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From: hreba <f_hreba@yahoo.com.br>
Newsgroups: comp.lang.ada
Subject: Re: How can one record component be local and another not?
Date: Tue, 5 May 2020 19:17:40 +0200
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Date: 2020-05-05T19:17:40+02:00
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On 5/5/20 5:45 PM, Jeffrey R. Carter wrote:
> On 5/5/20 1:04 PM, hreba wrote:
>>
>> (The reason for the above construction is the need to pass a pointer 
>> to a C library function.)
> 
> Most likely you do not need to pass a pointer to your C function. For 
> example, given the C function
> 
> void f (int* i);
> 
> You can do
> 
> procedure F (I : in out Interfaces.C.int) with Import, Convention => C, 
> ...;
> 
> and the compiler will call the C function correctly.
> 

It is more complicated, unfortunately. I got

    type gsl_odeiv2_system is record
       c_function : access function
            (arg1 : double;
             arg2 : access double;
             arg3 : access double;
             arg4 : System.Address) return int;  -- 
/usr/include/gsl/gsl_odeiv2.h:58
       jacobian : access function
            (arg1 : double;
             arg2 : access double;
             arg3 : access double;
             arg4 : access double;
             arg5 : System.Address) return int;  -- 
/usr/include/gsl/gsl_odeiv2.h:60
       dimension : aliased size_t;  -- /usr/include/gsl/gsl_odeiv2.h:61
       params : System.Address;  -- /usr/include/gsl/gsl_odeiv2.h:62
    end record;
    pragma Convention (C_Pass_By_Copy, gsl_odeiv2_system);  -- 
/usr/include/gsl/gsl_odeiv2.h:64

and I have to pass a variable
    sys: access gsl_odeiv2_system
to the initialization function of that C library, and the

   params: System.Address;

component in the record, which internally is then passed to c_function() 
and jacobian(), posed the problem.

-- 
Frank Hrebabetzky, Kronach	+49 / 9261 / 950 0565