> I just fear that the loop is "endless". Imagine the worst case: confstr() returns a counter (n, n+1, n+2, ...). In 64 bits, it can be long.

The returned length is supposed to be determined by the length of
the variable, not the length of the buffer passed by the caller,
so I don't see why the OS would have a bug like that, and it
would probably be exposed by the test suite anyway (there's
currently a simple test using CS_PATH).

> I would prefer to see a condition to stop after 2 steps. It should maybe stop when an error at the 3rd step.

That is, raise an exception?  Yeah, possibly, but I think it's
better to just believe what the OS tells you rather than have an
exception that's only raised once in a blue moon for something
that may just be a low-probability event, and not an error.