invalid usage in Release builds; see
<code>preconditionFailure</code>.</p>

<ul><li><p>In playgrounds and -Onone builds (the default for Xcode&#39;s Debug
configuration) stop program execution in a debuggable state
after printing <code>message</code>.</p></li><li><p>In -O builds, has no effect.</p></li><li><p>In -Ounchecked builds, the optimizer may assume that this
function will never be called. Failure to satisfy that assumption
is a serious programming error.</p></li></ul>

    <h4>Declaration</h4>    
 