build.mcpp

import std;
import mcpp;
import mcpp.tools.island;

// The lowest rung: the generated boundary module IS the interface, and this
// project contains no seam and no header.
//
// ONE ROOT, AND IT IS A TREE. `scan` reads every marked entry point under it
// and the directories below it extend the namespace, so `src/kernels/vec` is
// reached as `boundary::kernels::vec`. A root is also what makes ADDING a file
// re-run this program: declared inputs are hashed contents, and a new file
// changes none of them, so the root is registered as a glob as well.
//
// A single root is also the layout root, so nothing here has to say which tree
// decides where entry points live. `../cuda` has two and says so.
int main() {
    mcpp::tools::island::options opt;
    opt.module_name = "boundary.kernels";
    opt.out_dir     = std::string(mcpp::out_dir()) + "/island";
    opt.produced_by = "the boundary example";
    opt.roots       = { std::string(mcpp::manifest_dir()) + "/src/kernels" };

    // An island's symbol is global to the whole program, so an entry point
    // carries a prefix whether or not it sits in a namespace, and the namespace
    // then repeats it. This emits `saxpy` beside `boundary_saxpy`; the authored
    // name is the symbol and stays canonical.
    opt.strip_prefix = "boundary_";

    const auto entries = mcpp::tools::island::scan(opt);
    if (!entries) return 1;
    const auto out = mcpp::tools::island::emit(*entries, opt);
    if (!out) return 1;

    // The island reads the generated header through a forced-include flag, so
    // no source in this project names a generated file.
    //
    // `cflag` and not `cxxflag`: the island is C, and forcing a header into
    // every C++ translation unit would put declarations ahead of the
    // `export module` line of a module interface, which is ill-formed.
    for (auto const& f : mcpp::tools::island::force_include_flags(
             out->header_file, mcpp::compiler()))
        mcpp::cflag(f.c_str());
    mcpp::generated(out->interface_file.c_str());
    return 0;
}