Re: Pragma for conditional compilation? (Ada 2005 vs. 95)

[Stephen Leake <stephen_leake@stephe-leake.org>]

Stefan Bellon <sbellon@sbellon.de> writes:

> On Fri, 28 Sep, Pascal Obry wrote:
>
>>    case OS is
>>       when "Windows_NT" =>
>>          for Implementation ("OS_Services")
>>               use "os_services__win32.adb";
>>       when "UNIX" =>
>>          for Implementation ("OS_Services")
>>               use "os_services__linux.adb";
>>    end case;
>
> Interesting. What is the difference to the following (what we have been
> using for some time)?
>
>    package Naming is
>       case OS is
>          when "UNIX" =>
>             for Body ("Plugins.Internal_Load")
>               use "plugins-internal_load-unix.adb";
>          when "Windows_NT" =>
>             for Body ("Plugins.Internal_Load")
>               use "plugins-internal_load-windows.adb";
>       end case;
>    end Naming;
>
> The two Internal_Load being "separate" procedures for package body
> Plugins.
>
> Are the pros and cons versus the Implementation attribute above (which
> I didn't know about until now)?

The gnat reference manual (_not_ the gnat user guide) says, in section
13.13.1 Package Naming:

`Implementation'
     This is a synonym of `Body'.

So the real difference is in the double underscore.

-- 
-- Stephe