n> <span>&#45;&gt;</span> <a href="../../IR/Exp/index.html#type-t">IR.Exp.t</a> <span>&#45;&gt;</span> <a href="../../IBase/Location/index.html#type-t">IBase.Location.t</a> <span>&#45;&gt;</span> unit</code></dt><dd><p>Check for dereference errors: dereferencing 0, a freed value, or an undefined value</p></dd></dl><dl><dt class="spec value" id="val-check_call_to_objc_block_error"><a href="#val-check_call_to_objc_block_error" class="anchor"></a><code><span class="keyword">val</span> check_call_to_objc_block_