[aspectc-user] aspect conflict resolution

[Olaf Spinczyk]

HI,

Olaf Spinczyk wrote:
> Hi Matthias,
> 
> mathias.kurth at s2000.tu-chemnitz.de wrote:
> 
>> Hello,
>>
>> I've got a question about aspect conflict resolution in AspectC++. I 
>> have the following aspects:
>>
>>     aspect Outer1 {
>>       pointcut virtual p() = 0;
>>             advice p() : before() {
>>         printf("before p in Outer1\n");
>>       }
>>     };
>>
>>     aspect Outer2 : public Outer1 {
>>       pointcut virtual p() = call("% %::Print(...)");
>>     
>>       advice p() : before() {
>>         printf("before p in Outer2\n");
>>       }
>>     };
>>     
>> How is the order of the advices to p() defined?
>> In AspectJ it is said that all advices in the derived class
>> do have prefenence over the advices in the base class.
>> I've tried to apply this to the aspect compiler, but
>> the result was the following:
>>
>>     static inline void a0_before_Outer2_call_main_FiiPPcE_0() {
>>         printf("before p in Outer2\n");
>>     }
>>     static inline void a0_before_Outer2_call_main_FiiPPcE_0() {
>>         printf("before p in Outer1\n");
>>     }
>>     static inline void __call_main_FiiPPcE_0_0 (::test::CAspectTest1 
>> *dstthis) {
>>         a0_before_Outer2_call_main_FiiPPcE_0();
>>         a0_before_Outer2_call_main_FiiPPcE_0();
>>         dstthis->Print ();
>>     }
>>
>> I think this is surely not the expected result. The generated
>> output was not compileable with the backend compiler.
> 
> 
> This is a code generation bug. I added it to bugzilla (bug 99). We will 
> fix this problem as soon as possible.
> 
>> Another point is what would be if the pointcut was not virtual.
>> How is the order defined if the base and the derived aspects
>> do advice to some pointcuts which include the same join points?
> 
> 
> There is no rule, which defines the order of advice execution, in 
> AspectC++, yet. However, our goal is/was to adopt the AspectJ default 
> ordering, but, for example, before advice of a base aspect is executed 
> after before advice on the same join point in the derived aspect.
> 
> This behavior will change in the near future and a section on advice 
> ordering will be added to the reference manual, which defines a default 
> ordering rule that you can rely on.

I'm sorry, I was a bit confused, when I wrote this. As you said: in 
AspectJ the advice of the derived aspect has precedence. That's the way 
how it is implemented in AspectC++ as well. The only problem was the 
code generation bug, which is BTW already fixed.

However, we still have to check and document the other precedence rules.

Yours,

Olaf