[jarjoura]

Wouldn't C++ and Rust eventually call down into those same libc functions?

I guess for your example, qsort() it is optional, and you can chose another implementation of that. Though I tend to find that both standard libraries tend to just delegate those lowest level calls to the posix API.

[steveklabnik]

Rust doesn't call into libc for sort, it has its own implementation in the standard library.

[oguz-ismail2]

Obviously. How about more complex things like multi-threading APIs though? Can the Rust compiler determine that the subject program doesn't need TLS and produce a binary that doesn't set it up at all, for example?

[adgjlsfhk1]

Many of the libc functions are bad apis with traditionally bad implementations.