C++ – Eclipse content assist doesn’t recognize std::thread, but compiles correctly

I am running Ubuntu 14.04.

Steps I took to reproduce:

1. Create a new C++ project (New -> C++ -> Hello World project), which I called TestStdThread

2. Change the code in the main file to this:

   #include <thread>
   #include <iostream>
   
   int main() {
       std::cout << "You have " << std::thread::hardware_concurrency() << " cores." << std::endl;
       return 0;
   }
   

3. Go to TestStdThread -> Properties -> C/C++ Build -> Settings -> GCC C++ Compiler, and change the Command options from g++ to g++ -std=c++11

4. Go to TestStdThread -> Properties -> C/C++ Build -> Settings -> GCC C++ Compiler -> Includes, add /usr/include to the Include paths (-I), and add pthread.h to the Include files (-include)

5. Go to TestStdThread -> Properties -> C/C++ Build -> Settings -> GCC C++ Linker -> Libraries, add pthread to the Libraries (-l), and add /usr/lib/x86_64-linux-gnu to the Library search path (-L)

6. TestStdThread -> Build Project

7. Click "Run"

There were no build errors. Eclipse told me that the project had errors and asked if I wanted to run it anyway, and when I said yes, the output was, correctly: You have 4 cores.. However, Eclipse still underlined the std::thread::hardware_concurrency part in red, and reported it (on hover) as "Function 'hardware_concurrency' could not be resolved," and std::thread didn't show up when typing std:: Ctrl+Space.

This is the bash command I used to find where my pthread files were located within /usr (/usr/share omitted as it contains lots of doc files that I'm not looking for):

llama@llama-Satellite-E55-A:/usr$ find -name "*pthread*" -not -path "./share/*"
./include/pthread.h
./include/x86_64-linux-gnu/bits/pthreadtypes.h
./lib/x86_64-linux-gnu/pkgconfig/pthread-stubs.pc
./lib/x86_64-linux-gnu/libpthread.so
./lib/x86_64-linux-gnu/libpthread_nonshared.a
./lib/x86_64-linux-gnu/libgpgme-pthread.so.11.11.0
./lib/x86_64-linux-gnu/libgpgme-pthread.so.11
./lib/x86_64-linux-gnu/libpthread.a
./lib/perl/5.18.2/bits/pthreadtypes.ph
./lib/debug/lib/x86_64-linux-gnu/libpthread-2.19.so