I began testing a simple threads example. But, I had a little problems:

• The pre-compiler said: “thread could not be resolved”.
• The compiler said “… undefined reference to ‘pthread_create’ …”.

Here is the solution.

First, I began testing a simple thread example in C++.  The code is the follow:

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

using namespace std;

// The function we want to execute on the new thread.
void task1(string msg)
{
 cout << "task1 says: " << msg;
}

int main()
{
 // Constructs the new thread and runs it. Does not block execution.
 thread t1(task1, "Hello");

 // Makes the main thread wait for the new thread to finish execution, therefore blocks its own execution.
 t1.join();

 return 0;
}

The first problem was the pre-processor. It didn’t recognize the “thread” class and the IDE Eclipse Kepler showed an error on the line:

thread t1(task1, "Hello");

I found the solution in page, and I followed the instructions:

Go to Project -> Properties -> C/C++ General -> Preprocessor include paths, etc -> Providers -> CDT GCC Builtin Compiler Settings and append -std=c++11 to the compiler specs

Add “-std=c++11” flag

This answer solved that problem. But, when I “Build Project”, the console showed an error like the following:

... undefined reference to 'pthread_create' ...

I found several solutions in the Internet, but none solved my problem. When I was desperate this page appears and it solved the problem.  I updated the solution to Eclipse Kepler.

Add libraries to GCC C++ Linker

I “Clean Project” and “Build Project” again, and the console showed the follow:

...
Building target: BasicThread
Invoking: GCC C++ Linker
g++ -o "BasicThread" ./src/thread.o -lpthread
Finished building target: BasicThread

You can look at the final flag on compiler invocation. It solved the problem.