use runtime.Callers

referencing PR:
  * stretchr/testify#1614
  * stretchr/testify#1768

Author: bayashi

witness/trace/trace.go

@@ -13,49 +13,70 @@ func Info(traceFilterFunc ...func(filepath string) bool) []string {
 	var pc uintptr
 	var file string
 	var line int
-	var ok bool
-
 	var funcName string
 	var lastCaller string
 
-	callers := []string{}
-	for i := 0; ; i++ {
-		pc, file, line, ok = runtime.Caller(i)
-		if !ok {
-			break
-		}
-
-		// Avoid panic. https://github.com/stretchr/testify/issues/180
-		if file == "<autogenerated>" {
-			break
-		}
+	const stackFrameBufferSize = 10
+	pcs := make([]uintptr, stackFrameBufferSize)
 
-		f := runtime.FuncForPC(pc)
-		if f == nil {
-			break
-		}
+	callers := []string{}
+	offset := 1
 
-		funcName = f.Name()
+	for {
+		n := runtime.Callers(offset, pcs)
 
-		// testing.tRunner is the standard library function that calls
-		// tests. Subtests are called directly by tRunner, without going through
-		// the Test/Benchmark/Example function that contains the t.Run calls.
-		if funcName == "testing.tRunner" {
+		if n == 0 {
 			break
 		}
 
-		lastCaller = fmt.Sprintf("%s:%d", file, line)
-
-		if len(strings.Split(file, "/")) > 1 && // https://github.com/stretchr/testify/pull/402
-			!skipLibs(file, traceFilterFunc...) {
-			callers = append(callers, lastCaller)
+		frames := runtime.CallersFrames(pcs[:n])
+
+		for {
+			frame, more := frames.Next()
+			pc = frame.PC
+			file = frame.File
+			line = frame.Line
+
+			// This is a huge edge case, but it will panic if this is the case, see #180
+			if file == "<autogenerated>" {
+				break
+			}
+
+			f := runtime.FuncForPC(pc)
+			if f == nil {
+				break
+			}
+			funcName = f.Name()
+
+			// testing.tRunner is the standard library function that calls
+			// tests. Subtests are called directly by tRunner, without going through
+			// the Test/Benchmark/Example function that contains the t.Run calls, so
+			// with subtests we should break when we hit tRunner, without adding it
+			// to the list of callers.
+			if funcName == "testing.tRunner" {
+				break
+			}
+
+			lastCaller = fmt.Sprintf("%s:%d", file, line)
+
+			if len(strings.Split(file, "/")) > 1 && // https://github.com/stretchr/testify/pull/402
+				!skipLibs(file, traceFilterFunc...) {
+				callers = append(callers, lastCaller)
+			}
+
+			funcName = funcName[strings.LastIndexByte(funcName, '.')+1:]
+			if isGolangTestFunc(funcName) {
+				break
+			}
+
+
+			if !more {
+				break
+			}
 		}
 
-		funcName = funcName[strings.LastIndexByte(funcName, '.')+1:]
-
-		if isGolangTestFunc(funcName) {
-			break
-		}
+		// Next batch
+		offset += cap(pcs)
 	}
 
 	if len(callers) == 0 {
@@ -75,15 +96,15 @@ func skipLibs(filepath string, traceFilterFunc ...func(filepath string) bool) bo
 	return false
 }
 
-func isGolangTestFunc(name string) bool {
+func isGolangTestFunc(funcName string) bool {
 	for _, prefix := range [3]string{"Test", "Benchmark", "Example"} {
-		if !strings.HasPrefix(name, prefix) {
+		if !strings.HasPrefix(funcName, prefix) {
 			continue
 		}
-		if len(name) == len(prefix) {
+		if len(funcName) == len(prefix) {
 			return true
 		}
-		r, _ := utf8.DecodeRuneInString(name[len(prefix):])
+		r, _ := utf8.DecodeRuneInString(funcName[len(prefix):])
 		if !unicode.IsLower(r) {
 			return true
 		}