simulation: fix and test syscalls and logs during init

Make syscalls work during init, and make sure logs work
as well for when things during init go wrong.

internal/simulation/userspace.go

@@ -74,7 +74,8 @@ func setupSlog(machineLabel string) {
 		panic(err)
 	}
 
-	// TODO: capture stdout? stderr?
+	// stdout and stderr are currently captured with some special logic in
+	// LinuxOS for writes to their file descriptors, see TestStdoutStderr.
 
 	ho := slog.HandlerOptions{
 		Level:     level,
@@ -91,14 +92,15 @@ func setupSlog(machineLabel string) {
 }
 
 func setupUserspace(gosimOS_ *GosimOS, linuxOS_ *LinuxOS, machineID int, label string) {
-	// XXX: does logging work during global init?
-	gosimruntime.InitGlobals(false, false)
-
-	// yikes... how do we order this? should machine exist first? should these happen in an init() in here SOMEHOW? short-circuit this package?
-	// XXX: provide directoyr
+	// initialize gosimOS etc. before invoking initializers so that init() calls
+	// can make syscalls, see TestSyscallsDuringInit.
 	gosimOS = gosimOS_
 	linuxOS = linuxOS_
 	currentMachineID = machineID
 
+	gosimruntime.InitGlobals(false, false)
+
+	// setupSlog only works once globals are initialized.  logs during init are
+	// printed to stdout/stderr, see TestLogDuringInit.
 	setupSlog(label)
 }

internal/tests/behavior/log_meta_test.go

@@ -33,7 +33,7 @@ func parseLog(t *testing.T, log []byte) []map[string]any {
 	return logs
 }
 
-func TestMetaLogMachineGoroutineTime(t *testing.T) {
+func TestLogMachineGoroutineTime(t *testing.T) {
 	mt := metatesting.ForCurrentPackage(t)
 	run, err := mt.Run(t, &metatesting.RunConfig{
 		Test: "TestLogMachineGoroutineTime",
@@ -55,7 +55,7 @@ func TestMetaLogMachineGoroutineTime(t *testing.T) {
 	}
 }
 
-func TestMetaLogSLog(t *testing.T) {
+func TestLogSLog(t *testing.T) {
 	mt := metatesting.ForCurrentPackage(t)
 	run, err := mt.Run(t, &metatesting.RunConfig{
 		Test: "TestLogSLog",
@@ -74,7 +74,7 @@ func TestMetaLogSLog(t *testing.T) {
 	}
 }
 
-func TestMetaStdoutStderr(t *testing.T) {
+func TestStdoutStderr(t *testing.T) {
 	mt := metatesting.ForCurrentPackage(t)
 	run, err := mt.Run(t, &metatesting.RunConfig{
 		Test: "TestStdoutStderr",
@@ -93,3 +93,26 @@ func TestMetaStdoutStderr(t *testing.T) {
 		t.Error("diff", diff)
 	}
 }
+
+func TestLogDuringInit(t *testing.T) {
+	mt := metatesting.ForCurrentPackage(t)
+	run, err := mt.Run(t, &metatesting.RunConfig{
+		Test: "TestLogDuringInit",
+		Seed: 1,
+		ExtraEnv: []string{
+			"LOGDURINGINIT=1",
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	actual := parseLog(t, run.LogOutput)
+	expected := parseLog(t, []byte(`{"time":"2020-01-15T14:10:03.000001234Z","level":"INFO","msg":"hello\n","machine":"os","method":"stdout","from":"main","goroutine":1,"step":1}
+{"time":"2020-01-15T14:10:03.000001234Z","level":"INFO","msg":"2020/01/15 14:10:03 INFO help\n","machine":"os","method":"stderr","from":"main","goroutine":1,"step":2}
+`))
+
+	if diff := cmp.Diff(expected, actual); diff != "" {
+		t.Error("diff", diff)
+	}
+}

internal/tests/behavior/log_test.go

@@ -3,6 +3,7 @@
 package behavior_test
 
 import (
+	"fmt"
 	"log"
 	"log/slog"
 	"os"
@@ -62,3 +63,15 @@ func TestLogForPrettyTest(t *testing.T) {
 	m.Wait()
 	log.Println("never")
 }
+
+func init() {
+	// logs during init will print to stdout/stderr bypassing the gosim handler
+	if os.Getenv("LOGDURINGINIT") == "1" {
+		fmt.Println("hello")
+		slog.Info("help")
+	}
+}
+
+func TestLogDuringInit(t *testing.T) {
+	// logs in above init() should print
+}

internal/tests/behavior/os_sim_test.go

@@ -41,3 +41,30 @@ func TestGetpagesize(t *testing.T) {
 		t.Fatalf("bad page size %d", pgsize)
 	}
 }
+
+var globalHostname string
+
+func init() {
+	globalHostname, _ = os.Hostname()
+}
+
+func TestSyscallsDuringInit(t *testing.T) {
+	// Test that os.Hostname() called in an init func can make syscalls.
+
+	expected := "main"
+	if globalHostname != expected {
+		t.Errorf("bad name %q, expected %q", globalHostname, expected)
+	}
+
+	m := gosim.NewMachine(gosim.MachineConfig{
+		Label: "hello123",
+		MainFunc: func() {
+			expected := "hello123"
+			if globalHostname != expected {
+				t.Errorf("bad name %q, expected %q", globalHostname, expected)
+			}
+		},
+	})
+
+	m.Wait()
+}