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

From: Matthias Felleisen (matthias at ccs.neu.edu)
Date: Wed Sep 2 17:53:48 EDT 2009

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.

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/
> _________________________________________________
> For list-related administrative tasks:
> http://list.cs.brown.edu/mailman/listinfo/plt-scheme

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