在发布模式下提升 ASIO 段错误
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【中文标题】在发布模式下提升 ASIO 段错误【英文标题】：Boost ASIO segfault in release mode 【发布时间】：2021-01-01 22:32:55 【问题描述】：我制作了这个小的说明性代码，它展示了我正在编写的程序所遇到的相同问题：即，它在调试模式下工作正常，在发布时出现段错误。问题似乎是 ui_context 在发布模式下，当被调用来运行它分配的工作时，是 nullptr。
在 Fedora 33 中运行，使用 g++ (GCC) 10.2.1 20201125 (Red Hat 10.2.1-9) 和 clang version 11.0.0 (Fedora 11.0.0-2.fc33) 。两个编译器的行为方式相同。 Boost 版本是 1.75。
代码：
#include <iostream>
#include <vector>
#include <memory>
#include <chrono>
#include <thread>
#include <boost/asio.hpp>
#include <boost/signals2.hpp>
constexpr auto MAX_LOOP_COUNT = 100;
class network_client : public std::enable_shared_from_this<network_client>
private:
using Signal = boost::signals2::signal<void(int)>;
public:
network_client(boost::asio::io_context &context) :
strand(boost::asio::make_strand(context))
std::cout << "network client created" << std::endl;
void doNetworkWork()
std::cout << "doing network work" << std::endl;
boost::asio::post(strand,std::bind(&network_client::onWorkComplete,shared_from_this()));
void onWorkComplete()
std::this_thread::sleep_for(std::chrono::milliseconds(10));
std::cout << "signalling completion" << " from thread id:" << std::this_thread::get_id() << std::endl;
signal(42);
void workCompleteHandler(const typename Signal::slot_type &slot)
signal.connect(slot);
private :
boost::asio::strand<boost::asio::io_context::executor_type> strand;
Signal signal;
;
class network_client_producer
public :
network_client_producer() : work(boost::asio::make_work_guard(context))
using run_function = boost::asio::io_context::count_type (boost::asio::io_context::*)();
for (int i = 0; i < 2; i++)
context_threads.emplace_back(std::bind(static_cast<run_function>(&boost::asio::io_context::run), std::ref(context)));
~network_client_producer()
context.stop();
for(auto&& thread : context_threads)
if(thread.joinable())
thread.join();
using NetworkClientPtr = std::shared_ptr<network_client>;
NetworkClientPtr makeNetworkClient()
return std::make_shared<network_client>(context);
private :
boost::asio::io_context context;
std::vector<std::thread> context_threads;
boost::asio::executor_work_guard<boost::asio::io_context::executor_type> work;
;
class desktop : public std::enable_shared_from_this<desktop>
public:
desktop(const boost::asio::io_context::executor_type &executor):executor(executor)
void doSomeNetworkWork()
auto client = client_producer.makeNetworkClient();
client->workCompleteHandler([self = shared_from_this()](int i)
//post work into the UI thread
std::cout << "calling into the uiThreadWork with index " << i << " from thread id:" << std::this_thread::get_id() << std::endl;
boost::asio::post(self->executor, std::bind(&desktop::uiThreadWorkComplete, self, i));
);
client->doNetworkWork();
void showDesktop()
std::this_thread::sleep_for(std::chrono::milliseconds(20));
public:
void uiThreadWorkComplete(int i)
std::cout << "Called in the UI thread with index:" << i << ", on thread id:" << std::this_thread::get_id() << std::endl;
private:
const boost::asio::io_context::executor_type& executor;
network_client_producer client_producer;
;
int main()
std::cout << "Starting application. Main thread id:"<<std::this_thread::get_id() << std::endl;
int count = 0;
boost::asio::io_context ui_context;
auto work = boost::asio::make_work_guard(ui_context);
/*auto work = boost::asio::require(ui_context.get_executor(),
boost::asio::execution::outstanding_work.tracked);*/
auto ui_desktop = std::make_shared<desktop>(ui_context.get_executor());
ui_desktop->doSomeNetworkWork();
while(true)
ui_context.poll_one();
ui_desktop->showDesktop();
if (count >= MAX_LOOP_COUNT)
break;
count++;
ui_context.stop();
std::cout << "Stopping application" << std::endl;
return 0;
用g++ -std=c++17 -g -o main -pthread -O3 main.cpp 编译它和
在 gdb 中运行它我得到了这个：
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
Starting application. Main thread id:140737348183872
[New Thread 0x7ffff7a51640 (LWP 27082)]
[New Thread 0x7ffff7250640 (LWP 27083)]
network client created
doing network work
signalling completion from thread id:140737348179520
calling into the uiThreadWork with index 42 from thread id:140737348179520
Thread 2 "main" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff7a51640 (LWP 27082)]
0x000000000040b7b8 in boost::asio::io_context::basic_executor_type<std::allocator<void>, 0u>::execute<std::_Bind<void (desktop::*(std::shared_ptr<desktop>, int))(int)> >(std::_Bind<void (desktop::*(std::shared_ptr<desktop>, int))(int)>&&) const (this=<optimized out>, f=...) at /usr/local/include/boost/asio/impl/io_context.hpp:309
309 io_context_->impl_.post_immediate_completion(p.p,
在没有任何优化的情况下编译 g++ -std=c++17 -g -o main -pthread -O0 main.cpp 可以按预期工作。
我试图让它尽可能接近实际执行网络 IO 的真实程序，这就是为什么我在其中放置了那条链。
很明显，我在这里做错了什么。问题是：问题是什么？ 感谢您的任何指点。
【问题讨论】：
【参考方案1】：添加消毒剂-fsanitize=undefined,address：
Starting application. Main thread id:139902898299968
network client created
doing network work
signalling completion from thread id:139902399940352
calling into the uiThreadWork with index 42 from thread id:139902399940352
=================================================================
==29084==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7ffc8393d7c0 at pc 0x000000507ce0 bp 0x7f3d90d9e3d0 sp 0x7f3d90d9e3c8
READ of size 8 at 0x7ffc8393d7c0 thread T1
#0 0x507cdf in boost::asio::io_context::basic_executor_type<std::allocator<void>, ...
