Re: whither stack traces?

The SML'97 basis functions exnName and exnMessage are probably
being used for this purpose.

	- John

On Nov 28, 2006, at 5:07 PM, Dave Herman wrote:

>> exportML is setup to map uncaught exceptions to an exit with a
>> failure status. It does not print an exception trace, since people
>> may want to run executables in situations where I/O is not possible.
>> You can print your own  trace using the SMLofNJ.exnHistory function.
>
> I think I'm 95% of the way there. I can't completely reproduce the  
> behavior of the REPL's backtrace facility, since I don't know what  
> is used to print out information about the exception. The best I  
> could muster was:
>
>     fun exnDetails (Fail s)  = SOME ("Fail: " ^ s)
>       | exnDetails Bind      = SOME "nonexhaustive binding failure"
>       | exnDetails Match     = SOME "nonexhaustive match failure"
>       | exnDetails Div       = SOME "divide by zero"
>       | exnDetails Domain    = SOME "domain error"
>       | exnDetails Overflow  = SOME "overflow"
>       | exnDetails Size      = SOME "size"
>       | exnDetails Subscript = SOME "subscript out of bounds"
>       | exnDetails _         = NONE
>
>     fun printStackTrace e =
>         let val ss = SMLofNJ.exnHistory e
>         in
>             TextIO.print ("uncaught exception " ^ (exnName e));
>             (case (exnDetails e) of
>                   SOME s => TextIO.print (" [" ^ s ^ "]\n")
>                 | NONE => TextIO.print "\n");
>             List.app (fn s => TextIO.print ("\t" ^ s ^ "\n")) ss
>         end
>
> Since exportML doesn't print backtraces by default, it would be  
> nice if SMLofNJ had a monitorExn function, analogous to  
> BackTrace.monitor, for printing out backtraces exactly as at the REPL.
>
>> The Backtrace stuff provides a finer-grain trace, but at a runtime
>> performance cost.
>
> This took me quite some time to find. Is there documentation other  
> than in the HISTORY file?
>
> Thanks very much!
>
> Regards,
> Dave
>
>


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