libgo/go/runtime/example_test.go

   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
   5 package runtime_test
   6
   7 import (
   8         "fmt"
   9         "runtime"
  10         "strings"
  11 )
  12
  13 func 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/") {
  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 }