https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95640
--- Comment #6 from Bill Long <longb at cray dot com> --- (In reply to kargl from comment #3) > (In reply to Bill Long from comment #0) > > > cat test.f90 > > > Gfortran: > > > > > module swap PrgEnv-intel PrgEnv-gnu > > > gfortran test.f90 > > > ./a.out > > selected_real_kind(16) = 10 > > ieee_selected_real_kind(16) = 10 > > > > The output from gfortran is problematic because ieee_selected_real_kind > > should not return 10. If the users want KIND=10 (i.e. the > > Intel-proprietary 80-bit x87 floats), then they need to use > > selected_real_kind and not the IEEE version. > > IEEE-754 permits the extended double type (See 3.7 Extended and > extendable precisions). I do not see in the Fortran standard that > the output from ieee_seleted_real_kind must select binary32, > binary64, or binary128. > > That said, ieee_selected_real_kind is completely broken. > See PR69101. I used to have patch that fixed this PR, > but never got around to committing it. The patch attached > in 69101 is not correct. The description in the Fortran standard for IEEE_SELECTED_REAL_KIND includes "The result has a value equal to a value of the kind type parameter of an ISO/IEC/IEEE 60559:2011 floating-point format..." This, in practice, amounts to binary32, 64, 128 for RADIX=2 (the default). The 80-bit x87 format is not part of the quoted IEEE standard.
