c++ - 如何正确退出使用 Boost Log 的程序？

Question

下面的示例程序运行良好，但 valgrind 显示，退出后仍然可以访问 6 个 block 中的 520 个字节。

#include <iostream>
#include <string>

#include <boost/log/common.hpp>
#include <boost/log/sources/logger.hpp>
#include <boost/log/utility/setup/file.hpp>

#include <boost/phoenix/bind/bind_member_function.hpp>
#include <boost/shared_ptr.hpp>

namespace bl = boost::log;
namespace bp = boost::phoenix;

enum class MySeverityLevel
{
  panic,
  alert,
  critical,
  error,
  warning,
  notice,
  info,
  debug
};

BOOST_LOG_ATTRIBUTE_KEYWORD(Severity, "Severity", MySeverityLevel)
BOOST_LOG_ATTRIBUTE_KEYWORD(Channel, "Channel", std::string)

class Logger
{

public:

  Logger(const std::string& CH, const MySeverityLevel SEV):
  m_log(bl::keywords::channel = CH), m_channel(CH), m_severityMax(SEV)
  {
    m_sink = bl::add_file_log
    (
      bl::keywords::file_name = CH + ".log",
      bl::keywords::filter = bp::bind(&Logger::filter, this, Channel.or_none(), Severity.or_none())
    );
  }

  ~Logger()
  {
    this->terminate();
  }

  void terminate()
  {
    if (m_sink)
    {
      bl::core::get()->remove_sink(m_sink);
      m_sink->flush();
      m_sink.reset();
    }
  }

  void panic(const std::string& S)
  {
    BOOST_LOG_SEV(m_log, MySeverityLevel::panic) << S;
  }

  void debug(const std::string& S)
  {
    BOOST_LOG_SEV(m_log, MySeverityLevel::debug) << S;
  }

private:

  using ChannelValue = bl::value_ref<std::string, tag::Channel>;
  using MySeverityLevelValue = bl::value_ref<MySeverityLevel, tag::Severity>;

  bool filter(const ChannelValue& CH, const MySeverityLevelValue& SEV) const
  {
    if (CH && SEV)
    {
      return (CH.get() == m_channel) && (SEV.get() <= m_severityMax);
    }
    else
    {
      return false;
    }
  }

  bl::sources::severity_channel_logger<MySeverityLevel, std::string> m_log;
  boost::shared_ptr<bl::sinks::sink> m_sink;
  const std::string m_channel;
  const MySeverityLevel m_severityMax;

};

int main()
{
  Logger lgA("A", MySeverityLevel::error);
  lgA.panic("A: Panic");
  lgA.debug("A: Debug");
  lgA.terminate();
}

这是 valgrind 的输出:

