[Question] Toolchain and rustup packages

[xlouis027]

Hi Nihal,
I saw that in board nrf52840 use target thumbv7em-none-eabihf and rpi4 use target aarch64-unknown-none-softfloat.
I checked it and found reference on https://rust-lang.github.io/rustup-components-history/.
My question is how we know a board use what suitable target rustup package?
Another point, what is the differences of stable and nightly toolchains, of x86_64-pc-windows-msvc and x86_64-pc-windows-gnu?

[nihalpasham]

Rust support for different platforms ("targets") are organized into three tiers, each with a different set of guarantees. You can find more information - https://doc.rust-lang.org/nightly/rustc/platform-support.html

Stable - the rust compiler (used to compile rust programs) is stable
nightly - the rust compiler (used to compile rust programs) is not-stable i.e. it has some additions that are still under evaluation or testing.