cmd/go: use os.Rename to move files on Windows

The Go toolchain has been copying files instead of moving them on
Windows since CL 72910. It did this because os.Rename doesn't respect
the destination directory ACL permissions, and we want to honor them.

The drawback is that copying files is slower than moving them.

This CL reintroduces the use of os.Rename, but it also sets the
destination file's ACL to inherit the permissions from the
destination directory.

On my computer this change speeds up a simple "go build" (with warm
cache) by 1 second, going from 3 seconds to 2 seconds.

Updates #22343

Change-Id: I65b2b6f301e9e18bf2588959764eb06b9a01dfa2
Reviewed-on: https://go-review.googlesource.com/c/go/+/691255
Reviewed-by: Mark Freeman <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Damien Neil <[email protected]>

Author: qmuntal

src/cmd/go/internal/work/shell.go

@@ -132,47 +132,11 @@ func (sh *Shell) moveOrCopyFile(dst, src string, perm fs.FileMode, force bool) e
 		return sh.CopyFile(dst, src, perm, force)
 	}
 
-	// On Windows, always copy the file, so that we respect the NTFS
-	// permissions of the parent folder. https://golang.org/issue/22343.
-	// What matters here is not cfg.Goos (the system we are building
-	// for) but runtime.GOOS (the system we are building on).
-	if runtime.GOOS == "windows" {
-		return sh.CopyFile(dst, src, perm, force)
-	}
-
-	// If the destination directory has the group sticky bit set,
-	// we have to copy the file to retain the correct permissions.
-	// https://golang.org/issue/18878
-	if fi, err := os.Stat(filepath.Dir(dst)); err == nil {
-		if fi.IsDir() && (fi.Mode()&fs.ModeSetgid) != 0 {
-			return sh.CopyFile(dst, src, perm, force)
-		}
-	}
-
-	// The perm argument is meant to be adjusted according to umask,
-	// but we don't know what the umask is.
-	// Create a dummy file to find out.
-	// This avoids build tags and works even on systems like Plan 9
-	// where the file mask computation incorporates other information.
-	mode := perm
-	f, err := os.OpenFile(filepath.Clean(dst)+"-go-tmp-umask", os.O_WRONLY|os.O_CREATE|os.O_EXCL, perm)
-	if err == nil {
-		fi, err := f.Stat()
-		if err == nil {
-			mode = fi.Mode() & 0777
-		}
-		name := f.Name()
-		f.Close()
-		os.Remove(name)
-	}
-
-	if err := os.Chmod(src, mode); err == nil {
-		if err := os.Rename(src, dst); err == nil {
-			if cfg.BuildX {
-				sh.ShowCmd("", "mv %s %s", src, dst)
-			}
-			return nil
+	if err := sh.move(src, dst, perm); err == nil {
+		if cfg.BuildX {
+			sh.ShowCmd("", "mv %s %s", src, dst)
 		}
+		return nil
 	}
 
 	return sh.CopyFile(dst, src, perm, force)

src/cmd/go/internal/work/shell_nonwindows.go

@@ -0,0 +1,49 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !windows
+
+package work
+
+import (
+	"errors"
+	"io/fs"
+	"os"
+	"path/filepath"
+)
+
+// move moves a file from src to dst setting the permissions
+// on the destination file to inherit the permissions from the
+// destination parent directory.
+func (sh *Shell) move(src, dst string, perm fs.FileMode) error {
+	// If the destination directory has the group sticky bit set,
+	// we have to copy the file to retain the correct permissions.
+	// https://golang.org/issue/18878
+	if fi, err := os.Stat(filepath.Dir(dst)); err == nil {
+		if fi.IsDir() && (fi.Mode()&fs.ModeSetgid) != 0 {
+			return errors.ErrUnsupported
+		}
+	}
+	// The perm argument is meant to be adjusted according to umask,
+	// but we don't know what the umask is.
+	// Create a dummy file to find out.
+	// This works even on systems like Plan 9 where the
+	// file mask computation incorporates other information.
+	mode := perm
+	f, err := os.OpenFile(filepath.Clean(dst)+"-go-tmp-umask", os.O_WRONLY|os.O_CREATE|os.O_EXCL, perm)
+	if err == nil {
+		fi, err := f.Stat()
+		if err == nil {
+			mode = fi.Mode() & 0777
+		}
+		name := f.Name()
+		f.Close()
+		os.Remove(name)
+	}
+
+	if err := os.Chmod(src, mode); err != nil {
+		return err
+	}
+	return os.Rename(src, dst)
+}

