Simplify.

- Allocate temp buffers locally instead of with sync.Pool, just as fast, and causes fewer heap allocs.
- Call findSigpanic during init rather than from sync.Once.

Author: ChrisHines

stack.go

@@ -16,7 +16,6 @@ import (
 	"runtime"
 	"strconv"
 	"strings"
-	"sync"
 )
 
 // Call records a single function invocation from a goroutine stack.
@@ -193,16 +192,15 @@ func findSigpanic() *runtime.Func {
 	func() int {
 		defer func() {
 			if p := recover(); p != nil {
-				pcs := getUintptrs()
-				n := runtime.Callers(2, pcs)
+				var pcs [512]uintptr
+				n := runtime.Callers(2, pcs[:])
 				for _, pc := range pcs[:n] {
 					f := runtime.FuncForPC(pc)
 					if f.Name() == "runtime.sigpanic" {
 						fn = f
 						break
 					}
 				}
-				putUintptrs(pcs)
 			}
 		}()
 		// intentional division by zero fault
@@ -212,20 +210,12 @@ func findSigpanic() *runtime.Func {
 	return fn
 }
 
-var (
-	sigpanic *runtime.Func
-	spOnce   sync.Once
-)
+var sigpanic = findSigpanic()
 
 // Trace returns a CallStack for the current goroutine with element 0
 // identifying the calling function.
 func Trace() CallStack {
-	spOnce.Do(func() {
-		sigpanic = findSigpanic()
-	})
-
 	var pcs [512]uintptr
-
 	n := runtime.Callers(2, pcs[:])
 	cs := make([]Call, n)
 

stack12.go

@@ -120,12 +120,6 @@ func BenchmarkCallVFmt(b *testing.B) {
 	}
 }
 
-func BenchmarkCallerAndVFmt(b *testing.B) {
-	for i := 0; i < b.N; i++ {
-		fmt.Fprint(ioutil.Discard, stack.Caller(0))
-	}
-}
-
 func BenchmarkCallPlusVFmt(b *testing.B) {
 	c := stack.Caller(0)
 	b.ResetTimer()
@@ -202,31 +196,18 @@ func BenchmarkTrace(b *testing.B) {
 	}
 }
 
-func BenchmarkFuncForPC(b *testing.B) {
-	pc, _, _, _ := runtime.Caller(0)
-	pc--
-	var fn *runtime.Func
-	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
-		fn = runtime.FuncForPC(pc)
-	}
-	b.StopTimer()
-	fmt.Fprint(ioutil.Discard, fn.Entry())
-}
-
 func deepStack(depth int, b *testing.B) stack.CallStack {
 	if depth > 0 {
 		return deepStack(depth-1, b)
 	}
 	b.StartTimer()
 	s := stack.Trace()
-	b.StopTimer()
 	return s
 }
 
 func BenchmarkTrace10(b *testing.B) {
-	b.StopTimer()
 	for i := 0; i < b.N; i++ {
+		b.StopTimer()
 		deepStack(10, b)
 	}
 }
@@ -244,3 +225,55 @@ func BenchmarkTrace100(b *testing.B) {
 		deepStack(100, b)
 	}
 }
+
+////////////////
+// Benchmark functions followed by formatting
+////////////////
+
+func BenchmarkCallerAndVFmt(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		fmt.Fprint(ioutil.Discard, stack.Caller(0))
+	}
+}
+
+func BenchmarkTraceAndVFmt(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		fmt.Fprint(ioutil.Discard, stack.Trace())
+	}
+}
+
+func BenchmarkTrace10AndVFmt(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		b.StopTimer()
+		fmt.Fprint(ioutil.Discard, deepStack(10, b))
+	}
+}
+
+////////////////
+// Baseline against package runtime.
+////////////////
+
+func BenchmarkRuntimeCaller(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		runtime.Caller(0)
+	}
+}
+
+func BenchmarkFuncForPC(b *testing.B) {
+	pc, _, _, _ := runtime.Caller(0)
+	pc--
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		runtime.FuncForPC(pc)
+	}
+}
+
+func BenchmarkFuncFileLine(b *testing.B) {
+	pc, _, _, _ := runtime.Caller(0)
+	pc--
+	fn := runtime.FuncForPC(pc)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		fn.FileLine(pc)
+	}
+}