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From: Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>
Newsgroups: comp.lang.ada
Subject: Re: StdCall and pragma Import_Function
Date: Fri, 19 Aug 2011 11:10:27 -0700
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Date: 2011-08-19T11:10:27-07:00
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On 08/19/2011 09:24 AM, Felix Krause wrote:
> I'm writing a cross-platform Ada binding for a C library. It currently works on OSX and Linux, and I'm trying to get it to work on Windows. I have some code like this:

The first rule when interfacing to another language is to only use types 
declared as having the convention of that language.

> package P is
>     type ULong is mod 2 ** 64;
>     for ULong'Size use 64;

pragma Convention (C, Ulong);

>     type Bit_Vector is record
>        First_Bit  : Boolean;
>        Second_Bit : Boolean;
>     end record;
>     for Bit_Vector use record
>        First_Bit  at 0 range 0 .. 0;
>        Second_Bit at 0 range 1 .. 1;
>     end record;
>     for Bit_Vector'Size use ULong'Size;

pragma Convention (C_Pass_By_Copy, Bit_Vector);

>     function C_Function (Param : Bit_Vector) return ULong;
>     pragma Import (StdCall, C_Function, "cFunc");
>     pragma Import_Function (Internal =>  C_Function, External =>  "cFunc", Mechanism =>  (Param =>  Value));

Import_Function is not a standard pragma. C_Pass_By_Copy is standard, and seems 
to do the same thing.

> end P;

-- 
Jeff Carter
"Blessed is just about anyone with a vested interest in the status quo."
Monty Python's Life of Brian
73