问题出在人们有类似问题的情况下:经过与Mathworks支持的一些讨论之后，原来是系统boost和Matlab附带的boost库之间的冲突:当我使用system boost header 进行编译并与(较旧)的Matlab Boost库，它已分段。当我编译并与系统boost动态链接时，然后它动态加载Matlab boost库时，它将永远挂起。

静态链接到系统boost的工作原理，以及为Matlab随附的boost版本下载正确的 header 并进行编译时也是如此。当然，Mac版本的Matlab的文件名中没有版本号，尽管Linux和据说的Windows版本都有。 R2011b使用 boost 1.44作为引用。

我有一些多线程代码在直接编译时可以正常工作，但是当从Matlab mex接口(interface)调用它时会出现段错误和/或死锁。我不知道不同的环境是否正在揭示我的代码中的缺陷或什么缺陷，但是我无法弄清楚...。

我在三种机器配置上运行此程序(尽管有几个CentOS机器):

#include <queue>
#include <vector>

#include <boost/thread.hpp>
#include <boost/utility.hpp>

#ifndef NO_MEX
#include "mex.h"
#endif

class Worker : boost::noncopyable {
    boost::mutex &jobs_mutex;
    std::queue<size_t> &jobs;

    boost::mutex &results_mutex;
    std::vector<double> &results;

    public:

    Worker(boost::mutex &jobs_mutex, std::queue<size_t> &jobs,
           boost::mutex &results_mutex, std::vector<double> &results)
        :
            jobs_mutex(jobs_mutex), jobs(jobs),
            results_mutex(results_mutex), results(results)
    {}

    void operator()() {
        size_t i;
        float r;

        while (true) {
            // get a job
            {
                boost::mutex::scoped_lock lk(jobs_mutex);
                if (jobs.size() == 0)
                    return;

                i = jobs.front();
                jobs.pop();
            }

            // do some "work"
            r = rand() / 315.612;

            // write the results
            {
                boost::mutex::scoped_lock lk(results_mutex);
                results[i] = r;
            }
        }
    }
};

std::vector<double> doWork(size_t n) {
    std::vector<double> results;
    results.resize(n);

    boost::mutex jobs_mutex, results_mutex;

    std::queue<size_t> jobs;
    for (size_t i = 0; i < n; i++)
        jobs.push(i);

    Worker w1(jobs_mutex, jobs, results_mutex, results);
    boost::thread t1(boost::ref(w1));

    Worker w2(jobs_mutex, jobs, results_mutex, results);
    boost::thread t2(boost::ref(w2));

    t1.join();
    t2.join();

    return results;
}

#ifdef NO_MEX
int main() {
#else
void mexFunction(int nlhs, mxArray **plhs, int nrhs, const mxArray **prhs) {
#endif
    std::vector<double> results = doWork(10);
    for (size_t i = 0; i < results.size(); i++)
        printf("%g ", results[i]);
    printf("\n");
}

$ g++ -o testing testing.cpp -lboost_thread-mt -DNO_MEX
$ ./testing
53.2521 895008 5.14128e+06 3.12074e+06 3.62505e+06 1.48984e+06 320100 4.61912e+06 4.62206e+06 6.35983e+06

99      Worker w1(jobs_mutex, jobs, results_mutex, results);
(gdb) 
100     boost::thread t1(boost::ref(w1));
(gdb) 
[New Thread 0x47814940 (LWP 19390)]
102     Worker w2(jobs_mutex, jobs, results_mutex, results);
(gdb) 
103     boost::thread t2(boost::ref(w2));
(gdb) 
[Thread 0x47814940 (LWP 19390) exited]
[New Thread 0x48215940 (LWP 19391)]
[Thread 0x48215940 (LWP 19391) exited]
105     t1.join();

106     t1.join();
(gdb)
[Thread 0x47814940 (LWP 20255) exited]
[Thread 0x48215940 (LWP 20256) exited]
# still hanging

Thread 2:
Conflicting load by thread 2 at 0x0004b518 size 8
   at 0x3B837: void boost::call_once<void (*)()>(boost::once_flag&, void (*)()) (in /usr/local/boost/boost_1_48_0/stage/lib/libboost_thread-mt-d.dylib)
   by 0x2BCD4: boost::detail::set_current_thread_data(boost::detail::thread_data_base*) (in /usr/local/boost/boost_1_48_0/stage/lib/libboost_thread-mt-d.dylib)
   by 0x2BA62: thread_proxy (in /usr/local/boost/boost_1_48_0/stage/lib/libboost_thread-mt-d.dylib)
   by 0x2D88BE: _pthread_start (in /usr/lib/system/libsystem_c.dylib)
   by 0x2DBB74: thread_start (in /usr/lib/system/libsystem_c.dylib)
Allocation context: Data section of r/local/boost/boost_1_48_0/stage/lib/libboost_thread-mt-d.dylib
Other segment start (thread 1)
   at 0x41B4DE: __bsdthread_create (in /usr/lib/system/libsystem_kernel.dylib)
   by 0x2B959: boost::thread::start_thread() (in /usr/local/boost/boost_1_48_0/stage/lib/libboost_thread-mt-d.dylib)
   by 0x100001B54: boost::thread::thread<boost::reference_wrapper<Worker> >(boost::reference_wrapper<Worker>, boost::disable_if<boost::is_convertible<boost::reference_wrapper<Worker>&, boost::detail::thread_move_t<boost::reference_wrapper<Worker> > >, boost::thread::dummy*>::type) (thread.hpp:204)
   by 0x100001434: boost::thread::thread<boost::reference_wrapper<Worker> >(boost::reference_wrapper<Worker>, boost::disable_if<boost::is_convertible<boost::reference_wrapper<Worker>&, boost::detail::thread_move_t<boost::reference_wrapper<Worker> > >, boost::thread::dummy*>::type) (thread.hpp:201)
   by 0x100000B50: doWork(unsigned long) (testing.cpp:66)
   by 0x100000CE1: main (testing.cpp:82)
Other segment end (thread 1)
   at 0x41BBCA: __psynch_cvwait (in /usr/lib/system/libsystem_kernel.dylib)
   by 0x3C0C3: boost::condition_variable::wait(boost::unique_lock<boost::mutex>&) (in /usr/local/boost/boost_1_48_0/stage/lib/libboost_thread-mt-d.dylib)
   by 0x2D28A: boost::thread::join() (in /usr/local/boost/boost_1_48_0/stage/lib/libboost_thread-mt-d.dylib)
   by 0x100000B61: doWork(unsigned long) (testing.cpp:72)
   by 0x100000CE1: main (testing.cpp:82)

最佳答案

您确定这是段错误和/或挂起的最简单的情况吗？如果DRD的结果确实表明线程构建和连接之间存在竞争状态，则听起来您的代码可能没有错误(特别是因为您实际上并未使用任何mex特定的功能，而仅在mex下运行会触发该错误)。

也许尝试这个版本:

#include <boost/thread.hpp>

void doNothing() { return; }

void doWork() {
    boost::thread t1(doNothing);
    t1.join();
}

#ifdef NO_MEX
int main() {
#else
#include "mex.h"
void mexFunction(int nlhs, mxArray **plhs, int nrhs, const mxArray **prhs) {
#endif
    doWork();
}

关于c++ - 使用来自matlab的boost::threads时挂起和/或segfault，而不是直接调用时，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/9011780/