Is it just me, or does Rust feel much more bare-bones than other languages? I just started learning it recently and this is the one thing that stood out to me, much more so than the memory management business. A lot of things that would normally be part of the language has to be achieved through meta-programming in Rust.
Is this a deliberate design choice? What do we gain from this setup?
Edits:
- Somehow, this question is being interpreted as a complaint. It’s not a complaint. As a user, I don’t care how the language is designed as long as it has a good user experience, but the curious part of my mind always wants to know why things are the way they are. Maybe another way to phrase my question: Is this decision to rely more on meta-programming responsible for some of the good UX we get in Rust? And if so, how?
- I’m using meta-programming to mean code that generates code in the original language. So if I’m programming in Rust, that would be code that generate more Rust code. This excludes compilation where Rust gets converted into assembly or any other intermediate representation.


printfuses macros in its implementation.int __printf (const char *format, ...) { va_list arg; int done; va_start (arg, format); done = __vfprintf_internal (stdout, format, arg, 0); va_end (arg); return done; }^ This is from glibc. Do you know what
va_startandva_endare?Derives expand to “regular code”. You can run
cargo expandto see it. And I’m not sure how that’s an indication of “bare bone”-ness in any case.Such derives are actually using a cool trick, which is the fact that proc macros and traits have separate namespaces. so
#[derive(Debug)]is using the proc macro namedDebugwhich happens to generate “regular code” that implements theDebugtrait. The proc macro namedDebugand implemented traitDebugdon’t point to the same thing, and don’t have to match name-wise.Does anyone? 🙃
For functions that want to accept variadic arguments in C/Cpp
Yup; I was referring to their implementation being dark magic, depending on calling convention, argument type, argument order and possibly other properties specific to the processor’s instruction set…
“If you think you understand
va_*, you don’t.”Yeah, didn’t catch your sarcasm there :D
I was just referring to the fact that they are macros.