Rene Rivera <grafik.list@redshift-software.com> writes:
To correct that a bit.. In the code in question we actually do the equivalent of:
template <typename T> void f() { void * t = &A<T>::t; }
That clearly requires A<T>::t to exist, and thus causes its instantiation: 14.7.1 Implicit instantiation [temp.inst] 1 Unless a class template specialization has been explicitly instantiated (14.7.2) or explicitly specialized (14.7.3), the class template specialization is implicitly instantiated when the specialization is referenced in a context that requires a completely-defined object type or when the completeness of the class type affects the semantics of the program. The implicit instantiation of a class template specialization causes the implicit instantiation of the declarations, but not of the definitions or default arguments, of the class member functions, member classes, static data members and member templates; and it causes the implicit instantiation of the definitions of member anonymous unions. Unless a member of a class template or a member template has been explicitly instantiated or explicitly specialized, the specialization of the member is implicitly instantiated when the specialization is referenced in a context that requires the member definition to exist; in particular, the initialization (and any associated side-effects) of a static data member does not occur unless the static data member is itself used in a way that requires the definition of the static data member to exist. Note in particular that last sentence.
Hence the implicit aspect of the instantiation. Which I think CW decides is not sufficient for the semantic requirement that the other rules in 14.7.1 refer to. But it's not clear how the other rules of 14.7.1 should apply for the implicit instantiation case that 14.7.1.7 refers to. --
I think you mean 14.7.1ΒΆ7 or 14.7.1/7 if you prefer.
Well at least not clear to me :-) But 14.7.1.1 does say this... which possibly supports what 14.7.1.7 says.
14.7.1.1: "The implicit instantiation of a class template specialization causes the implicit instantiation of the declarations, _but not of the definitions_ or default arguments, of the class member functions, member classes, _static data members_ and member templates; and it causes the implicit instantiation of the definitions of member anonymous unions."
But you missed the most important part of that paragraph ;-)
We expect A<T>::t to be instanticiated and the program to link and run as expected. In fact on most compilers it does this. This group includes those known to be the most conforming ones including the latest GCC, VC and Comeau compilers. With CW, it seems that A<T> t is allocated but the constructor for t isn't being called - at least at pre-compile time. It might be being called on first usage as it would be in the following case. void f() { static T t; .. }
It's not getting called, no matter what. Or more precisely CW is not adding the constructor+instance to the global initialization function list that CW generates.
I think it's a bug and should be reported to MW, but that said, check out boost/python/detail/force_instantiate.hpp, which I use for this exact purpose. -- Dave Abrahams Boost Consulting www.boost-consulting.com