list" style="list-style-type: disc; ">
<li class="listitem">
                Thread-safe if there is only one thread running before <code class="computeroutput"><span class="identifier">main</span><span class="special">()</span></code>
                begins and after <code class="computeroutput"><span class="identifier">main</span><span class="special">()</span></code> ends. All of the static functions
                of singleton_pool synchronize their access to <code class="computeroutput"><span class="i