NewObj use on template with several typename.

  • On 09/03/2016 at 15:38, xxxxxxxx wrote:

    User Information:
    Cinema 4D Version:   R17 
    Platform:      Mac OSX  ; 
    Language(s) :     C++  ;

    I'm not sure if we can call that a bug or if it's problem with my syntax.

    i've defined a class using template with several typename. NewObj doesn't want those templates.
    i've got the message "parse issue"
    : Expected '>'
    : Type name requires a specifier or qualifier

    a very simplified class :

    template <typename T, typename T2>
    class myclass
        T toto;
        T2 tata;
    template <typename T, typename T2> myclass<T, T2>::myclass() {  }
    template <typename T, typename T2> myclass<T, T2>::~myclass(){  }
    //somewhere else
    // got the error message
     myclass<Int32, Vector>* titi = NewObj(myclass<Int32, Vector>); 

    the following code generate error :
    : Too many arguments provided to function-like macro invocation
    : Use of undeclared identifier 'SIZEOF'

    Int theSize = SIZEOF(myclass<Int32, Vector>);

    but the following compile with no errors (but i know it's not a clean solution) :

    myclass<Int32, Vector>* toto = MAXON_SAFE_PLACEMENT_NEW(maxon::DefaultAllocator::Alloc((maxon::Int)sizeof(myclass<Int32, Vector>), C4D_MISC_ALLOC_LOCATION)) myclass<Int32, Vector>(); 

    It does work if myclass only got one typename.

    Thanks a lot.

  • On 10/03/2016 at 04:06, xxxxxxxx wrote:

    Hey Valkaari, this is a known problem with macros. The comma in the template arguments is used as
    separator for the macro arguments instead. This answer from SO might help you:

    Basically, you build another macro that wraps the type for you, like this:

    template<typename T> struct get_first_param;
    template<typename R, typename P1> struct get_first_param<R(P1)> {
      typedef P1 type;
    #define Identity(...) get_first_param<void(__VA_ARGS__)>::type
    // Then to use NewObj() :
    myclass<Int32, Vector>* obj = NewObj(Identity(myclass<Int32, Vector>));

  • On 10/03/2016 at 06:21, xxxxxxxx wrote:


    As specified on the stackoverflow thread, the type wrapper is useful because it works with previous C++11 standard where variadics arguments in macro weren't introduced yet.
    If you can use __VA_ARGS__ then this should works:

    #define FIX_ARG(...) __VA_ARGS__
    myclass<Int32, Vector>* tata = NewObj(FIX_ARG(myclass<Int32, Vector>));

    or (worst) :

    #ifdef SIZEOF 
        #undef SIZEOF 
    #define SIZEOF(x...) ((maxon::Int)sizeof(x)) 
    #define COMMA , 
    myclass<Int32, Vector>* tata = NewObj(myclass<Int32 COMMA Vector>); 

  • On 10/03/2016 at 09:24, xxxxxxxx wrote:


    it seems that using a typedef may also help:

    typedef myclass<Int32, Vector> IntVectorClass;  
    IntVectorClass* intVector = NewObj(IntVectorClass);  

    best wishes,

  • On 11/03/2016 at 02:26, xxxxxxxx wrote:

    Thanks for the answers, several solutions, i like it :)
    And more important i think i understood all the solutions.

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