build.mcpp

import std;

// A build program that answers one question: whose tools does this build see?
//
// IT DOES NOT CONSTRUCT A PATH TO ONE. `MCPP_XPKG_QEMU_RISCV` gives the
// payload directory, and a program can join `/bin/qemu-system-riscv64` onto it
// — that works, and it means every build program in the ecosystem repeats the
// same joining, each with its own idea of the layout. Asking `PATH` is what a
// program would do anyway; what `[xlings].subos` changed is the answer.
int main() {
    std::string_view path(std::getenv("PATH") ? std::getenv("PATH") : "");
    std::string_view first;
    for (auto part : std::views::split(path, ':')) { first = std::string_view(part); break; }

    // Reported through the advisory channel, so a successful build still says
    // it. mcpp prints a build program's stdout only when the program fails,
    // and a probe whose evidence only appears on failure has none.
    std::println("mcpp:warning=PATH begins at {}", first);
    std::println("mcpp:warning=this project's subos is {}",
                 std::getenv("MCPP_XPKG_QEMU_RISCV_DIR")
                     ? "populated" : "not installed yet");
    return 0;
}