Support versions of Go prior to the addition of sync.Pool.

Author: ChrisHines

stack.go

@@ -183,8 +183,7 @@ func findSigpanic() *runtime.Func {
 	func() int {
 		defer func() {
 			if p := recover(); p != nil {
-				pcs := pcStackPool.Get().([]uintptr)
-				pcs = pcs[:cap(pcs)]
+				pcs := getUintptrs()
 				n := runtime.Callers(2, pcs)
 				for _, pc := range pcs[:n] {
 					f := runtime.FuncForPC(pc)
@@ -193,7 +192,7 @@ func findSigpanic() *runtime.Func {
 						break
 					}
 				}
-				pcStackPool.Put(pcs)
+				putUintptrs(pcs)
 			}
 		}()
 		// intentional division by zero fault
@@ -208,19 +207,14 @@ var (
 	spOnce   sync.Once
 )
 
-var pcStackPool = sync.Pool{
-	New: func() interface{} { return make([]uintptr, 1000) },
-}
-
 // Trace returns a CallStack for the current goroutine with element 0
 // identifying the calling function.
 func Trace() CallStack {
 	spOnce.Do(func() {
 		sigpanic = findSigpanic()
 	})
 
-	pcs := pcStackPool.Get().([]uintptr)
-	pcs = pcs[:cap(pcs)]
+	pcs := getUintptrs()
 
 	n := runtime.Callers(2, pcs)
 	cs := make([]Call, n)
@@ -236,7 +230,7 @@ func Trace() CallStack {
 		}
 	}
 
-	pcStackPool.Put(pcs)
+	putUintptrs(pcs)
 
 	return cs
 }

stack12.go

@@ -0,0 +1,25 @@
+// +build !go1.3
+
+package stack
+
+import (
+	"runtime"
+)
+
+func getUintptrs() []uintptr {
+	select {
+	case s := <-pcStackPool:
+		return s[:cap(s)]
+	default:
+		return make([]uintptr, 1000)
+	}
+}
+
+func putUintptrs(s []uintptr) {
+	select {
+	case pcStackPool <- s:
+	default:
+	}
+}
+
+var pcStackPool = make(chan []uintptr, runtime.GOMAXPROCS(n))

stack13.go

@@ -0,0 +1,21 @@
+// +build go1.3
+
+package stack
+
+import (
+	"sync"
+)
+
+func getUintptrs() []uintptr {
+	s := pcStackPool.Get().([]uintptr)
+	s = s[:cap(s)]
+	return s
+}
+
+func putUintptrs(s []uintptr) {
+	pcStackPool.Put(s)
+}
+
+var pcStackPool = sync.Pool{
+	New: func() interface{} { return make([]uintptr, 1000) },
+}