How to install a Rust target for a specific rustup toolchain? - rust

Question

I am using rustc and cargo on my 64-bit Windows machine to compile a 32-bit application. This work fine when using the stable toolchain, but when I try to use the beta toolchain it fails.
The beta toolchain was successfully installed with rustup install beta. In the project folder there is a .cargo/config file containing the following lines:
[build]
target = "i686-pc-windows-msvc"
[target.i686-pc-windows-msvc]
rustflags = ["-Ctarget-feature=+crt-static"]
When running cargo +beta build the following error occurs:
error[E0463]: can't find crate for `core`
|
= note: the `i686-pc-windows-msvc` target may not be installed
I have tried running rustup target add i686-pc-windows-msvc to fix the issue but it didn't help; rustup target list even displays it as "installed". Possibly this command only adds the target for stable, and I couldn't find out how to specify the beta toolchain.
How can I add another (non-default) target for the beta toolchain?

Answer 1

Read the help for rustup target add:
$ rustup target add --help
rustup-target-add
Add a target to a Rust toolchain
USAGE:
rustup target add [OPTIONS] <target>...
FLAGS:
-h, --help Prints help information
OPTIONS:
--toolchain <toolchain> Toolchain name, such as 'stable', 'nightly', or '1.8.0'. For more information see
`rustup help toolchain`
Thus you want:
rustup target add i686-pc-windows-msvc --toolchain beta
I believe it will add the target to the "current" toolchain by default, so you could also do:
rustup override set beta # in your project directory
rustup target add i686-pc-windows-msvc #
cargo build # no more +beta
rustup target list even displays it as "installed"
Read the help for rustup target list:
$ rustup target list --help
rustup-target-list
List installed and available targets
USAGE:
rustup target list [OPTIONS]
FLAGS:
-h, --help Prints help information
OPTIONS:
--toolchain <toolchain> Toolchain name, such as 'stable', 'nightly', or '1.8.0'. For more information see
`rustup help toolchain`
Thus you want:
rustup target list --toolchain beta

Answer 2

Apart of installing a new target described in the answer above, you might also need to setup your new installed target as a default target.
In order to check all available or installed targets you use:
rustup target list
You can also check your default target by executing:
rustup default
If you want to change the default target you can use the following command:
rustup default <YOUR_TARGET_NAME>
for example: rustup default stable-x86_64-pc-windows-msvc
Also if you need to change a default target to your specific directory, you can create a file with name rust-toolchain and include the target name as a content:
stable-x86_64-pc-windows-msvc