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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: architecture-independent GNAT project files?
Newsgroups: comp.lang.ada
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Date: Tue, 28 Apr 2009 09:24:03 +0200
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Date: 2009-04-28T09:24:02+02:00
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On Mon, 27 Apr 2009 23:16:13 +0200, Bj�rn Persson wrote:

> Dmitry A. Kazakov wrote:
> 
>> On Mon, 27 Apr 2009 09:32:29 +0200, Bj�rn Persson wrote:
>> 
>>> When I write GNAT project files for shared libraries I find that I have
>>> to hardcode the paths to some architecture-specific directories. 32-bit
>>> libraries are in /usr/lib/ while 64-bit libraries are in /usr/lib64/, and
>>> I would like to have a single project file that works for both cases.
>> 
>> The way I am using is to have a platform variable in the project file:
>> 
>>    type Platform_Type is ("x86_Windows", "x86_VxWorks");
>>    Platform : Platform_Type := external ("Platform", "x86_Windows");
>> 
>> and then somewhere later
>> 
>>    case Platform is
>>       when "x86_Windows" =>
>>          for Source_Dirs use "os/Windows/i586" & ...;
>>       when "x86_VxWorks" =>
>>          for Source_Dirs use "os/vxworks/i586" & ...;
>>    end case;
>> 
>> then same for library things etc.
> 
> The analog for my case would be:
> 
>    type Architecture is ("i386", "x86_64");
>    Target : Architecture := external ("Target", "i386");
> 
> The problem with that is of course that on x86_64 systems the default will
> almost always be wrong, and if I set the default to x86_64 it will be wrong
> on i386 systems.

New GPS remembers the last choices of the project variables (well almost
always (:-)). So it should not be a great problem. Of course object and
executable files have to land into disparate directories (switched by the
same variable).

>>> The way to find out the architecture of a Unix-like system appears to be
>>> to invoke uname, but GNAT project files don't seem to have a shell-out
>>> feature. As far as I can see in the manual the only ways they can get
>>> input is by environment variables and command line parameters. I don't
>>> suppose Gnatmake provides some variable to project files that shows what
>>> the architecture is?
>> 
>> I don't know if it has, but if any, how that is supposed to work for cross
>> platform developing?
> 
> The cross-compiler would know its target platform and would assign that
> value to the hypothetical variable. The project file would then select the
> right library directories for that platform.

Hmm, I see no obvious way to do it. In my case there are several GNAT
compilers installed. The project variable Platform chooses the compiler as
well. For example, I have:

   package Ide is
      case Platform is
         when "x86_Windows" =>
            for Gnatlist use "gnatls";
            for Gnat use "gnat";
            for Compiler_Command ("ada") use "gnatmake";
            for Debugger_Command use "gdb";
         when "x86_VxWorks" =>
            for Gnatlist use "i586-wrs-vxworks-gnatls";
            for Gnat use "i586-wrs-vxworks-gnat";
            for Compiler_Command ("ada") use "i586-wrs-vxworks-gnatmake";
            for Debugger_Command use "i586-wrs-vxworks6-gdb";
      end case;
   end Ide;

This changes gnatlist, gnat, gnatmake, everything...

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