Bug #252221 “Infinite loop on broken pipe” : Bugs : Ikarus Scheme

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Abdulaziz Ghuloum (aghuloum) wrote on 2008-07-27:

#1

I tried the command line that you mention but nothing happens. I tried it on Mac OS X and Debian and it was terminating as usual:

Can you list what happens when you issue that command line. Also, can you provide more information about your operating system/environment. Thanks.

Revision history for this message

Derick Eddington (derick-eddington) wrote on 2008-07-27: Re: [Bug 252221] Re: Infinite loop on broken pipe

#2

On Sun, 2008-07-27 at 07:02 +0000, Abdulaziz Ghuloum wrote:
> I tried the command line that you mention but nothing happens.

The problem happens to me on Ubuntu 8.04.

$ strace ikarus 2>/tmp/ikarus-read-read.strace | (read;read)

ikarus-read-read.strace:

execve("/home/d/bin/ikarus", ["ikarus"], [/* 45 vars */]) = 0
[...all the start-up stuff...]
write(1, "Ikarus Scheme version 0.0.3+ (re"..., 62) = 62
write(1, "\n", 1) = 1
write(1, "Copyright (c) 2006-2008 Abdulazi"..., 43) = 43
write(1, ">", 1) = -1 EPIPE (Broken pipe)
write(1, ">", 1) = -1 EPIPE (Broken pipe)
write(1, ">>", 2) = -1 EPIPE (Broken pipe)
write(1, ">>", 2) = -1 EPIPE (Broken pipe)
write(1, ">>>", 3) = -1 EPIPE (Broken pipe)
write(1, ">>>", 3) = -1 EPIPE (Broken pipe)
write(1, ">>>>", 4) = -1 EPIPE (Broken pipe)
write(1, ">>>>", 4) = -1 EPIPE (Broken pipe)
write(1, ">>>>>", 5) = -1 EPIPE (Broken pipe)
write(1, ">>>>>", 5) = -1 EPIPE (Broken pipe)
write(1, ">>>>>>", 6) = -1 EPIPE (Broken pipe)
write(1, ">>>>>>", 6) = -1 EPIPE (Broken pipe)
write(1, ">>>>>>>", 7) = -1 EPIPE (Broken pipe)
write(1, ">>>>>>>", 7) = -1 EPIPE (Broken pipe)
write(1, ">>>>>>>>", 8) = -1 EPIPE (Broken pipe)
write(1, ">>>>>>>>", 8) = -1 EPIPE (Broken pipe)
[...]
write(1, ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>"..., 4775) = -1 EPIPE (Broken pipe)
write(1, ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>"..., 4775) = -1 EPIPE (Broken pipe)
write(1, ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>"..., 4776) = -1 EPIPE (Broken pipe)
write(1, ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>"..., 4776) = -1 EPIPE (Broken pipe)

The cause is in ikarus.cafe.ss. The (read;read) consumes the first two
lines of the banner, then when (display-prompt 0) is attempted it raises
a broken pipe exception, the handler then attempts (flush-output-port
(console-output-port)) which raises a broken pipe exception, the next
handler invokes the reset continuation which loops back to attempting
another (display-prompt 0).

On Sun, 2008-07-27 at 07:02 +0000, Abdulaziz Ghuloum wrote:
> I tried the command line that you mention but nothing happens.

The problem happens to me on Ubuntu 8.04.

$ strace ikarus 2>/tmp/ikarus-read-read.strace | (read;read)

ikarus-read-read.strace:

execve("/home/d/bin/ikarus", ["ikarus"], [/* 45 vars */]) = 0
[...all the start-up stuff...]
write(1, "Ikarus Scheme version 0.0.3+ (re"..., 62) = 62
write(1, "\n", 1)                       = 1
write(1, "Copyright (c) 2006-2008 Abdulazi"..., 43) = 43
write(1, ">", 1)                        = -1 EPIPE (Broken pipe)
write(1, ">", 1)                        = -1 EPIPE (Broken pipe)
write(1, ">>", 2)                       = -1 EPIPE (Broken pipe)
write(1, ">>", 2)                       = -1 EPIPE (Broken pipe)
write(1, ">>>", 3)                      = -1 EPIPE (Broken pipe)
write(1, ">>>", 3)                      = -1 EPIPE (Broken pipe)
write(1, ">>>>", 4)                     = -1 EPIPE (Broken pipe)
write(1, ">>>>", 4)                     = -1 EPIPE (Broken pipe)
write(1, ">>>>>", 5)                    = -1 EPIPE (Broken pipe)
write(1, ">>>>>", 5)                    = -1 EPIPE (Broken pipe)
write(1, ">>>>>>", 6)                   = -1 EPIPE (Broken pipe)
write(1, ">>>>>>", 6)                   = -1 EPIPE (Broken pipe)
write(1, ">>>>>>>", 7)                  = -1 EPIPE (Broken pipe)
write(1, ">>>>>>>", 7)                  = -1 EPIPE (Broken pipe)
write(1, ">>>>>>>>", 8)                 = -1 EPIPE (Broken pipe)
write(1, ">>>>>>>>", 8)                 = -1 EPIPE (Broken pipe)
[...]
write(1, ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>"..., 4775) = -1 EPIPE (Broken pipe)
write(1, ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>"..., 4775) = -1 EPIPE (Broken pipe)
write(1, ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>"..., 4776) = -1 EPIPE (Broken pipe)
write(1, ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>"..., 4776) = -1 EPIPE (Broken pipe)

