On Wed, Jan 04, 2017 at 03:08:57PM +0100, Niels Möller wrote: > I'm also a bit puzzled. And after a quick look, I can't find any > lshift_com function in mul_fft.c (or anywhere else but acinclude.m4). It's mpn_lshiftc (and by the way the comment in ./mpn/generic/lshiftc.c is misleading -- lshiftc is not lshift). E.