glog: make zero value of vModuleFlag usable

The flag package ensures that the zero value of a flag.Value is usable. This commit fixes this. This was raised in https://groups.google.com/g/golang-nuts/c/Atlr8uAjn6U/m/iId17Td5BQAJ. cl/517349579 (google-internal)
golang · Mar 17, 2023 · 9c9801e · 9c9801e
1 parent 2cef961
commit 9c9801e
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/glog_flags.go b/glog_flags.go
@@ -133,6 +133,11 @@ func (l *Level) Set(value string) error {
 type vModuleFlag struct{ *verboseFlags }
 
 func (f vModuleFlag) String() string {
+	// Do not panic on the zero value.
+	// https://groups.google.com/g/golang-nuts/c/Atlr8uAjn6U/m/iId17Td5BQAJ.
+	if f.verboseFlags == nil {
+		return ""
+	}
 	f.mu.Lock()
 	defer f.mu.Unlock()