title: Programmatically cause Undefined Instruction exception
body: <p>I want to cause an ARM Cortex-M3 Undefined Instruction exception for the test of my test fixture. The IAR compiler supports this with inline assembly like this:</p>
  <pre><code>asm(&quot;udf.w #0&quot;);
  </code></pre>
  <p>Unfortunately the GNU CC inline assembler does not know this opcode for the NXP LPC177x8x. It writes the diagnostic:</p>
  <pre><code>ccw3kZ46.s:404: Error: bad instruction `udf.w #0'
  </code></pre>
  <p>How can I create a function that causes a Undefined Instruction exception?</p>