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Aleksandar Donev asked:

> Absoft claims that this interface is ambiguous:
>
>   INTERFACE C_LOC_Function
>    MODULE PROCEDURE C_LOC_Function_i_sp
>    MODULE PROCEDURE C_LOC_Function_i_dp
>   END INTERFACE
>
> where the aformentioned procedures have interfaces:
>
>   FUNCTION C_LOC_Function_i_sp (X) RESULT (c_pointer)
>    INTEGER (i_sp), EXTERNAL :: X
>    INTEGER (KIND=C_ADDRESS) :: c_pointer
>   END FUNCTION
>
>   FUNCTION C_LOC_Function_i_dp (X) RESULT (c_pointer)
>    INTEGER (i_dp), EXTERNAL :: X
>    INTEGER (KIND=C_ADDRESS) :: c_pointer
>   END FUNCTION
>
> I recall J3 recently discussed interps related to this. All my other
> compilers accept it just fine.
>
> Is the above interface in fact legal in F95?

Presumably there's more to it than this -- definition of kind type
parameters in particular.

This could well be a portability problem, not a language problem.

If, for example, i_sp is selected_int_kind(4) and i_dp is selected_int_kind(8),
it may be that i_sp and i_dp have the same value on some processors, and
different values on others.

This is one of the reasons to want to be able to develop new types from
existing ones (actually, I would call them "subtypes" because you'd want
the new ones to inherit operations from the original ones).

If we could have, for example

  subtype :: integer_i_sp => integer(i_sp), integer_i_dp => integer(i_dp)

then integer_i_sp and integer_i_dp would be different subtypes, even if
i_sp and i_dp happen to have the same value on some platforms.

The function declarations could be something like

  FUNCTION C_LOC_Function_i_sp (X) RESULT (c_pointer)
   type(INTEGER_i_sp), EXTERNAL :: X
   INTEGER (KIND=C_ADDRESS) :: c_pointer
  END FUNCTION

and mutatis mutandis for C_LOC_Function_i_dp

That the subtypes are different could be exploited for generic resolution.

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