Update contribute docs with cross platform code development guide

[Cloud0310]

Problem you are trying to solve

The current contributor documentation does not explain how to develop and lint platform specific Rust code from another operating system.

While working on PR #4861, I was developing #[cfg(windows)] code from Linux and found that the experience was difficult without additional tooling configuration. By default:

• rust-analyzer does not analyze Windows specific code paths
• clippy and cargo check only validate the host target
• autocomplete and diagnostics for Windows code are incomplete
• contributors may end up writing platform specific code without proper linting or IDE support

This creates friction for contributors working on cross platform functionality.

Solution you'd like

Add a contributor guide section describing cross platform Rust development workflows, especially for developing Windows specific code from Linux or macOS.

Suggested documentation topics:

Install Cross Rust target

rustup target add x86_64-pc-windows-gnu

Configure Cargo for cross target development

Example .cargo/config.toml using mingw-w64-gcc:

[target.x86_64-pc-windows-gnu]
linker = "x86_64-w64-mingw32-gcc"

[target.x86_64-pc-windows-gnu.env]
CC = "x86_64-w64-mingw32-gcc"
CXX = "x86_64-w64-mingw32-g++"
AR = "x86_64-w64-mingw32-ar"

Example using llvm-mingw:

[target.x86_64-pc-windows-gnu]
linker = "/opt/llvm-mingw/bin/clang"

rustflags = [
  "-Clink-arg=--config",
  "-Clink-arg=/opt/llvm-mingw/bin/x86_64-w64-windows-gnu.cfg"
]

[target.x86_64-pc-windows-gnu.env]
CC = "/opt/llvm-mingw/bin/clang --config /opt/llvm-mingw/bin/x86_64-w64-windows-gnu.cfg"
CXX = "/opt/llvm-mingw/bin/clang++ --config /opt/llvm-mingw/bin/x86_64-w64-windows-gnu.cfg"
AR = "/opt/llvm-mingw/bin/llvm-ar"

Run cross target checks and lints

cargo check --target=x86_64-pc-windows-gnu
cargo clippy --target=x86_64-pc-windows-gnu

This enables diagnostics for #[cfg(windows)] code paths.

Configure rust-analyzer

Example VS Code settings:

.vscode/settings.json

{
  "rust-analyzer.cargo.target": "x86_64-pc-windows-gnu",
  "rust-analyzer.check.command": "clippy",
  "rust-analyzer.check.allTargets": true
}

This allows rust-analyzer to properly analyze Windows specific code and improves diagnostics, autocomplete, and linting support.

Mention optional tooling

Potentially useful tools and toolchains:

• cargo-xwin
• cargo-zigbuild
• llvm-mingw
• mingw-w64

Windows Server containers may also be useful for contributors or CI jobs that need a real Windows environment instead of cross compiling from Linux.

For example, a project could document a Windows container workflow for validating:

rustup target add x86_64-pc-windows-msvc
cargo check --target=x86_64-pc-windows-msvc
cargo clippy --target=x86_64-pc-windows-msvc

This may be helpful for validating MSVC specific behavior, native Windows dependencies, or build scripts that are difficult to support through x86_64-pc-windows-gnu cross compilation.

Notes

I tested both llvm-mingw and mingw-w64 based workflows on Linux and found that they significantly improve the experience of developing and linting Windows specific Rust code from non-Windows environments

[Cloud0310]

Any more ideas for this? I'd love to try out the cargo-xwin and cargo-zigbuild out, and give correspondening setup here.

[djc]

I've so far used cargo-zigbuild for this, but it was a bit problematic with aws-lc-rs. That has reportedly been solved, but I haven't tried it since.

[ChrisDenton]

Hm, we should be able to make cross checking (not compiling) relatively painless. The issue would be build scripts that want to build platform things but surely we can skip that (or provide some cfg to).

[Cloud0310]

Hm, we should be able to make cross checking (not compiling) relatively painless. The issue would be build scripts that want to build platform things but surely we can skip that (or provide some cfg to).

Yes, my thoughts for PR is basically two parts:

1. Doc side updates
2. Add cross compile commands by comments (if we need extra toolchain config by manual config PATHs or installing things) or pre-configured checking command into .cargo/config.toml

[rami3l]

@Cloud0310 Thanks again for the investigation on cross-checking!

How universal are your .cargo/config.toml contents? In any case, I believe that committing those to .cargo/config.toml in this repo isn't correct (because that will almost certainly break our MINGW builds), however I'd be okay if template files are placed there or in the guide as code snippets (if short enough) instead.

[Cloud0310]

@Cloud0310 Thanks again for the investigation on cross-checking!

How universal are your .cargo/config.toml contents? In any case, I believe that committing those to .cargo/config.toml in this repo isn't correct (because that will almost certainly break our MINGW builds), however I'd be okay if template files are placed there or in the guide as code snippets (if short enough) instead.

I mean just commented out template for use with extra manual config here. Or as you said, put it in docs instead of .cargo/config.toml.

[Cloud0310]

And, if possible, add universal config for enabling things like, cargo lint-windows and cargo lint-unix to minimal the painless new comers may meet with.