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From: "Alex R. Mosteo" <devnull@mailinator.com>
Newsgroups: comp.lang.ada
Subject: Re: [GNAT 2006] Project file and conditional withing/linking
Date: Fri, 09 Jun 2006 09:45:40 +0200
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Date: 2006-06-09T09:45:40+02:00
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Simon Wright wrote:

> "Alex R. Mosteo" <devnull@mailinator.com> writes:
> 
>> I'm using a project file and, depending on some external variables,
>> I want to include some library for linking or not. The library is
>> defined in its own project file.
>>
>> The problem is that withing the library project causes its linker
>> options to be added no matter what I try, and I'd like to remove
>> these linker options (otherwise the library is always linked).
> 
> I don't see why you use Linker_Options? I would have thought you could
> do everything with Default_Switches ("ada").

Actually, the previous GtkAda version used Default_Switches and current one
uses Linker_Options. I don't know the reason nor the implications. In any
case, I'm just using the installed GtkAda project files.

>> Conditionally withing seems out of the question: the "with"s are to be at
>> the top. I've tried overriding with
>>
>> for Gtkada.Linker'Default_Switches ("ada") use ();
>> for Gtkada.Linker.Linker_Options use ();
> 
> No, you can define your own switches, not theirs.
> 
>> I could remove the withing and copy the switches to my project file,
>> but I'd strongly prefer to keep using the stock installed library
>> project file.
> 
> We have defined environment-dependent symbols in non-source Projects
> and then used the symbols to create the appropriate switches in the
> user project. Something like
> 
>    package Linker is
>      case Use_Other_Package is
>        when Yes =>
>          for Default_Switches ("ada")
>            use ("-foo") & Other_Package.Linker_Switches;
>        when No =>
>          for Default_Switches ("ada") use ("-bar");
>      end case;
>    end Linker;

I used to do this with the GAP 2005 release, but it seems the GAP/GPL 2006
release will pass the linker options to gnatlink no matter what, once you
with the project. Maybe this is the difference between Default_Switches and
Linker_Options. Going to set up a test case.

Certainly, there are several solutions when you have control over all the
project files. I'm attempting to find a solution without modifying the
GtkAda stock project file.