What are the exact requirements for MyType to allow std::atomic

I would like to communicate some Informations between threads. Atomics sound like the thing to use. I had a look at this. And found that a simple struct like

struct MyType{
  int val_a,val_b;
  float vals_c[5];
};

should fullfill the assert:

static_assert( 
  std::is_trivially_copyable<MyType>::value &&
  std::is_copy_constructible<MyType>::value &&
  std::is_move_constructible<MyType>::value &&
  std::is_copy_assignable<MyType>::value &&
  std::is_move_assignable<MyType>::value, 
  "MyType is not suitable for std::atomic");

)

But a simple program as

//... MyType and static_assert

int main(int argc,char *argv[]){
   MyType a;
   std::atomic<MyType> b;
   b = a;
   a = b;
   return 0;
}

fails to compile with:

undefined reference to `__atomic_store'
undefined reference to `__atomic_load'

I am using gcc version 5.4 on a 64-bit ubuntu 16.04.

Flags used are: -pipe -g -std=gnu++11 -Wall -W -fPIC

Is it that this is a total wrong use of std::atomic? What are the requirements to MyType? Or is just something missing from this setup?