test

        while (i < r.size() && r[i] == '/') i++; // collapse "./////"

        r = r.substr(i);

    }

    // Collapse internal duplicate slashes ("a//b" -> "a/b"). The tools/ build

    // framework concatenates variables with trailing '/' producing paths like

    // "tools/objtool//libsubcmd/libsubcmd.a"; GNU make resolves these to the

    // single-slash file, so a target and its prerequisite must compare equal

    // regardless of repeated separators.

    if (r.find("//") != std::string::npos) {

        std::string collapsed;

        collapsed.reserve(r.size());

        for (size_t i = 0; i < r.size(); i++) {

            if (r[i] == '/' && !collapsed.empty() && collapsed.back() == '/') continue;

            collapsed += r[i];

        }

        r.swap(collapsed);

    }

    // A path consisting solely of "./" (or ".///") denotes the current

    // directory; GNU make keeps it as a directory target. Map it to "." so

    // it does not collapse to an empty (and therefore unbuildable) target.