CODEWITHSUNDEEP
c++multithreadingmacoscompiler-errorsg++
Jacques-A Portal
Jacques-A Portal

Reputation: 57

Threads in c++, cannot use parameters

I am trying to start a thread t:

#include <iostream>
#include <fstream>
#include <string>
#include <thread>

void function(int p1, int p2, int p3){
  std::cout<<p1<<p2<<p3<<std::endl;
}

int main(int argc, char const *argv[]) {
  std::cout<<"starting"<<std::endl;
  std::thread t(function, 1, 2, 3);
  std::cout<<"created thread"<<std::endl;
  t.join();
  std::cout<<"end"<<std::endl;
  return 0;
}

My compiler tells me this:

doesntwork.cpp:12:15: error: no matching constructor for
      initialization of 'std::thread'
  std::thread t(function, 1, 2, 3);
              ^ ~~~~~~~~~~~~~~~~~
/Library/Developer/CommandLineTools/usr/include/c++/v1/thread:408:9: note: 
      candidate constructor template not viable: requires single
      argument '__f', but 4 arguments were provided
thread::thread(_Fp __f)
        ^
/Library/Developer/CommandLineTools/usr/include/c++/v1/thread:289:5: note: 
      candidate constructor not viable: requires 1 argument, but 4
      were provided
    thread(const thread&);
    ^
/Library/Developer/CommandLineTools/usr/include/c++/v1/thread:296:5: note: 
      candidate constructor not viable: requires 0 arguments, but
      4 were provided
    thread() _NOEXCEPT : __t_(_LIBCPP_NULL_THREAD) {}
    ^
1 error generated.

In the first case it tells me that for the thread t, there is no constructor that can use more than 1 parameter, while if I just remove the arguments (p1, p2, p3) it doesn't work either because I am not passing any argmuent....

Compiler information:

Configured with: --prefix=/Library/Developer/CommandLineTools/usr 

--with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 10.0.0 (clang-1000.10.44.2)
Target: x86_64-apple-darwin17.7.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

built command used: g++ doesntwork.cpp -o doesntwork.out

Is there something different you have to do when compiling with threads? Am I missing something very obvious?

Upvotes: 1

Views: 791

Answers (1)

Jacques-A Portal
Jacques-A Portal

Reputation: 57

On macOS, g++ (from Xcode: Version 10.0 (10A255)) is aliased to clang which by default does not work with c++11 threads. To solve the problem you have to use the -std=c++11 switch.

Example:

g++ -std=c++11 fileToCompile.cpp -o outputFile.out

This should let you compile c++ code using c++11 threads.

Thank you to @M.M for providing the answer above in the comments.

Upvotes: 2

Related Questions