Petr Viktorin <encukou@gmail.com> added the comment:
> 
> Exactly, a platform-dependent default is a bad idea. A default allows using the function without the code author & reviewer even being *aware* that there is a choice, and that is dangerous.

I’m not convinced.  I’m more concerned with the obscurity of the API.  If I saw its use in some code I was reviewing, I’d look it up, and then I’d know exactly what it was doing.