Re: [Guile-commits] GNU Guile branch, stable-2.0, updated. v2.0.1-40-g2252321

[ludo@gnu.org (Ludovic Courtès)]

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Hi Andreas,

(Sorry for the laaaate reply, I'm just slowly catching up.)

Andreas Rottmann <a.rottmann@gmx.at> skribis:

> Andreas Rottmann <a.rottmann@gmx.at> writes:
>
>> ludo@gnu.org (Ludovic Courtès) writes:
>>
>>> Hi Andreas,
>>>
>>> Thanks for taking care of this, and thanks for the great doc too!
>>>
>>> "Andreas Rottmann" <a.rottmann@gmx.at> writes:
>>>
>>>> commit 2252321bb77fe83d98d5bcc9db1c76b914e9dd6a
>>>> Author: Andreas Rottmann <a.rottmann@gmx.at>
>>>> Date:   Sat May 7 23:40:14 2011 +0200
>>>>
>>>>     Make the R6RS simple I/O library use conditions
>>>>     
>>>>     * module/rnrs/io/ports.scm (display): Implement as an
>>>>       exception-converting wrapper around Guile's core display.
>>>>     * module/rnrs/io/simple.scm: Don't export Guile's corresponding core
>>>>       procedures, but use `(rnrs io ports)' instead.  This way, we get the
>>>>       conditions required by R6RS raised.
>>>>     
>>>>     * doc/ref/r6rs.texi (rnrs io simple): Mention that these procedures are
>>>>       supposed to raise R6RS conditions.
>>>
>>> Could you add one or more test cases?
>>>
>> I've started to hack on this, aiming for at least providing tests of a
>> "control sample" of exception-related behaviors in `(rnrs io simple)'
>> and parts of `(rnrs io ports)'.  However, as this is already
>> significantly more than one test, it may take a bit.  I could however
>> push my existing work at any point, if that's needed for any reason.
>>
> I've now pushed a first patch (b6a66c2), in the process fixing two bugs.
> These were not directly related to the simple I/O change you referenced,
> but located in its base library `(rnrs io ports)'.


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+(define (with-i/o-port-error port make-primary-condition thunk)
+  (with-throw-handler 'system-error
+      thunk
+    (lambda args
+      (let ((errno (system-error-errno args)))
+        (if (memv errno (list EIO EFBIG ENOSPC EPIPE))
+            (raise (condition (make-primary-condition)
+                              (make-i/o-port-error port)))
+            (apply throw args))))))
+
+(define-syntax with-textual-output-conditions
+  (syntax-rules ()
+    ((_ port body0 body ...)
+     (with-i/o-port-error port make-i/o-write-error
+       (lambda () (with-i/o-encoding-error body0 body ...))))))

[...]

 (define (put-char port char)
-  (with-i/o-encoding-error (write-char char port)))
+  (with-textual-output-conditions port (write-char char port)))
 
 (define (put-datum port datum)
-  (with-i/o-encoding-error (write datum port)))
+  (with-textual-output-conditions port (write datum port)))

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I'm a bit concerned about the performance implications of the above
change: ‘put-char’, ‘put-datum’, etc. now expand to something like

     (with-i/o-port-error p xxx
       (lambda ()
         (with-throw-handler 'decoding-error
           (lambda ()
             (write-char c p))
           (lambda (key subr message errno port)
             (raise (make-i/o-decoding-error port))))))

So there are at least 4 additional function calls (2
‘with-throw-handler’ calls, and 2 anonymous closure calls.)

Did you do any measurements?  Would be nice to add micro-benchmarks
under benchmark-suite/.

One optimization would be to instead do something such that ‘put-char’
would expand to something like:

  (define (put-char p c)
    (with-throw-handler #t
           (lambda ()
             (write-char c p))
           (lambda args
             (case (car args)
               ((decoding-error)
                (raise (make-i/o-decoding-error p)))
               ((system-error)
                (if (memv (system-error-errno args)
                          `(,EIO ,EFBIG ,ENOSPC ,EPIPE))
                    ...))
               (else
                ;; Not for us.
                (apply throw args))))))

What do you think?

Thanks,
Ludo’.