The cause is in ikarus.cafe.ss.  The (read;read) consumes the first two
lines of the banner, then when (display-prompt 0) is attempted it raises
a broken pipe exception, the handler then attempts (flush-output-port
(console-output-port)) which raises a broken pipe exception, the next
handler invokes the reset continuation which loops back to attempting
another (display-prompt 0).

Revision history for this message

Derick Eddington (derick-eddington) wrote on 2008-07-27:

#3

On Sun, 2008-07-27 at 03:30 -0700, Derick Eddington wrote:
> The cause is in ikarus.cafe.ss.

Do you think the handlers which do the reset behavior should only be
around the (eval-proc x)? That way any bizarre exceptions raised by
non- user code propagate to the base handler which just exits.

Revision history for this message

Derick Eddington (derick-eddington) wrote on 2008-07-27:

#4

On Sun, 2008-07-27 at 04:07 -0700, Derick Eddington wrote:
> Do you think the handlers which do the reset behavior should only be
> around the (eval-proc x)?

No. Reader exceptions need to reset the REPL too.

Revision history for this message

Abdulaziz Ghuloum (aghuloum) wrote on 2008-07-27:

#5

There are two other situations that make the cafe go berserk. Try:
(close-output-port (current-output-port))
and
(close-input-port (current-input-port))

I think that the cafe handler around "read" should only handle &lexical and &interrupted conditions and propagate the rest upwards while the handler around eval should trap all conditions. Need to try it out.

Revision history for this message

Derick Eddington (derick-eddington) wrote on 2008-07-28:

#6

Download full text (8.0 KiB)

On Sun, 2008-07-27 at 16:39 +0000, Abdulaziz Ghuloum wrote:
> There are two other situations that make the cafe go berserk. Try:
> (close-output-port (current-output-port))
> and
> (close-input-port (current-input-port))

Hehe :)

> I think that the cafe handler around "read" should only handle &lexical
> and &interrupted conditions and propagate the rest upwards while the
> handler around eval should trap all conditions. Need to try it out.

I've tried this:

=== modified file 'scheme/ikarus.cafe.ss'
--- scheme/ikarus.cafe.ss 2008-07-13 03:05:45 +0000
+++ scheme/ikarus.cafe.ss 2008-07-28 02:34:31 +0000
@@ -53,48 +53,58 @@
(display ">" (console-output-port))
(display-prompt (fx+ i 1))))))

- (define my-read
- (lambda (k)
- (parameterize ([interrupt-handler
- (lambda ()
- (flush-output-port (console-output-port))
- (reset-input-port! (console-input-port))
- (newline (console-output-port))
- (k))])
- (read (console-input-port)))))
-
+ (define (print-ex ex)
+ (flush-output-port (console-output-port))
+ (display "Unhandled exception\n" (console-error-port))
+ (print-condition ex (console-error-port)))
+
+ (define (reset k)
+ (reset-input-port! (console-input-port))
+ (k))
+
   (define wait
     (lambda (eval-proc escape-k)
       (call/cc
         (lambda (k)
- (with-exception-handler
- (lambda (con)
- (reset-input-port! (console-input-port))
- (k (void)))
- (lambda ()
- (with-exception-handler
- (lambda (con)
- (flush-output-port (console-output-port))
- (display "Unhandled exception\n" (console-error-port))
- (print-condition con (console-error-port))
- (when (interrupted-condition? con)
- (raise-continuable con)))
- (lambda ()
- (display-prompt 0)
- (let ([x (my-read k)])
- (cond
- [(eof-object? x)
- (newline (console-output-port))
- (escape-k (void))]
- [else
- (call-with-values
- (lambda () (eval-proc x))
- (lambda v*
- (unless (andmap (lambda (v) (eq? v (void))) v*)
- (for-each
- (lambda (v)
- (pretty-print v (console-output-port)))
- v*))))]))))))))
+ (display-prompt 0)
+ (let ([x (with-exception-handler
+ (lambda (ex)
+ (cond [(lexical-violation? ex)
+ (print-ex ex)
+ (reset k)]
+ [(interrupted-condition? ex)
+ (flush-output-port (console-output-port))
+ (newline (console-output-port))
+ ...

