fmsg: implement suspend in writer

This removes the requirement to call fmsg.Exit on every exit path, and enables direct use of the "log" package. However, fmsg.BeforeExit is still encouraged when possible to catch exit on suspended output.

Signed-off-by: Ophestra <cat@gensokyo.uk>

main.go

@@ -5,6 +5,7 @@ import (
 	_ "embed"
 	"flag"
 	"fmt"
+	"log"
 	"os"
 	"os/signal"
 	"os/user"
@@ -37,6 +38,8 @@ var (
 )
 
 func init() {
+	fmsg.Prepare("fortify")
+
 	flag.BoolVar(&flagVerbose, "v", false, "Verbose output")
 	flag.BoolVar(&flagJSON, "json", false, "Format output in JSON when applicable")
 }
@@ -62,13 +65,12 @@ func main() {
 	init0.TryArgv0()
 
 	if err := internal.PR_SET_DUMPABLE__SUID_DUMP_DISABLE(); err != nil {
-		fmsg.Printf("cannot set SUID_DUMP_DISABLE: %s", err)
+		log.Printf("cannot set SUID_DUMP_DISABLE: %s", err)
 		// not fatal: this program runs as the privileged user
 	}
 
 	if os.Geteuid() == 0 {
-		fmsg.Fatal("this program must not run as root")
-		panic("unreachable")
+		log.Fatal("this program must not run as root")
 	}
 
 	flag.CommandLine.Usage = func() {
@@ -96,12 +98,12 @@ func main() {
 		fmt.Println()
 	}
 	flag.Parse()
-	fmsg.SetVerbose(flagVerbose)
+	fmsg.Store(flagVerbose)
 
 	args := flag.Args()
 	if len(args) == 0 {
 		flag.CommandLine.Usage()
-		fmsg.Exit(0)
+		internal.Exit(0)
 	}
 
 	switch args[0] {
@@ -111,16 +113,20 @@ func main() {
 		} else {
 			fmt.Println("impure")
 		}
-		fmsg.Exit(0)
+		internal.Exit(0)
+
 	case "license": // print embedded license
 		fmt.Println(license)
-		fmsg.Exit(0)
+		internal.Exit(0)
+
 	case "template": // print full template configuration
 		printJSON(os.Stdout, false, fst.Template())
-		fmsg.Exit(0)
+		internal.Exit(0)
+
 	case "help": // print help message
 		flag.CommandLine.Usage()
-		fmsg.Exit(0)
+		internal.Exit(0)
+
 	case "ps": // print all state info
 		set := flag.NewFlagSet("ps", flag.ExitOnError)
 		var short bool
@@ -130,7 +136,8 @@ func main() {
 		_ = set.Parse(args[1:])
 
 		printPs(os.Stdout, time.Now().UTC(), state.NewMulti(sys.Paths().RunDirPath), short)
-		fmsg.Exit(0)
+		internal.Exit(0)
+
 	case "show": // pretty-print app info
 		set := flag.NewFlagSet("show", flag.ExitOnError)
 		var short bool
@@ -142,6 +149,7 @@ func main() {
 		switch len(set.Args()) {
 		case 0: // system
 			printShowSystem(os.Stdout, short)
+
 		case 1: // instance
 			name := set.Args()[0]
 			config, instance := tryShort(name)
@@ -149,14 +157,15 @@ func main() {
 				config = tryPath(name)
 			}
 			printShowInstance(os.Stdout, time.Now().UTC(), instance, config, short)
-		default:
-			fmsg.Fatal("show requires 1 argument")
-		}
 
-		fmsg.Exit(0)
+		default:
+			log.Fatal("show requires 1 argument")
+		}
+		internal.Exit(0)
+
 	case "app": // launch app from configuration file
 		if len(args) < 2 {
-			fmsg.Fatal("app requires at least 1 argument")
+			log.Fatal("app requires at least 1 argument")
 		}
 
