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From: Petro Kazmirchuk <vivid.tree7955@fastmail.com>
Newsgroups: comp.lang.tcl
Subject: Re: Crash in Itcl when using Iwidgets in multiple threads
Date: Fri, 23 Aug 2024 16:18:51 +0200
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On 23/08/2024 14:52, Harald Oehlmann wrote:
> Am 23.08.2024 um 14:29 schrieb Petro Kazmirchuk:
>> Minimal example:
>>
>> package require Thread
>>
>> set thread_script {
>>      package require Iwidgets
>>      iwidgets::pushbutton .btn -text [thread::id]
>>      pack .btn
>>      after 4000 [list thread::release [thread::id]]
>>      thread::wait
>> }
>>
>> for {set i 0} {$i<1000} {incr i} {
>>      thread::create -preserved $thread_script
>>      after 500
>> }
>>
>> This code runs 8 threads in parallel each showing an iwidget 
>> (pushbutton or anything else, doesn't matter) and after ~1 minute it 
>> crashes with:
>>
>> Unhandled exception at 0x00007FF8846DA6E4 (itcl424t.dll) in 
>> tclsh86t.exe: 0xC0000005: Access violation reading location 
>> 0x0000000000000018.
>>
>> Windows, Tcl 8.6.14, Itcl 4.2.4, Itk 4.2.6, Iwidgets 4.1.
>> The same crash happens when using the Itk written in pure Tcl: 
>> https://chiselapp.com/user/rene/repository/itk/home
>>
>> That's why I'm convinced the problem is in Itcl rather than Itk, and 
>> the stack trace points to Itcl as well. Probably, there is a mutex 
>> missing somewhere.
>>
>> I didn't try to reproduce it on Linux.
>>
>> I understand that both Iwidgets and Itcl are legacy that is barely 
>> maintained, that's why I'm not raising a bug in Fossil that very few 
>> people would notice. What I'm asking instead from a much wider 
>> audience here is for a workaround. Is it possible to change my code 
>> somehow to avoid the crash? Of course, preserving the basic 
>> multi-threaded architecture.
>>
>> The original code is a huge framework that can't be rewritten to 
>> separate GUI into one main thread.
>>
>> Thanks in advance,
>> Petro
> 
> Petro,
> if you look here:
> https://core.tcl-lang.org/itcl/timeline?udc=1&ss=v&n=&y=all&advm=0
> ITCL has commits two days ago. So, there is some care.
> It is a bundled package.
> So it would be great to file a bug report.
> 
> Thanks,
> Harald
> 

ok done: 
https://core.tcl-lang.org/itcl/tktview/0e55608dbd661663d7efeb4dc91c1c815ab5ba6e

fingers crossed :)