is allocateUTF8 safe to use ?

In sql.js, we [use](https://github.com/kripken/sql.js/blob/master/src/api.coffee#L321) the `allocateUTF8OnStack` function, and it works. However, the function is nowhere to be found in [the official API documentation](https://emscripten.org/docs/api_reference/preamble.js.html#preamble-js). Is this an oversight, or is there a reason the function should not be used outside of emscripten itself ?