Supported toolchains

Flecha 0.1.1 uses explicit major-version ranges for source builds and pinned major-version baselines for release production. Patch releases within a listed major version are accepted. Versions outside these ranges are not supported until they pass the complete CI, sanitizer, packaging, installed-layout, and clean-install matrix.

Source-build policy

Component	Supported versions
CMake	3.20 or newer
LLVM development package	17 through 23
Clang C/C++ compiler	17 through 23
GCC C/C++ compiler	13 through 16
Apple Clang	16 through 17
Microsoft Visual C++	Not supported

The C and C++ compilers must come from the same toolchain and support C++23. CMake rejects unsupported compiler and LLVM versions during configuration. LLVM_DIR must identify the matching LLVM CMake package when it is not on the default search path.

Release baselines

Release archives are built and consumed on these pinned GitHub-hosted runner families:

Archive	Build toolchain	Clean-install linker and SDK
Linux x86-64	Ubuntu 24.04, Clang 18, LLVM 18	Clang 18, GNU binutils and Ubuntu 24.04 system development/startup files
Windows x86-64	Windows Server 2025, MSYS2 UCRT64, Clang 23, LLVM 23	MSYS2 UCRT64 Clang 23 and the UCRT64 runtime/startup packages
macOS x86-64	macOS 15, Homebrew Clang 18 and LLVM 18	Xcode 16.4, Apple Clang 17, macOS SDK 15
macOS arm64	macOS 15, Homebrew Clang 18 and LLVM 18	Xcode 16.4, Apple Clang 17, macOS SDK 15

The supported binary-package hosts are Ubuntu 24.04 x86-64, Windows Server 2025 x86-64 under MSYS2 UCRT64, and macOS 15.x on x86-64 or arm64 with Xcode 16.4 and a macOS 15.x SDK. Other host OS and SDK combinations are untested.

The Linux test suite also builds with GCC 14. Sanitizer jobs use Clang 18. Every CI and release job prints the detected compiler, LLVM, linker, target, and platform runtime or SDK version, then fails if it differs from its matrix baseline.

Installation packages

Ubuntu 24.04

Install the pinned release-build toolchain with:

sudo apt-get install clang-18 llvm-18-dev ninja-build cmake

GCC validation additionally uses gcc-14 and g++-14. A binary archive user installs the host linker and system startup files with:

sudo apt-get install binutils clang-18 libc6-dev

LLVM development files are not required.

Windows Server 2025 and MSYS2

Flecha supports the MSYS2 UCRT64 environment. Release builds use the shared LLVM and Clang 23 packages:

pacman -S --needed \
    mingw-w64-ucrt-x86_64-clang \
    mingw-w64-ucrt-x86_64-cmake \
    mingw-w64-ucrt-x86_64-ninja \
    mingw-w64-ucrt-x86_64-llvm

The workflow verifies LLVM and Clang 23 before configuring, so an MSYS2 rolling upgrade cannot silently change the release toolchain. Binary archive users install only mingw-w64-ucrt-x86_64-clang, which supplies the native driver, UCRT libraries, and startup files without requiring the LLVM development package.

macOS 15

Source builds use Homebrew llvm@18. Native linking uses Xcode 16.4 and the macOS 15 SDK:

brew install llvm@18 cmake ninja
export LLVM_DIR="$(brew --prefix llvm@18)/lib/cmake/llvm"
export CC="$(brew --prefix llvm@18)/bin/clang"
export CXX="$(brew --prefix llvm@18)/bin/clang++"

Select Xcode 16.4 through DEVELOPER_DIR or xcode-select. Binary archive users need only the corresponding Xcode command-line tools and SDK, not the Homebrew LLVM development package.

Updating the matrix

Changing a supported range or release baseline requires updating cmake/toolchain_policy.cmake, both GitHub Actions workflows, and this page in the same change. New versions become supported only after all protected CI jobs pass on the affected release platforms.