Trying to decr ref count of Tcl_Obj allocated in another thread - tcl

Question

I compiled the sourceforge tcl executable, it passes all the tests supplied, and it runs with the same segfault I see in my downloaded executable, 8.6.9. I'm running on Ubuntu 16.04 (for legacy reasons) on an AMD processor. ( I have run on ubuntu 18.04 on my laptop, it has the same failure. )
So, next I recompiled with "--enable-symbols=mem" turned on to see if a memory leak is causing the segfault, and now it fails immediately with:
Trying to decr ref count of Tcl_Obj allocated in another thread
./runMeg.sh: line 3: 29972 Aborted (core dumped) ../source/main_megatron.
I'm not seeing any answer on what to do with this response, can someone advise on what this means I need to fix?
All my threads are of the form:
set graphDisplayThread [ thread::create {
after [expr {int(1000) }]
.....
puts "...Initialized graphDisplayUpdate_02 ID $c update."
thread::wait
}]
and:
thread::send $::graphDisplayThread {
incr b
graphDisplayUpdate .c
}
All shared variables are referenced AFTER mutex is captured, and through TSV variables. There are 5 threads in the application, which has no C-code in it at all. Around 2000 lines of code, in total.
The app runs thousands of cycles and then segfaults at random points with a prior ActiveState 8.6.9 pre-compiled version. So, now I'm trying to isolate the failure point with compiled SourceForge 8.6.9 memory checks as a first step, but the issue above is the first one I encounter - and it occurs immediately after starting.
Update (5/16/19 8:28 EST): New Detail to answer comments below.... This application has no C-code in it, and the Tcl_Obj error ONLY appears in the sourceForge-based, 8.6.9 compiles (2) I did myself, not the ActiveState 8.6.9 pre-built download. And the error in the sourceForge code occurs in both the twin "MEM_DEBUG" and NO-"MEM_DEBUG" builds I made in tandem and tested. Both passed all install tests.
To summarize:
sourceForge 8.6.9 compile w/MEM_DEBUG option: Tcl_Obj Abort error
sourceForge 8.6.9 compile w/o MEM_DEBUG option: Tcl_Obj Abort error
ActiveState 8.6.9 build: does not Abort, random seg fault
Why should I trust the sourceForge build I made myself, more than the ActiveState pre-built executable which does not exhibit the problem? And if we do trust the sourceForge compiled version, how do I isolate where the TclObject error is created by the offending TCL code?
Update 5/16/19#13:34EST: The same segfault appears with ActiveState 8.6.9 on Ubuntu 18.04. Haven't checked my builds of SourceForge yet to see how they behave.

Answer 1

By methodically hacking out code blocks and watching to see if the Tcl_Obj error dissappeared or not, I found 2 errors:
I had re-declared my mutex and cond variables more than once. Now it is declared once and referenced in all other places.
A code remnant removing a TSV was found in a place I no longer wanted it.
This also fixed the segfault.
Thanks for all the help and hints, mrcalvin.