main: Correct defer handling in main entrypoint.

config.go

@@ -244,9 +244,8 @@ func genCertPair(certFile, keyFile string) error {
 }
 
 // newConfigParser returns a new command line flags parser.
-func newConfigParser(cfg *config, options flags.Options) (*flags.Parser, error) {
-	parser := flags.NewParser(cfg, options)
-	return parser, nil
+func newConfigParser(cfg *config, options flags.Options) *flags.Parser {
+	return flags.NewParser(cfg, options)
 }
 
 // cleanAndExpandPath expands environment variables and leading ~ in the
@@ -370,13 +369,8 @@ func loadConfig() (*config, []string, error) {
 	// help message error can be ignored here since they will be caught by
 	// the final parse below.
 	preCfg := cfg
-	preParser, err := newConfigParser(&preCfg, flags.HelpFlag)
-	if err != nil {
-		fmt.Fprintln(os.Stderr, err)
-		os.Exit(1)
-	}
-
-	_, err = preParser.Parse()
+	preParser := newConfigParser(&preCfg, flags.HelpFlag)
+	_, err := preParser.Parse()
 	if err != nil {
 		var e *flags.Error
 		if errors.As(err, &e) {
@@ -491,12 +485,7 @@ func loadConfig() (*config, []string, error) {
 
 	// Load additional config from file.
 	var configFileError error
-	parser, err := newConfigParser(&cfg, flags.Default)
-	if err != nil {
-		fmt.Fprintln(os.Stderr, err)
-		return nil, nil, err
-	}
-
+	parser := newConfigParser(&cfg, flags.Default)
 	err = flags.NewIniParser(parser).ParseFile(preCfg.ConfigFile)
 	if err != nil {
 		var e *os.PathError

dcrpool.go

@@ -133,7 +133,9 @@ func newPool(db pool.Database, cfg *config) (*miningPool, error) {
 	return p, nil
 }
 
-func main() {
+// realMain is the real main function for dcrpool.  It is necessary to work
+// around the fact that deferred functions do not run when os.Exit() is called.
+func realMain() error {
 	// Listen for interrupt signals.
 	interrupt := make(chan os.Signal, 1)
 	signal.Notify(interrupt, signals...)
@@ -142,7 +144,7 @@ func main() {
 	// logging and configures it accordingly.
 	cfg, _, err := loadConfig()
 	if err != nil {
-		os.Exit(1)
+		return err
 	}
 	defer func() {
 		if logRotator != nil {
@@ -160,13 +162,13 @@ func main() {
 
 	if err != nil {
 		mpLog.Errorf("failed to initialize database: %v", err)
-		os.Exit(1)
+		return err
 	}
 
 	p, err := newPool(db, cfg)
 	if err != nil {
 		mpLog.Errorf("failed to initialize pool: %v", err)
-		os.Exit(1)
+		return err
 	}
 
 	if cfg.Profile != "" {
@@ -215,4 +217,12 @@ func main() {
 
 	db.Close()
 	mpLog.Info("dcrpool shut down.")
+	return nil
+}
+
+func main() {
+	// Work around defer not working after os.Exit()
+	if err := realMain(); err != nil {
+		os.Exit(1)
+	}
 }