Fortran configury: Ensure F08 real_kinds are actually valid kinds

[lrbison]

Issue: #5090

[brtnfld]

If the KIND is not supported, then the maximum decimal precision, max_decimal_prec, should not be set for that KIND.

[brtnfld]

For consistency, the same changes should be made to FC_AVAIL_KINDS.

[brtnfld]

please use uppercase keyword intrinsics

[lrbison]

Addressed.

[brtnfld]

I have to ensure this does not suppress detected kinds of other compilers since that scenario would not cause tests to fail.

[lrbison]

please use uppercase keyword intrinsics

Done!

I have to ensure this does not suppress detected kinds of other compilers since that scenario would not cause tests to fail.

Sure. In my testing I saw that GNU Fortran was unaffected. You can see output here.

For these next two points let me clarify that SELECTED_REAL_KIND is correct in ACfL, it is only the F08 ISO_FORTRAN_ENV array REAL_KINDS that was wrong. That array was only used to print the real kinds the compiler supported (not max precision), so I don't think the following comments items require a change:

If the KIND is not supported, then the maximum decimal precision, max_decimal_prec, should not be set for that KIND.

The REAL_KINDS array was not used in the loop to determine max decimal precision, so it is already correct.

For consistency, the same changes should be made to FC_AVAIL_KINDS.

The non-F08 version of this loop builds the list of kinds based on the return values of SELECTED_REAL_KIND, so it never had the problem.

... however it makes me wonder if the preferred fix is just to ignore REAL_KINDS altogether and use FC_AVAIL_KINDS's logic to find real kinds.

[brtnfld]

The non-F08 version of this loop builds the list of kinds based on the return values of SELECTED_REAL_KIND, so it never had the problem.

I'm not sure the compiler does not also have an issue with SELECTED_REAL_KIND, as from our discussion, #5090,

k = SELECTED_REAL_KIND(19,2)
print*,k
end

Printed -1, so it does not support KIND=16.

[lrbison]

Printed -1, so it does not support KIND=16.

Correct. ACfL does not support KIND=16, yet it includes 16 in REAL_KINDS (a compiler bug). This caused HDF5 configuration to make code with REAL(KIND=16) which then fails to compile. I am suggesting this patch to work around the compiler bug.