使用std :: shared_ptr对象实例创建boost :: thread

Question

我有以下两个代码段.第一个块编译并按预期工作.但是第二个块不能编译.

我的问题是,根据下面的代码,尝试基于被shared_ptr代理的对象的实例创建线程时,正确的语法是什么？

#include <iostream>
#include <new> 
#include <memory>

#include <boost/thread.hpp>

struct foo
{
   void boo() {}
};

int main()
{
   //This works
   {
      foo* fptr = new foo;
      boost::thread t(&foo::boo,fptr);
      t.join();
      delete fptr;
   }

   //This doesn't work
   {
      std::shared_ptr<foo> fptr(new foo);
      boost::thread t(&foo::boo,fptr);
      t.join();
   }

   return 0;
}

编译错误:

Error   5   error C2784: 'T *boost::get_pointer(T *)' : could not deduce template argument for 'T *' from 'std::tr1::shared_ptr<_Ty>'   c:\program files (x86)\boost\boost_1_47\boost\bind\mem_fn_template.hpp  40  1   htest
Error   3   error C2784: 'T *boost::get_pointer(const std::auto_ptr<_Ty> &)' : could not deduce template argument for 'const std::auto_ptr<_Ty> &' from 'std::tr1::shared_ptr<_Ty>' c:\program files (x86)\boost\boost_1_47\boost\bind\mem_fn_template.hpp  40  1   htest
Error   4   error C2784: 'T *boost::get_pointer(const std::auto_ptr<_Ty> &)' : could not deduce template argument for 'const std::auto_ptr<_Ty> &' from 'std::tr1::shared_ptr<_Ty>' c:\program files (x86)\boost\boost_1_47\boost\bind\mem_fn_template.hpp  40  1   htest
Error   8   error C2784: 'T *boost::get_pointer(const boost::shared_ptr<X> &)' : could not deduce template argument for 'const boost::shared_ptr<X> &' from 'std::tr1::shared_ptr<_Ty>' c:\program files (x86)\boost\boost_1_47\boost\bind\mem_fn_template.hpp  40  1   htest
Error   9   error C2784: 'T *boost::get_pointer(const boost::shared_ptr<X> &)' : could not deduce template argument for 'const boost::shared_ptr<X> &' from 'std::tr1::shared_ptr<_Ty>' c:\program files (x86)\boost\boost_1_47\boost\bind\mem_fn_template.hpp  40  1   htest
Error   1   error C2784: 'T *boost::get_pointer(const boost::scoped_ptr<T> &)' : could not deduce template argument for 'const boost::scoped_ptr<T> &' from 'std::tr1::shared_ptr<_Ty>' c:\program files (x86)\boost\boost_1_47\boost\bind\mem_fn_template.hpp  40  1   htest
Error   2   error C2784: 'T *boost::get_pointer(const boost::scoped_ptr<T> &)' : could not deduce template argument for 'const boost::scoped_ptr<T> &' from 'std::tr1::shared_ptr<_Ty>' c:\program files (x86)\boost\boost_1_47\boost\bind\mem_fn_template.hpp  40  1   htest
Error   6   error C2784: 'T *boost::get_pointer(const boost::reference_wrapper<T> &)' : could not deduce template argument for 'const boost::reference_wrapper<T> &' from 'std::tr1::shared_ptr<_Ty>'   c:\program files (x86)\boost\boost_1_47\boost\bind\mem_fn_template.hpp  40  1   htest
Error   7   error C2784: 'T *boost::get_pointer(const boost::reference_wrapper<T> &)' : could not deduce template argument for 'const boost::reference_wrapper<T> &' from 'std::tr1::shared_ptr<_Ty>'   c:\program files (x86)\boost\boost_1_47\boost\bind\mem_fn_template.hpp  40  1   htest
Error   10  error C2784: 'T *boost::get_pointer(const boost::intrusive_ptr<T> &)' : could not deduce template argument for 'const boost::intrusive_ptr<T> &' from 'std::tr1::shared_ptr<_Ty>'   c:\program files (x86)\boost\boost_1_47\boost\bind\mem_fn_template.hpp  40  1   htest
Error   11  error C2784: 'T *boost::get_pointer(const boost::intrusive_ptr<T> &)' : could not deduce template argument for 'const boost::intrusive_ptr<T> &' from 'std::tr1::shared_ptr<_Ty>'   c:\program files (x86)\boost\boost_1_47\boost\bind\mem_fn_template.hpp  40  1   htest

Answer 1

问题是boost::thread依赖于boost::mem_fn处理成员函数,并且boost::mem_fn(或者至少你正在使用的版本)不知道如何使用a std::shared_ptr来调用成员函数,因为它希望你使用boost::shared_ptr或者无数的其他智能指针之一错误列表中的类型.

原始指针有效,因为boost::mem_fn已经有了这个重载.解决方案是使用boost::shared_ptr或std::mem_fn.后者的作用是因为std::mem_fn知道如何与之互动std::shared_ptr

boost::thread t(std::mem_fn(&foo::boo), fptr);