If the question had been tagged c, your code block would have worked. But, it wasn't.
You could add the tag, I suppose... But that seems lame, since the question wasn't about C.
So your next best option is to simply force syntax highlighting for your code blockforce syntax highlighting for your code block, by prefixing it with a special comment:
<!-- language: lang-c -->
... code goes here, indented by four spaces as usual ...
I've done this for you. Enjoy!