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Re: GCC considering enabling Ada by default

Florian Weimer writes:
> * Ludovic Brenta:
>>>> I think it is premature to speculate about the outcome of this
>>>> thread.  Moreover, the discussion so far has been only about which
>>>> languages to enable *by default*, not about changing the
>>>> bootstrapping process completely.  Nothing in this thread suggests
>>>> that a change to the Debian packaging should be necessary.
>>> Nevertheless, I guess I should mention the version discrepancy on
>>> that list.  In the past, bootstrapping with the C and Ada compilers
>>> built from separate GCC releases was not supported.
>> What version discrepancy? i.e. between the version of what and the
>> version of what?
> gnatgcc and g++ (4.6 vs 4.7 in wheezy).
>> Note that gnat-X.Y contains its own copy of the C compiler
>> (/usr/bin/gnatgcc) so there is no situation where the C and Ada
>> compilers have different versions.
> There's no gnatg++, and GCC is now mostly compiled as C++ (but not
> exclusively).  Mixing different C and C++ compiler versions is
> probably not supported upstream.

Yes it is because the ABI has not changed.  Thus it is perfectly
possible to link object files produced by gnat-4.6, gcc-4.7 and g++-4.7
to form a working executable that can compile Ada sources.  This is
exactly how I bootstrapped gnat-4.8 initially.  Nowadays, I bootstrap
gnat-4.8 using gnat-4.6, gcc-4.8 and g++-4.8 on all platforms, even
those where the default C++ compiler is still g++-4.6.

>>> What's the reason for the version difference in Debian?  Better
>>> tooling support outside GCC for older releases?
>> I'll be able to answer when I undertsand what you mean by "the
>> version difference in Debian" (i.e. between what and what?)
> Why isn't GNAT built from the regular gcc-4.7 source package?

Because I don't have the manpower for *two* transitions of all Ada
packages in a single Debian release cycle.  And the transition to 4.7 as
the default took place very late in the Wheezy release cycle.

For that matter, I've skipped gnat-4.7 entirely and am now starting the
transition to gnat-4.8 for Debian 8 "Jessie".

Bottom line: there is no problem to worry about.

Ludovic Brenta.

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