src/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. 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 }