https://svn.boost.org/trac10/ticket/12343 <pre class="wiki">#include &lt;boost/multiprecision/cpp_int.hpp&gt; #include &lt;iostream&gt; #include &lt;cstdint&gt; int main() { boost::multiprecision::int128_t a = INT64_MIN; std::cout &lt;&lt; a &lt;&lt; " " &lt;&lt; INT64_MIN &lt;&lt; " " &lt;&lt; static_cast&lt;int64_t&gt;(a) &lt;&lt; " " &lt;&lt; std::endl; return 0; } </pre><p> With apple clang (xcode 7.3.1): "clang++ -stdlib=libc++ -std=c++14 int128casterror.cpp -I/usr/local/include" the output is -9223372036854775808 -9223372036854775808 <strong>-9223372036854775807</strong> , while the correct output should be (<a class="ext-link" href="http://ideone.com/3UhgWQ"><span class="icon">​</span>http://ideone.com/3UhgWQ</a>): -9223372036854775808 -9223372036854775808 -9223372036854775808 </p> en-us /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/12343 Trac 1.4.3 John Maddock Fri, 22 Jul 2016 16:56:17 GMT https://svn.boost.org/trac10/ticket/12343#comment:1 https://svn.boost.org/trac10/ticket/12343#comment:1 <ul> <li><strong>status</strong> <span class="trac-field-old">new</span> → <span class="trac-field-new">closed</span> </li> <li><strong>resolution</strong> → <span class="trac-field-new">fixed</span> </li> <li><strong>milestone</strong> <span class="trac-field-old">To Be Determined</span> → <span class="trac-field-new">Boost 1.62.0</span> </li> </ul> <p> Thanks, fixed in <a class="ext-link" href="https://github.com/boostorg/multiprecision/commit/9f43e1c88ecc0b746962ba8024aacc2b37b4650b"><span class="icon">​</span>https://github.com/boostorg/multiprecision/commit/9f43e1c88ecc0b746962ba8024aacc2b37b4650b</a> </p> Ticket