version/cmdname.go

@@ -13,6 +13,7 @@ import (
 	"os"
 	"path"
 	"runtime"
+	"runtime/debug"
 	"strings"
 )
 
@@ -20,6 +21,15 @@ import (
 // using os.Executable. If os.Executable fails (it shouldn't), then
 // "cmd" is returned.
 func CmdName() string {
+	// On non-Windows, the modinfo embedded in the running binary is
+	// authoritative and avoids re-reading the executable from disk.
+	// Windows needs the executable-name-based GUI override in cmdName,
+	// so it still takes the slower path.
+	if runtime.GOOS != "windows" {
+		if info, ok := debug.ReadBuildInfo(); ok && info.Path != "" {
+			return path.Base(info.Path)
+		}
+	}
 	e, err := os.Executable()
 	if err != nil {
 		return "cmd"

version/version_test.go

@@ -6,6 +6,8 @@ package version_test
 import (
 	"bytes"
 	"os"
+	"path"
+	"runtime/debug"
 	"testing"
 
 	ts "tailscale.com"
@@ -49,3 +51,21 @@ func TestShortAllocs(t *testing.T) {
 		t.Errorf("allocs = %v; want 0", allocs)
 	}
 }
+
+func BenchmarkCmdName(b *testing.B) {
+	b.ReportAllocs()
+	for b.Loop() {
+		_ = version.CmdName()
+	}
+}
+
+func BenchmarkReadBuildInfo(b *testing.B) {
+	b.ReportAllocs()
+	for b.Loop() {
+		info, ok := debug.ReadBuildInfo()
+		if !ok {
+			b.Fatal("ReadBuildInfo failed")
+		}
+		_ = path.Base(info.Path)
+	}
+}