title: How to disable specified warning for specified file while using autotools?
body: <p>I use autotools to manage my CPP project. When compile my code, gcc has these flags: <code>-Wall -Werror</code></p>
  
  <p>So, when there is an warning in my code, gcc will treat it as error, the compile will be interrupted.</p>
  
  <p>My project also includes antlr3, which generate several files. The generated files contain several warnings, which interrupt compiling.</p>
  
  <pre><code>error: unused variable ‘index21_49’
  in CongerCQLLexer.c, line 20589, column 24
  20587&gt;                 ANTLR3_UINT32 LA21_49;
  20588&gt; 
  20589&gt;                 ANTLR3_MARKER index21_49;
  20590&gt; 
  20591&gt; 
  
  error: unused variable ‘index21_131’
  in CongerCQLLexer.c, line 20622, column 24
  20620&gt;                 ANTLR3_UINT32 LA21_131;
  20621&gt; 
  20622&gt;                 ANTLR3_MARKER index21_131;
  20623&gt; 
  20624&gt; 
  </code></pre>
  
  <p>I want to know how to disable warnings for the generated files?
  thank you.</p>