> The whole point of abstraction is that the implementation details aren't known.
I disagree with that phrasing; it is better to say that abstractions allow a programmer to ignore unimportant details. For example, when developing two modules (possibly even by different teams), all they know about each other is a lean interface, without any implementation details. However, the compiler might know everything.
> So in C++ we always suffer from this problem called "zero overhead abstractions" or "abstraction costs"
This is another odd term. In Rust, the term used instead is "zero-cost abstractions," referring to cases where the compiler can generate instructions for higher-level code just as efficiently.
> So the main practical benefit of a JIT isn't that at all, but that it can do the "mother of all optimisations" - inlining - far more aggressively.
I’ll reiterate that I disagree with this: inlining is performed very efficiently during monomorphization. And monomorphization is used very frequently in Rust.
> After more than 25 years of working with C++
I don't have much experience with C++; I mostly use Rust. I can only assume that the C++ development experience is far worse than Rust - especially when trying to write software that is both reliable and fast. This may be particularly relevant to older C++.
So, a Dog, a Cat, and an Abstract Mammal walk into a bar...
https://godbolt.org/z/dEsW1sfM8
I didn't want to do this, but I went ahead and created a small example showing that monomorphization and inlining work remarkably well. (Obviously, this example does not address memory management)
I disagree with that phrasing; it is better to say that abstractions allow a programmer to ignore unimportant details. For example, when developing two modules (possibly even by different teams), all they know about each other is a lean interface, without any implementation details. However, the compiler might know everything.
> So in C++ we always suffer from this problem called "zero overhead abstractions" or "abstraction costs"
This is another odd term. In Rust, the term used instead is "zero-cost abstractions," referring to cases where the compiler can generate instructions for higher-level code just as efficiently.
> So the main practical benefit of a JIT isn't that at all, but that it can do the "mother of all optimisations" - inlining - far more aggressively.
I’ll reiterate that I disagree with this: inlining is performed very efficiently during monomorphization. And monomorphization is used very frequently in Rust.
> After more than 25 years of working with C++
I don't have much experience with C++; I mostly use Rust. I can only assume that the C++ development experience is far worse than Rust - especially when trying to write software that is both reliable and fast. This may be particularly relevant to older C++.
So, a Dog, a Cat, and an Abstract Mammal walk into a bar...
https://godbolt.org/z/dEsW1sfM8
I didn't want to do this, but I went ahead and created a small example showing that monomorphization and inlining work remarkably well. (Obviously, this example does not address memory management)