procfs: do not use RHEL 8 backported fsopen(2)

internal/gocompat/README.md

@@ -0,0 +1,10 @@
+## gocompat ##
+
+This directory contains backports of stdlib functions from later Go versions so
+the filepath-securejoin can continue to be used by projects that are stuck with
+Go 1.18 support. Note that often filepath-securejoin is added in security
+patches for old releases, so avoiding the need to bump Go compiler requirements
+is a huge plus to downstreams.
+
+The source code is licensed under the same license as the Go stdlib. See the
+source files for the precise license information.

internal/gocompat/doc.go

@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: BSD-3-Clause
+//go:build linux && go1.20
+
+// Copyright (C) 2025 SUSE LLC. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package gocompat includes compatibility shims (backported from future Go
+// stdlib versions) to permit filepath-securejoin to be used with older Go
+// versions (often filepath-securejoin is added in security patches for old
+// releases, so avoiding the need to bump Go compiler requirements is a huge
+// plus to downstreams).
+package gocompat

gocompat_errors_go120.go → internal/gocompat/gocompat_errors_go120.go

@@ -5,15 +5,15 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package securejoin
+package gocompat
 
 import (
 	"fmt"
 )
 
-// wrapBaseError is a helper that is equivalent to fmt.Errorf("%w: %w"), except
+// WrapBaseError is a helper that is equivalent to fmt.Errorf("%w: %w"), except
 // that on pre-1.20 Go versions only errors.Is() works properly (errors.Unwrap)
 // is only guaranteed to give you baseErr.
-func wrapBaseError(baseErr, extraErr error) error {
+func WrapBaseError(baseErr, extraErr error) error {
 	return fmt.Errorf("%w: %w", extraErr, baseErr)
 }

gocompat_errors_test.go → internal/gocompat/gocompat_errors_test.go

@@ -6,7 +6,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package securejoin
+package gocompat
 
 import (
 	"errors"
@@ -20,7 +20,7 @@ func TestGoCompatErrorWrap(t *testing.T) {
 	baseErr := errors.New("base error")
 	extraErr := errors.New("extra error")
 
-	err := wrapBaseError(baseErr, extraErr)
+	err := WrapBaseError(baseErr, extraErr)
 
 	require.Error(t, err)
 	assert.ErrorIs(t, err, baseErr, "wrapped error should contain base error")   //nolint:testifylint // we are testing error behaviour directly

gocompat_errors_unsupported.go → internal/gocompat/gocompat_errors_unsupported.go

@@ -6,7 +6,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package securejoin
+package gocompat
 
 import (
 	"fmt"
@@ -29,10 +29,10 @@ func (err wrappedError) Error() string {
 	return fmt.Sprintf("%v: %v", err.isError, err.inner)
 }
 
-// wrapBaseError is a helper that is equivalent to fmt.Errorf("%w: %w"), except
+// WrapBaseError is a helper that is equivalent to fmt.Errorf("%w: %w"), except
 // that on pre-1.20 Go versions only errors.Is() works properly (errors.Unwrap)
 // is only guaranteed to give you baseErr.
-func wrapBaseError(baseErr, extraErr error) error {
+func WrapBaseError(baseErr, extraErr error) error {
 	return wrappedError{
 		inner:   baseErr,
 		isError: extraErr,

internal/gocompat/gocompat_generics_go121.go

@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build linux && go1.21
+
+// Copyright (C) 2024-2025 SUSE LLC. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gocompat
+
+import (
+	"cmp"
+	"slices"
+	"sync"
+)
+
+// SlicesDeleteFunc is equivalent to Go 1.21's slices.DeleteFunc.
+func SlicesDeleteFunc[S ~[]E, E any](slice S, delFn func(E) bool) S {
+	return slices.DeleteFunc(slice, delFn)
+}
+
+// SlicesContains is equivalent to Go 1.21's slices.Contains.
+func SlicesContains[S ~[]E, E comparable](slice S, val E) bool {
+	return slices.Contains(slice, val)
+}
+
+// SlicesClone is equivalent to Go 1.21's slices.Clone.
+func SlicesClone[S ~[]E, E any](slice S) S {
+	return slices.Clone(slice)
+}
+
+// SyncOnceValue is equivalent to Go 1.21's sync.OnceValue.
+func SyncOnceValue[T any](f func() T) func() T {
+	return sync.OnceValue(f)
+}
+
+// SyncOnceValues is equivalent to Go 1.21's sync.OnceValues.
+func SyncOnceValues[T1, T2 any](f func() (T1, T2)) func() (T1, T2) {
+	return sync.OnceValues(f)
+}
+
+// CmpOrdered is equivalent to Go 1.21's cmp.Ordered generic type definition.
+type CmpOrdered = cmp.Ordered
+
+// CmpCompare is equivalent to Go 1.21's cmp.Compare.
+func CmpCompare[T CmpOrdered](x, y T) int {
+	return cmp.Compare(x, y)
+}
+
+// Max2 is equivalent to Go 1.21's max builtin (but only for two parameters).
+func Max2[T CmpOrdered](x, y T) T {
+	return max(x, y)
+}