> That is a pointer size per code object. The most standard way is to calculate the size of all pyc files in the stdlib after compiling them all with "-m compileall -r 1000 Lib".

This yields the following numbers between what was main when I branched off and the tip of my branch:

# main (7569c0fe91): 25_059_438 bytes
# bpo-445303-code-qualname (a0252ab9ad): 25_511_492 bytes

So that seems to be about half a MB increase over 25 MB (about 2% relative increase).

This is potentially just an interim result, as at first sight it looks like MAKE_FUNCTION could require one less argument (the qualname), which can now be taken from the code object. So not quite the final picture yet.