isfinite
========

POSIX specification:
 https://pubs.opengroup.org/onlinepubs/9699919799/functions/isfinite.html

Gnulib module: isfinite

Portability problems fixed by Gnulib:

  * This macro is missing on some platforms: macOS 11.1, OpenBSD 6.7, AIX 5.1, IRIX 6.5, Solaris 11.4.

  * This macro incorrectly yields true for some double and for some long double arguments, on some platforms: Linux/ia64 (NaNs).

Portability problems not fixed by Gnulib:

  * It is implementation-dependent whether isfinite raises an exception given a signaling NaN operand.

  * This macro returns an unspecified result when given noncanonical values such as unnormalized numbers, pseudo-denormals, pseudo-NaNs, pseudo-Infinities, and pseudo-zeroes.