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. This can happen if the first argument to
20			// runtime.Callers is large.
21			//
22			// Return now to avoid processing the zero Frame that would
23			// otherwise be returned by frames.Next below.
24			return
25		}
26
27		pc = pc[:n] // pass only valid pcs to runtime.CallersFrames
28		frames := runtime.CallersFrames(pc)
29
30		// Loop to get frames.
31		// A fixed number of PCs can expand to an indefinite number of Frames.
32		for {
33			frame, more := frames.Next()
34
35			// Process this frame.
36			//
37			// To keep this example's output stable
38			// even if there are changes in the testing package,
39			// stop unwinding when we leave package runtime.
40			if !strings.Contains(frame.File, "runtime/") {
41				break
42			}
43			fmt.Printf("- more:%v | %s\n", more, frame.Function)
44
45			// Check whether there are more frames to process after this one.
46			if !more {
47				break
48			}
49		}
50	}
51
52	b := func() { c() }
53	a := func() { b() }
54
55	a()
56	// Output:
57	// - more:true | runtime.Callers
58	// - more:true | runtime_test.ExampleFrames.func1
59	// - more:true | runtime_test.ExampleFrames.func2
60	// - more:true | runtime_test.ExampleFrames.func3
61	// - more:true | runtime_test.ExampleFrames
62}
63