title: Where can I find the function definition in atomicity.h?
body: <p>atomicity.h is part of c++ stl. In its source file, it declares two functions about atomic operation. Here is the whole source code. Where can I find the definition of these functions. I don't find it in stl source code.</p>
  
  <pre><code>#ifndef _GLIBCXX_ATOMICITY_H
  #define _GLIBCXX_ATOMICITY_H    1
  #include &lt;bits/atomic_word.h&gt;
  namespace __gnu_cxx
  {
    _Atomic_word 
    __attribute__ ((__unused__))
    __exchange_and_add(volatile _Atomic_word* __mem, int __val); 
  
    void
    __attribute__ ((__unused__))
    __atomic_add(volatile _Atomic_word* __mem, int __val); 
  } // namespace __gnu_cxx
  #endif 
  </code></pre>