glog: check that stderr is valid before using it by default

glog_file.go

@@ -158,7 +158,10 @@ var sinks struct {
 func init() {
 	// Register stderr first: that way if we crash during file-writing at least
 	// the log will have gone somewhere.
-	logsink.TextSinks = append(logsink.TextSinks, &sinks.stderr, &sinks.file)
+	if shouldRegisterStderrSink() {
+		logsink.TextSinks = append(logsink.TextSinks, &sinks.stderr)
+	}
+	logsink.TextSinks = append(logsink.TextSinks, &sinks.file)
 
 	sinks.file.flushChan = make(chan logsink.Severity, 1)
 	go sinks.file.flushDaemon()

glog_file_nonwindows.go

@@ -4,6 +4,13 @@ package glog
 
 import "os/user"
 
+// shouldRegisterStderrSink determines whether we should register a log sink that writes to stderr.
+// Today, this always returns true on non-Windows platforms, as it specifically checks for a
+// condition that is only present on Windows.
+func shouldRegisterStderrSink() bool {
+	return true
+}
+
 func lookupUser() string {
 	if current, err := user.Current(); err == nil {
 		return current.Username

glog_file_windows.go

@@ -3,9 +3,22 @@
 package glog
 
 import (
+	"os"
 	"syscall"
 )
 
+// shouldRegisterStderrSink determines whether we should register a log sink that writes to stderr.
+// Today, this checks if stderr is "valid", in that it maps to a non-NULL Handle.
+// Windows Services are spawned without Stdout and Stderr, so any attempt to use them equates to
+// referencing an invalid file Handle.
+// os.Stderr's FD is derived from a call to `syscall.GetStdHandle(syscall.STD_ERROR_HANDLE)`.
+// Documentation[1] for the GetStdHandle function indicates the return value may be NULL if the
+// application lacks the standard handle, so consider Stderr valid if its FD is non-NULL.
+// [1]: https://learn.microsoft.com/en-us/windows/console/getstdhandle
+func shouldRegisterStderrSink() bool {
+	return os.Stderr.Fd() != 0
+}
+
 // This follows the logic in the standard library's user.Current() function, except
 // that it leaves out the potentially expensive calls required to look up the user's
 // display name in Active Directory.