 may not contain any previously set
value.
</p>
<p>
You're advised to call this function only when needed and as close as
possible after the return of the related C&nbsp;function. The
<tt>errno</tt> value is preserved across hooks, memory allocations,
invocations of the JIT compiler and other internal VM activity. The same
applies to the value returned by <tt>GetLastError()</tt> on Windows, but
you need to declare and call it yourself.
</p>

<h3 id="ffi_string"><tt>str = ffi.string(ptr [,len])</tt></h3>
<p>