title: Compiling linux kernel module, KBUILD_CFLAGS in makefile does not work
body: <p>I run the <code>make</code> file with adding below line in the Makefile.</p>
  
  <pre><code>KBUILD_CFLAGS += -DXFLAGS
  </code></pre>
  
  <p>In my .c file I have:</p>
  
  <pre><code>#ifdef XFLAGS
  printk(...);
  #endif
  </code></pre>
  
  <p>The make compilation is successful, however, I am not able to see the message in the log files like <code>/var/log/syslog</code>.
  I'm wondering to know what can cause this problem? (the flags can not be set)
  Note that inside the printk has no problem. As I commented the <code>#ifdef</code> and the printk works fine.</p>