Function getLockDir

src/storage/shared_memory.cpp:233–294

}

std::filesystem::path getLockDir()
{
    auto logOnce = [](const std::filesystem::path &dir)
    {
        static bool logged = false;
        if (!logged)
        {
            util::Log() << "Using shared memory lock directory: " << dir;
            logged = true;
        }
    };

    // 1. Explicit override via environment variable
    if (const char *env = std::getenv("SHM_LOCK_DIR"))
    {
        std::filesystem::path dir(env);
        if (!tryLockDir(dir))
        {
            throw util::exception("SHM_LOCK_DIR directory is not usable: " + dir.string() +
                                  SOURCE_REF);
        }
        logOnce(dir);
        return dir;
    }

    // 2. Platform-specific candidates
#ifdef __linux__
    // /dev/shm is a RAM-backed tmpfs that is always local and never cleaned by
    // systemd-tmpfiles-clean. It is only cleared on reboot, which matches the
    // lifetime of System V shared memory segments.
    {
        auto dir = std::filesystem::path("/dev/shm") / ("osrm-" + std::to_string(::getuid()));
        if (tryLockDir(dir))
        {
            logOnce(dir);
            return dir;
        }
    }
#endif

    // 3. User home directory
    {
        const char *home = std::getenv("HOME");
#ifdef _WIN32
        if (!home)
            home = std::getenv("USERPROFILE");
#endif
        if (home)
        {
            auto dir = std::filesystem::path(home) / ".osrm";
            if (tryLockDir(dir))
            {
                logOnce(dir);
                return dir;
            }
        }
    }