From: David Thompson <dave.thompson2@verizon.net>
Subject: Re: pragma import (C, , ); -- import a constant value from C library
Date: Sun, 04 Nov 2012 22:41:46 -0500
Date: 2012-11-04T22:41:46-05:00 [thread overview]
Message-ID: <bvce98p1nff9uc6p7htblrt26jn0qdol2n@4ax.com> (raw)
In-Reply-To: 1c65196f-68e4-4b50-8ad0-e9555d3f1b50@googlegroups.com
On Sat, 27 Oct 2012 00:15:06 -0700 (PDT), Maciej Sobczak
<see.my.homepage@gmail.com> wrote:
> W dniu sobota, 27 pa?dziernika 2012 01:06:14 UTC+2 u?ytkownik Simon Wright napisa?:
>
> > const double m_euler_for_gnat = M_EULER;
>
> You might want to declare this variable with external linkage (the logic is: if you want to
import something from Ada, then you have to export it from C), so:
>
> extern "C" const double m_euler_for_gnat = M_EULER;
No, that's a syntax error in C. (C has static, and extern, but not
extern "language"; that's a creation of C++.)
In C++ officially you need extern "C" to specify language linkage
(although in many implementations this is actually needed only on
routines not variables).
A global definition in C (at file scope, with "extern" or with no
storage-class specifier) has external linkage, which means the name is
visible to separately compiled modules (including Ada).
next prev parent reply other threads:[~2012-11-05 3:41 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-26 22:45 pragma import (C, , ); -- import a constant value from C library Enzo Guerra
2012-10-26 23:06 ` Simon Wright
2012-10-27 7:15 ` Maciej Sobczak
2012-11-05 3:41 ` David Thompson [this message]
2012-10-27 7:40 ` Dmitry A. Kazakov
2012-10-27 8:15 ` Simon Wright
2012-10-27 8:19 ` Simon Wright
2012-10-27 8:47 ` Dmitry A. Kazakov
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