On 17.03.22 16:11, Paolo Bonzini wrote:
On 3/16/22 13:32, Stefan Hajnoczi wrote:
You can define rules and a way to enforce a subset of C++, but I think
over time the code will be C++. A policy that is complicated discourages
contributors.
For these reasons I think that if code runs through a C++ compiler we
should just allow C++. Either way, it will take time but that way no one
will feel betrayed when C++ creeps in.
Fair enough. We even already have some conventions that will make any
C++ that creeps in less weird (for example, mandatory typedef of
structs).
I don't think it would be a big deal overall. I actually agree that
we should "just allow C++", what matters more to have style rules that
make QEMU's flavors of C and C++ consistent.
I just want to throw in that I personally am absolutely not confident in
reviewing C++ code. As for Rust, you keep mentioning that we don’t have
anyone who would “shepherd us through the learning experience”, but I
find the very same argument applies to C++.
C++ may start out looking like C, but if used ideally, then it is a very
different language, too. I understand the difference is that we can
incrementally convert our C code to C++, but I’m not comfortable
overseeing that process, which I would have to do as a maintainer.
Assuming our overall stance does change to “just allowing C++”, I’d feel
unjust if I were to reject C++isms just based on the fact that I don’t
know C++, so I’d be forced to learn C++. I’m not strictly opposed to
that (though from experience I’m more than hesitant), but forcing
maintainers to learn C++ is something that has a cost associated with it.
My biggest gripe about C++ is that as far as I understand there are many
antipatterns, many of which I think stem from the exact fact that it is
kind of compatible with C, and so you can easily accidentally write
really bad C++ code; but without years of experience, I’m absolutely not
confident that I could recognize them. Now, I might say I’d just
disallow complicated stuff, and keep everything C-like, but from what
I’ve heard, C-like C++ seems to be exactly one case that is considered
bad C++. I’m really under the impression that I’d need years of
experience to discern good from bad C++, and I don’t have that experience.
Hanna
