Hi to everyone 
My first post in here.
OS: Linux mint cinnamon 21.3
Zenity: 3.42.1 (shipped with Mint)
Problem
These days I tried to merge some larger bash shell scripts .
My usual approach is to use Zenity and the --list option for more complex scripts which need user interaction. Of course, if you merge multiple scripts, your option list grows too so, I had to look for a more compact way to display my script options in zenity.
Therefore I switched to zenity’s --form option, followed by multiple combo-boxes.
The result worked nicely, but shortly after I found out, that long lists in combo boxes or multiple combo boxes cause a double free tcache memory leak error, IF you cancel your zenity dialog.
Since this kind of bug is rather severe (otherwise I’d not bother to write about) and very easy to reproduce, I suggest somebody responsible of the maintenance of zenity/gnome looks into this issue. At the bottom, I’ve linked some reference with possible solutions to fix or hunt this kind of bug.
How to reproduce
Create a bash script, add a zenity dialog with the --form option and then, add multiple add-combo "A" --combo-value "|a|b|c|d|e|f|g|h|I|j|k|l|m|n|o|p|q|r|s|t|u|v|w|x|y|z" box entries with at least 24- or more menu points separated by a pipe “|”. Of course, all combo-values must have a list of unique items. Scripts should not throw this kind of bug just for some simple text lists.