hekto@ubuntu:~$ valgrind --leak-check=full --show-leak-kinds=all ./tc0013
==48934== Memcheck, a memory error detector
==48934== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==48934== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==48934== Command: ./tc0013
==48934== 
==48934== 
==48934== HEAP SUMMARY:
==48934==     in use at exit: 520 bytes in 6 blocks
==48934==   total heap usage: 83 allocs, 77 frees, 97,276 bytes allocated
==48934== 
==48934== 8 bytes in 1 blocks are still reachable in loss record 1 of 6
==48934==    at 0x4C3017F: operator new(unsigned long) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==48934==    by 0x4E98C61: boost::log::v2_mt_posix::sources::aux::get_severity_level() (in /usr/lib/x86_64-linux-gnu/libboost_log.so.1.65.1)
==48934==    by 0x11723B: boost::log::v2_mt_posix::sources::aux::severity_level<MySeverityLevel>::set_value(MySeverityLevel) (severity_feature.hpp:135)
==48934==    by 0x115E74: boost::log::v2_mt_posix::record boost::log::v2_mt_posix::sources::basic_severity_logger<boost::log::v2_mt_posix::sources::basic_channel_logger<boost::log::v2_mt_posix::sources::basic_logger<char, boost::log::v2_mt_posix::sources::severity_channel_logger<MySeverityLevel, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::log::v2_mt_posix::sources::single_thread_model>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, MySeverityLevel>::open_record_unlocked<boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> >(boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> const&) (severity_feature.hpp:252)
==48934==    by 0x114961: boost::log::v2_mt_posix::record boost::log::v2_mt_posix::sources::basic_composite_logger<char, boost::log::v2_mt_posix::sources::severity_channel_logger<MySeverityLevel, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::log::v2_mt_posix::sources::single_thread_model, boost::log::v2_mt_posix::sources::features<boost::log::v2_mt_posix::sources::severity<MySeverityLevel>, boost::log::v2_mt_posix::sources::channel<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >::open_record<boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> >(boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> const&) (basic_logger.hpp:575)
==48934==    by 0x1135A5: Logger::panic(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (tc0013.cpp:81)
==48934==    by 0x11097B: main (tc0013.cpp:120)
==48934== 
==48934== 8 bytes in 1 blocks are still reachable in loss record 2 of 6
==48934==    at 0x4C3017F: operator new(unsigned long) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==48934==    by 0x4E9EF69: boost::log::v2_mt_posix::aux::this_thread::get_id() (in /usr/lib/x86_64-linux-gnu/libboost_log.so.1.65.1)
==48934==    by 0x4E8BB96: boost::log::v2_mt_posix::core::open_record(boost::log::v2_mt_posix::attribute_set const&) (in /usr/lib/x86_64-linux-gnu/libboost_log.so.1.65.1)
==48934==    by 0x118DEA: boost::log::v2_mt_posix::record boost::log::v2_mt_posix::sources::basic_logger<char, boost::log::v2_mt_posix::sources::severity_channel_logger<MySeverityLevel, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::log::v2_mt_posix::sources::single_thread_model>::open_record_unlocked<boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> >(boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> const&) (basic_logger.hpp:259)
==48934==    by 0x11825B: boost::log::v2_mt_posix::record boost::log::v2_mt_posix::sources::basic_channel_logger<boost::log::v2_mt_posix::sources::basic_logger<char, boost::log::v2_mt_posix::sources::severity_channel_logger<MySeverityLevel, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::log::v2_mt_posix::sources::single_thread_model>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >::open_record_with_channel_unlocked<boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> >(boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> const&, boost::parameter::void_) (channel_feature.hpp:195)
==48934==    by 0x1172B2: boost::log::v2_mt_posix::record boost::log::v2_mt_posix::sources::basic_channel_logger<boost::log::v2_mt_posix::sources::basic_logger<char, boost::log::v2_mt_posix::sources::severity_channel_logger<MySeverityLevel, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::log::v2_mt_posix::sources::single_thread_model>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >::open_record_unlocked<boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> >(boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> const&) (channel_feature.hpp:171)
==48934==    by 0x115E8B: boost::log::v2_mt_posix::record boost::log::v2_mt_posix::sources::basic_severity_logger<boost::log::v2_mt_posix::sources::basic_channel_logger<boost::log::v2_mt_posix::sources::basic_logger<char, boost::log::v2_mt_posix::sources::severity_channel_logger<MySeverityLevel, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::log::v2_mt_posix::sources::single_thread_model>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, MySeverityLevel>::open_record_unlocked<boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> >(boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> const&) (severity_feature.hpp:253)
==48934==    by 0x114961: boost::log::v2_mt_posix::record boost::log::v2_mt_posix::sources::basic_composite_logger<char, boost::log::v2_mt_posix::sources::severity_channel_logger<MySeverityLevel, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::log::v2_mt_posix::sources::single_thread_model, boost::log::v2_mt_posix::sources::features<boost::log::v2_mt_posix::sources::severity<MySeverityLevel>, boost::log::v2_mt_posix::sources::channel<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >::open_record<boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> >(boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> const&) (basic_logger.hpp:575)
==48934==    by 0x1135A5: Logger::panic(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (tc0013.cpp:81)
==48934==    by 0x11097B: main (tc0013.cpp:120)
==48934== 
==48934== 16 bytes in 1 blocks are still reachable in loss record 3 of 6
==48934==    at 0x4C3017F: operator new(unsigned long) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==48934==    by 0x512A5BA: boost::detail::add_thread_exit_function(boost::detail::thread_exit_function_base*) (in /usr/lib/x86_64-linux-gnu/libboost_thread.so.1.65.1)
==48934==    by 0x4E98C9A: boost::log::v2_mt_posix::sources::aux::get_severity_level() (in /usr/lib/x86_64-linux-gnu/libboost_log.so.1.65.1)
==48934==    by 0x11723B: boost::log::v2_mt_posix::sources::aux::severity_level<MySeverityLevel>::set_value(MySeverityLevel) (severity_feature.hpp:135)
==48934==    by 0x115E74: boost::log::v2_mt_posix::record boost::log::v2_mt_posix::sources::basic_severity_logger<boost::log::v2_mt_posix::sources::basic_channel_logger<boost::log::v2_mt_posix::sources::basic_logger<char, boost::log::v2_mt_posix::sources::severity_channel_logger<MySeverityLevel, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::log::v2_mt_posix::sources::single_thread_model>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, MySeverityLevel>::open_record_unlocked<boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> >(boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> const&) (severity_feature.hpp:252)
