On Tue, 4 Aug 2015, Jonathan Wakely wrote: > The extern template tells the compiler it doesn't *need* to > instantiate the template, because it will be explicitly instantiated > in another translation unit. But that doesn't mean it *must not* > instantiate it. The compiler can choose to inline the function and in > that case it will implicitly instantiate it. That should be > unobservable because the One Definition Rule means that the implicitly > instantiated definition that gets inlined and the explicitly > instantiation definition in the other translation unit must be > identical. The Windows linkage model seems to break that assumption > ... so I don't know what the right behaviour is. OK, thanks. AFAIU, a very similar problem existed with GCC on Linux prior to introduction of STB_GNU_UNIQUE (consider what happened when multiple DSOs with a common singleton are loaded with RTLD_LOCAL -- they didn't have a way to end up with a common location). In light of that, perhaps it's best to structure code in a way that prevents implementation of a singleton from being visible in translation units that can be linked into different libraries. Alexander
