Issue with std::thread from c++11

Question

I have some troubles trying to compile a program with multi-threading from the standard template library. It return me a obscure error when i try to compile the following program :

#include <iostream>
#include <thread>

void foo()
{
    std::cout << "Thread 1\n";
}

int main(int argc, char** argv)
{
    std::thread tr(foo);
    std::cout << "Main thread\n";
    tr.join();

    return 0;
}

I don't understand the error :

/tmp/ccE8EtL1.o : In the function « std::thread::thread<void (&)()>(void (&)()) » :
 file.cpp:(.text._ZNSt6threadC2IRFvvEJEEEOT_DpOT0_[_ZNSt6threadC5IRFvvEJEEEOT_DpOT0_]+0x21) : undefined reference to « pthread_create »
  collect2: error : ld has return 1 execution status code

I compile it with :

g++ -std=c++14 file.cpp -o test -Wall

Can anyone help me please ?

Answer 1

Pass -pthread to the compiler. This flag combines what is necessary to compile and link the pthread library ( -lpthread is not always enough) . See this question .