[dataflow]

You're seeing the compiler opportunistically make an optimization by taking constexpr as an extra inlining hint. I showed you it's not something you can rely on in my example. You have to realize constexpr only talks about what is allowed to happen, not what is guaranteed to happen. You want consteval for that.

[thezilch]

Of course I want consteval, if a later C++ is available to me, but that doesn't excuse you writing constexpr does absolutely nothing, when it clearly does. It's no surprise your example doesn't fold calls without `-O3` or that one could produce a `constexpr` that doesn't fold to a constant (go ahead and try though :>).

But consteval function is also not a literal replacement constexpr. For example, you can't take a pointer to the former. There's a reason they co-exist and are not useless.

[dataflow]

> Of course I want consteval, if a later C++ is available to me, but that doesn't excuse you writing constexpr does absolutely nothing, when it clearly does.

consteval wasn't intended to be excusing anything. I was just letting you know you're misunderstanding what constexpr does, and that what you're thinking it's supposed to do is in fact consteval's job.

You seem very confused about language specifications. That GCC and Clang happen to interpret constexpr as an extra "please inline" hint under -O3 is not evidence of constexpr "doing" something, and certainly not justification for including it in the language standard. That's like saying HN's orange color is "doing something" just because you really like to go eat an orange every time you see it.

I suspect you will have a hard time finding any evidence that constexpr was ever intended to be a "this is technically optional but please really, really try to inline this" hint of sorts to the compiler by the committee.

> But consteval function is also not a literal replacement constexpr.

I didn't say it was.

> For example, you can't take a pointer to the former.

"Therefore constexpr is useful" does not follow from this.

> There's a reason they co-exist and are not useless.

There's a mediocre reason for consteval, and a bad reason for constexpr. The former is probably unnecessary IMO though still of marginal utility, and in any case I can concede there's a debate that could be had there. The latter would be practically useless if the language cared to just make it the implicit default. It's really only solving a problem it created.

If you're using constexpr as an "optional but highly recommended inline" hint like you're showing me in your examples, you're doing the equivalent of pulling up HN's orange color so it coaxes you (or someone else) to go eat an orange. You are certainly welcome do that (hopefully it's a free country where you live) and I'm not stopping you per se, but it's missing both the letter and the spirit of the keyword(/color) by a colossal margin.