I mean... my first reading of that is "what a dumb idea, the reason it isn't const is that there are legit reasons to switch userid". But then I have used exac

I mean... my first reading of that is "what a dumb idea, the reason it isn't const is that there are legit reasons to switch userid". But then I have used exactly this pattern, and it looks something like: struct protected_stuff { int userid; ... }; void set_userid(const struct protected_stuff prot, int newuserid) { struct protected_stuff backdoor = (struct protected_stuff *)prot; backdoor->userid = newuserid; } and then the compiler complains if you go fiddling with userid outside this function where you deliberately opened a backdoor to write to it. (and you can wrap pragmas around that function to turn off warnings).