[Tcl-bugs] [ tcl-Bugs-1374582 ] invalid object modification

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Bugs item #1374582, was opened at 2005-12-06 13:11
Message generated for change (Comment added) made by msofer
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Category: 14. List Object
Group: current: 8.5a3
Status: Open
>Resolution: None
Priority: 5
Submitted By: Ulrich Ring (uring)
Assigned to: miguel sofer (msofer)
Summary: invalid object modification

Initial Comment:

(1) run the following script:

proc touch {listValue} {
    lset listValue 1 4 5
    return $listValue
}
set data [list a [list 1 2 3] b]
puts $data
touch $data
puts $data

(2) you get the expected output:

a {1 2 3} b
a {1 2 3} b

... the proc "touch" has _not_ changed the variable
"data"

(3) now uncomment the first "puts $data" command and
    rerun the script

(4) the output is

a {1 7 3} b

BTW: This does _not_ happen with tcl8.5a2.



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>Comment By: miguel sofer (msofer)
Date: 2005-12-06 18:44

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AHA! Repro succesfull with 8.5a3!

It looks like a bug that has been fixed in HEAD. Could you
verify with a current tclsh? My impression is that this is
another aspect of Bug #1333036, fixed on 2005-10-20.

PS: cvs nightly snapshots at
ftp://www.tcl.tk/pub/tcl/nightly-cvs/

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

Comment By: Ulrich Ring (uring)
Date: 2005-12-06 17:56

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No custom code, pure tcl.

Well, it's embarassing, since I've no idea what's going
on.

I just ran the following script:

mkdir /tmp/tcltest
cd /tmp/tcltest

tar zxvf /archiv/tcl/tcl8.5a3-src.tar.gz
cd tcl8.5a3/unix

./configure --disable-shared
make

./tclsh /tmp/test0

./tclsh /tmp/test1

...and could repro the misbehaviour.

i.e.

- no custom tclsh
- no custom extensions

Well, tomorrow I'll go to think about how
to improve the documentation of the facts
we're observing. 

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

Comment By: miguel sofer (msofer)
Date: 2005-12-06 16:19

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Neither I nor 4 other core maintainers could repro this bug. 

Let me give you some questions and homework to try to narrow
it down. 

(1) these is obviously self-compiled tclsh; what compile
flags did you use? 

(2) Did you run 'make install'? (not necessary if
--disable-shared passed to ./configure)

(3) Is your tclsh linked with any custom C code, or using
extensions?

(4) Are you running this at the command line? Could the  
   a {1 7 3} b
just be the return value of [touch] being output to the
console? Or do you see this effect when running in batch mode?

(5) Please repro what I did and confirm that you get
different results:
 cd path/to/Tcl/unix
 make distclean
 ./configure --disable-shared
 make
 ...
 ./tclsh path/to/test0
 ...
 ./tclsh path/to/test1



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

Comment By: Ulrich Ring (uring)
Date: 2005-12-06 15:24

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> I cannot reproduce the bug here; am I following your
> instructions correctly?

Your approach is perfect.

On our sites the version of TCL matters.

[info patchlevel] should report something >=8.5a3

We can reproduce the bug on:

linux - gcc 2.95.x
linux - gcc 3.3.x
windows VC7

I even checked the "latest" snapshot ( actually 
it was of yesterday ).

If you can't reproduce the bug, what can we do to
give you more precise information?





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Comment By: miguel sofer (msofer)
Date: 2005-12-06 13:54

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I cannot reproduce the bug here; am I following your
instructions correctly?

mig@uhu:/home/CVS/tcl_SF_clean/unix$ cat /tmp/test0
proc touch {listValue} {
    lset listValue 1 1 7
    return $listValue
}
set data [list a [list 1 2 3] b]
puts $data
touch $data
puts $data
mig@uhu:/home/CVS/tcl_SF_clean/unix$ ./tclsh /tmp/test0
a {1 2 3} b
a {1 2 3} b
mig@uhu:/home/CVS/tcl_SF_clean/unix$ cat /tmp/test1
proc touch {listValue} {
    lset listValue 1 1 7
    return $listValue
}
set data [list a [list 1 2 3] b]
#puts $data
touch $data
puts $data
mig@uhu:/home/CVS/tcl_SF_clean/unix$ ./tclsh /tmp/test1
a {1 2 3} b


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

Comment By: Ulrich Ring (uring)
Date: 2005-12-06 13:40

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oops. the command in proc touch must read:

lset listValue 1 1 7

sorry;

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

Comment By: miguel sofer (msofer)
Date: 2005-12-06 13:26

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Something is wrong in your description:

mig@uhu:/home/CVS/tcl_SF_clean/unix$ cat /tmp/test0
proc touch {listValue} {
    lset listValue 1 4 5
    return $listValue
}
set data [list a [list 1 2 3] b]
puts $data
touch $data
puts $data
mig@uhu:/home/CVS/tcl_SF_clean/unix$ ./tclsh /tmp/test0
a {1 2 3} b
list index out of range
    while executing
"lset listValue 1 4 5"
    (procedure "touch" line 2)
    invoked from within
"touch $data"
    (file "/tmp/test0" line 7)



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