Daniel J Sebald wrote:
> I guess it doesn't pay to understand what it is beyond the fact we
> know gamma() = tgamma() on your system.
Except that we don't actually know that. And even if we knew it, it
wouldn't matter, because gnuplot doesn't use gamma() on a system that,
like Chris', also has lgamma(). See specfun.c, line 91 ff.
I.e. the actual bug is independent of what gamma() does on MacOS,
because gnuplot isn't calling gamma(). We call lgamma(), and the bug is
that signgam is garbage.
Chris: please verify that in your src build directory,
nm specfun.o | grep -i gam
prints something equivalent to this:
00000150 T _f_gamma
00000240 T _f_igamma
000001f0 T _f_lgamma
The lines with the 'U' are the important ones. They tell us that
1) this gnuplot calls lgamma
2) gnuplot uses the library's signgam, under the name __signgam