[Bug libstdc++/89991] Complex numbers: Calculation of imaginary part is not correct

[sgk at troutmask dot apl.washington.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89991

--- Comment #22 from Steve Kargl <sgk at troutmask dot apl.washington.edu> ---
On Mon, Apr 08, 2019 at 10:17:00PM +0000, redi at gcc dot gnu.org wrote:
> (In reply to kargl from comment #19)
> > I get the expected.  So, if you're on a system that has
> > _GLIBCXX_USE_C99_COMPLEX, you won't see the bug.
> 
> Wow, why isn't libstdc++ using the C99 <math.h> functions on FreeBSD?
> 

Because it is all or nothing.  See comment #8 and #9 in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89125
If you're too busy to look at PR89125 the upshot is that
FreeBSD is missing ccoshl, ccosl, cexpl, csinhl, csinl,
ctanhl, and ctanl.  I have BSD licensed versions of 
ccoshl, ccosl, cexpl, csinhl, and csinl, but testing
on FreeBSD ran into what I consider to be a very bad
bug in clang (FreeBSD system compiler).