Re: libgfortran.so SONAME and powerpc64le-linux ABI changes

[Thomas Koenig <tkoenig@netcologne.de>]

Hi Iain,

>> Things get interesting for user code, calling a routine compiled
>> for double double with newer IEEE QP will result in breakage.
> That would not happen with the proposal above, since the library would
> have different entry points for the two formats.

I meant the case where the user writes, with an old, KIND=16 is double
double compiler,

   subroutine foo(a)
     real(kind=16) :: a
     a = a + 1._16
   end subroutine foo

and puts it in a library or an old object file, and in new code with an
IEEE QP compiler calls that with

   real(kind=16) :: a
   a = 2._16
   call foo(a)
   print *,a

this will result in silent generation of garbage values, since Fortran
does not mangle the function name based on it types. For both cases, the
subroutine will be called foo_  (or MOD..._foo).

There is no choice - we need to make object code compiled by the user
incompatible between the old and the new format on the systems where
we make the switch.

This is starting to look like a can of worms from Pandora's box,
if you pardon my mixed metaphors.

Best regards

	Thomas