BESA

BESA is a declarative CMake project model. Projects describe features, valid feature spaces, and semantic source units; BESA lowers that model into CMake targets and a machine-readable manifest. The same model is consumed by cpdocs, so documentation does not require a second project description.

Features and source languages are independent concepts. A project feature such as gpu may select a CUDA source unit, but the feature is still just a project capability while cuda is the unit's language.

cmake_minimum_required(VERSION 3.25)
project(example VERSION 1.0.0 LANGUAGES NONE)
find_package(besa CONFIG REQUIRED)

besa_add_feature(mpi)
besa_add_feature(gpu)

besa_keyso_zero_or_one(parallel mpi)
besa_keyso_zero_or_one(acceleration gpu)
besa_keyso_create_feature_space(supported PRODUCT parallel acceleration)
besa_set_feature_space(supported)
besa_configure_complete()

besa_add_subdirectory(DIRECTORY src/core TYPE cpp)
besa_add_subdirectory(DIRECTORY src/gpu TYPE cuda CONDITION gpu)
besa_add_subdirectory(DIRECTORY bin TYPE bin)

Built-in semantic types are c, cpp, cuda, hip, fortran, and bin. Their manifest languages are respectively c, cpp, cuda, hip, fortran, and no single language for bin. C/C++/CUDA/HIP units use include/ and lib/; Fortran additionally uses mod/; bin turns top-level .c/.cpp files into executables.

Generators register a custom type that resolves to one built-in type:

besa_register_subdirectory_type(
  jnum
  FUNCTION jnum_add_subdirectory
  RESOLVES_TO cpp
  GENERATED
)

besa_add_subdirectory(DIRECTORY schema TYPE jnum)

BESA owns the generated prefix and the global codegen target. The callback receives SOURCE_DIR, BUILD_DIR, OUTPUT_DIR, and OUTPUT_TARGET_VARIABLE; any extra ARGS supplied to besa_add_subdirectory() are forwarded unchanged. This lets cpdocs build codegen on the host and then read the generated include/, lib/, and (for Fortran) mod/ roots without building the target application.