Re: Interfaces.C questions

[Simon Wright <simon@pushface.org>]

hreba <f_hreba@yahoo.com.br> writes:

> On 03/19/2017 08:22 PM, Simon Wright wrote:
>> hreba <f_hreba@yahoo.com.br> writes:
>>
>>>    function func (x: C.double; params: Void_Ptr) return C.double is
>>>    begin
>>>       return C.double (real_func (Real(x)));
>>>    end func;
>>>    pragma Convention (C, func);		-- this is line 37
>>
>> Try
>>
>>    function func (x: C.double; params: Void_Ptr) return C.double;
>>    pragma Convention (C, func);
>>    function func (x: C.double; params: Void_Ptr) return C.double is
>>    begin
>>       return C.double (real_func (Real(x)));
>>    end func;
>>
>> You have to have a spec, but there's nothing stopping it being declared
>> right before the body.
>>
>> Of course, in most cases you'd prefer to do that earlier.
>>
>
> Did that. Now I get:
>
> gsl.adb:35:26: pragma "CONVENTION" argument must be in same declarative part

This compiles for me (with a warning, 'variable "real_func" is read but
never assigned'):

generic
   type Real is digits <>;
   type Parameters is private;
package GSL with Elaborate_Body is
   type Real_Function is access function (x: Real) return Real;
end Gsl;
with Interfaces.C;
package body Gsl is

   use Interfaces;

   type Void_Ptr is access all Integer;
   pragma Convention (C, Void_Ptr);

   type GSL_Function is record
      func:   access
	function (x: C.double; params: Void_Ptr) return C.double;
      params: Void_Ptr;
   end record;
   pragma Convention (C, GSL_Function);

   real_func:	Real_Function;

   function func (x: C.double; params: Void_Ptr) return C.Double;
   pragma Convention (C, func);

   function func (x: C.double; params: Void_Ptr) return C.double is
   begin
      return C.double (real_func (Real(x)));
   end func;

   procedure P is
      gslf:	aliased GSL_Function;
   begin
      gslf.func:= func'Access;
   end P;
end Gsl;