922 (closed)
• os: Remove empty directory fails with "process cannot access the file because it is being used by another process" on <= Windows 10 #58860 (closed)
• os.RemoveAll Bug? #41747 (closed)
• os: regression with reading empty root directories on Windows with go1.21rc2 #61159 (closed)
• os: on windows RemoveAll removing directories containing read-only files errors with `unlinkat ... Access is denied`, ReOpenFile error handling followup [1.25 backport] #76360 (closed)
• os: possible regression from Go 1.23 to Go 1.24 when opening DevNull with O_TRUNC #71752 (closed)
• os: File.ReadDir returns "The parameter is incorrect." when passed Windows device path (1.22 regression) #67834
• os: Go 1.25.x regression on RemoveAll for windows [1.26 backport] #77407 (closed)
• os: ReadDir("\tsclient\d") fails with go1.21 on Windows #62044 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[qmuntal]

If this analysis looks correct, I'd be happy to try working on a fix.

Thanks for the analysis. I don't have such an old version at hand, but it could well be that the current flag combinations are not supported in there.

Feel free to send a fix. Just take into account that CL 684515 was submitted to fix #74134. Whatever the fix it, it should also work for that use case (at least on newer Windows).

[BasavarajBankolli]

Thanks for the guidance.

My initial thought is to try opening the parent directory with the flags introduced in CL 684515, and if that fails on Windows (e.g., with ERROR_INVALID_PARAMETER on older builds like 10240), fall back to opening it with O_RDONLY.

Something along the lines of:

flag := O_RDONLY
if runtime.GOOS == "windows" {
flag = O_WRONLY | O_RDWR
}
parent, err := OpenFile(parentDir, flag, 0)
if err != nil && runtime.GOOS == "windows" {
// fallback for older Windows versions
parent, err = OpenFile(parentDir, O_RDONLY, 0)
}

This would preserve the behavior introduced in CL 684515 for newer Windows versions while maintaining compatibility with older ones. Does this approach sound reasonable?

[qmuntal]

The error reported in this issue is openfdat .\test: The parameter is incorrect. This means that OpenFile(parentDir, O_RDONLY|O_WRONLY|O_RDWR, 0) succeeds, but it might trip operations in the resulting handle down the line. This means that the fallback you propose will not fix the issue.

If you could bisect to pin-point the offending CL, then it means that you can reproduce it. I suggest you to try to find a solution yourself and send a CL so that I can give feedback and guidance in Gerrit instead of polluting this issue, which is not the right tool to review code.

[ethanmontgomery148-hub]

Yes the error still persist is there any work around

…

On Fri, Mar 13, 2026, 1:11 PM Quim Muntal ***@***.***> wrote: *qmuntal* left a comment (golang/go#78131) <#78131 (comment)> The error reported in this issue is openfdat .\test: The parameter is incorrect. This means that OpenFile(parentDir, O_RDONLY|O_WRONLY|O_RDWR, 0) succeeds, but it might trip operations in the resulting handle down the line. This means that the fallback you propose will not fix the issue. If you could bisect to pin-point the offending CL, then it means that you can reproduce it. I suggest you to try to find a solution yourself and send a CL so that I can give feedback and guidance in Gerrit instead of polluting this issue, which is not the right tool to review code. — Reply to this email directly, view it on GitHub <#78131 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/B7BKMDXCXUHD3CHQ7THWGD34QQCILAVCNFSM6AAAAACWQC74W2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHM2DANJUHE3DSNJYGU> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[alain91]

Due to text of error (openfdat) there is only one location to raise this error.
It is line 100 recurseErr in file removeall_at.go
Then one have to look in this area of code.

[ethanmontgomery148-hub]

Yes It not even clear to me

…

On Sun, Mar 15, 2026, 9:24 PM alain91 ***@***.***> wrote: *alain91* left a comment (golang/go#78131) <#78131 (comment)> Due to text of error (openfdat) there is only one location to raise this error. It is line 100 recurseErr in file removeall_at.go Then one have to look in this area of code. — Reply to this email directly, view it on GitHub <#78131 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/B7BKMDUMOJNT33EDO2TQWVL4Q4NSFAVCNFSM6AAAAACWQC74W2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHM2DANRTHEZDAMJXGA> . You are receiving this because you commented.Message ID: ***@***.***>