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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Problems with SPARK 2015 and XMLAda
Date: Wed, 19 Aug 2015 21:21:40 +0100
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Date: 2015-08-19T21:21:40+01:00
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Serge Robyns <serge.robyns@gmail.com> writes:

>     11.    Library_Type : Xmlada_Kind_Type := external ("LIBRARY_TYPE");
>            1                                  2
>         >>> no value defined for "library_type"
>         >>> warning: undefined external reference

I would expect the required value to be "static" or "dynamic" (perhaps
"relocatable").

'external ("FOO")' means 'look for a scenario variable[1] "FOO" and take
its value; fail if not found'.

You can define a scenario variable either as an environment variable
(export LIBRARY_TYPE=static, for bash) or on the command line,

   $ gprbuild -P prj -XLIBRARY_TYPE=static

but you might find it easier to define a default value,

   Library_Type : Xmlada_Kind_Type := external ("LIBRARY_TYPE", "static");

>     14.    Xmlada_Build : Build_Kind := external ("XMLADA_BUILD");
>            1                            2
>         >>> no value defined for "xmlada_build"
>         >>> warning: undefined external reference

xmlada.gpr & friends say e.g.

   library project XmlAda_Dom is
      type BUILD_KIND is ("static", "relocatable");
      BUILD : BUILD_KIND := external("XMLADA_BUILD", "static");


[1] http://docs.adacore.com/gprbuild-docs/html/share/gnat_project_manager.html#scenarios-in-projects