https://svn.boost.org/trac10/ticket/13551 <p> Hi, in 1.66 was the following feature introduced: On newer compilers optional is now trivially-copyable for scalar Ts. This uses a different storage (just T rather than aligned_storage). We require the compiler to support defaulted functions. </p> <p> Gcc 4.4.7 in C++98 mode is incorrectly recognizes because Boost tries to use tc_optional_base however without C++11 defaulted functions are not working. This is causing boost::optional&lt;unsigned char&gt;::&lt;anonymous&gt;.boost::optional_detail::tc_optional_base&lt;unsigned char&gt;::m_storage’ may be used uninitialized in this function warning. </p> en-us /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/13551 Trac 1.4.3