On 30Nov2018 1133, Antoine Pitrou wrote:
On Fri, 30 Nov 2018 13:06:11 -0600 Neil Schemenauer email@example.com wrote:
On 2018-11-29, Armin Rigo wrote:
...Also, although I'm discussing it here, I think the whole approach would be better if done as a third-party extension for now, without requiring changes to CPython---just use the existing C API to implement the CPython version.
Thank you for providing your input on this subject. I too like the idea of an API "shim layer" as a separate project.
What do you think of writing the shim layer in C++? I'm not a C++ programmer but my understanding is that modern C++ compilers are much better than years ago. Using C++ would allow us to provide a higher level API with smaller runtime costs.
The main problem with exposing a C++ *API* is that all people implementing that API suddenly must understand and implement the C++ *ABI* (with itself varies from platform to platform :-)). That's trivially easy if your implementation is itself written in C++, but not if it's written in something else such as RPython, Java, Rust, etc.
C is really the lingua franca when exposing an interface that can be understood, implemented and/or interfaced with from many different languages.
So I'd turn the proposal on its head: you can implement the internals of your interpreter or object layer in C++ (and indeed I think it would be crazy to start writing a new Python VM in raw C), but you should still expose a C-compatible API for third-party providers and consumers.
I totally agree with Antoine here. C++ is great for internals, but not the public interfaces.
The one additional point I'd add is that there are other ABIs that C++ can use (such as xlang, Corba and COM), which can provide stability in ways the plain-old C++ ABI does not. So we wouldn't necessarily have to design a new C-based ABI for this, we could adopt an existing one that is already proven and already has supporting tools.