==48934==    by 0x114961: boost::log::v2_mt_posix::record boost::log::v2_mt_posix::sources::basic_composite_logger<char, boost::log::v2_mt_posix::sources::severity_channel_logger<MySeverityLevel, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::log::v2_mt_posix::sources::single_thread_model, boost::log::v2_mt_posix::sources::features<boost::log::v2_mt_posix::sources::severity<MySeverityLevel>, boost::log::v2_mt_posix::sources::channel<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >::open_record<boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> >(boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> const&) (basic_logger.hpp:575)
==48934==    by 0x1135A5: Logger::panic(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (tc0013.cpp:81)
==48934==    by 0x11097B: main (tc0013.cpp:120)
==48934== 
==48934== 24 bytes in 1 blocks are still reachable in loss record 4 of 6
==48934==    at 0x4C3017F: operator new(unsigned long) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==48934==    by 0x4E98C84: boost::log::v2_mt_posix::sources::aux::get_severity_level() (in /usr/lib/x86_64-linux-gnu/libboost_log.so.1.65.1)
==48934==    by 0x11723B: boost::log::v2_mt_posix::sources::aux::severity_level<MySeverityLevel>::set_value(MySeverityLevel) (severity_feature.hpp:135)
==48934==    by 0x115E74: boost::log::v2_mt_posix::record boost::log::v2_mt_posix::sources::basic_severity_logger<boost::log::v2_mt_posix::sources::basic_channel_logger<boost::log::v2_mt_posix::sources::basic_logger<char, boost::log::v2_mt_posix::sources::severity_channel_logger<MySeverityLevel, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::log::v2_mt_posix::sources::single_thread_model>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, MySeverityLevel>::open_record_unlocked<boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> >(boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> const&) (severity_feature.hpp:252)
==48934==    by 0x114961: boost::log::v2_mt_posix::record boost::log::v2_mt_posix::sources::basic_composite_logger<char, boost::log::v2_mt_posix::sources::severity_channel_logger<MySeverityLevel, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::log::v2_mt_posix::sources::single_thread_model, boost::log::v2_mt_posix::sources::features<boost::log::v2_mt_posix::sources::severity<MySeverityLevel>, boost::log::v2_mt_posix::sources::channel<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >::open_record<boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> >(boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> const&) (basic_logger.hpp:575)
==48934==    by 0x1135A5: Logger::panic(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (tc0013.cpp:81)
==48934==    by 0x11097B: main (tc0013.cpp:120)
==48934== 
==48934== 24 bytes in 1 blocks are still reachable in loss record 5 of 6
==48934==    at 0x4C3017F: operator new(unsigned long) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==48934==    by 0x512A1BC: boost::detail::make_external_thread_data() (in /usr/lib/x86_64-linux-gnu/libboost_thread.so.1.65.1)
==48934==    by 0x512A5AD: boost::detail::add_thread_exit_function(boost::detail::thread_exit_function_base*) (in /usr/lib/x86_64-linux-gnu/libboost_thread.so.1.65.1)
==48934==    by 0x4E98C9A: boost::log::v2_mt_posix::sources::aux::get_severity_level() (in /usr/lib/x86_64-linux-gnu/libboost_log.so.1.65.1)
==48934==    by 0x11723B: boost::log::v2_mt_posix::sources::aux::severity_level<MySeverityLevel>::set_value(MySeverityLevel) (severity_feature.hpp:135)
==48934==    by 0x115E74: boost::log::v2_mt_posix::record boost::log::v2_mt_posix::sources::basic_severity_logger<boost::log::v2_mt_posix::sources::basic_channel_logger<boost::log::v2_mt_posix::sources::basic_logger<char, boost::log::v2_mt_posix::sources::severity_channel_logger<MySeverityLevel, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::log::v2_mt_posix::sources::single_thread_model>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, MySeverityLevel>::open_record_unlocked<boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> >(boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> const&) (severity_feature.hpp:252)
==48934==    by 0x114961: boost::log::v2_mt_posix::record boost::log::v2_mt_posix::sources::basic_composite_logger<char, boost::log::v2_mt_posix::sources::severity_channel_logger<MySeverityLevel, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::log::v2_mt_posix::sources::single_thread_model, boost::log::v2_mt_posix::sources::features<boost::log::v2_mt_posix::sources::severity<MySeverityLevel>, boost::log::v2_mt_posix::sources::channel<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >::open_record<boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> >(boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> const&) (basic_logger.hpp:575)
==48934==    by 0x1135A5: Logger::panic(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (tc0013.cpp:81)
==48934==    by 0x11097B: main (tc0013.cpp:120)
==48934== 
==48934== 440 bytes in 1 blocks are still reachable in loss record 6 of 6
==48934==    at 0x4C3017F: operator new(unsigned long) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==48934==    by 0x512A03D: boost::detail::make_external_thread_data() (in /usr/lib/x86_64-linux-gnu/libboost_thread.so.1.65.1)
==48934==    by 0x512A5AD: boost::detail::add_thread_exit_function(boost::detail::thread_exit_function_base*) (in /usr/lib/x86_64-linux-gnu/libboost_thread.so.1.65.1)
==48934==    by 0x4E98C9A: boost::log::v2_mt_posix::sources::aux::get_severity_level() (in /usr/lib/x86_64-linux-gnu/libboost_log.so.1.65.1)
==48934==    by 0x11723B: boost::log::v2_mt_posix::sources::aux::severity_level<MySeverityLevel>::set_value(MySeverityLevel) (severity_feature.hpp:135)
==48934==    by 0x115E74: boost::log::v2_mt_posix::record boost::log::v2_mt_posix::sources::basic_severity_logger<boost::log::v2_mt_posix::sources::basic_channel_logger<boost::log::v2_mt_posix::sources::basic_logger<char, boost::log::v2_mt_posix::sources::severity_channel_logger<MySeverityLevel, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::log::v2_mt_posix::sources::single_thread_model>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, MySeverityLevel>::open_record_unlocked<boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> >(boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> const&) (severity_feature.hpp:252)
==48934==    by 0x114961: boost::log::v2_mt_posix::record boost::log::v2_mt_posix::sources::basic_composite_logger<char, boost::log::v2_mt_posix::sources::severity_channel_logger<MySeverityLevel, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::log::v2_mt_posix::sources::single_thread_model, boost::log::v2_mt_posix::sources::features<boost::log::v2_mt_posix::sources::severity<MySeverityLevel>, boost::log::v2_mt_posix::sources::channel<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >::open_record<boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> >(boost::parameter::aux::tagged_argument<boost::log::v2_mt_posix::keywords::tag::severity, MySeverityLevel const> const&) (basic_logger.hpp:575)
==48934==    by 0x1135A5: Logger::panic(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (tc0013.cpp:81)
==48934==    by 0x11097B: main (tc0013.cpp:120)
==48934== 
==48934== LEAK SUMMARY:
==48934==    definitely lost: 0 bytes in 0 blocks
==48934==    indirectly lost: 0 bytes in 0 blocks
==48934==      possibly lost: 0 bytes in 0 blocks
==48934==    still reachable: 520 bytes in 6 blocks
==48934==         suppressed: 0 bytes in 0 blocks
==48934== 
==48934== For counts of detected and suppressed errors, rerun with: -v 
==48934== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

