SPDX standardizes how source code conveys its copyright and licensing information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX tags are adopted in many large projects, including things like the Linux kernel.
This header doesn't actually make use of any std::string facilities.
Ensures the destruction logic is kept local to the translation unit. It also doesn't really do much to have it specified in the header.
Pierre Bourdon