base/debug/task_trace.cc

// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/debug/task_trace.h"

#include <algorithm>
#include <iostream>

#include "base/pending_task.h"
#include "base/task/common/task_annotator.h"

namespace base {
namespace debug {

TaskTrace::TaskTrace() {
  const PendingTask* current_task = TaskAnnotator::CurrentTaskForThread();
  if (!current_task)
    return;
  std::array<const void*, PendingTask::kTaskBacktraceLength + 1> task_trace;
  task_trace[0] = current_task->posted_from.program_counter();
  std::copy(current_task->task_backtrace.begin(),
            current_task->task_backtrace.end(), task_trace.begin() + 1);
  size_t length = 0;
  while (length < task_trace.size() && task_trace[length])
    ++length;
  if (length == 0)
    return;
  stack_trace_.emplace(task_trace.data(), length);
  trace_overflow_ = current_task->task_backtrace_overflow;
}

bool TaskTrace::empty() const {
  return !stack_trace_.has_value();
}

void TaskTrace::Print() const {
  OutputToStream(&std::cerr);
}

void TaskTrace::OutputToStream(std::ostream* os) const {
  *os << "Task trace:" << std::endl;
  if (!stack_trace_) {
    *os << "No active task.";
    return;
  }
  *os << *stack_trace_;
  if (trace_overflow_) {
    *os << "Task trace buffer limit hit, update "
           "PendingTask::kTaskBacktraceLength to increase."
        << std::endl;
  }
}

base::span<const void* const> TaskTrace::AddressesForTesting() const {
  if (empty())
    return {};
  size_t count = 0;
  const void* const* addresses = stack_trace_->Addresses(&count);
  return {addresses, count};
}

std::ostream& operator<<(std::ostream& os, const TaskTrace& task_trace) {
  task_trace.OutputToStream(&os);
  return os;
}

}  // namespace debug
}  // namespace base