alt Hacker NewsI am disappointed you're downvoted, Richard. This is a fine reply, and I hope you know that a minor quibble with a single line in the post doesn't mean that I think it's a bad one overall. (EDIT: a few minutes later, the parent comment is no longer grey.)
I also think it's a good thing that you wrote the post in general, when I saw it pop up I was like "oh, of course, this post should exist!" I'm surprised I didn't think about it earlier.
> evaluating userspace code at compile time
Usually this would be done via an interpreter, so I'm not sure that it really requires unsafe either. If you are literally executing machine code, sure, but const fn in Rust and constexpr in C++ and many other languages do not do that, as it causes a number of problems (for example, cross-compilation).
Replies
> Usually this would be done via an interpreter, so I'm not sure that it really requires unsafe either.
Well, I've personally have written a const-expression evaluator that actually reuses the rest of the compiler: it compiles the expression in the current environment with some specific adjustments to the codegen settings, launches the temporary executable and gathers its output... frankly, it's more hassle than it's worth compared to writing a separate const-expression interpreter. Plus, of course, it also runs slower since most constant expressions are usually pretty trivial.
[delayed]