log: change isDiscard type to atomic.Bool

Change-Id: Iff881cc6cc2ec34c7cf8bbd5dd1b0a05a19e1c23
Reviewed-on: https://go-review.googlesource.com/c/go/+/422175
Run-TryBot: Rob Pike <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Rob Pike <[email protected]>
Run-TryBot: Ian Lance Taylor <[email protected]>
Run-TryBot: Ian Lance Taylor <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>

Author: ludi317

src/log/log.go

@@ -54,12 +54,12 @@ const (
 // the Writer's Write method. A Logger can be used simultaneously from
 // multiple goroutines; it guarantees to serialize access to the Writer.
 type Logger struct {
-	mu        sync.Mutex // ensures atomic writes; protects the following fields
-	prefix    string     // prefix on each line to identify the logger (but see Lmsgprefix)
-	flag      int        // properties
-	out       io.Writer  // destination for output
-	buf       []byte     // for accumulating text to write
-	isDiscard int32      // atomic boolean: whether out == io.Discard
+	mu        sync.Mutex  // ensures atomic writes; protects the following fields
+	prefix    string      // prefix on each line to identify the logger (but see Lmsgprefix)
+	flag      int         // properties
+	out       io.Writer   // destination for output
+	buf       []byte      // for accumulating text to write
+	isDiscard atomic.Bool // whether out == io.Discard
 }
 
 // New creates a new Logger. The out variable sets the
@@ -70,7 +70,7 @@ type Logger struct {
 func New(out io.Writer, prefix string, flag int) *Logger {
 	l := &Logger{out: out, prefix: prefix, flag: flag}
 	if out == io.Discard {
-		l.isDiscard = 1
+		l.isDiscard.Store(true)
 	}
 	return l
 }
@@ -80,11 +80,7 @@ func (l *Logger) SetOutput(w io.Writer) {
 	l.mu.Lock()
 	defer l.mu.Unlock()
 	l.out = w
-	isDiscard := int32(0)
-	if w == io.Discard {
-		isDiscard = 1
-	}
-	atomic.StoreInt32(&l.isDiscard, isDiscard)
+	l.isDiscard.Store(w == io.Discard)
 }
 
 var std = New(os.Stderr, "", LstdFlags)
@@ -202,7 +198,7 @@ func (l *Logger) Output(calldepth int, s string) error {
 // Printf calls l.Output to print to the logger.
 // Arguments are handled in the manner of fmt.Printf.
 func (l *Logger) Printf(format string, v ...any) {
-	if atomic.LoadInt32(&l.isDiscard) != 0 {
+	if l.isDiscard.Load() {
 		return
 	}
 	l.Output(2, fmt.Sprintf(format, v...))
@@ -211,7 +207,7 @@ func (l *Logger) Printf(format string, v ...any) {
 // Print calls l.Output to print to the logger.
 // Arguments are handled in the manner of fmt.Print.
 func (l *Logger) Print(v ...any) {
-	if atomic.LoadInt32(&l.isDiscard) != 0 {
+	if l.isDiscard.Load() {
 		return
 	}
 	l.Output(2, fmt.Sprint(v...))
@@ -220,7 +216,7 @@ func (l *Logger) Print(v ...any) {
 // Println calls l.Output to print to the logger.
 // Arguments are handled in the manner of fmt.Println.
 func (l *Logger) Println(v ...any) {
-	if atomic.LoadInt32(&l.isDiscard) != 0 {
+	if l.isDiscard.Load() {
 		return
 	}
 	l.Output(2, fmt.Sprintln(v...))
@@ -339,7 +335,7 @@ func Writer() io.Writer {
 // Print calls Output to print to the standard logger.
 // Arguments are handled in the manner of fmt.Print.
 func Print(v ...any) {
-	if atomic.LoadInt32(&std.isDiscard) != 0 {
+	if std.isDiscard.Load() {
 		return
 	}
 	std.Output(2, fmt.Sprint(v...))
@@ -348,7 +344,7 @@ func Print(v ...any) {
 // Printf calls Output to print to the standard logger.
 // Arguments are handled in the manner of fmt.Printf.
 func Printf(format string, v ...any) {
-	if atomic.LoadInt32(&std.isDiscard) != 0 {
+	if std.isDiscard.Load() {
 		return
 	}
 	std.Output(2, fmt.Sprintf(format, v...))
@@ -357,7 +353,7 @@ func Printf(format string, v ...any) {
 // Println calls Output to print to the standard logger.
 // Arguments are handled in the manner of fmt.Println.
 func Println(v ...any) {
-	if atomic.LoadInt32(&std.isDiscard) != 0 {
+	if std.isDiscard.Load() {
 		return
 	}
 	std.Output(2, fmt.Sprintln(v...))