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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: Thick bindings to a C library and gnattest: suggestions?
Date: Mon, 1 Jul 2013 14:42:09 +0200
Organization: cbb software GmbH
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Date: 2013-07-01T14:42:09+02:00
List-Id: <comp.lang.ada>

On Mon, 1 Jul 2013 05:00:50 -0700 (PDT), Maurizio Tomasi wrote:

> Many thanks Simon, my problem was that I cannot decide "a priori" when to
> link statically and when dynamically, but you helped me in devise a
> solution:
> 
> project cfitsio is 
>   for Externally_Built use "true";
>   for Source_Files use ();
>   for Library_Dir use external("CFITSIO_LIB_DIR");
>   for Library_Name use "cfitsio";
>   for Library_Kind use external("CFITSIO_LINKING");
> end cfitsio; 
> 
> On my laptop running Linux Mint I have both the static and dynamic
> versions of CFITSIO, and now I am able to compile them using these
> commands:
> 
> CFITSIO_LIB_DIR=/usr/lib/x86_64-linux-gnu CFITSIO_LINKING=dynamic gprbuild test_driver.gpr
> 
> CFITSIO_LIB_DIR=/usr/lib/ CFITSIO_LINKING=static gprbuild test_driver.gpr
> 
> So, one of my problems is fully solved!

Use scenario variables instead of environment variables:

   type Library_Type is ("static", "dynamic");
   Linkage : Library_Type := external ("Linkage", "static");

   case Linkage is         -- You could do it directly without case, but
       when "static" => -- case illustrates how powerful this method is
          for Library_Kind use "static";
       when "dynamic"
          for Library_Kind use "dynamic";
   end case;

Scenario variables appear in GPS and can be selected there on the fly.

When compiled using gnatmake or gprbuild you specify them this way:

gnatmake -Pmy_project.gpr -XLinkage="dynamic"

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de