bugKawa - Bugs: bug #40869, self-referential (cyclic) syntax...


bug #40869: self-referential (cyclic) syntax template

Submitted by:  John Tobey <jtobey>
Submitted on:  Wed 11 Dec 2013 04:04:51 AM UTC  
Category:  Scheme language Severity:  3 - Normal
Item Group:  Run-time exception Status:  Fixed
Privacy:  Public Assigned to:  Per Bothner <bothner>
Open/Closed:  Closed

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Fri 20 Dec 2013 08:33:47 PM UTC, comment #5:

Checked in the patch.

Per Bothner <bothner>
Project AdministratorIn charge of this item.
Mon 16 Dec 2013 01:02:22 PM UTC, comment #4:

This patch works for me, thanks.

John Tobey <jtobey>
Sun 15 Dec 2013 11:38:52 PM UTC, comment #3:

Could you try SyntaxTemplate.patch ?
It seems that would still catch cycles, while ruling out some classes of false positives related to macro-generated macros,

(file #29929)

Per Bothner <bothner>
Project AdministratorIn charge of this item.
Sat 14 Dec 2013 08:00:17 PM UTC, comment #2:

Thanks. I haven't got as far as debugging the Java, but simply disabling the cycle check works around the problem.

If it is hard to fix in the current design, perhaps a limit of 1000 (or some configurable number) of template expansions would serve the same purpose, albeit less elegantly. Or an --i-know-what-im-doing flag to disable the check at run time.

In case it helps, at the point of error, form.toString() is "(false)".

John Tobey <jtobey>
Wed 11 Dec 2013 04:27:23 AM UTC, comment #1:

If you grep though kawa/lang/*Syntax*.java for the string DEBUGGING you'll see things can be uncommented to get debugging output. If you want to try to debug it yourself, you might find this link a useful (if slightly dated) introduction:

Per Bothner <bothner>
Project AdministratorIn charge of this item.
Wed 11 Dec 2013 04:04:51 AM UTC, original submission:

Given this comment in kawa/lang/SyntaxTemplate.java:
Would you like me to create a minimal test case? I do not want to waste my time, since you seem to know about a bug that causes this error. My program dies with this error under Kawa but works under Chibi. Looking at my syntax templates, I do not see how they can be cyclic, but they are very complex, so I am unsure. Perhaps there is some --debug option to print each template as it is applied...

John Tobey <jtobey>


(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

Attach Files:

Attached Files
file #29929:  SyntaxTemplate.patch added by bothner (2KiB - text/x-patch - Possible patch.)


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    Follow 4 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2013-12-20 bothner StatusNone => Fixed
        Open/ClosedOpen => Closed
    2013-12-15 bothner Attached File- => Added SyntaxTemplate.patch, #29929
        Assigned toNone => bothner

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