build.rs prevents cross-compiling. Solution: remove it! 🎉

[bmisiak]

Build scripts, such as your build.rs, since they are built for execution on the compiling machine, don't receive the --target i686-… memo. As a result, their cfg!(target_arch) always matches the architecture of the rustc which compiles them - usually x86_64.

Because build.rs always sees x86_64, cross-compilation of your library from x86_64 hosts always fails, except for the scenario where a Windows user installs the whole 32-bit Rust toolchain (which 64-bit Windows happens to be able to execute thanks to WOW64) and uses it to compile the 32-bit plugin - I believe this is what you did.

When I removed build.rs in my fork, cross-compilation from x86_64 Windows (using the default stable-x86_64-pc-windows-msvc toolchain) to the i686-unknown-linux-gnu target worked perfectly! 🎈 There is no need to install a linux toolchain (which wouldn't even execute on Windows if you tried) nor the 32-bit windows toolchain. All that's needed to compile for Linux is:

rustup target add i686-unknown-linux-gnu
cargo build --target=i686-unknown-linux-gnu

And likewise, for 32-bit Windows:

rustup target add i686-pc-windows-msvc
cargo build --target=i686-pc-windows-msvc

You don't have to run the 32-bit version of rustc to compile for 32-bit targets. You're only supposed to change the target. The library, because of the build.rs quirk, needlessly restricts cross-compilation. 😟

[Pycckue-Bnepeg]

Hi! Thanks to you for the notice!
I'll think about it. There is HOST and TARGET environment variables in compile time which may replace cfg!(target_arch).
I guess it's also a reason why https://docs.rs couldn't build documentation for samp-sdk

[bmisiak]

For sure.
Please mind rust-lang/cargo#4423.
The issue also bit me because WSL only supports 64-bit binaries, so I wasn't able to run the 32-bit toolchain on it. I had to remove build.rs to compile my Linux binaries from WSL.

[jameshilliard]

Possible fix for this in #9322.