#1 0x507cdf in boost::asio::detail::initiate_post_with_executor<boost::asio::io_co...
#2 0x507cdf in auto boost::asio::post<boost::asio::io_context::basic_executor_type...
#3 0x5077cf in desktop::doSomeNetworkWork()::'lambda'(int)::operator()(int) const ...
#4 0x518ce2 in boost::function1<void, int>::operator()(int) const /home/sehe/custo...
#5 0x518481 in boost::signals2::detail::void_type boost::signals2::detail::call_wi...
#6 0x518481 in boost::signals2::detail::void_type boost::signals2::detail::variadi...
#7 0x517f43 in boost::signals2::detail::slot_call_iterator_t<boost::signals2::deta...
#8 0x516397 in void boost::signals2::optional_last_value<void>::operator()<boost::...
#9 0x516397 in void boost::signals2::detail::combiner_invoker<void>::operator()<bo...
#10 0x516397 in boost::signals2::detail::signal_impl<void (int), boost::signals2::...
#11 0x50d9d4 in network_client::onWorkComplete() /home/sehe/Projects/***...
#12 0x51021d in void std::_Bind<void (network_client::* (std::shared_ptr<network_c...
#13 0x51021d in void boost::asio::asio_handler_invoke<std::_Bind<void (network_cli...
#14 0x51021d in void boost_asio_handler_invoke_helpers::invoke<std::_Bind<void (ne...
#15 0x51021d in boost::asio::detail::executor_op<std::_Bind<void (network_client::...
#16 0x51188e in boost::asio::detail::strand_executor_service::invoker<boost::asio:...
#17 0x514311 in void boost::asio::asio_handler_invoke<boost::asio::detail::strand_...
#18 0x514311 in void boost_asio_handler_invoke_helpers::invoke<boost::asio::detail...
#19 0x514311 in boost::asio::detail::executor_op<boost::asio::detail::strand_execu...
#20 0x4d8704 in boost::asio::detail::scheduler::do_run_one(boost::asio::detail::co...
#21 0x4d70dc in boost::asio::detail::scheduler::run(boost::system::error_code&) /h...
#22 0x523a6e in boost::asio::io_context::run() /home/sehe/custom/boost_1_75_0/boos...
#23 0x5258ef in unsigned long std::_Bind<unsigned long (boost::asio::io_context::*...
#24 0x5258ef in unsigned long std::__invoke_impl<unsigned long, std::_Bind<unsigne...
#25 0x5258ef in std::__invoke_result<std::_Bind<unsigned long (boost::asio::io_con...
#26 0x5258ef in unsigned long std::thread::_Invoker<std::tuple<std::_Bind<unsigned...
#27 0x7f3da660bd7f (/usr/lib/x86_64-linux-gnu/libstdc++.so.6+0xd0d7f)
#28 0x7f3da5f856da in start_thread (/lib/x86_64-linux-gnu/libpthread.so.0+0x76da)
#29 0x7f3da5a9671e in clone /build/glibc-S7xCS9/glibc-2.27/misc/../sysdeps/unix/sy...
