for posterity:
```
<trevnorris> tjfontaine: wanted to do that, the problem is the only way to detect the length of the source/dest is to use v8 api.
<trevnorris> tjfontaine: so there's nothing we can check from js
<tjfontaine> trevnorris: it's not that there's anything to check, it's just that we dont' generally expose the functions directly, the jit will opt it out
<trevnorris> tjfontaine: ok. just seem silly to do exports.copyOnto = function copyOnto(a, b, c, d, e) { return smalloc.copyOnto(a, b, c, d, e); }
```