在我的实际应用程序中，Logger 类位于库中，这就是我需要正确终止它的原因(终止由 systemctl 执行)。但是，在退出我的应用程序期间，我仍然在 syslog 中看到异常:

terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::log::v2_mt_posix::system_error> >'

我认为找到一种方法在退出后摆脱这些“6 个 block 中的 520 个字节”将帮助我清楚地终止我的应用程序。

如何正确编写 terminate 函数(见上文)- 为了不让 Boost Log 内部的任何东西都可以访问？

• 操作系统:Ubuntu 18.04.1 LTS
• 编译器:g++ 7.3.0
• 提升:1.65.1
• Valgrind:3.13.0

Answer 1

tl;dr; boost.log 注定要失败，使用其他东西......

这些调用堆栈中的特殊细节是重复调用 boost::detail::add_thread_exit_function，这是显然使用的 boost::this_thread::at_thread_exit 的实现在线程即将结束时执行一些清理操作。但是，此函数不能与系统特定的线程结束 API 和函数(例如 exit)一起使用。如文档中所述:

In particular, returning from main() is equivalent to call to exit(), so will not call any functions registered with at_thread_exit()

因此 boost.log 在从主线程调用时不执行任何清理。此外，(除其他丑陋的东西外)boost.log 使用 Meyer 的单例来保存核心上下文的实例，因此库用户无法控制核心上下文(及其拥有的对象)的生命周期并且容易出现静态 [un] 初始化顺序惨败。