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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Newcomers to comp.lang.ada: welcome and how did you end up here ?
Date: Wed, 08 Oct 2014 10:15:38 +0100
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Date: 2014-10-08T10:15:38+01:00
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Brian Drummond <brian3@shapes.demon.co.uk> writes:

> One hardware interface library in C (to the Aardvark I2C/SPI USB
> interface from totalphase.com ) used a lot of macros for defining
> constants. These were untranslated, appearing as comments in the Ada
> package (apparently because they were untyped numbers).

Apparently one should use g++ rather than gcc, because it makes a better
job of it.

GNAT GPL 2014 does translate (some) macros; it doesn't always get it
right, eg

   #define M_SQRT2     1.41421356237309504880168872420969808   /* sqrt(2)        */
   #define M_SQRT1_2   0.707106781186547524400844362104849039  /* 1/sqrt(2)      */
   #define MAXFLOAT    0x1.fffffep+127f

   // have to have _something_ besides the constants or no .ads gets
   // generated.
   extern float sinf(float);

turns into

   pragma Ada_2005;
   pragma Style_Checks (Off);

   with Interfaces.C; use Interfaces.C;

   package math_h is


      M_SQRT2 : constant := 1.41421356237309504880168872420969808;  --  ./math.h:1
      M_SQRT1_2 : constant := 8#.707106781186547524400844362104849039#;  --  ./math.h:2
      MAXFLOAT : constant := 16#1.fffffep+127f#;  --  ./math.h:3

      function sinf (arg1 : float) return float;  -- ./math.h:7
      pragma Import (CPP, sinf, "_Z4sinff");

   end math_h;

And I should have written

   extern "C" {
     extern float sinf(float);
   }

which would have produced

   function sinf (arg1 : float) return float;  -- math.h:8
   pragma Import (C, sinf, "sinf");