Hi, I've implemented a simple, low level json formatting utility to complement tinyjson's lightweight parser. To do this, I've extended boost::any only to add a "format()" function to it that is aware of what types the content can take in a json structure and produces the appropriate string. The default constructor and the constructor with a value are the only things I implemented, aside from the format function. Both just call the base constructor. Compiled in gcc, everything works fabulously. Apparently, a functioning assignment operator and copy constructor are appropriately inherited and everything runs great. On windows, however, some subtle difference causes assignment and copies to seg-fault. The real problem is that, for the life of me, I can't find a way to implement assignment or copies explicitly, that doesn't also bomb out. I can probably come up with a work around that stores my type in shared pointers so they're never actually copied, but I'm really curious if anyone could explain what causes this. Here are some code snippets to illustrate the behavior: void test(){ std::cout<<"messing around with boost any"<<std::endl; boost::any tAny; boost::any tStringAny(std::string("some string")); tAny = tStringAny; std::cout<<"string any assignable to any"<<std::endl; std::cout<<"messing around with value type"<<std::endl; sysshep::json::Value tValue; std::cout<<"formatted blank value "<<tValue.format()<<std::endl; std::cout<<"making string value"<<std::endl; sysshep::json::Value tStringValue(std::string("some_string")); std::cout<<"formatted string value "<<tStringValue.format()<<std::endl; std::cout<<"assigning string value to blank value"<<std::endl; tValue = tStringValue; /// FAILS std::cout<<"formatted blank value after assignment"<<tValue.format()<<std::endl; } class Value : public boost::any { public: Value():boost::any(){}; template<typename ValueTypeTA> Value(const ValueTypeTA & aValue): : boost::any(aValue) {} virtual ~Value(); std::string format() const; }; I'm not going to list the different ways I've attempted to implement copy and assignment, some more plausible than others, out of respect for brevity. If you try a build on windows, VC8, you should be able to mess around with this to your hearts content. It's really annoying because it was a factor in the fundamental elegance of the parsing implementation, because I see no reason why it shouldn't work, because it worked fine in linux, and because it put my windows port at least a day behind customer expectations. thanks for any insight.