The data of the wrapper class boost::value_initialized<T> may not be initialized properly, when using Microsoft Visual C++. The problem is caused by two different compiler issues regarding value initialization. For details, please read the ticket that I submitted yesterday evening (#1217): http://svn.boost.org/trac/boost/ticket/1217 Fernando Cacciola and I developed a new version of value_init.hpp, offering a workaround. The file is attached to the ticket: http://svn.boost.org/trac/boost/attachment/ticket/1217/value_init_MSVC_worka... The workaround version stores the bytes of the T object that is wrapped by value_initialized<T> as an instance of aligned_storage::type. During the construction of value_initialized<T>, it clears the bytes of T (using memset), just before constructing T itself, by placement new: std::memset(&x, 0, sizeof(x)); new (&x) T(); The workaround is enabled by defining a macro, BOOST_UTILITY_VALUE_INIT_WORKAROUND. As I never contributed to a Boost library before, what should I do in order to get this workaround reviewed, and hopefully get it into the library? Kind regards, -- Niels Dekker http://www.xs4all.nl/~nd/dekkerware Scientific programmer at LKEB, Leiden University Medical Center