func NewGetObjectReaderFromReader(r io.Reader, oi ObjectInfo, opts ObjectOptions, cleanupFns ...func()) (*GetObjectReader, error) {
	if opts.CheckPrecondFn != nil && opts.CheckPrecondFn(oi) {
		// Call the cleanup funcs
		for i := len(cleanupFns) - 1; i >= 0; i-- {
			cleanupFns[i]()
		}
		return nil, PreConditionFailed{}
	}
	return &GetObjectReader{
		ObjInfo:    oi,
		Reader:     r,
		cleanUpFns: cleanupFns,

<pre>
i := *p
if i &lt; 0 || i &gt;= len(funcs) {
	panic("invalid function index")
}
... complex code ...
// compiler must NOT reload i = *p here
funcs[i]()
</pre>

<p>
If the complex code needs many registers, a compiler for single-threaded programs
could discard <code>i</code> without saving a copy and then reload
<code>i = *p</code> just before
<code>funcs[i]()</code>.