Portability problems fixed by Gnulib:
@itemize
@item
+This macro is missing on some platforms:
+MSVC 9.
+@item
@code{isnan} was introduced with C99 and is thus commonly not present
on pre-C99 systems.
@item
@code{isnan} is not a macro on some platforms:
-IRIX 6.5, OSF/1 5.1 with gcc, Solaris 11 2010-11.
+IRIX 6.5, OSF/1 5.1 with gcc, Solaris 11 2011-11.
@item
On IRIX 6.5 with @code{cc}, @code{isnan} does not recognize some NaNs.
@item