side-effect-free-fns

side-effect-free-fns

[Eli Zaretskii]

The ELisp manual says in the node "Writing Emacs Primitives":

       If you define a function which is side-effect free, update the code
    in `byte-opt.el' which binds `side-effect-free-fns' and
    `side-effect-and-error-free-fns' so that the compiler optimizer knows
    about it.

I notice that none of the w32-* primitives are on that list, although
quite a few of them are side-effect free and error free.  Is there any
reason not to add those functions to byte-opt.el now?  Are there any
known dangers?

Is there anything else to determining whether a function can be added
to that list besides examining the code for absence of calls to
Fsignal and making sure it doesn't produce any effects except the
values it returns?

Re: side-effect-free-fns

[Richard Stallman]

    I notice that none of the w32-* primitives are on that list, although
    quite a few of them are side-effect free and error free.  Is there any
    reason not to add those functions to byte-opt.el now?  Are there any
    known dangers?

I don't know of any danger, but they are probably not used enough
to be worth the trouble to add.