Re: Current statu of ASIS for GNAT 2012, please ?

[Ludovic Brenta <ludovic@ludovic-brenta.org>]

Georg Bauhaus <rm.dash-bauhaus@futureapps.de> writes:
> On 02.10.11 18:38, Ludovic Brenta wrote:
>
>>> Somewhere on this long line you mentioned libaunit1-dev depending on
>>> GNAT 4.4; the package says it depends on ada-compiler.  Actually,
>>> AUnit v.1 indeed only needs an Ada compiler, no fancy configuration,
>>> Ada 95 should do.
>>
>> No.  Debian is a binary distribution and respects the Ada Reference
>> Manual regarding consistency of binary executables, in particular clause
>> 10.1.4(5).
>
> The consistency is cool as ever, but I don't think LRM 10.1.4(5)
> justifies anything ;-) After all, if we put GCC x.y.z in /where/ever,
> there is no problem regarding the LRM.  I will assume that it means
> much more work to have a switch for system compilers, and there might
> be little incentive to have two versions.

LRM 10.1.4(5) does not affect the sources, it affects the binaries
produced from (different versions of) the sources.  Debian is a binary
distribution, therefore it must obey 10.1.4(5) and this justifies the
Debian Policy for Ada regarding dependencies between binary packages.
Note that the .ali files in -dev packages are considered "binary" for
the purposes of this discussion, because they are the way GNAT uses to
obey LRM 10.1.4(5).

>>  Debian does this by stating and enforcing dependencies between
>> binary packages.
>
>> - gnat-4.4 and gnat-4.6 conflict with each other because they both
>>    provide /usr/bin/gnatmake et al.
>
> Ah, well, I have become used to switching between different versions
> of compilers and interpreters.

Yes.  It should be possible for Debian to provide several versions of
GNAT in parallel but I decided, long ago, that this would go against one
of my design goals, which is to make it possible to compile an Ada
program against all of the installed Ada libraries.  The consistency
rule implies that a program cannot be linked, directly or indirectly,
against two different versions of the GNAT run-time library.

You are entirely correct in the context of a source distribution such as
Gentoo or GNAT GPL Edition, however.  In a source distribution, you can
have as many compilers as you want; the price to pay for this is that
you must recompile everything each time you switch compilers, taking
into account that some versions of some libraries might be incompatible
with some versions of the compiler (see ASIS for one example).

-- 
Ludovic Brenta.