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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: How to detect OS type and version?
Date: 13 Oct 2005 17:21:32 -0400
Organization: The World Public Access UNIX, Brookline, MA
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Date: 2005-10-13T17:21:32-04:00
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Stefan Bellon <bellon@bauhaus-tec.com> writes:

> Nothing more than historical reasons. In some files where OS specific
> code resides, we have something like the following on package level:
> 
>    Is_MSWindows : constant Boolean := Get_OS = "Windows";
> 
> We hope that GNAT can optimize enough to propagate the Boolean constant
> and only include the active configuration in a case like
> 
>    if Is_MSWindows then
>       Do_It_The_MSWindows_Way;
>    else
>       Do_It_The_UNIX_Way;
>    end if;

Compilers will probably not be able to optimize this unless Get_OS is
inlined.  I believe GNAT refuses to inline functions that return String.

> But yes, making it an enumeration is a neater solution (done now).

... and add pragma Inline to the function.

By the way, a case statement would be better than an if statement,
because then you get the benefit of the full coverage rules.  "Not
windows" might imply "unix" today, but what if you add a third
possible value?

- Bob