Dear All, In November Sergey Skorniakov wrote to this list asking about the non-thread-safety of Boost.Function and consequently of Boost.Thread itself. Steven Watanbee replied pointing out that the problem is resolved in the trunk. See: http://thread.gmane.org/gmane.comp.lib.boost.devel/167877 My thought at the time was "chocolate teapot". I put understanding this issue on my to-do list and it has finally got to the top. However, looking at the trac pages that Steven linked to, I am none the wiser; they contain patches but with no comments in the code and don't mention thread safety in the commit messages. So can someone please help me understand the scope of this problem? i.e. - Are all uses of Boost.Function affected, or only certain uses (e.g. member functions vs. free functions)? - What exactly is the race between? E.g. if I know that I'll never create two threads at the same time, do I still need to worry about other uses of Boost.Function that may be concurrent? Is the race between creating the function objects or between using them, or both? - Can I avoid the problem by using a new version of Boost.Function, without upgrading other libraries? (Is Boost.Function header-only?) - What would the symptom of failure be? I'm currently debugging a double-free somewhere below std::string::assign, which is probably unrelated. I'm also curious to know how much more serious than this a bug would need to be before a Boost release would be recalled, or a new point-release released, or an announcement made on the Boost web page (which links to bugs fixed in 1.34.1, but not bugs introduced). Surely there aren't many users of Boost.Thread who are happy to use a non-thread-safe thread library..... Many thanks, Phil.