src/cmd/go/internal/work/shell_windows.go

@@ -0,0 +1,37 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package work
+
+import (
+	"internal/syscall/windows"
+	"io/fs"
+	"os"
+	"unsafe"
+)
+
+// move moves a file from src to dst, setting the security information
+// on the destination file to inherit the permissions from the
+// destination parent directory.
+func (sh *Shell) move(src, dst string, perm fs.FileMode) (err error) {
+	if err := os.Rename(src, dst); err != nil {
+		return err
+	}
+	defer func() {
+		if err != nil {
+			os.Remove(dst) // clean up if we failed to set the mode or security info
+		}
+	}()
+	if err := os.Chmod(dst, perm); err != nil {
+		return err
+	}
+	// We need to respect the ACL permissions of the destination parent folder.
+	// https://go.dev/issue/22343.
+	var acl windows.ACL
+	if err := windows.InitializeAcl(&acl, uint32(unsafe.Sizeof(acl)), windows.ACL_REVISION); err != nil {
+		return err
+	}
+	secInfo := windows.DACL_SECURITY_INFORMATION | windows.UNPROTECTED_DACL_SECURITY_INFORMATION
+	return windows.SetNamedSecurityInfo(dst, windows.SE_FILE_OBJECT, secInfo, nil, nil, &acl, nil)
+}

src/internal/syscall/windows/security_windows.go

@@ -262,3 +262,6 @@ func GetSidSubAuthorityCount(sid *syscall.SID) uint8 {
 	defer runtime.KeepAlive(sid)
 	return *(*uint8)(unsafe.Pointer(getSidSubAuthorityCount(sid)))
 }
+
+//sys	InitializeAcl(acl *ACL, length uint32, revision uint32) (err error) = advapi32.InitializeAcl
+//sys	SetNamedSecurityInfo(objectName string, objectType SE_OBJECT_TYPE, securityInformation SECURITY_INFORMATION, owner *syscall.SID, group *syscall.SID, dacl *ACL, sacl *ACL) (ret error) = advapi32.SetNamedSecurityInfoW

src/internal/syscall/windows/types_windows.go

@@ -260,3 +260,21 @@ type FILE_COMPLETION_INFORMATION struct {
 // https://learn.microsoft.com/en-us/windows/win32/api/winnt/ns-winnt-osversioninfoexa
 // https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/wdm/ns-wdm-_osversioninfoexw
 const VER_NT_WORKSTATION = 0x0000001
+
+// https://learn.microsoft.com/en-us/windows/win32/api/accctrl/ne-accctrl-se_object_type
+type SE_OBJECT_TYPE uint32
+
+const (
+	SE_UNKNOWN_OBJECT_TYPE SE_OBJECT_TYPE = 0
+	SE_FILE_OBJECT         SE_OBJECT_TYPE = 1
+)
+
+// https://learn.microsoft.com/en-us/windows/win32/secauthz/security-information
+type SECURITY_INFORMATION uint32
+
+const (
+	DACL_SECURITY_INFORMATION             SECURITY_INFORMATION = 0x00000004
+	UNPROTECTED_DACL_SECURITY_INFORMATION SECURITY_INFORMATION = 0x20000000
+)
+
+const ACL_REVISION = 2