[gentoo-dev] Light changes in Ada handling in Gentoo

[gentoo-dev] Light changes in Ada handling in Gentoo

[George Shapovalov]

Dear Ada users.

I have finally implemented the multiple gnat handling in full, resolving bug 
#151343. The operational procedures on user side remain largerly the same 
(as for the last year), however there is one modification everybody using Ada 
compilers in Gentoo should be aware of.

Now (as was discussed in #151343) gnatbuild.eclass gnat.eclass and 
eselect-gnat  support the notion of "primary" compilers. The idea here is 
that most users will want one or, possibly, two variants of Ada compilers 
used for everyday work at most, while, occasionally, wishing to test some 
other variant(s).

These "everyday" compilers (designated "primary" further on) have to be listed 
in /etc/ada/primary-compilers. The file simply contains a listing of gnat 
profiles user desires to designate primary, one per line. Mine, for example, 
contains:

gerr@dornoir ~ $ cat /etc/ada/primary_compilers
x86_64-pc-linux-gnu-gnat-gcc-4.2
x86_64-pc-linux-gnu-gnat-gpl-4.1

All Ada libs will be built only for these compilers and not for any other 
installed. However "eselect gnat set" will allow user to set 
any installed gnat, as before. Thus we avoid ABI issues when updating 
packages that have some Ada lib as a dependency (there are already a few) via 
enforcing a consistent set of ABIs, cut compilation time (libs are now not 
getting built for an "occasional" compiler) while still providing an ability 
to test any gnat in portage.

As a safeguard gnatbuild.eclass has also been modified to
populate /etc/ada/primary-compilers, if this file does not exist yet, with 
the corresponding profile upon emerging gnat for the first time. Please, 
however, take your destiny in your own hands and update that file accordingly 
to your desires.


On a related note.
I have been composing a description of inner workings of the whole Ada setup. 
A preliminary text is available here:
http://www.gentoo.org/proj/en/prog_lang/ada/dev_reference.xml

However doc writing takes even more time than development itself. Therefore I 
would appreciate any contribution towards the "user guide" part of the 
description, (already referenced and planned to be available here:
http://www.gentoo.org/proj/en/prog_lang/ada/ada_ug.xml
but still empty), even partial. Just think about it, you will be listed as an 
author of that page (given significant contribution)!
I will also be interested in receiving any critique or 
suggestions on improving the 1st referenced text, at least for the parts that 
are already complete.

George
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