Ca marche plutôt bien, on l'enlèvera si ca pose pb ... Index: metalic/ChangeLog from Nicolas Burrus &lt;burrus_n(a)lrde.epita.fr&gt; * mlc/type.hh (any_with_diamond): Use the static offset technique. Index: metalic/mlc/type.hh --- metalic/mlc/type.hh Mon, 01 Sep 2003 20:12:38 +0200 burrus_n (oln/c/21_type.hh 1.26 640) +++ metalic/mlc/type.hh Fri, 07 Nov 2003 17:19:10 +0100 burrus_n (oln/c/21_type.hh 1.27 640) @@ -34,6 +34,8 @@ # include <string> # include <cassert> +// FIXME: make a hierarchy of any with the different implementations + // any and any_with_diamond types are not defined in namespace mlc to // avoid namespace clashes. Indeed, a type inheriting from another in // a namespace foo will have implicit access to the foo namespace. @@ -53,12 +55,10 @@ E& exact() { - assert(offset_assigned); return *(E*)((char*)this - exact_offset); } const E& exact() const { - assert(offset_assigned); return *(const E*)((const char*)this - exact_offset); } @@ -67,25 +67,30 @@ return std::string("any_with_diamond<") + E::name() + ">"; } - public: + private: // This stores the actual value of the offset between the this - // pointer and the this pointer of the exact type. This enables - // diamond hierarchies, as static_cast cannot perform it and - // reinterpret_cast or (Exact*)(void*) cast are unsafe and - // compiler dependent. These members should be initialized by - // every concrete classes, using the mlc_init_static_hierarchy - // macro. - static int exact_offset; - // This Boolean determines if the exact_offset value has already - // been affected. - static bool offset_assigned; + // pointer and the address of the exact type. This enables diamond + // shaped hierarchies (static_cast can't and reinterpret_cast or + // (Exact*)(void*) cast are unsafe and compiler dependent). + static const int exact_offset; + + // Utility members used to determine the exact_offset + static const E exact_obj; + static const any_with_diamond<E>& ref_exact_obj; }; template <class E> - int any_with_diamond<E>::exact_offset = 0; + const E any_with_diamond<E>::exact_obj = E(); + + template <class E> + const any_with_diamond<E>& + any_with_diamond<E>::ref_exact_obj = any_with_diamond<E>::exact_obj; template <class E> - bool any_with_diamond<E>::offset_assigned = false; + const int any_with_diamond<E>::exact_offset = + (const char*)(void*)(&any_with_diamond<E>::ref_exact_obj) + - (const char*)(void*)(&any_with_diamond<E>::exact_obj); + // Warning, this class does not allow diamond hierarchies, consider // any_with_diamond if you really need it. @@ -284,7 +289,14 @@ | mlc_init_static_hierarchy | `--------------------------*/ -# define mlc_init_static_hierarchy(Exact) \ -mlc::assign_exact_offset<Exact, mlc::final>::doit(this) +// # define mlc_init_static_hierarchy(Exact) +// mlc::assign_exact_offset<Exact, mlc::final>::doit(this) + +// FIXME: this is for backward compatibility purposes only. This +// macro is called in every constructor of the classes, so we let them +// in place for the moment until we are sure that the static offset +// method works fine. + +# define mlc_init_static_hierarchy(Exact) #endif // ! METALIC_TYPE_HH