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Re: [Chicken-hackers] Chicken 4.13: New bug in syntax-rules

From: Jörg F . Wittenberger
Subject: Re: [Chicken-hackers] Chicken 4.13: New bug in syntax-rules
Date: 26 Feb 2018 10:59:17 +0100

On Feb 24 2018, Peter Bex wrote:

On Mon, Jan 15, 2018 at 10:11:05PM +0100, Peter Bex wrote:
On Sat, Jan 13, 2018 at 03:28:09PM +0100, Jörg F. Wittenberger wrote:
> Hi all,
> > I just boiled down an issue with syntax-rules processing new in chicken
> 4.13.
> > It is a bit involved. I needed three modules to demonstrate it.

Good find!

I've created ticket #1441 to track this.  It also contains a highly
simplified version of this situation which indeed also breaks in
CHICKEN 4.13 but not 4.12.

Hi again,

I did some more research into this bug, and I'm less and less convinced
it's really a bug.  See my findings in the ticket.

If it's not a bug, then I'd need another word to excuse my embarrassment. After all such code used to work for several years (since define-macros went away) until 4.13 came along, broke it and the bug reports I got where: "your code does not even compile!!1!".

I'm not sure that this is "undefined behavior" in the spec. Even though some other Schemes have implementation issues too. Your findings in the ticket seem to indicate that at least Chibi does the right thing, as did 4.12.

We may be able to make it work, but I don't see how just yet.

Neither see I.

However if not, we should at least document under known limitations that there are issues wrt. hygienic macro expansion. (After all it is not nice to send users spending a couple of days to hunt down situations, be them called a bug or a not-bug, where importing unrelated modules breaks things.)



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