I found a bug in the format library and fixed it. strm << boost::format("%64.64s") % "hello"; gave an access violation. It was caused by passing an argument greater than the string length to std::string::erase. I added a check so as not to try to erase text that is not there. Here is a diff of my small fix. < is feed_args.hpp from the boost_1_29_0 distribution.

is my fixed file.

158c158,162 < if (specs.truncate_ >= 0) ---

// @@@@@ fjackson 20021022 Added test to make sure we don't call // std::string::erase with an arg greater than the length - this // caused an access violation, noted on outputting a short string // with a %64.64 format specifier. if (specs.truncate_ >= 0 && specs.truncate_ < res.length())