Getting started

Requirements:

CMake 3.28+ and a C++23-capable compiler.
On Windows, an installed Clang executable on PATH or under Program Files/LLVM/bin; configuration fails immediately if it is missing or cannot run.
LLVM 23.1.x (>=23.1.1) C++ SDK for compiler builds. CMake prefers a global installation, then downloads the pinned 23.1.2 SDK into thirdparty/ if missing; see SDK setup and compilation contract.
Boost 1.90+ with Boost.Multiprecision for compiler and runtime; the compiler also requires Boost.Parser. Multiprecision is header-only and needs no Boost binary library.
toml++ 3.4.0 for project manifests; see dependency setup.
Normal builds and tests do not require Erlang/OTP. Tests use project-owned golden fixtures. Optional live audits and explicit fixture regeneration require Erlang/OTP 29+.

On macOS:

xcode-select --install
brew install cmake boost erlang tomlplusplus llvm@23

On Windows, install LLVM/Clang globally for the host compiler tools. Install Visual Studio's Desktop development with C++ workload and a Windows SDK, plus Ninja. Use an x64 Native Tools command prompt or Developer PowerShell configured for x64, with clang-cl, cmake, and ninja on PATH. CMake checks the MSVC ABI, Windows SDK linkage, and C++23 std::expected support. The LLVM command-line tools alone do not provide the required C++ SDK; CMake downloads it separately when LLVMConfig.cmake and matching libraries are absent.

CMake downloads Boost 1.90.0 and toml++ 3.4.0 into the ignored thirdparty/ directory on first use, verifies their SHA-256 checksums, and retains both archives and extracted sources. Subsequent configurations, including fresh build directories, reuse those files without network access. Removing build/ does not remove dependencies. When CMake's own TLS stack cannot verify certificates (for example the CMake bundled with Strawberry Perl), downloads are retried with the host curl and still verified. Runtime-only builds download only Boost. Explicit dependency roots below take precedence and allow offline setup; an invalid explicit root fails without downloading. Linux and macOS continue to use installed dependencies or local thirdparty/ sources. LLVM SDK fallback downloads apply on all three platforms, with SHA-256-pinned official archives for Windows x64/ARM64, Linux x64/ARM64, and macOS ARM64. Archives and extracted SDKs stay in thirdparty/ for offline reuse. Other host architectures and cross-builds require an explicit matching LLVM_DIR.

For compiler builds, LLVM's zlib and zstd dependencies are detected from installed libraries. On Windows, missing libraries trigger SHA-256-verified downloads of zlib 1.3.2 and zstd 1.5.7, followed by static Debug/Release builds under thirdparty/. These builds are reused across build directories and match the host compiler, architecture and CRT. Set ZLIB_ROOT or zstd_ROOT to prefer an installed library; CLAUSE_DOWNLOAD_ZLIB=OFF and CLAUSE_DOWNLOAD_ZSTD=OFF disable the respective fallbacks. MSVC SDK discovery rejects cached MinGW .a libraries such as those bundled with Strawberry Perl. Linux and macOS use installed development packages.