1// Copyright 2017 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package runtime_test
6
7import (
8	"fmt"
9	"runtime"
10	"strings"
11)
12
13func ExampleFrames() {
14	c := func() {
15		// Ask runtime.Callers for up to 10 pcs, including runtime.Callers itself.
16		pc := make([]uintptr, 10)
17		n := runtime.Callers(0, pc)
18		if n == 0 {
19			// No pcs available. Stop now.
20			// This can happen if the first argument to runtime.Callers is large.
21			return
22		}
23
24		pc = pc[:n] // pass only valid pcs to runtime.CallersFrames
25		frames := runtime.CallersFrames(pc)
26
27		// Loop to get frames.
28		// A fixed number of pcs can expand to an indefinite number of Frames.
29		for {
30			frame, more := frames.Next()
31			// To keep this example's output stable
32			// even if there are changes in the testing package,
33			// stop unwinding when we leave package runtime.
34			if !strings.Contains(frame.File, "runtime/") && !strings.Contains(frame.File, "/test/") {
35				break
36			}
37			fmt.Printf("- more:%v | %s\n", more, frame.Function)
38			if !more {
39				break
40			}
41		}
42	}
43
44	b := func() { c() }
45	a := func() { b() }
46
47	a()
48	// Output:
49	// - more:true | runtime.Callers
50	// - more:true | runtime_test.ExampleFrames..func1
51	// - more:true | runtime_test.ExampleFrames..func2
52	// - more:true | runtime_test.ExampleFrames..func3
53	// - more:true | runtime_test.ExampleFrames
54}
55