[plt-scheme] Hang in macro stepper when macro expansion does not terminate

On Sep 2, 2009, at 5:53 PM, Matthias Felleisen wrote:

> Sadly Ryan thinks that the macro stepper should execute the code  
> through which you step. I am hoping that everyone on this list can  
> help me convince him that this shouldn't be the case ...
>
> Use STOP to kill the execution as normal.

Matthias: This is not about nonterminating execution. It is about  
nonterminating expansion.

Brian: Clicking Stop is supposed to interrupt expansion. I'll try to  
see why it isn't working. BTW, what platform do you see the problem on?

Ryan



> On Sep 2, 2009, at 5:38 PM, Brian Mastenbrook wrote:
>
>> Hello,
>>
>> When trying to use the macro stepper on a program whose macro  
>> expansion does not terminate, the macro stepper will hang, and  
>> clicking Stop in the editor window toolbar does not help. Sending a  
>> SIGINT to the DrScheme process resolves the issue. I'm not  
>> expecting it to not hang if a form on the right-hand side of a  
>> `define-syntax' or `let-syntax' recurses infinitely, but when the  
>> expansion process does not terminate, it would still be nice to be  
>> able to use the macro stepper to determine what's going on.
>>
>> Just for clarity, this is an example of the type of program I'm  
>> talking about:
>>
>> #lang r5rs
>>
>> (define-syntax foo
>> (syntax-rules ()
>>   ((_) (foo))))
>>
>> (foo)
>> --
>> Brian Mastenbrook
>> brian at mastenbrook.net
>> http://brian.mastenbrook.net/
>>
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