There are other places where the symbol table could change. For
example, the loop in eval_string in oct-parse.yy, which is similar to
the one in main_loop in toplev.cc and the one in get_debug_input in
input.cc. Command history can also change in get_debug_input, though
I don't think it should be changing in eval_string.
And, as Michael mentions, if Octave code is executing in the readline
idle loop, then it is possible that the symbol table will change
there, but I'm not sure how often that happens in practice, since most
callbacks that are executing there are functions, correct? Is it
typical for them to change the top-level symbol table (which is what I
assume is usually displayed in the IDE)?
I would argue that whether or not it's typical is not really relevant. As long as it's possible you should consider that possibility.
Michael.