On a modern system you can't usually do that because of W^X rules (also on a non-x86 modern system the performance would be abysmal if you tried because why waste transistors supporting something only crazy people would want?)

So perhaps notionally in the abstract machine if I have sixteen Clowns in a C++ vector there are sixteen copies of the Clown method squirt_water_at() in the vector too, but I assure you all the compiler emits is one copy of squirt_water_at() for Clowns, to the text segment with the rest of the program code, and maybe if Clowns are virtual, a pointer to a table of such functions lives with each Clown just in case there are Jugglers and LionTamers in the vector too - although compilers can sometimes figure out a rationale for not bothering.