Cleanup glog and add real caller information.

In general, we've learned that logging must be avoided at all
costs in the hot path. It's unlikely that the optimizations
here were significant in any case, since buffer would certainly
escape.

This also adds a test to ensure that the caller identification
works as expected, and so that logging can be benchmarked.

Original:
BenchmarkGoogleLogging-6   	 1222255	       949 ns/op

With this change:
BenchmarkGoogleLogging-6   	  517323	      2346 ns/op

Fixes #184

PiperOrigin-RevId: 291815420

1 files changed, 16 insertions, 4 deletions

diff --git a/pkg/log/log.go b/pkg/log/log.go
index 91a81b288..5056f17e6 100644
--- a/pkg/log/log.go
+++ b/pkg/log/log.go
@@ -17,6 +17,18 @@
 // This is separate from the standard logging package because logging may be a
 // high-impact activity, and therefore we wanted to provide as much flexibility
 // as possible in the underlying implementation.
+//
+// Note that logging should still be considered high-impact, and should not be
+// done in the hot path. If necessary, logging statements should be protected
+// with guards regarding the logging level. For example,
+//
+//	if log.IsLogging(log.Debug) {
+//		log.Debugf(...)
+//	}
+//
+// This is because the log.Debugf(...) statement alone will generate a
+// significant amount of garbage and churn in many cases, even if no log
+// message is ultimately emitted.
 package log
 
 import (
@@ -138,8 +150,8 @@ func (l *Writer) Emit(level Level, timestamp time.Time, format string, args ...i
 type MultiEmitter []Emitter
 
 // Emit emits to all emitters.
-func (m MultiEmitter) Emit(level Level, timestamp time.Time, format string, v ...interface{}) {
-	for _, e := range m {
+func (m *MultiEmitter) Emit(level Level, timestamp time.Time, format string, v ...interface{}) {
+	for _, e := range *m {
 		e.Emit(level, timestamp, format, v...)
 	}
 }
@@ -155,7 +167,7 @@ type TestEmitter struct {
 }
 
 // Emit emits to the TestLogger.
-func (t TestEmitter) Emit(level Level, timestamp time.Time, format string, v ...interface{}) {
+func (t *TestEmitter) Emit(level Level, timestamp time.Time, format string, v ...interface{}) {
 	t.Logf(format, v...)
 }
 
@@ -332,5 +344,5 @@ func CopyStandardLogTo(l Level) error {
 
 func init() {
 	// Store the initial value for the log.
-	log.Store(&BasicLogger{Level: Info, Emitter: GoogleEmitter{&Writer{Next: os.Stderr}}})
+	log.Store(&BasicLogger{Level: Info, Emitter: &GoogleEmitter{Writer{Next: os.Stderr}}})
 }