C++ Compilation error about running io_context in different thread - c++

Question

I am trying to use the asio::io_context in multiple threads.
#include <iostream>
#include <vector>
#include <asio.hpp>
#include <thread>
#include <future>
#include <functional>
int main()
{
asio::io_context ctx;
std::vector<std::future<asio::io_context::count_type>> tasks;
for(int i = 0; i < 3; ++i)
{
tasks.push_back(std::async(std::launch::async, std::bind(&asio::io_context::run, &ctx));
}
for(auto &task: tasks){tasks.get();}
return 0;
}
However, I am getting a compilation error
asio_blah.cpp: In function ‘int main()’:
asio_blah.cpp:101:94: error: no matching function for call to ‘bind(<unresolved overloaded function type>, asio::io_context*)’
tasks.push_back(std::async(std::launch::async, std::bind(&asio::io_context::run, &ctx));
Not sure whey the compiler is not able to figure the member function pointer ( I believe the member func type is asio::io_context::count_type (asio::io_context*)() and the function signature should visible to the compiler since asio.hpp is included) and report the error unresolved overloaded function type.
Any suggestions to fix the error?

Answer 1

You may go for lambda something like this:
#include <iostream>
#include <vector>
#include <boost/asio.hpp>
#include <thread>
#include <future>
#include <functional>
using namespace boost;
int main()
{
asio::io_context ctx;
std::vector<std::future<asio::io_context::count_type>> tasks;
for(int i = 0; i < 3; ++i)
{
tasks.push_back(std::async(std::launch::async, [&ctx]() {
return ctx.run();
}));
}
for(auto &task: tasks){task.get();}
return 0;
}
Edit:
As rightly said by Miles Budnek, io_context::run has multiple overloads. You cannot take a pointer to it without forcing overload resolution with a cast.
If you really want to use std::bind, go for casting.
My opinion is same as that of others. GO FOR LAMBDA!!!