Hi all! I'm struggeling to understand what cFlow(P) && cFlow(Q) and cFlow(P && Q) do, how they differ - and why.
I've already posted to StackOverflow, but there don't seem that many AspectJ users around, so I thought I'd ask the question again, on the mailing list. (Here's the URL to the original post, by the way: http://stackoverflow.com/q/30039559/2018047 ) Basically, I was looking at the doc's section on Pointcut composition: https://www.eclipse.org/aspectj/doc/released/progguide/language-joinPoints.html#pointcut-composition As I already pointed out, I'm a bit confused how the two concepts, cFlow(P) && cFlow(Q) and cFlow(P && Q), work. I did a bit of googeling, and found a rather helpful PowerPoint presentation (for a course at the university of Utrecht), which explains: >>cflow is the collection of join points flowing from the argument pointcut. >>This means that cflow(P) && cflow(Q) is the intersection of the two >>collections, while cflow(P && Q) means that you first combine the pointcuts P >>and Q, and all the join points flowing from that are in this collection.<< They go on to list all join points for cFlow(P) && cFlow(Q) (pointcut flowPAndflowQ() : cflow(execution(* Example.P(..))) && cflow(execution(* Example.Q(..))) && within(Example);), and to me it looks like an intersection of all the control flow points of the individual statements - P ∩ Q, if you will (just like they said): Flow from P - execution(void Example.P()) Flow from P - call(void Example.Q()) Flow from P - execution(void Example.Q()) Flow from Q - execution(void Example.Q()) Flow from P && flow from Q - execution(void Example.Q()) (Their example is like the one in the AspectJ docs, except for the lacking println() statement.) What I still struggle with is to understand what cFlow(P && Q) does, and how it differs from cFlow(P) && cFlow(Q). On StackOverflow, medvedev1088 tried to explain it, and pointed out that the last section of the quote above should read >>cflow(P && Q) means that you first _intersect_ the pointcuts P and Q, and all the join points flowing from that are in this collection<< But I still don't really get it. (For example, how can both be an intersection?) Could someone please provide me with an example when cFlow(P && Q) would work, maybe even with a list of all the join points concerned, like above? Initially, I had thought it meant 'add all flow points in P and Q (i.e. P + Q)', which should be the superset (union) to P ∩ Q, P ∪ Q? But apparently, that's not it. I've also been told it's not all flow points that could be triggered by both, P and Q, i.e. all flow points within X() below: public void P() { X(); } public void Q() { X(); } public void X() { /* all that is in the body of X() */ } medvedev1088 pointed out that >>pointcut P defines a single join point: execution(void Example.P()), and pointcut Q defines a single join point: execution(void Example.Q()). Because these join points are different the intersection for them is an empty set. cflow taken from an empty set is an empty set too.<< But for the above example, isn't that precisely what the execution of X() would represent? (Or would that only be true if both, P and Q would call X() together and at the same time?) Just for my own sake, I think cFlow(P && Q) would look as follows when written out, right? pointcut cFlowOfPandQ : cFlow(execution(* Example.P()) && execution(* Example.Q())) && within(Example); Is the whole point that you can't execute P and Q at the same time? (Isn't that what happens when P calls Q, though?) Any help in disentangling this for me would be much appreciated! Kind regards, Christian _______________________________________________ aspectj-users mailing list aspectj-users@eclipse.org To change your delivery options, retrieve your password, or unsubscribe from this list, visit https://dev.eclipse.org/mailman/listinfo/aspectj-users