On Sun, 2008-07-27 at 16:39 +0000, Abdulaziz Ghuloum wrote:
> There are two other situations that make the cafe go berserk.  Try:
>   (close-output-port (current-output-port))
> and 
>   (close-input-port (current-input-port))

Hehe :)

> I think that the cafe handler around "read" should only handle &lexical
> and &interrupted conditions and propagate the rest upwards while the
> handler around eval should trap all conditions.  Need to try it out.

I've tried this:

=== modified file 'scheme/ikarus.cafe.ss'
--- scheme/ikarus.cafe.ss	2008-07-13 03:05:45 +0000
+++ scheme/ikarus.cafe.ss	2008-07-28 02:34:31 +0000
@@ -53,48 +53,58 @@
             (display ">" (console-output-port))
             (display-prompt (fx+ i 1))))))
 
-  (define my-read
-    (lambda (k)
-      (parameterize ([interrupt-handler
-                      (lambda ()
-                        (flush-output-port (console-output-port))
-                        (reset-input-port! (console-input-port))
-                        (newline (console-output-port))
-                        (k))])
-         (read (console-input-port)))))
-
+  (define (print-ex ex)
+    (flush-output-port (console-output-port))
+    (display "Unhandled exception\n" (console-error-port))
+    (print-condition ex (console-error-port)))
+  
+  (define (reset k)
+    (reset-input-port! (console-input-port))
+    (k))
+  
   (define wait
     (lambda (eval-proc escape-k)
       (call/cc
         (lambda (k)
-          (with-exception-handler
-            (lambda (con)
-              (reset-input-port! (console-input-port))
-              (k (void)))
-            (lambda ()
-              (with-exception-handler
-                (lambda (con)
-                  (flush-output-port (console-output-port))
-                  (display "Unhandled exception\n" (console-error-port))
-                  (print-condition con (console-error-port))
-                  (when (interrupted-condition? con)
-                    (raise-continuable con)))
-                (lambda ()
-                  (display-prompt 0)
-                  (let ([x (my-read k)])
-                    (cond
-                      [(eof-object? x) 
-                       (newline (console-output-port))
-                       (escape-k (void))]
-                      [else
-                       (call-with-values
-                         (lambda () (eval-proc x))
-                         (lambda v*
-                           (unless (andmap (lambda (v) (eq? v (void))) v*)
-                             (for-each
-                               (lambda (v)
-                                 (pretty-print v (console-output-port)))
-                               v*))))]))))))))
+          (display-prompt 0)
+          (let ([x (with-exception-handler
+                     (lambda (ex)
+                       (cond [(lexical-violation? ex)
+                              (print-ex ex)                              
+                              (reset k)]
+                             [(interrupted-condition? ex)
+                              (flush-output-port (console-output-port))
+                              (newline (console-output-port))
+                              (reset k)]
+                             [else (raise-continuable ex)]))
+                     (lambda ()
+                       (read (console-input-port))))])
+            (cond
+              [(eof-object? x) 
+               (newline (console-output-port))
+               (escape-k (void))]
+              [else
+               (call-with-values
+                 (lambda () 
+                   (with-exception-handler
+                     (lambda (ex)
+                       (if (non-continuable-violation? ex)
+                         (reset k)
+                         (raise-continuable ex)))
+                     (lambda ()
+                       (with-exception-handler
+                         (lambda (ex)
+                           (print-ex ex)
+                           (when (serious-condition? ex)
+                             (reset k)))
+                         (lambda ()
+                           (eval-proc x))))))
+                 (lambda v*
+                   (unless (andmap (lambda (v) (eq? v (void))) v*)
+                     (for-each
+                       (lambda (v)
+                         (pretty-print v (console-output-port)))
+                       v*))))]))))
       (wait eval-proc escape-k)))
 
