CODEWITHSUNDEEP
c++multithreadingclassobjective-c++
Padzak
Padzak

Reputation: 41

Multi-threading with classes in C++

I have a problem with threads in C++. I want to create threads consisting of class member method with a specific object assigned. What is more, an object of another user-defined class is passed to that method. Please find the code below:

Grid an_chan(NX, NY, xmax, ymax);
an_chan.calc_paraFlow(anode);

Grid *ptr_grid = &an_chan;    

Variable T(Tin, Tinit, lambda_m, rho_m, Cp_m);
Variable *ptr_T = &T;

std::thread first (&Variable::initialize, ptr_T, ptr_grid);

first.join();

Here is the initialize method prototype:

void Variable::initialize(Grid& grid_obj)

Before I tried to add the thread, everything worked just right.

I am just wondering if this is not a compiler issue? Maybe something is wrong with my code I can not notice? Any possible fixes? Below I included the error returned by the compiler. As you can see I am using TDM GCC 5.1.0. I was using it with threads before and everything was working quite ok.

In file included from C:/TDM-GCC-64/lib/gcc/x86_64-w64-mingw32/5.1.0/include/c++/thread:39:0, from main.cpp:13: C:/TDM-GCC-64/lib/gcc/x86_64-w64-mingw32/5.1.0/include/c++/functional: In instantiation of 'struct std::_Bind_simple(chal::Variable, chal::Grid)>': C:/TDM-GCC-64/lib/gcc/x86_64-w64-mingw32/5.1.0/include/c++/thread:142:59: required from 'std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = void (chal::Variable::*)(chal::Grid&); _Args = {chal::Variable&, chal::Grid&}]' main.cpp:45:61: required from here C:/TDM-GCC-64/lib/gcc/x86_64-w64-mingw32/5.1.0/include/c++/functional:1505:61: error: no type named 'type' in 'class std::result_of(chal::Variable, chal::Grid)>' typedef typename result_of<_Callable(_Args...)>::type result_type; ^ C:/TDM-GCC-64/lib/gcc/x86_64-w64-mingw32/5.1.0/include/c++/functional:1526:9: error: no type named 'type' in 'class std::result_of(chal::Variable, chal::Grid)>' _M_invoke(_Index_tuple<_Indices...>)

Upvotes: 0

Views: 1076

Answers (2)

Anurag
Anurag

Reputation: 17

As @acraig5075 mentioned:

The second parameter to the std::thread constructor should be a pointer to the object. You're dereferencing ptr_T.

After this you might also want to bind the function before passing to thread:

std::thread first(std::bind(&Variable::initialize, ptr_T, *ptr_grid));

Upvotes: -1

acraig5075
acraig5075

Reputation: 10756

As your initialize function takes it's parameter by reference you should wrap the argument in std::ref.

std::thread first(&Variable::initialize, ptr_T, std::ref(*ptr_grid));

Upvotes: 2

Related Questions