[ clisp-Bugs-1220548 ] unwind-protect confuses abort restart

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Bugs item #1220548, was opened at 2005-06-14 18:36
Message generated for change (Comment added) made by hoehle
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Jörg Höhle (hoehle)
Assigned to: Nobody/Anonymous (nobody)
Summary: unwind-protect confuses abort restart

Initial Comment:
Hi,

I mentioned that in clisp-devel around October 2004
["confused debugger, aborts to outer break level --
repeatable"], but did not submit a bug report. The bug
is still in clisp-cvs.

When there's an unwind-protect frame somewhere on the
stack, restarts may get confused. As a result, Lisp
sessions get mixed up (e.g. today it affected my SLIME
session).
I originally noticed this with cl-sql, which uses
with-foreign-string, which does the same as unwind-protect.

[17]> (unwind-protect (error "hi") (print "out"))
*** - hi
Mögliche Optionen:
ABORT          :R1      ABORT
Break 1 [18]> (unwind-protect (error "hi") (print "out"))
*** - hi
Mögliche Optionen:
ABORT          :R1      ABORT
ABORT          :R2      ABORT
Break 2 [19]> abort
"out" 
"out" 
[20]>
Failed Expectation: get out only one level. The :r1
restart does this correctly.

In contrast, using the :r1 restarts gets out only one
level, as expected.
This also happens using the interpreted memory image.

Regards,
 Jörg Höhle

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>Comment By: Jörg Höhle (hoehle)
Date: 2005-06-20 18:56

Message:
Logged In: YES 
user_id=377168

I had hoped my examples demonstrate that a restart named
ABORT behaves differently than other names, for no apparent
reason. This is very confusing to users, causing trouble in
the REPL which even lead to CLISP quitting a SLIME session
(and exiting).

Please explain "closest to your stack frame": while
navigating the stack with up and down commands, I did not
observe that the restarts would vary according to the
current position.

Furthermore, repeating the exercise with 3 times
(unwind-protect (error "hi")(print "uh"))
shows that it's the outermost ABORT restart (it's not even
skipping one to the second) that's choosen! I.e. CLISP seems
to choose the last restart, not the first one (while other
names lead to the expected behaviour).

----------------------------------------------------------------------

Comment By: Sam Steingold (sds)
Date: 2005-06-14 22:53

Message:
Logged In: YES 
user_id=5735

when there are several identically named restarts available,
one should use the ":R*" command to ensure the right one.
if you use the restart name, the first (closest to your
current frame)
restart is invoked, and it may take you up the stack 
beyond your other restarts with the same name.
see condition.lisp (*active-restarts* &c)

----------------------------------------------------------------------

Comment By: Jörg Höhle (hoehle)
Date: 2005-06-14 18:52

Message:
Logged In: YES 
user_id=377168

It seems like the topmost 'abort restart is sometimes
skipped, as the following shows:
[60]> (with-simple-restart (foo "my foo restart")
(print(break)))
1. Trace: (SYSTEM::BREAK-LOOP 'NIL '#<SIMPLE-CONDITION
#x2042A01E> 'T)
** - Continuable Error
Break
Wenn Sie (mit Continue) fortfahren: BREAK-Schleife beenden.
Weitere mögliche Optionen:
FOO            :R1      my foo restart
ABORT          :R2      ABORT
Break 1 [61]> (with-simple-restart (abort "my foo restart")
(print(break)))
2. Trace: (SYSTEM::BREAK-LOOP 'NIL '#<SIMPLE-CONDITION
#x2042EE46> 'T)
** - Continuable Error
Break
Wenn Sie (mit Continue) fortfahren: BREAK-Schleife beenden.
Weitere mögliche Optionen:
ABORT          :R1      my foo restart
ABORT          :R2      ABORT
FOO            :R3      my foo restart
ABORT          :R4      ABORT
Break 2 [62]> abort
Break 1 [61]> abort ; --- this prompt shows that "my foo
restart" was not invoked
[63]> (with-simple-restart (foo "my foo restart")
(print(break)))
1. Trace: (SYSTEM::BREAK-LOOP 'NIL '#<SIMPLE-CONDITION
#x204353E6> 'T)
** - Continuable Error
Break
Wenn Sie (mit Continue) fortfahren: BREAK-Schleife beenden.
Weitere mögliche Optionen:
FOO            :R1      my foo restart
ABORT          :R2      ABORT
Break 1 [64]> foo
NIL ;
T ; --- here my foo restart was invoked
[65]> 

Maybe this has to do with the ANSI-CL / Paul Dietz'
testsuite related change that always supplies an abort
restart in the repl? cf. Changelog 2004-02-25?

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