title: Possible misuse of comma operator here
body: <p>I'm getting warnings in Xcode after updating to the recommended pod settings.  The warning is </p>
  
  <pre><code>Possible misuse of comma operator here
  </code></pre>
  
  <p>with a suggested fix of</p>
  
  <pre><code>Cast expression to void to silence warning
  </code></pre>
  
  <p>The warnings occur in leveldb-library/db/c.cc at the start and limit keys:</p>
  
  <pre><code>void leveldb_compact_range(
      leveldb_t* db,
      const char* start_key, size_t start_key_len,
      const char* limit_key, size_t limit_key_len) {
    Slice a, b;
    db-&gt;rep-&gt;CompactRange(
        // Pass NULL Slice if corresponding "const char*" is NULL
        (start_key ? (a = Slice(start_key, start_key_len), &amp;a) : NULL),
        (limit_key ? (b = Slice(limit_key, limit_key_len), &amp;b) : NULL));
  }
  </code></pre>
  
  <p>Has anyone else had the same or know what's causing it?  I'm running Cocoapods 1.2.0.</p>