Conditional dependencies

A minimal C++ package that shows off if(...) conditional dependencies in a Pixi [package] section.

cuda_probe is a tiny executable that reports which compiler built it and whether it was compiled with CUDA support. The CUDA runtime is only available on conda-forge for Linux and Windows, so the manifest asks for it only there:

toml

[package.host-dependencies."if(linux or win)"]
cuda-version = "12.*"
cuda-cudart-dev = "12.*"

On Linux/Windows the build links against the CUDA runtime and the program queries the visible device count. On macOS the block is skipped entirely and the very same sources build a CPU-only binary.

Run it

bash

pixi run start

On a machine without conditional-dependency support you would instead see the old [package.target.*] tables. The if(<expression>) form accepts anything rattler-build understands (and, or, not, matches(...), ...) and exposes these variables:

build_platform the platform the build runs on
host_platform the platform the package is built for (differs when cross-compiling)
target_platform the run platform (differs from host_platform for noarch)
the bare booleans unix, linux, win and osx