src/runtime/example_test.go

// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package runtime_test

import (
	"fmt"
	"runtime"
	"strings"
)

func ExampleFrames() {
	c := func() {
		// Ask runtime.Callers for up to 10 PCs, including runtime.Callers itself.
		pc := make([]uintptr, 10)
		n := runtime.Callers(0, pc)
		if n == 0 {
			// No PCs available. This can happen if the first argument to
			// runtime.Callers is large.
			//
			// Return now to avoid processing the zero Frame that would
			// otherwise be returned by frames.Next below.
			return
		}

		pc = pc[:n] // pass only valid pcs to runtime.CallersFrames
		frames := runtime.CallersFrames(pc)

		// Loop to get frames.
		// A fixed number of PCs can expand to an indefinite number of Frames.
		for {
			frame, more := frames.Next()

			// Process this frame.
			//
			// To keep this example's output stable
			// even if there are changes in the testing package,
			// stop unwinding when we leave package runtime.
			if !strings.Contains(frame.File, "runtime/") {
				break
			}
			fmt.Printf("- more:%v | %s\n", more, frame.Function)

			// Check whether there are more frames to process after this one.
			if !more {
				break
			}
		}
	}

	b := func() { c() }
	a := func() { b() }

	a()
	// Output:
	// - more:true | runtime.Callers
	// - more:true | runtime_test.ExampleFrames.func1
	// - more:true | runtime_test.ExampleFrames.func2
	// - more:true | runtime_test.ExampleFrames.func3
	// - more:true | runtime_test.ExampleFrames
}