https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121570
--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
As gfortran uses the C standard library IEEE interfacing, if that interface
agrees with the Fortran language requirement we can rely on a correct
implementation of the C standard library. Having a testcase in the testsuite
pointing out wrong behavior therein would be a good thing to have, of course.
The manpage on nextafter says
The following errors can occur:
Range error: result overflow
errno is set to ERANGE. An overflow floating-point exception
(FE_OVERFLOW) is raised.
Range error: result is subnormal or underflows
errno is set to ERANGE. An underflow floating-point exception
(FE_UNDERFLOW) is raised.
otherwise set exception flags should be unchanged by a call to nextafter().