Address 0x7ffc8393d7c0 is located in stack of thread T0 at offset 224 in frame
#0 0x4cb30f in main /home/sehe/Projects/***/test.cpp:109
This frame has 6 object(s):
[32, 40) 'ref.tmp.i85' (line 96)
[64, 80) 'ref.tmp.i'
[96, 112) 'ui_context' (line 113)
[128, 152) 'work' (line 114)
[192, 208) 'ui_desktop' (line 117)
[224, 240) 'ref.tmp' (line 117) <== Memory access at offset 224 is inside this variable
HINT: this may be a false positive if your program uses some custom stack unwind mechanism, swapcontext or vfork
(longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-use-after-scope /home/sehe/custom/boost_1_75_0/boost/asio/io_context.hpp:678:25 in boost::asio::io_context::basic_executor_type<std::allocator<void>, 0u>::basic_executor_type(boost::asio::io_context::basic_executor_type<std::allocator<void>, 0u> const&)
Shadow bytes around the buggy address:
0x10001071faa0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10001071fab0: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 f8 f2 f2 f2
0x10001071fac0: f8 f2 f2 f2 00 f2 f2 f2 00 00 f3 f3 00 00 00 00
0x10001071fad0: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
0x10001071fae0: 00 f2 f2 f2 f8 f8 f2 f2 00 00 f2 f2 00 00 00 f2
=>0x10001071faf0: f2 f2 f2 f2 00 00 f2 f2[f8]f8 f3 f3 00 00 00 00
0x10001071fb00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10001071fb10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10001071fb20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10001071fb30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x10001071fb40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
Shadow gap: cc
Thread T1 created by T0 here:
#0 0x483a6a in pthread_create (/home/sehe/Projects/***/sotest+0x483a6a)
#1 0x7f3da660c014 in std::thread::_M_start_thread(std::unique_ptr<std::thread::_State, std...
#2 0x5241d4 in void std::vector<std::thread, std::allocator<std::thread> >::_M_realloc_ins...
#3 0x523517 in std::thread& std::vector<std::thread, std::allocator<std::thread> >::emplac...
==29084==ABORTING
这是你的罪魁祸首。
寻找罪魁祸首
This frame has 6 object(s):
[32, 40) 'ref.tmp.i85' (line 96)
[64, 80) 'ref.tmp.i'
[96, 112) 'ui_context' (line 113)
[128, 152) 'work' (line 114)
[192, 208) 'ui_desktop' (line 117)
[224, 240) 'ref.tmp' (line 117) <== Memory access at offset 224 is inside this variable
那是什么变量？显然在行中
auto ui_desktop = std::make_shared<desktop>(ui_context.get_executor());
有一个临时的被保留参考。它必须是 ui_context.get_executor()，因为 ui_desktop 已命名并且具有“明显”的生命周期。
果然desktop通过引用声明了它的executor成员：
const boost::asio::io_context::executor_type& executor;
这是一个明显的错误。执行器是不是服务或执行上下文，并且被设计成廉价可复制和按值传递。修复很简单：
boost::asio::io_context::executor_type executor;
奖金
作为奖励，这是一个运行演示半秒的简化版本。备注：
使用线程池而不是手动滚动有缺陷的池 考虑不要在执行上下文中使用.stop()，或者忘记多余的单词保护？
Live On Compiler Explorer
#include <iostream>
#include <chrono>
#include <iomanip>
#include <memory>
#include <thread>
#include <boost/asio.hpp>
#include <boost/signals2.hpp>
namespace
using namespace std::chrono_literals;
auto now = std::chrono::high_resolution_clock::now;
auto elapsed = [start=now()] return (now()-start)/1ms; ;
inline std::string thread_hash()
static constexpr std::hash<std::thread::id> h;
std::ostringstream oss;
oss << std::hex << std::setw(2) << std::setfill('0')
<< h(std::this_thread::get_id()) % 0xff;
return oss.str();
auto trace = [](auto const&... args)
std::cout << "thread #" << thread_hash() << " at t+" << std::setw(3) << elapsed() << "ms\t";
(std::cout << ... << args) << std::endl;
;
// namespace
struct network_client : std::enable_shared_from_this<network_client>
explicit network_client(const boost::asio::any_io_executor& context) : strand(make_strand(context))
trace("network client created");
void doNetworkWork()
trace("doing network work");
post(strand, std::bind(&network_client::onWorkComplete, shared_from_this()));
void onWorkComplete()
std::this_thread::sleep_for(10ms);
trace("signalling completion");
signal(42);
template <typename F> void workCompleteHandler(F slot)
signal.connect(std::move(slot));
private:
boost::asio::strand<boost::asio::any_io_executor> strand;
