[LC++]C++ Template Instantiation problems

[Dr Mark H Phillips]

Hi Charles,

I compiled your code on my machine, using gcc version 2.95.4
and got error messages which are a bit different from what you
reported.  I include them below. Hopefully they are helpful to 
you.

Cheers,

Mark.


cr2.cc: In function `int main(int, const char *const *)':
cr2.cc:67: initialization of non-const reference type `void (A::* &)()'
cr2.cc:67: from rvalue of type `void (A::*)()'
cr2.cc:47: in passing argument 2 of `gx_callback::make_M2<A, void
(A::*)()>(A &,
void (A::* &)())'
cr2.cc: In function `static class gx_callback gx_callback::make_M2<A,
void (A::*)()>(A &, void (A::* &)())':
cr2.cc:67:   instantiated from here
cr2.cc:49: cannot allocate an object of type `gx_memberCB<A,void
(A::*)()>'
cr2.cc:49:   since the following virtual functions are abstract:
cr2.cc:7:       void gx_callbackBaseBody::operator ()() const




On Sat, 2002-08-31 at 01:17, Charles Randle wrote:
> Hi All,
> This is a repost due to an email address change :
> 
> I have the following code :
> #include <iostream>
> 
>   class gx_callbackBaseBody {
>   public:
>     gx_callbackBaseBody() {}
>     virtual ~gx_callbackBaseBody() {}
>     virtual void operator ()() const = 0;
>   };
> 
> 
> 
>   class gx_callback {
>   public:
> 
>     gx_callback(gx_callbackBaseBody *ptr) :
> entity(ptr) {}
>     gx_callback(gx_callback const & arg) :
> entity(arg.entity) {}
>     ~gx_callback() { delete entity;entity = 0;return;}
>     void operator ()() { (*entity)();}
> 
>     template <class CLIENT,class CLIENTMEMBER>
>     static gx_callback make_M2(CLIENT &,CLIENTMEMBER
> &);
> 
>   private:
>     gx_callbackBaseBody *entity;
>   };
> 
> 
> 
>   template <class CLIENT,class MEMBER>
>   class gx_memberCB : public gx_callbackBaseBody {
>   public:
>     gx_memberCB(CLIENT &clnt,MEMBER &clntmem) :
> client(clnt),clientmember(clntmem) {}
>     virtual void operator () () { ((&client)
> ->*member)();}
> 
>   private:
>     CLIENT &client;
>     MEMBER &clientmember;
>   };
> 
>   template <class CLIENT,class CLIENTMEMBER>
>   gx_callback gx_callback::make_M2(CLIENT
> &c,CLIENTMEMBER &cm) {
>     return gx_callback(new
> gx_memberCB<CLIENT,CLIENTMEMBER>(c,cm));
>   }
> 
> 
> class A {
> public:
>   A(){}
>   ~A(){}
>   void noretsnoargs() {::std::cerr << "NO returns & No
> Args !!" << ::std::endl;return;}
>  };
> 
> 
> int main (int argc,char const * const * const argv) {
> 
>   A objectA;
> 
>   gx_callback test1
> (gx_callback::make_M2(objectA,&A::noretsnoargs));
>   //
>   // Execute object
>   test1();
> }
> 
> 
> Which gives the following error on compilation:
> 
> g++     cbtest.cpp   -o cbtest
> cbtest.cpp: In function `int main(int, const char*
> const*)':
> cbtest.cpp:62: no matching function for call to
> `gx_callback::make_M2(A&, void
>    (A::*)())'
> cbtest.cpp:42: candidates are: static gx_callback
> gx_callback::make_M2(CLIENT&,
>    CLIENTMEMBER&) [with CLIENT = A, CLIENTMEMBER =
> void (A::*)()]
> make: *** [cbtest] Error 1
> 
> 
> Can anyone explain this and possibly suggest a
> solution.
> 
> Best Regards,
> Charles Randle
> 
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-- 
Dr Mark H Phillips
Research Analyst (Mathematician)

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