c++ - 将 C++11 std::thread 移植到 boost::thread 编译问题

Question

我正在尝试使用 boost::thread 将 C++11 std::thread 代码移植到 VC9 (VS 2008)。下面的“等效”C++11 代码在 msvc12 上编译良好:

#include <iostream>
#include <thread>
#include <vector>
#include <algorithm>
#include <cassert>

void thFun(int i) 
{
    std::cout << "Hello from thread " << i << " !\n";
}
int main()
{
    std::vector<std::thread> workers;
    for (int i = 0; i < 10; ++i)
    {
        auto th = std::thread(&thFun, i);
        workers.push_back(std::move(th));
        assert(!th.joinable());
    }
    std::cout << "Hello from main!\n";
    std::for_each(workers.begin(), workers.end(), [](std::thread& th)
    {
        assert(th.joinable());
        th.join(); 
    });
    return 0;
}    

我想使用 msvc9 编译器和 Boost 1.55 将代码移植到 C++03。如何解决以下编译错误:

#include <iostream>
#include <boost/thread.hpp>
#include <cassert>
#include <boost/foreach.hpp>
#include <boost/container/vector.hpp>

void thFun(int i) 
{
    std::cout << "Hello from thread " << i << " !\n";
}
void foo(boost::thread& th)
{
    assert(th.joinable());
    th.join(); 
}

int main()
{    
    boost::container::vector<boost::thread> workers;
            for (int i = 0; i < 10; ++i)
    {
        BOOST_AUTO(th, boost::thread(&thFun, i));
        workers.push_back(boost::move(th));
        assert(!th.joinable());
    }

    std::cout << "Hello from main!\n";
    BOOST_FOREACH(boost::thread& t, workers)
    {
        foo(t);
    }
    return 0;
}

编译错误为:

d:\program data\boost\boost_1_55_0\boost\preprocessor\iteration\detail\local.hpp(37): error C2770: invalid explicit template argument(s) for '::boost::move_detail::enable_if_c<boost::enable_move_utility_emulation<T>::value&&!boost::move_detail::is_rv<T>::value,const T&>::type boost::forward(const ::boost::move_detail::identity<T>::type &)'
          d:\program data\boost\boost_1_55_0\boost\move\utility.hpp(78) : see declaration of 'boost::forward'
          d:\program data\boost\boost_1_55_0\boost\container\vector.hpp(1797) : see reference to function template instantiation 'void boost::container::allocator_traits<Alloc>::construct<T,T>(Alloc &,T *,const P0 &)' being compiled
          with
          [
              Alloc=std::allocator<boost::thread>,
              T=boost::thread,
              P0=boost::thread
          ]
          d:\program data\boost\boost_1_55_0\boost\container\vector.hpp(1791) : while compiling class template member function 'void boost::container::vector<T>::priv_push_back(const T &)'
          with
          [
              T=boost::thread
          ]
          d:\work\boostthreadscratch\boostthreadscratch\boostthreadscratch.cpp(19) : see reference to class template instantiation 'boost::container::vector<T>' being compiled
          with
          [
              T=boost::thread
          ]

Answer 1

放在开头:

#define BOOST_THREAD_USES_MOVE

参见 here以供引用。它启用由 Boost.Move (boost::move) 为 boost::thread 提供的仿真，这在 Boost.Thread 版本 2 中默认禁用(可能是在您的案例中由 MSVC9 使用)。