On Tue, Apr 26, 2016 at 2:56 PM Robert Bradshaw <rober...@gmail.com> wrote:
> On Tue, Apr 26, 2016 at 8:36 AM, Erik Bray <erik.m.b...@gmail.com> wrote: > >> On Tue, Apr 26, 2016 at 5:16 PM, Dima Pasechnik >> <dimpase+git...@gmail.com> wrote: >> > Hi, >> > certainly we did something with Sage on cygwin to work around these... >> > Just in case, >> >> From what I can tell there are several places where Sage has hacked >> around this issue in different packages, but it's not doing anything >> specifically with it for Cython. Sage uses the Cephes math lib to >> support these functions on FreeBSD--and apparently used to use it on >> Cygwin too, but disabled that for some reason. >> >> Regardless, Cython should ultimately do something sensible in these cases. >> >> My general thinking is that in cases where Cython generates code >> containing C math functions, it ought to support a fallback. This >> will require some feature checks so that Cython can generate wrappers, >> when necessary, around the double versions of those functions (as >> Numpy currently does). >> > > Let's make things concrete. You're complaining that something like > > cdef extern from "math.h": > long double sqrtl(long double) > > def foo(long double x): > return sqrtl(x) > > Doesn't work on Cygwin? > > The same is true for *any* C function that you use that's not totally > portable (this is the bane of trying to use C). I don't think Cython should > be detecting this and substituting a (less accurate) sqrt for sqrtl in this > case. If you want do do this, write your own headers that (conditionally) > define these things however you want. > > Or, are you complaining that Cython's test suite doesn't pass on some > Cygwin because there are tests of features not available on Cygwin? (Your > original email isn't clear.) If so, the test framework can be set up to > exclude these tests on that platform. > > Right, this sounds like a good place to exclude some tests. long double's behavior is pretty platform dependent. I wouldn't expect to be able to write platform independent code that uses it. There's not much Cython can do to change the situation either. Best, -Ian
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