modern c++ design & loki

Loki VC 6.0 Port or how to produce C1001 - Internal Compiler Errors ------------------------------------------------------------------- Version: 0.5d Introduction/Compatibility: --------------------------- This is a partial MSVC 6.0 Sp5 compatible port of Andrei Alexandrescu's excellent Loki Library. Because I could not retain the originial interface in all places, this port is not compatible to the original library and therefore code using this port *cannot* generally be used together with the original lib. This is, of course, a great pity. So if you know of a complete and full interface-compatible VC 6.0 port or if you know how to improve this port, please let me know. Contact: -------- For any suggestions, bug reports, comments and questions please email me to Hume@c-plusplus.de Using this port: ---------------- To use this port, simply extract the files from the archive, give your compiler access to their path, and include them appropriately in your code via #include. If you use the small object allocator directly or indirectly (through the Functor class) you must add SmallObj.cpp to your project/makefile. If you use Singletons with longevity you must add Singleton.cpp to your project/makefile. Fixes: ------ Mar 21, 2003: ------------- * In MultiMethods.h: Added a new explicit template argument specification (ETAS)-workaround for FnDispatcher::Add which is more compliant with other ETAS-workarounds used in this port. Mar 20, 2003: ------------- * In MultiMethods.h: Fixed bugs in FnDispatcher and FunctorDispatcher. Fixing FnDispatcher led to an Interface change (see section "Interface changes"). Mar 08, 2003: ------------- * In HierarchyGenerators.h: implemented transparent workaround for 'explicit template argument specification for nonmeber functions'-bug. The Field-Functions can now be called as in the original lib. Mar 06, 2003: ------------- * In SmartPointer.h: Added helper-macros for convenient specialization of std::less for Smart-Pointers. * I found a way to use void as a default value for template parameters. Therefore I changed MultiMethods.h and Visitor.h accordingly. Feb 2003: --------- * created new versions of Functor.h, Visitor.h and MultiMethods.h that now can handle void return types transparently. * ported SmartPtr's Ownership-Policy RefCountedMT * Added isFunctionPointer to TypeTraits. * Replaced all pointer-type dummy-parameters needed as a workaround for VC's 'explicit template argument specification'-bug with Typ2Type-dummy parameters. * fixed the problems with BindFirst (Functor.h) that led to C1001-Internal compiler errors. * fixed numerous other bugs. Jan 30, 2003: ------------- * In TypeTraits.h: Fixed bugs in TypeTraits' scalar and array detection. const and volatile detection is now based on techniques from boost's type traits (see http://www.boost.org/libs/type_traits/) Added Enum- and pointer-to-member-function-detection code. Thanks to M. Yamada. Jan 12, 2003: ------------- * changed the signature of SmallObject's op new. Now it matches the corresponding op delete. Thanks to M.Yamada for the hint and the solution. Dec 08, 2002: ------------- * In HierarchyGenerators.h: Sergey Khachatrian reported a bug in GenScatterHierarchy when used with a typelist containing equal types (e.g. GenScatterHierarchy<TYPELIST_2(int, int), UnitWrapper> resp. Tuple<TYPELIST_2(int, int)>) Fixing the bug I found another MSVC6-Problem in the Field-function. The workaround for this problems results in an interface change. please refer to the section "Interface changes" below for further information. Dec 03, 2002 ------------- * In MSVC6Helpers.h: The original version failed to qualify some types from the Private-Namespace. Thanks to Adi Shavit for pointing that out * In Threads.h: Changed wrong ctor/dtor names in ObjectLevelLockable. Thanks to Adi Shavit for pointing that out Nov 19, 2002: ------------- * In SmartPtr.h: Changed template ctors. See Notes. Notes: ------ The original Loki Lib uses some pretty advanced (resp. new) C++ features like: A. partial template specialization. B. template template parameters. C. explicit template argument specification for member- and nonmeber functions. D. covariant return types. E. Template parameters with default type void F. return statements with an expression of type cv void in functions with a return type of cv void. Unfortunately the MSVC 6.0 supports neither of them. A. I used various techniques to simulate partial template specialization. In some cases these techniques allowed me to retain the original interfaces but often that was not possible (or better: i did not find a proper solution). In any case it led to increasing code complexity :-) B. One way to simulate template template parameters is to replace the template class with a normal class containing a nested template class. You then move the original functionality to the nested class. The problem with this approach is MSVC's 'dependent template typedef bug'. MSVC 6.0 does not allow something like this: [code] template <class APolicy, class T> struct Foo { // error C2903: 'In' : symbol is neither a class template nor a function template typedef typename APolicy::template In<T> type; }; [/code] To make a long story short, I finally decided to use boost::mpl's apply-technique to simulate template template parameters. This approach works fine with MSVC 6.0. But be warned, this technique uses not valid C++. Of course, replacing template template parameters always results in some interface changes. C. I added dummy-Parameters to (Member-)Functions that depend on explicit template argument specification. These dummy-Parameters help the compiler in deducing the template parameters that otherwise need to be explicitly specified. Example: [code] struct Foo { template <class T> T Func(); }; [/code] becomes [code] struct Foo { template <class T> T Func(Type2Type<T>); }; [/code] in this port. Update: ------- The MSVC 6.0 sometimes does not overload normal functions depending on explicit argument specification correctly (see: Microsoft KB Article - 240871) The following code demonstrates the problem: [code] template <unsigned i, class T> void BugDemonstration(T p) { printf("BugDemonstration called with i = %d\n", i); } int main() { GenScatterHierarchy<TYPELIST_3(int, int, int), TestUnitWrapper> Bla; // will always print: "BugDemonstration called with i = 2"; BugDemonstration<0>(Bla); BugDemonstration<1>(Bla); BugDemonstration<2>(Bla); } [/code] Fortunately there is a transparent workaround for this problem. Simply add a dummy-parameter with a proper default value: [code] template <unsigned i, class T> void BugDemonstration(T p, Int2Type<i>* = (Int2Type<i>*)0) { printf("BugDemonstration called with i = %d\n", i); } int main() { GenScatterHierarchy<TYPELIST_3(int, int, int), TestUnitWrapper> Bla; // will now work correctly BugDemonstration<0>(Bla); BugDemonstration<1>(Bla); BugDemonstration<2>(Bla); } [/code] Unfortunately adding dummy-parameters does not always work. For example for one of FnDispatcher's