C++: Update documentation on 'cpp/iterator-to-expired-container'.

Author: MathiasVP

cpp/ql/src/Security/CWE/CWE-416/IteratorToExpiredContainer.qhelp

@@ -30,6 +30,12 @@ This is because the temporary container is not bound to a rvalue reference.
 </p>
 <sample src="IteratorToExpiredContainerExtendedLifetime.cpp" />
 
+<p>
+To fix <code>lifetime_of_temp_not_extended</code> consider rewriting the code so that the temporary's lifetime is extended.
+In <code>fixed_lifetime_of_temp_not_extended</code> the lifetime of the temporary object has been extended by storing it in an rvalue reference.
+</p>
+<sample src="IteratorToExpiredContainerExtendedLifetime-fixed.cpp" />
+
 </example>
 <references>
 

cpp/ql/src/Security/CWE/CWE-416/IteratorToExpiredContainerExtendedLifetime-fixed.cpp

@@ -0,0 +1,6 @@
+void fixed_lifetime_of_temp_not_extended() {
+  auto&& v = get_vector();
+  for(auto x : log_and_return_argument(v)) {
+    use(x); // GOOD: The lifetime of the container returned by `get_vector()` has been extended to the lifetime of `v`.
+  }
+}