Jam requires Clang 23+, CMake 4.4+ and Ninja on macOS, Linux or Windows 10 1803+. CMake checks the C++26 features and platform page size. It fetches a pinned native for SIMD, target dispatch and attributes. To use an existing checkout, set FETCHCONTENT_SOURCE_DIR_JAM_NATIVE=/path/to/native.

cmake -S . -B build -G Ninja -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_BUILD_TYPE=Release
cmake --build build --parallel
ctest --test-dir build --output-on-failure
cmake --install build --prefix /path/to/jam

Tests default on when building Jam as the top-level project. Exceptions are enabled; see generation limits for failure behavior.

Windows

Use clang-cl, matching clang-scan-deps, and LLD from LLVM 23, in a Visual Studio developer shell with the MSVC C++ library and Windows SDK.

cmake -S . -B build -G Ninja -DCMAKE_CXX_COMPILER=clang-cl -DCMAKE_LINKER_TYPE=LLD -DCMAKE_BUILD_TYPE=Release
cmake --build build --parallel
ctest --test-dir build --output-on-failure

CI exercises Debug and Release. Mapping details cover Windows page size, aliases and commit behavior.

CMake consumers

cmake_minimum_required(VERSION 4.4)
project(example LANGUAGES CXX)
set(CMAKE_CXX_EXTENSIONS OFF)
find_package(jam CONFIG REQUIRED)
add_executable(example example.cc)
target_link_libraries(example PRIVATE jam::jam)

Set CMAKE_PREFIX_PATH to the installation prefix. The package includes native and module sources; CMake regenerates consumer BMIs after installation or relocation. The compiler, standard library, exception mode and extension mode must match the module build. jam::jam supplies C++26.

With Clang 23.1.2 and libc++ on macOS, include <new> before importing Jam. Without it, the README example crashes the compiler while emitting libc++'s allocation helper. The example includes it for that reason.

For cross compilation, set JAM_PAGE_BYTES to the target's page size. The heap checks it at runtime. JAM_CONTEXT_X28=ON selects the optional AArch64 register carrier; TLS is the default.

Benchmarking

Enable JAM_BUILD_BENCHMARKS=ON to build heap-bench:

build/heap-bench --bytes 16MiB --workers 4 --reserve-list 32,64,128 --repeats 11

This times compaction after marking, excluding allocation, tracing and fixture setup. It verifies relocated payloads and pointer fields after each trial. It is not an end-to-end GC benchmark. Tests compare every compactor admitted on the host with the baseline, including mixed-generation forwarding.

Documentation

With Doxygen 1.18+ and Graphviz installed:

cmake -S . -B build -DJAM_BUILD_DOCS=ON

cmake --build build --target jam-docs

Open build/docs/html/index.html. It includes the README, these guides, API contracts and source links. XML is in build/docs/xml. Warnings fail the build; each run replaces generated output so deleted declarations leave no stale pages.

CI builds the library, runs tests and builds the docs. Successful main builds publish the reference; pull requests validate it without publishing.

Topic guides