[aspectc-user] aspect inheritance

Fabian Scheler fabian.scheler at gmail.com
Thu Jul 14 09:00:28 CEST 2005


the explanation for the error message is as follows:
AspectC++ transforms aspects into classes and by default such a class
is instantiated once in global scope, so the constructor of the
particular aspect class has to be called. In your aspect you did not
specify any constructor at all, so the default constructor is used for
this purpose. Now your aspects inherits from class A, t.m. the
constructor of class A has to be executed, too, again the default
constructor is used (how should the C++-compiler know which
constructor to use, if you did not specify it, and you did not specify
it, because your aspect does not provide a constructor). And this
default constructor of class A is not available, because you defined
another one with a different signature (t.m. your constructor takes an
argument, while the default constructor does not).

possible solution:
- define a constructor for your aspect 'asp'
- specify the constructor to be used for the construction of
'A'-Objects within the constructor of aspect 'asp'
- define a method 'asp* asp:aspectof()' that instantiates your aspect
using the user-defined constructor

Ciao, Fabian

On 7/14/05, Jamal Siadat <siadat at cpsc.ucalgary.ca> wrote:
> Hi,
> I have tried to add a methods to a class using aspects. It works really
> fine when the constructor of the class that I'm adding the methods to does
> not take any arguments. But When the constructor is taking arguments for
> some reason the weaving process is not performed correctly. Here is an
> example of what I mean:
> aspect file (asp.ah):
> aspect asp :public A {
> pointcut calls()=  "A" ;
> advice calls() :   void initialize () {p=0;j=0;}
> };
> A.h:
> class A {
>  public:
>     A(int x);
>   int j;
>   int a(const char *name, float b);
>  private:
>   int p;
> };
> A.cc:
> A::A(int x) {j=x; }
> int A::a( const char *name, float b) {
>   int jam=7;
> return jam;
> }
> int main (){
>   A b(5);
>   return 0;}
> now if you run "ag++ -o t A.cc -a asp.ah" the weaving process works fine
> but you'll have the following c++ errors:
> asp.ah:7: error: base `A' with only non-default constructor in class
> without a constructor
> : In static member function `static asp* asp::aspectof()':
> :4: error: no matching function for call to `asp::asp()'
> asp.ah:7: error: candidates are: asp::asp(const asp&)
> does anyone know how to get around this? I know you can remove public A
> and then it wont give you this error but you wont be able to access the
> variables in A! so I need to inherite A.
> Thanks in advance
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