Cannot install target with rustup-init but can add later

help
1

Hi All,

If I run

./rustup-init -y --no-modify-path --profile minimal \
    --default-toolchain $RUST_VERSION \
    --default-host armv7-linux-androideabi

it fails with error: target 'armv7-linux-androideabi' not found in channel.

But I can run

./rustup-init -y --no-modify-path --profile minimal \
    --default-toolchain $RUST_VERSION

rustup target add armv7-linux-androideabi

and it succeeds.

I tried a bunch of different RUST_VERSIONs, stable and nightly alike.

What gives?

[EDIT] I am running this on an amd64 host, i.e. I'm setting up a toolchain for cross-compilation.

2

there's no toolchain for android hosts, they are all tier 2 without host tools. you can only cross compile to these platforms. see the list:

https://doc.rust-lang.org/nightly/rustc/platform-support.html#tier-2-without-host-tools

https://doc.rust-lang.org/nightly/rustc/platform-support/android.html

3

Instead of --default-host use --target:

./rustup-init -y --no-modify-path --profile minimal \
    --default-toolchain $RUST_VERSION \
    --target armv7-linux-androideabi
4

Thank you for the reply.

I've read those pages, but apparently I do not understand what that means and how toolchains fall together.

I am only beginning to experiment with android builds, but previously I used to rustup target add arm7-unknown-linux-gnueabihf (another Tier 2 target) while running on amd64 and was able to build for that target just like I do for native, cross-compiling handled transparently by cargo and rustc.

From your answer I gather that if I wanted to install arm7-unknown-linux-gnueabihf as the only toolchain, I would have failed, just like with android. But why? What would be missing?

Is it because a native toolchain is always needed to compile procedural macros?

The Platform Support page mentions this as the distinction of targets with host tools:

Tier X targets with host tools additionally support running tools like rustc and cargo natively on the target

but that's not what I am trying to do.

[EDIT] Sorry, I only now realized that I've omitted this piece of information from my question: I'm setting up a cross-compilation toolchain on an amd64 host, not running rustup-init on Android.

5

Thank you, indeed this works!

The end result is the same as my two-step process though: I end up both with a native toolchain and the android toolchain.

Still, it's an improvement.

6

Yes. Proc macro must be compiled for host architecture which means you need toolchain which can do that.

Sometimes you may even have a choice: I can use aarch64-apple-darwin as my main toolchain or x86_64-apple-darwin but obviously Android toolchain couldn't be the main one (except if you are using Android for development).

7

Thanks, this makes sense.

8

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