title: What is the cause of the warning: implicit declaration of function 'swprintf_s'?
body: <p>I am wondering why my use of <code>swprintf_s</code> is generating the 
  linker warning <code>warning: implicit declaration of function 'swprintf_s'</code></p>
  
  <p>I have this headers:</p>
  
  <pre><code>#include &lt;stdio.h&gt;
  #include &lt;stdlib.h&gt;
  #include &lt;wchar.h&gt;
  #include &lt;windows.h&gt;
  #include &lt;tchar.h&gt;
  </code></pre>
  
  <p>And </p>
  
  <pre><code>LPCWSTR foo = L"É %s";
  LPCWSTR arg = "bá";
  LPCWSTR msg = malloc(wcslen((wchar_t*)foo) + wcslen((wchar_t*)arg) + 1);
  swprintf_s(msg, (wchar_t*)foo, (wchar_t*)arg);
  </code></pre>
  
  <p>How can I fix this?</p>