Problem compiling multithreading process regarding arguments

Question

I'm trying to compile a program but it keeps coming up with errors; I have searched through the forum and I think it has to do with passing by reference, but I can't find where I went wrong.

Here is an extract of the code:

#include <iostream>
#include <thread>

using namespace std;

const int N = 512;
const int N_BUSC = 8;
using VectInt = int[N];

void coord (VectInt v, bool& lectura, bool acabados[N_BUSC], int resultados[N_BUSC]);

int main(int argc, char *argv[]){
    bool leido = false; 
    VectInt v;
    int acabados [N_BUSC], resultados [N_BUSC];

...

    thread coordinacion (&coord, v, std::ref(leido), acabados, resultados);

...
}

The error it keeps showing is:

/usr/include/c++/9/thread: In instantiation of ‘std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = void (*)(int*, bool&, bool*, int*); _Args = {int (&)[512], std::reference_wrapper<bool>, int (&)[8], int (&)[8]}; <template-parameter-1-3> = void]’:
ej1.cpp:43:74:   required from here
/usr/include/c++/9/thread:120:44: error: static assertion failed: std::thread arguments must be invocable after conversion to rvalues
  120 |           typename decay<_Args>::type...>::value,
      |                                            ^~~~~
/usr/include/c++/9/thread: In instantiation of ‘struct std::thread::_Invoker<std::tuple<void (*)(int*, bool&, bool*, int*), int*, std::reference_wrapper<bool>, int*, int*> >’:
/usr/include/c++/9/thread:131:22:   required from ‘std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = void (*)(int*, bool&, bool*, int*); _Args = {int (&)[512], std::reference_wrapper<bool>, int (&)[8], int (&)[8]}; <template-parameter-1-3> = void]’
ej1.cpp:43:74:   required from here
/usr/include/c++/9/thread:243:4: error: no type named ‘type’ in ‘struct std::thread::_Invoker<std::tuple<void (*)(int*, bool&, bool*, int*), int*, std::reference_wrapper<bool>, int*, int*> >::__result<std::tuple<void (*)(int*, bool&, bool*, int*), int*, std::reference_wrapper<bool>, int*, int*> >’
  243 |    _M_invoke(_Index_tuple<_Ind...>)
      |    ^~~~~~~~~
/usr/include/c++/9/thread:247:2: error: no type named ‘type’ in ‘struct std::thread::_Invoker<std::tuple<void (*)(int*, bool&, bool*, int*), int*, std::reference_wrapper<bool>, int*, int*> >::__result<std::tuple<void (*)(int*, bool&, bool*, int*), int*, std::reference_wrapper<bool>, int*, int*> >’
  247 |  operator()()
      |  ^~~~~~~~

Thank you in advance.

Ted Lyngmo · Accepted Answer · 2021-10-28 20:44:11Z

1

The arguments you pass to coord do not match its signature.

void coord (VectInt v, bool& lectura, bool acabados[N_BUSC], int resultados[N_BUSC])
                                      ^^^^

It should be int if you want to pass an array of int to the function - or you should pass an array of bool to it instead:

bool acabados [N_BUSC];  // not  int[N_BUSC]
int resultados [N_BUSC];

thread coordinacion (&coord, v, std::ref(leido), acabados, resultados);

Demo

edited Oct 28, 2021 at 20:44

answered Oct 28, 2021 at 20:38

Ted Lyngmo

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2 Comments

Peter Over a year ago

I'm so stupid, thank you very much; i thought int were similar to bool, but i must have forgotten to change it between versions. Thank you again.

Ted Lyngmo Over a year ago

@Peter It seems my answer was removed (not by me) which seems cold. No, that's not studpidity, that's "staring at a problem long enough to go blind"-syndrome. I don't know anyone in the business who doesn't get that from time to time.

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