 		// config extraArgs...
@@ -166,6 +175,7 @@ func main() {
 		// invoke app
 		runApp(config)
 		panic("unreachable")
+
 	case "run": // run app in permissive defaults usage pattern
 		set := flag.NewFlagSet("run", flag.ExitOnError)
 
@@ -208,8 +218,7 @@ func main() {
 		}
 
 		if aid < 0 || aid > 9999 {
-			fmsg.Fatalf("aid %d out of range", aid)
-			panic("unreachable")
+			log.Fatalf("aid %d out of range", aid)
 		}
 
 		// resolve home/username from os when flag is unset
@@ -219,13 +228,13 @@ func main() {
 			passwdFunc = func() {
 				var us string
 				if uid, err := sys.Uid(aid); err != nil {
-					fmsg.Fatalf("cannot obtain uid from fsu: %v", err)
+					log.Fatalf("cannot obtain uid from fsu: %v", err)
 				} else {
 					us = strconv.Itoa(uid)
 				}
 
 				if u, err := user.LookupId(us); err != nil {
-					fmsg.VPrintf("cannot look up uid %s", us)
+					fmsg.Verbosef("cannot look up uid %s", us)
 					passwd = &user.User{
 						Uid:      us,
 						Gid:      us,
@@ -267,7 +276,7 @@ func main() {
 				config.Confinement.SessionBus = dbus.NewConfig(fid, true, mpris)
 			} else {
 				if c, err := dbus.NewConfigFromFile(dbusConfigSession); err != nil {
-					fmsg.Fatalf("cannot load session bus proxy config from %q: %s", dbusConfigSession, err)
+					log.Fatalf("cannot load session bus proxy config from %q: %s", dbusConfigSession, err)
 				} else {
 					config.Confinement.SessionBus = c
 				}
@@ -276,7 +285,7 @@ func main() {
 			// system bus proxy is optional
 			if dbusConfigSystem != "nil" {
 				if c, err := dbus.NewConfigFromFile(dbusConfigSystem); err != nil {
-					fmsg.Fatalf("cannot load system bus proxy config from %q: %s", dbusConfigSystem, err)
+					log.Fatalf("cannot load system bus proxy config from %q: %s", dbusConfigSystem, err)
 				} else {
 					config.Confinement.SystemBus = c
 				}
@@ -291,17 +300,18 @@ func main() {
 
 		// invoke app
 		runApp(config)
+		panic("unreachable")
 
 	// internal commands
 	case "shim":
 		shim.Main()
-		fmsg.Exit(0)
+		internal.Exit(0)
 	case "init":
 		init0.Main()
-		fmsg.Exit(0)
+		internal.Exit(0)
 
 	default:
-		fmsg.Fatalf("%q is not a valid command", args[0])
+		log.Fatalf("%q is not a valid command", args[0])
 	}
 
 	panic("unreachable")
@@ -313,15 +323,15 @@ func runApp(config *fst.Config) {
 		syscall.SIGINT, syscall.SIGTERM)
 	defer stop() // unreachable
 
-	if fmsg.Verbose() {
-		seccomp.CPrintln = fmsg.Println
+	if fmsg.Load() {
+		seccomp.CPrintln = log.Println
 	}
 
 	if a, err := app.New(sys); err != nil {
-		fmsg.Fatalf("cannot create app: %s\n", err)
+		log.Fatalf("cannot create app: %s", err)
 	} else if err = a.Seal(config); err != nil {
 		logBaseError(err, "cannot seal app:")
-		fmsg.Exit(1)
+		internal.Exit(1)
 	} else if err = a.Run(ctx, rs); err != nil {
 		if !rs.Start {
 			logBaseError(err, "cannot start app:")
@@ -334,8 +344,7 @@ func runApp(config *fst.Config) {
 		}
 	}
 	if rs.WaitErr != nil {
-		fmsg.Println("inner wait failed:", rs.WaitErr)
+		log.Println("inner wait failed:", rs.WaitErr)
 	}
-	fmsg.Exit(rs.ExitCode)
-	panic("unreachable")
+	internal.Exit(rs.ExitCode)
 }