Println-debugging alloc and core > format! - instruction incomplete

[peter-lyons-kehl]

Thank you for this guide (and, of course, for core, alloc, std).

std-dev-guide.rust-lang.org/development/building-and-debugging.html#println-debugging-alloc-and-core suggests to use format!. But format is not available under core (at least not as std::format!, nor as core::format! - and I thought that format! generates String, which, of course, requires alloc, so format! can't be under core).

Would it work as alloc::format! with #[uses_alloc] or (whatever that is), or how?

If all that people need to debug are tests, or alloc/core functionality invoked from tests, how about mentioning something like the following (if it works):

/// inside (the body of) a non-test core or alloc function:
#[cfg(test)]
{
    use std::format;
    ...
}

Or, could we mention 3rd party #[no_std] (limited) heap-less formatting crates (there is at least one).

[peter-lyons-kehl]

Related: Debugging alloc, core... in GDB or VS Code: rust-lang/rustc-dev-guide#443.