i try to creat a _calculator and save the commands in _linked list
the code compile but it crashes :sad:

i attached my project

i think you find the error in linkedlist.cpp in push_back(CalcCommand* data)

Can you shrink down your code to something small enough to post? I don't think anyone wants to download your attachment, unzip it, create a collection of source files to match their environment's needs, compile and run your program, then debug it to find the problem. If your program is large, that makes it even harder and most people, like me, don't have the time to go through all that mess.