   (define do-new-cafe

[d@eep:~]-> ikarus | (read;read)
Unhandled exception:
 Condition components:
   1. &i/o-write
   2. &who: write
   3. &message: "EPIPE: Broken pipe"
   4. &irritants: (*stdout*)
[d@eep:~]-> ikarus | read
Unhandled exception:
 Condition components:
   1. &i/o-write
   2. &who: write
   3. &message: "EPIPE: Broken pipe"
   4. &irritants: (*stdout*)
[d@eep:~]-> ikarus | (read;read;read)
Unhandled exception:
 Condition components:
   1. &i/o-write
   2. &who: write
   3. &message: "EPIPE: Broken pipe"
   4. &irritants: (*stdout*)
[d@eep:~]-> ikarus | (read;read;read;read)
map
map
Unhandled exception:
 Condition components:
   1. &i/o-write
   2. &who: write
   3. &message: "EPIPE: Broken pipe"
   4. &irritants: (*stdout*)
[d@eep:~]-> ikarus
Ikarus Scheme version 0.0.3+ (revision 1559, build 2008-07-27)
Copyright (c) 2006-2008 Abdulaziz Ghuloum

> (close-port (current-output-port))
Unhandled exception:
 Condition components:
   1. &assertion
   2. &who: display
   3. &message: "port is closed"
   4. &irritants: (#<output-port (textual) *stdout*>)
[d@eep:~]-> ikarus
Ikarus Scheme version 0.0.3+ (revision 1559, build 2008-07-27)
Copyright (c) 2006-2008 Abdulaziz Ghuloum

> (close-port (current-input-port))
> Unhandled exception:
 Condition components:
   1. &assertion
   2. &who: get-char
   3. &message: "port is closed"
   4. &irritants: (#<input-port (textual) *stdin*>)
[d@eep:~]-> ikarus
Ikarus Scheme version 0.0.3+ (revision 1559, build 2008-07-27)
Copyright (c) 2006-2008 Abdulaziz Ghuloum

> (begin (close-port (current-output-port)) (display "foo\n"))
Unhandled exception:
 Condition components:
   1. &assertion
   2. &who: flush-output-port
   3. &message: "port is closed"
   4. &irritants: (#<output-port (textual) *stdout*>)
[d@eep:~]-> ikarus
Ikarus Scheme version 0.0.3+ (revision 1559, build 2008-07-27)
Copyright (c) 2006-2008 Abdulaziz Ghuloum

> (begin (close-port (current-input-port)) (read))
Unhandled exception
 Condition components:
   1. &assertion
   2. &who: get-char
   3. &message: "port is closed"
   4. &irritants: (#<input-port (textual) *stdin*>)
> Unhandled exception:
 Condition components:
   1. &assertion
   2. &who: get-char
   3. &message: "port is closed"
   4. &irritants: (#<input-port (textual) *stdin*>)
[d@eep:~]-> ikarus
Ikarus Scheme version 0.0.3+ (revision 1559, build 2008-07-27)
Copyright (c) 2006-2008 Abdulaziz Ghuloum

> -asdf
Unhandled exception
 Condition components:
   1. &lexical
   2. &message: "invalid numeric sequence"
   3. &irritants: ("-a")
   4. &lexical-position:
       file-name: *stdin*
       character: 1
>   ;; ^C
>   ;; ^C
>   ;; ^C
> (let loop () (loop))
Unhandled exception
 Condition components:
   1. &interrupted
   2. &message: "received an interrupt signal"
>   ;; ^C
>   ;; ^C
> (begin (raise-continuable 'foo) 'continued)
Unhandled exception
 Non-condition object: foo
continued
> (begin (raise-continuable (make-warning)) 'continued)
Unhandled exception
 Condition components:
   1. &warning
continued
> (begin (raise (make-warning)) 'continued)
Unhandled exception
 Condition components:
   1. &warning
> (begin (raise-continuable (make-error)) 'continued)
Unhandled exception
 Condition components:
   1. &error
>

If anything anywhere goes wrong with the non- user code / ikarus
infrastructure, it's guaranteed to propagate to the base handler which
just exits (at least, that's the goal).  Also, it's more consistent with
the --r6rs-script default handler than before w.r.t. the default handler
not returning for &serious, even if the &serious was
raise-continuable'd.  I.e., previously it would do:

> (begin (raise-continuable (make-error)) 'continued)
Unhandled exception
 Condition components:
   1. &error
continued
>

Revision history for this message

Abdulaziz Ghuloum (aghuloum) wrote on 2008-08-03:

#7

Applied Derick's patch in revision 1569. Thanks to the both of you.

Changed in ikarus:
assignee:	nobody → aghuloum
importance:	Undecided → Low
status:	New → Fix Committed

Abdulaziz Ghuloum (aghuloum) on 2008-12-26

Changed in ikarus:
milestone:	none → 0.0.4

Ikarus Scheme

Infinite loop on broken pipe

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