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// Copyright 2018 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 darwin && go1.12
package unix
import (
type darwinTest struct {
name string
f uintptr
// TODO(khr): decide whether to keep this test enabled permanently or
// only temporarily.
func TestDarwinLoader(t *testing.T) {
// Make sure the Darwin dynamic loader can actually resolve
// all the system calls into libSystem.dylib. Unfortunately
// there is no easy way to test this at compile time. So we
// implement a crazy hack here, calling into the syscall
// function with all its arguments set to junk, and see what
// error we get. We are happy with any error (or none) except
// an error from the dynamic loader.
// We have to run each test in a separate subprocess for fault isolation.
// Hopefully the junk args won't accidentally ask the system to do "rm -fr /".
// In an ideal world each syscall would have its own test, so this test
// would be unnecessary. Unfortunately, we do not live in that world.
for _, test := range darwinTests {
// Call the test binary recursively, giving it a magic argument
// (see init below) and the name of the test to run.
cmd := exec.Command(os.Args[0], "testDarwinLoader",
// Run subprocess, collect results. Note that we expect the subprocess
// to fail somehow, so the error is irrelevant.
out, _ := cmd.CombinedOutput()
if strings.Contains(string(out), "dyld: Symbol not found:") {
t.Errorf("can't resolve %s in libSystem.dylib",
if !strings.Contains(string(out), "success") {
// Not really an error. Might be a syscall that never returns,
// like exit, or one that segfaults, like gettimeofday.
t.Logf("test never finished: %s: %s",, string(out))
func init() {
// The test binary execs itself with the "testDarwinLoader" argument.
// Run the test specified by os.Args[2], then panic.
if len(os.Args) >= 3 && os.Args[1] == "testDarwinLoader" {
for _, test := range darwinTests {
if == os.Args[2] {
syscall_syscall(test.f, ^uintptr(0), ^uintptr(0), ^uintptr(0))
// Panic with a "success" label, so the parent process can check it.