On 3 March 2016 at 09:27, Sandro Santilli <s...@keybit.net> wrote: > On Wed, Mar 02, 2016 at 05:21:33PM +0100, Mateusz Loskot wrote: >> On 2 March 2016 at 17:13, Sandro Santilli <s...@keybit.net> wrote: >> > >> > This is the snippet, in configure.ac, to look for it: >> > >> > AC_LANG_PUSH([C++]) >> > AC_CACHE_CHECK([for isnan], ac_cv_isnan, >> > [AC_TRY_LINK([#include <cmath>], >> > [double x; int y; y = isnan(x);], >> >> I presume the test fails because it does not look for the function >> inside std [1], but assumes nan is in global namespace. >> I presume, it's especially the case for C++11 compilers. >> >> [1] http://en.cppreference.com/w/cpp/numeric/math/isnan > > I noticed the tests for finite/isfinite include <math.h> > rather than <cmath>, could that also change the namespacing > of isnan ?
Possibly, yes. I'm not sure about GCC extensions thought that might make isnan or isfinite available as global names even if C++ #include <cmath> is used, IOW, #include <cmath> might have the same effect as #include <math.h>. However, we should be able to rely on that any C++11 compliant toolset seeing #include <cmath> makes std::nan and std::isfinite available. Best regards, -- Mateusz Loskot, http://mateusz.loskot.net _______________________________________________ geos-devel mailing list geos-devel@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/geos-devel