Re: [aspectj-dev] Use of non-statically resolvable pointcut designators

[Adrian Colyer <adrian_colyer@xxxxxxxxxx>]

That's exactly what I was looking for
:) - couldn't find it because we were searching on "error" and
"warning" - neither of which appear in that section.

The presence of this section in the
docs, and the previous discussions, lead me to conclude that the correct
behaviour is to put out a compilation error when any of the forbidden forms
are used inside a deow (or in fact, any other form of declare).  [Andy,
could you extend the test case to include the other declare forms too please?].


Might be worth an FAQ entry too before
we're done.

-- Adrian
Adrian_Colyer@xxxxxxxxxx

Wes Isberg <wes@xxxxxxxxxxxxxx> Sent by: aspectj-dev-admin@xxxxxxxxxxx 23/02/2004 18:24 Please respond to aspectj-dev

To:        aspectj-dev@xxxxxxxxxxx         cc:                 Subject:        Re: [aspectj-dev] Use of non-statically resolvable pointcut designators in declare error/warning.

 > ...but I couldn't find it clearly stated
 > anywhere.

It's documented in the semantics appendix to the programming guide;
see "Staticly determinable pointcuts"

http://dev.eclipse.org/viewcvs/indextech.cgi/~checkout~/aspectj-home/doc/progguide/semantics-declare.html#d0e6499

Anything of note should be in the semantics or limitations appendices
or be in Buzilla with the keyword "info".

Wes

Adrian Colyer wrote:
> As a follow-up - Andy & I went searching all through our docs
looking for 
> the place where we say that you can only use statically evaluable
> pointcuts in declare eow statements, but I couldn't find it clearly
stated 
> anywhere. (I half recall seeing a list that said "You can only
use the 
> following pcds..." but if it's there, I couldn't find it).
> 
> I think the simplest thing for users to understand is a compilation
error 
> if any of this, target, args, cflow, cflowbelow or 'if' are used in
the 
> pointcut _expression_ associated with a deow. But, this might break
many 
> existing programs that are currently "getting away with it."
> 
> The next best option seems to me to be to emit a compiler warning
saying 
> that "xxx pcd cannot be used in declare error or warning statements
and 
> will be ignored." (And then of course, make sure that we really
do ignore 
> it). Given our current position, this is possibly what we should do
for 
> 1.2 (leaving us the option to make it an error in 1.3 once programs
have 
> been tidied up perhaps?).
> 
> Both of these options have the drawback of not supporting some deow
tests 
> that would have succumbed to full static evaluation. If that's important
> enough, we could consider warning only when a non-statically determinable
> situation occurs - but what I dislike about this option is that this
can't 
> be determined when compiling the aspect, but only during shadow matching
> (which could be at a completely different time if e.g. you are binary
> weaving). 
> 
> So I think at the moment I'm leaning towards:=
> 1) making the docs clearer about exactly which pcds are supported
for 
> deow, and
> 2) following a warn-and-ignore strategy for violations of that policy
> 
> Open to counter-arguments though...
> 
> -- Adrian
> Adrian_Colyer@xxxxxxxxxx
> 
> 
> 
> 
> Andrew Clement/UK/IBM@IBMGB
> Sent by: aspectj-dev-admin@xxxxxxxxxxx
> 23/02/2004 16:16
> Please respond to aspectj-dev
>  
>         To:     aspectj-dev@xxxxxxxxxxx
>         cc: 
>         Subject:        [aspectj-dev]
Use of non-statically resolvable 
> pointcut designators in declare error/warning.
> 
> 
> 
> Hi, 
> 
> I'm looking at a bug on this - and I noticed someone else mailed 
> the list on a similar topic earlier today. 
> 
> Eric Bodden reported a problem with using if() in a declare 
> warning/error message.  This was a ClassCastException - which
of 
> course I'll fix - but it made me think more about what our 
> position is on allowing users to use pointcuts that can't 
> be wholely resolved at compile time with the declare error/warning
> mechanism. 
> 
> At the moment, if a pointcut cannot be entirely statically 
> evaluated then it will behave as if it has matched and the error 
> or warning message will be produced.  I don't think this is 
> quite what we want. 
> 
> However, it is not clear whether we should be flagging an 
> error if any of the designators that exhibit this behavior 
> are used against declare error/warning or if we should be 
> flagging an error/warning if it just the case that the entire 
> pointcut cannot be completely resolved statically.  There are
> some designators that *could* lead to runtime tests but might 
> not if there is enough static info around.  For example 
> target()/this() may or may not create an instanceof test for 
> execution at runtime depending on what the compiler can 
> determine statically. 
> 
> So, we have the options: 
> 
> Error/Warning if we see a declare error/warning statement whose 
> pointcut uses any of the designators that *might* 
> lead to dynamic residue. 
> 
> Error/Warning if we see a declare error/warning statement whose 
> pointcut cannot be completely statically evaluated. 
> 
> Any comments? 
> Andy. 
> --- 
> Andy Clement 
> AJDT/AspectJ Development
> 

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