docs: function resolveSymbols(pid, trace) {
    var file = path.join(mapFilesDir, 'perf-' + pid + '.map')
  
    if (!fs.existsSync(file)) {
      return {
          resolved: false
        , reason: 'Could not find "' + file + '". Did you run your process with --perf-basic-prof flag?'
      }
    }
  
    var stats = fs.statSync(file)
    if (!stats.size) {
      return {
          resolved: false
        , reason:
            'File "' + file + '" did you properly shut down your process?.\n'
          + 'Try either of the following to ensure the perf-<pid>.map file gets flushes:\n'
          + '  - Handle SIGTERM: https://github.com/thlorenz/talks/blob/gh-pages/jit/slides.md#handle-sigterm\n'
          + '  - Patch v8 and rebuild io.js: https://github.com/thlorenz/talks/blob/gh-pages/jit/slides.md#apply-v8-patch'
      }
    }
  
    var map = fs.readFileSync(file, 'utf8')
    return resolveSymbolsFromMap(map, trace)
  }