I don’t understand why techniques valid in small spaces aren’t also valid in slightly larger spaces.

If you don’t have the budget for the standard library, don’t use it. If you somehow have the budget for glibc and not the rust standard library, call into glibc instead of the rust standard library.

glibc can be shared by 20 c executables.

rust stdlib will be bundled with those 20 rust executables, they blow up quickly.

mcu does not use stdlib of rust, it uses no-std, c++ has its own nonstdlib as well, on mcu they're similar.

Yes, I understand what you're saying. I am saying that if you find yourself in that situation, don't use the Rust standard library. Your Rust programs can share glibc with your C programs just fine. This isn't a disqualifying situation for Rust. Heck, when you use the Rust standard library, dynamically linking to glibc is the norm!

maybe OP doen't know about #![no_std] !? You can not (as far as I know) have the Rust std lib as a dll, but you can chose to not use/include the std lib: https://web.mit.edu/rust-lang_v1.25/arch/amd64_ubuntu1404/sh...

Just FYI, these docs are very old. They’re for rust 1.25.0. Since rust is stable that means they’re still accurate, just not complete.

of course I knew no_std, it's for MCUs, similar to c++'s nostdlib, I'm comparing rust's stdlib to libstdc++ though, but the former is not shared-lib friendly to say the least.