https://svn.boost.org/trac10/ticket/13632 <p> The Passenger application server is a C++ application and uses Boost. Our FreeBSD 11.2 users ran into a crash bug: <a class="ext-link" href="https://github.com/phusion/passenger/issues/2097"><span class="icon">​</span>https://github.com/phusion/passenger/issues/2097</a> </p> <p> Upon further investigation, it turns out that the underlying problem is boost::function operator==. The following test program... </p> <pre class="wiki">boost::function&lt;void ()&gt; f; printf("is null: %d\n", f == NULL); </pre><p> ...prints 1 on macOS (as it should) and 0 on FreeBSD 11.2. I haven't tested this small test program on FreeBSD 11.1, but users reported that Passenger worked fine on FreeBSD 11.1 so the problem likely did not exist there. </p> <p> Digger deeper, on FreeBSD the == operator calls this function (in boost/function/function_base.hpp): </p> <pre class="wiki"># if !(defined(__GNUC__) &amp;&amp; __GNUC__ == 3 &amp;&amp; __GNUC_MINOR__ &lt;= 3) // Comparisons between boost::function objects and arbitrary function // objects. GCC 3.3 and before has an obnoxious bug that prevents this // from working. template&lt;typename Functor&gt; BOOST_FUNCTION_ENABLE_IF_NOT_INTEGRAL(Functor, bool) operator==(const function_base&amp; f, Functor g) { if (const Functor* fp = f.template target&lt;Functor&gt;()) return function_equal(*fp, g); else return false; } </pre><p> ...and returns false (the else branch). </p> <p> While on macOS it calls this function: </p> <pre class="wiki">inline bool operator!=(const function_base&amp; f, detail::function::useless_clear_type*) { return !f.empty(); } </pre><p> Just looking at the #if there already gives me the feeling that it is not right. Boost is trying to work around a GCC 3 bug but it wrongly detects Clang 6.0.0 as GCC 3. </p> <p> This bug has been confirmed on both Boost 1.64 and Boost 1.67. </p> en-us /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/13632 Trac 1.4.3 VVD Wed, 11 Jul 2018 18:52:36 GMT