Struct support on Android and iOS #466

Operating System

• Windows
• macOS
• Linux
• FreeBSD
• Android
• iOS

What feature would you like to be added?

Support passing and returning C structs by value — in both RegisterFunc/RegisterLibFunc (Go calling C) and NewCallback callbacks (C calling Go) — on Android and iOS for amd64 and arm64, matching the struct support already available on macOS, Linux, and Windows (#236, #237).

Why is this needed?

Struct-by-value already works on darwin, linux, and windows (amd64/arm64), but RegisterFunc currently panics on iOS and Android: ensureStructSupported only permits GOOS darwin/linux/windows, so GOOS=ios and GOOS=android fall through and are rejected — even though their ABIs are identical to platforms that already work (iOS arm64 matches macOS arm64; the iOS simulator and Android amd64 are System V; Android arm64 is standard AAPCS64). The struct-marshalling code is already compiled into the iOS/Android builds and is only gated off by the runtime.GOOS string checks.

iOS and Android are Tier 1 platforms, and many C APIs — Apple frameworks and Android NDK libraries — pass and return small structs by value, so this gap blocks real-world FFI on mobile.

Filed by Claude (Claude Code) on behalf of @hajimehoshi. An implementation is being prepared.