# Cross-compile for Linux on ARM64 (aarch64-linux-gnu) from x86_64.
#
# clang-21 + libc++ (for `import std;`) with the arm64 libc++ and SDL3 taken
# from Ubuntu's arm64 packages (installed with dpkg multiarch), and the arm64
# glibc headers/libs from `gcc-aarch64-linux-gnu`. lld links the result; the C
# multiarch include directory is added explicitly because clang does not always
# infer Debian's `bits/` layout from the target triple alone.

# The `import std` gate must be set before the compiler is probed; a toolchain
# file is processed earlier than the project's own top-level settings.
set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD "d0edc3af-4c50-42ea-a356-e2862fe7a444")

set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_PROCESSOR aarch64)

set(OPENRA3_AARCH64_TRIPLE "aarch64-linux-gnu")
# Multiarch paths the arm64 packages install into.
set(OPENRA3_AARCH64_INCLUDE "/usr/include/${OPENRA3_AARCH64_TRIPLE}")
set(OPENRA3_AARCH64_LIB "/usr/lib/${OPENRA3_AARCH64_TRIPLE}")

# Compiler + libc++ module description are cache vars so a distro with a
# differently-versioned clang (e.g. Debian's clang-19) can override on the
# command line.
set(OPENRA3_AARCH64_CC "clang-21" CACHE STRING "aarch64 C compiler")
set(OPENRA3_AARCH64_CXX "clang++-21" CACHE STRING "aarch64 C++ compiler")
set(OPENRA3_AARCH64_STDLIB_MODULES_JSON "/usr/lib/llvm-21/lib/libc++.modules.json" CACHE FILEPATH
    "libc++ std module description for the aarch64 target")

set(CMAKE_C_COMPILER ${OPENRA3_AARCH64_CC})
set(CMAKE_CXX_COMPILER ${OPENRA3_AARCH64_CXX})
set(CMAKE_C_COMPILER_TARGET ${OPENRA3_AARCH64_TRIPLE})
set(CMAKE_CXX_COMPILER_TARGET ${OPENRA3_AARCH64_TRIPLE})
# CMake's standard-library detection does not pass COMPILER_TARGET, so without
# this it probes the host standard library.
set(CMAKE_C_COMPILER_ARG1 "--target=${OPENRA3_AARCH64_TRIPLE}")
set(CMAKE_CXX_COMPILER_ARG1 "--target=${OPENRA3_AARCH64_TRIPLE}")

# libc++ standard-library module description for the aarch64 target. On a
# multiarch image only the arm64 libc++ is installed, so the standard path
# already resolves to the aarch64 module description.
set(CMAKE_CXX_STDLIB_MODULES_JSON "${OPENRA3_AARCH64_STDLIB_MODULES_JSON}")

# Strip with the cross binutils, so CPack can strip the arm64 binary.
set(CMAKE_STRIP aarch64-linux-gnu-strip)

set(CMAKE_C_FLAGS_INIT "-isystem ${OPENRA3_AARCH64_INCLUDE}")
set(CMAKE_CXX_FLAGS_INIT "-stdlib=libc++ -isystem ${OPENRA3_AARCH64_INCLUDE}")
set(CMAKE_EXE_LINKER_FLAGS_INIT "-stdlib=libc++ -fuse-ld=lld -L${OPENRA3_AARCH64_LIB}")
set(CMAKE_SHARED_LINKER_FLAGS_INIT "-stdlib=libc++ -fuse-ld=lld -L${OPENRA3_AARCH64_LIB}")

# Run arm64 test binaries through qemu when it is installed, so `ctest` works
# during the image build; harmless when the tests are only cross-compiled.
set(CMAKE_CROSSCOMPILING_EMULATOR qemu-aarch64-static)