[envp]

But what if one of the arguments is a function call? Then it isn't easy to prove there are no side effects

[chrisseaton]

If it’s too big to in-line then yes.

[vlovich123]

That’s says absolutely nothing about whether the function has a side effect.

[chrisseaton]

If you can inline it into the compilation unit, then you can see if it has side effects or not.