[Tcl-bugs] [ tcl-Bugs-2824981 ] lack of [set] causes infinite loop through [unknown]

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Bugs item #2824981, was opened at 2009-07-21 12:47
Message generated for change (Comment added) made by dgp
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>Category: 38. Init - Library - Autoload
>Group: current: 8.5.11
Status: Open
Resolution: None
>Priority: 9
Private: No
Submitted By: Zbigniew (zbigniew_b)
>Assigned to: Don Porter (dgp)
Summary: lack of [set] causes infinite loop through [unknown]

Initial Comment:
It seems, that "rename" command is faulty - by trying, as example:

  % rename set asd
  % asd a 0

...one can see, that any other input is impossible, while CPU is at full power. Tested on Linux. Test with tclsh8.5 revealed no such problem, but still another one:
$tclsh8.5
% rename set asd
% asd a 1
1
% asd b 2
2
% set a 1
too many nested evaluations (infinite loop?)

...and since this time, every try to run any other non-existing command is answered with "too many nested evaluations (infinite loop?)" instead of with usual "invalid command name".

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>Comment By: Don Porter (dgp)
Date: 2012-01-27 06:32

Message:

This bug fix didn't get backported to 8.5.

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Comment By: miguel sofer (msofer)
Date: 2009-12-30 05:52

Message:
The problem with [unknown] is now fixed in HEAD: errors in setting two
variables were [catch]ed, so that the infinite loop was not being
detected.

Bug kept open because there is a deeper problem: this behaviour should NOT
be triggerable with a plain script, infinite recursion of the unknown
handler should never happen.

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Comment By: Donal K. Fellows (dkf)
Date: 2009-12-29 09:11

Message:
Updated title to be more descriptive of the real issue

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Comment By: miguel sofer (msofer)
Date: 2009-12-10 19:29

Message:
still present

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Comment By: miguel sofer (msofer)
Date: 2009-07-21 16:47

Message:
8.6 seems to be miscounting recursion levels from [unknown]
   proc history args {}
   rename set xx
   set x 1
enters a busy loop and never hits the recursion limit.

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Comment By: miguel sofer (msofer)
Date: 2009-07-21 14:24

Message:
The 8.5 behaviour is correct - it is a consequence of your breaking
[unknown] (which uses [set]) by not providing a reasonable implementation
of [set]. This causes [unknown] to call itself recursively.

Not sure yet about what is happening with 8.6 

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