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Targets & cross-compilation

The same C+ source builds for more than the machine you are on. A --target flag selects where the code is headed, and the compiler emits that target's ABI and intrinsics, not the host's.

cpc build --target ios-arm64
cpc check --target android-arm64
cpc --emit-asm --target esp32-xtensa src/pid.cplus

--target works on build, check, and the --emit-ll / --emit-ll-opt / --emit-asm / --emit-obj emitters. Omitting it builds for host and reproduces the previous behavior byte for byte.

The named targets

Target	What it is
`host`	The machine you are building on (the default).
`ios-arm64`	iOS device (arm64).
`ios-arm64-simulator`	iOS Simulator (arm64).
`android-arm64`	Android (`aarch64-linux-android24`), via the NDK.
`esp32-xtensa`	Espressif ESP32 (32-bit Xtensa). See Embedded & ESP32.

An unknown name fails with the supported list. A TargetSpec (triple, pointer width, endianness, object format, ABI and intrinsic selectors) drives codegen's per-target choices, so HFA classification, struct size buckets, register pairs, byval, spin-loop hints, and NEON selection all resolve against the selected target. Host output is unchanged.

Who runs the final link

C+ emits objects; for the platforms with their own build systems, that build system owns the final link. cpc build of a [lib] staticlib writes the object, the archive, and a C header into target/<target-name>/<mode>/.

iOS stops at object emission — Xcode owns the link. clang gets -target <triple> and an -isysroot from xcrun when available. [[bin]] binaries, cdylib, cpc test, and single-file builds are rejected for the iOS targets, with the supported staticlib flow named in the message.
Android emits aarch64-linux-android24 ELF objects and staticlibs through the NDK's clang (resolved from $CPC_NDK_CLANG, $ANDROID_NDK_HOME and friends, or the SDK's newest ndk/), archived with the NDK's llvm-ar (the host ar cannot index ELF members). The NDK's clang must report LLVM 19+ (NDK r28.2+).

A cross build pins target triple = "<triple>" into the emitted IR, so a handed-off .ll carries its target. Bundled vendor artifacts resolve by the target's stable artifact triple (vendor/<dep>/src/lib/arm64-apple-ios/...); only host consults clang -print-target-triple. A host-vs-target triple mismatch is reported as E0862.

Verified end to end

These are not paper targets. A C+ staticlib linked by NDK clang has run on a Pixel 9 Pro XL emulator; a C+-driven UIKit screen renders on an iPhone 16 Pro simulator; and a #[realtime] controller runs closed-loop on a physical ESP32. The platform UI bindings are uikit for iOS, appkit for macOS, and espidf for the ESP32.