Itk - the [incr Tk] extension

The error is a segfault that doesn't always happen. In my case and on my machine, I always either got a segfault OR an error. Here's some sample code, but you may need to add empty loops, some [puts] or [packs] or similar to try to trigger it.

package require Tk
package require itk
package require Iwidgets

set mainf [frame .f]
set lf1 [iwidgets::labeledframe $mainf.lf1 -labeltext "label 1" -labelpos nw -ipadx 8 -ipady 8]
set lf2 [iwidgets::labeledframe $mainf.lf2 -labeltext "label 2" -labelpos nw -ipadx 8 -ipady 8]

The culprit seems to be _initTable called by the labeledframe constructor. That thing deletes itself after running. (For no good reason that I can see, but still, that's an allowed action.)  My guess is that leaves a dangling pointer in the first object created.

The iwidgets trunk mirrored at core.tcl.tk has the
redefinition of _initTable commented out and
another approach taken.  I'd guess that means
Rene has encountered the same issue and introduced
this workaround into the patch.

I put the redef back in place in Labeledframe, and when
I close the window,  get the panic

Tcl_Release couldn't find reference for 0x7ff3dcb34290

It does look like a resource management bug.....somewhere....

There's an ITCL_PRESERVE_DEBUG setting.  Now we just need someone
who knows how to use it.  :)

Tracked that down to  Preserve/Release imbalance in Itcl 4.0.3rc

Committed a fix, and now this demo script doesn't panic on me anymore.

Testing to see if that fixes the problem on your end as well would be
appreciated.

I took the 2 line patch from itcl and applied it to itcl 4.0.3rc0 and it didn't fix anything.

After doing that, I realized my test program doesn't even include itcl...

I took the 2 line patch from itcl and applied it to itcl 4.0.3rc0 and it didn't fix anything.

After doing that, I realized my test program doesn't even include itcl...

Any script using itk is also using itcl.

Any script using itk is also using itcl.

Any script using itk is also using itcl.

Afterwards, I thought that might be true. Just to be sure, I checked this report again. 

I applied this patch: http://core.tcl.tk/itcl/ci/0206ee920837fec7?sbs=1
to the itcl4.0.3rc0 release.

In my test program, I also explicitly [package require]d itcl 4.0.3 before itk and printed out the [package ifneeded] to make sure that's what it was actually using. 

As far as I can tell it should be using that patch, but I still get a segfault.

Thanks for the additional testing.

I've not been able to reproduce any segfault
with the submitted test script.  Since you
report that you can get one fairly reliably,
I suspect we'll see more reports of the issue
continue to come in.  Hopefully one will enable
me to reproduce and work on the problem.

For now I'll set this aside, pending more info.

This was probably related to Itcl Bug

https://core.tcl.tk/itcl/tktview?name=19fa152b36

That's fixed in the latest branches of Itcl, 4.0.6 and 4.1.0

Suspect this is fixed now too.