@Flash Gordon:
As far as C is concerned stderr is a write only stream. It could, for an
extreme example, be going direct to a printer in which case the only way
to read it would be to feed the paper from the printer in to a scanner
and then OCR it. What I've said may sound daft and extreme, but it is to
make a point. The point is that in C the only way to achieve what you
want is to change the library. Annoying I'm sure, but true.