I have a stupid question Now i build boost 1.49 on x64 platform with vc2005 I find such many warnings: warning C4267: '=' : conversion from 'size_t' to 'unsigned int', possible loss of data  or conversion from '_int64' to 'unsigned int', possible loss of data I want to make sure that these warnings really do lose data whether or not on x64 flatform. Put another way, could these warning be neglected or should i  change the source code?

Just neglect these warnings. These would only be a problem if size_t had > 4 billion elements. I certainly do not put that many elements into my structures yet! John