using Signal = boost::signals2::signal<void(int)>;
Signal signal;
;
struct network_client_producer
auto makeNetworkClient()
return std::make_shared<network_client>(context_threads.get_executor());
private :
boost::asio::thread_pool context_threads 2;
;
struct desktop : std::enable_shared_from_this<desktop>
explicit desktop(boost::asio::io_context::executor_type executor) : executor(std::move(executor))
void doSomeNetworkWork()
auto client = client_producer.makeNetworkClient();
client->workCompleteHandler([this, self = shared_from_this()](int i)
// post work into the UI thread
trace("calling into the uiThreadWork with index ", i);
post(executor, std::bind(&desktop::uiThreadWorkComplete, self, i));
);
client->doNetworkWork();
static void showDesktop()
trace("showDesktop");
std::this_thread::sleep_for(20ms);
void uiThreadWorkComplete(int i) const
trace("Called in the UI thread with index:", i);
private:
boost::asio::io_context::executor_type executor;
network_client_producer client_producer;
;
int main()
trace("Starting application. Main thread is #", thread_hash());
boost::asio::io_context ui_context;
auto work = boost::asio::make_work_guard(ui_context);
/*auto work = boost::asio::require(ui_context.get_executor(),
boost::asio::execution::outstanding_work.tracked);*/
auto ui_desktop = std::make_shared<desktop>(ui_context.get_executor());
ui_desktop->doSomeNetworkWork();
for (auto deadline = now() + 0.5s; now() < deadline;)
ui_context.poll_one();
ui_desktop->showDesktop();
trace("Stopping application");
work.reset();
ui_context.run();
// ui_context.stop();
trace("Bye\n");
打印
thread #97 at t+ 0ms Starting application. Main thread is #97
thread #97 at t+ 0ms network client created
thread #97 at t+ 1ms doing network work
thread #97 at t+ 1ms showDesktop
thread #2d at t+ 11ms signalling completion
thread #2d at t+ 11ms calling into the uiThreadWork with index 42
thread #97 at t+ 21ms Called in the UI thread with index:42
thread #97 at t+ 21ms showDesktop
thread #97 at t+ 41ms showDesktop
thread #97 at t+ 61ms showDesktop
thread #97 at t+ 81ms showDesktop
thread #97 at t+101ms showDesktop
thread #97 at t+122ms showDesktop
thread #97 at t+142ms showDesktop
thread #97 at t+162ms showDesktop
thread #97 at t+182ms showDesktop
thread #97 at t+202ms showDesktop
thread #97 at t+222ms showDesktop
thread #97 at t+242ms showDesktop
thread #97 at t+262ms showDesktop
thread #97 at t+282ms showDesktop
thread #97 at t+302ms showDesktop
thread #97 at t+323ms showDesktop
thread #97 at t+343ms showDesktop
thread #97 at t+363ms showDesktop
thread #97 at t+383ms showDesktop
thread #97 at t+403ms showDesktop
thread #97 at t+423ms showDesktop
thread #97 at t+443ms showDesktop
thread #97 at t+463ms showDesktop
thread #97 at t+483ms showDesktop
thread #97 at t+503ms Stopping application
thread #97 at t+504ms Bye
【讨论】：
添加了一个演示 Live On Compiler Explorer，其中包含一些简化建议 谢谢，很有教育意义。 执行器既不是服务也不是执行上下文，它们被设计为可廉价复制并按值传递。 我不知道。谢谢你启发我。【参考方案2】：问题是您的executor 是对临时对象的引用。在您的main 方法中，您调用ui_context.get_executor()，它返回一个临时对象。您将临时值传递给desktop 构造函数，该构造函数将对该对象的引用存储在成员变量executor 中。在main 中的auto ui_desktop = ... 行完成后，临时对象超出范围，executor 持有的引用变为无效。
在编译启用地址清理的程序时也会检测到此问题 (-fsanitize=address)：
==24629==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7ffe8bee0270 at pc 0x5584b2d89b0c bp 0x7f3ac42fd970 sp 0x7f3ac42fd960
READ of size 8 at 0x7ffe8bee0270 thread T1
#0 0x5584b2d89b0b in boost::asio::io_context::basic_executor_type<std::allocator<void>, 0u>::basic_executor_type(boost::asio::io_context::basic_executor_type<std::allocator<void>, 0u> const&) /usr/include/boost/asio/io_context.hpp:678
...
我怀疑在您的调试版本中，临时对象的寿命会稍长一些，即临时对象占用的堆栈内存不会在临时对象超出范围后立即回收。而在发布版本中，应用了更积极的优化，这导致内存被更快地回收，从而更快地使引用失效，然后在访问引用时使程序崩溃。
要解决这个问题，您必须确保get_executor 返回的执行程序不会超出范围，以便ui_desktop 对象持有的引用仍然有效。例如，您可以将get_executor 的结果分配给main 中的变量：
auto executorui_context.get_executor();
auto ui_desktop = std::make_shared<desktop>(executor);
【讨论】：
哇，是的，你是对的。我不知道为什么我认为context.get_executor() 会给我一个执行者，只要上下文存在，它就会存在。老实说，我认为这是上下文本身的一部分。但这现在是有道理的。以上是关于在发布模式下提升 ASIO 段错误的主要内容，如果未能解决你的问题，请参考以下文章