Platform-detection defines, baked at generation time.

FFI conventions

Unsuffixed aliases are unsafe foreign imports; aliases suffixed Safe are safe. Functions whose callbacks fire during the call export only the Safe alias (the genuine unsafe import stays reachable under SDL3.Sys.Bindgen.PlatformDefines.Unsafe); functions curated unsafe-only export only the unsuffixed one. Each alias's documentation records its flavor and rationale.

Full conventions: SDL3.Sys.