Re: [abc-dev] Modifying context capture behavior

From: Eduardo S. Cordeiro <>
Date: Tue Oct 24 2006 - 16:18:36 BST

So...I've managed to fix the problem, with not much further effort. The
problem was that I was filtering /context /right after the call to
/findLocalsGoingIn/, but the repeated variables are needed to assemble
the proceed call inside /extractShadowIntoLocalMethod/. So moving the
filtering code to that part of the method works, and there are no more
repeated context variables.

Thanks and sorry for the trouble,
Eduardo Cordeiro
Master Student - UFMG

Eduardo S. Cordeiro wrote:
> Hello there,
> I've recently sent a personal "help wanted" email to Eric Bodden about
> modifying the context capture behavior of abc for around advices, and
> he mentioned this list as a better reference. Since then, I've been
> studying the abc source-code and trying to get this done, with not
> much success, and I hope that maybe someone can give me a hand with this.
> When weaving around advices, the weaver creates inlined
> implementations of the advice body, and captures available context to
> be used as signature for these methods. However, variables can be
> needed for an advice implementations for two reasons: the programmer
> has explicitly captured them (via args, target and this clauses) or
> they're required for the execution of the extracted join point. There
> might be an interception between these sets, but abc doesn't detect
> this, and some context variables are repeated on inlined advice
> implementation's signatures.
> While trying to fix this problem, I've been reading the source-code
> for around weaving, and at this time I'm concentrating on the
> AdviceApplicationInfo class. The list of context variables implicitly
> needed for the shadow execution is calculated by the
> /findLocalsGoingIn/ method of this class, which returns a list I'll
> call /context/. The variables captured by the programmer are stored in
> /Bind/ residues, which, I assume (as I haven't studied the code to
> this level), are built by the front-end.
> Inside /AdviceApplicationInfo.doWeave/, after the call to
> /findLocalsGoingIn/, if one removes from /context/ the locals that are
> contained in the residue's bindings, the inlined advice's signature is
> simplified correctly, and repeated context variables disappear.
> However, the method's body, as one might expect, becomes corrupted,
> specifically at the proceed method call, which uses uninitialized locals.
> I've spent the last week trying to identify a way to fix this problem,
> with no success. It seems that, in the beginning of the advice body,
> context values are loaded from the first list of variables to other
> frame positions, and these positions are used to load arguments for
> the proceed call. However, after removing the repeated variables from
> /context/, these store instructions are no longer generated. Can
> anyone give me hints on relevant portions of the weaver source-code
> to modify so that the advice body doesn't become corrupted by this
> instruction?
> Thanks and best regards,
> Eduardo Cordeiro
> Master Student - UFMG
Received on Tue Oct 24 17:36:30 2006

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