logb
====

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

Gnulib module: logb

Portability problems fixed by Gnulib:

  * This function is missing on some platforms: Minix 3.1.8, MSVC 9.

  * This function is missing a declaration on some platforms: Cygwin 1.5.x.

  * This function produces wrong results for subnormal numbers on some platforms: glibc 2.11/ppc, glibc 2.7/sparc, glibc 2.7/hppa, Solaris 11.4, Cygwin 1.5.x.

Portability problems not fixed by Gnulib: