Gnulib module: isnan
Portability problems fixed by Gnulib:
isnanwas introduced with C99 and is thus commonly not present on pre-C99 systems.
isnanis not a macro on some platforms: IRIX 6.5, OSF/1 5.1 with gcc, Solaris 11 2011-11.
isnandoes not recognize some NaNs.
Portability problems not fixed by Gnulib: