使用GCC 9.x的WSL Ubuntu 20.04 LTS上的std :: atomic分段错误

问题描述

基于this问题，我扩展了std::mutex，以便可以检查互斥对象是否已被当前线程锁定：

class mutex : public std::mutex
{
  public:
    void lock()
    {
      std::mutex::lock();
      lock_holder_ = std::this_thread::get_id();
    }

    void unlock()
    {
      lock_holder_ = std::thread::id();
      std::mutex::unlock();
    }
 
    [[nodiscard]] bool locked_by_caller() const
    {
      return lock_holder_ == std::this_thread::get_id();
    }

    private:
      std::atomic<std::thread::id> lock_holder_;
};

在具有GCC 9.x的Linux（通过Windows 10上的WSL，使用Ubuntu 20.04 LTS）上，locked_by_caller()函数中引发了分段错误。使用Valgrind时，我得到以下输出：

==2120== Memcheck,a memory error detector
==2120== copyright (C) 2002-2017,and GNU GPL'd,by Julian Seward et al.
==2120== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
==2120== Command: ./WSL-GCC-Debug/eventbus/eventbus.tests
==2120==
==2120== error calling PR_SET_PTRACER,vgdb might block
Running main() from /mnt/d/repositories/eventbus/eventbus-src/out/build/WSL-GCC-Debug/_deps/googletest-src/googletest/src/gtest_main.cc
[==========] Running 4 tests from 2 test cases.
[----------] Global test environment set-up.
[----------] 3 tests from EventBusTestFixture
[ RUN      ] EventBusTestFixture.LambdaRegistrationAndDeregistration
Lambda 3 take by copy.
Lambda 1
Lambda 3 take by copy.
Lambda 1
Lambda 3 take by copy.
Lambda 3 take by copy.
[       OK ] EventBusTestFixture.LambdaRegistrationAndDeregistration (83 ms)
[ RUN      ] EventBusTestFixture.RegisterWhiledispatching
Loop 0 Handler count: 2
==2120== Invalid read of size 8
==2120==    at 0x11C036: std::atomic<std::thread::id>::load(std::memory_order) const (atomic:254)
==2120==    by 0x11AE5A: std::atomic<std::thread::id>::operator std::thread::id() const (atomic:207)
==2120==    by 0x11A22E: dp::event_bus::mutex::locked_by_caller() const (event_bus.hpp:153)

然后gdb输出以下内容：

Program received signal SIGSEGV,Segmentation fault.
std::atomic<std::thread::id>::load (this=0x2a,__m=std::memory_order_seq_cst) at /usr/include/c++/9/atomic:254
254     __atomic_load(std::__addressof(_M_i),__ptr,int(__m));
Segmentation fault

我注意到invalid read of size 8，并在进行研究后发现这是旧版GCC中的bug（也在Stackoverflow上），但在5.x中已修复。因为我在std::thread::id中使用std::atomic，这仍然是对齐问题吗？有没有解决此问题的方法？

完整的代码（用于上下文）在我的Github上。

解决方法

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