The state of Ada on Gentoo

Lucretia · n00b Joined: 15 Oct 2002 Posts: 69

I stupidly installed Gentoo thinking it would have decent Ada support, how wrong was I? So, I'd like to try to start a constructive thread about how this can be rectified.

I've have a look around portage for Ada related stuff, the unmasked available compiler is ancient, so no chance of Ada 2012 (the version I use now). The unmasked latest version is 4.6.4, still ancient and doesn't seem to build cleanly at all failing at the last step with a missing /etc/ada/primary_compilers, whatever that is, then it doesn't add the compiler to the usual PATH.

Seems there aren't many Ada developers for Gentoo, George and Nerdboy (who I know from #Ada). Nerdboy tells me that George has gone off to a warzone, so there'll be no Ada update on Gentoo for god knows how long. Nerdboy's ebuilds don't work for me, told him, got no reply. Are there any other Ada developers here? Please chime in and show who you are.

From looking at how the compilers are built, it seems that fortran, go and c++ all have USE flags, why doesn't Ada have a USE flag for gcc? That would make a lot more sense. That way the compiler would be a first class citizen on Gentoo rather than the ugly stepchild it currently is. People will probably argue that the GPL GNAT would be a conflicting package, why can't they sit along side each other?

Also, the gnatboot archive is a little strange, having the gnat1 and cc1 compilers in /usr/bin, is there a reason for this?

On a side note, I have scripts that I've been using for a while to get access to updated GNAT/GCC trees, I build most of the compilers in my scripts, but it gives me access to the latest 2012 features of the language. I've been using one I built on Debian successfully on Gentoo since I realised the state it was in here. That is, until I tried an interlanguage linking, seems 4.9 introduces an ABI change re libstdc++ that hasn't been rectified, I'm trying to wrack my brain to remember what it was, but I think it was time related. I don't have a log of the build and I can't remember what it was I was linking (as soon as I remember I'll retest and post the result, I did find a thread about it online as well).

Thanks,
Luke.

Lucretia · n00b Joined: 15 Oct 2002 Posts: 69

131 views and nothing? I can only assume nobody cares about Ada on Gentoo then?

depontius · Advocate Joined: 05 May 2004 Posts: 3509

I saw it, and left no comment because I had nothing to say. To be perfectly honest, I've never actually done anything with Ada besides look at it and fiddle around with it some. Back in the day I did a pile of stuff with Pascal (Extended of course, is there any other useful kind of Pascal?) and did quite a bit with Modula-2, again extended.

As far as I can tell, Ada is about the only surviving strongly-typed language. In this day when buffer overflows and unreferenced pointers are still a problem, it's rather annoying that the road not taken was quite plainly there and functional.

I keep thinking that some time when I have more time I might try Ada again.
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miket · Posted: Mon Oct 27, 2014 3:32 am Post subject:

Lucretia · n00b Joined: 15 Oct 2002 Posts: 69

Ada 2012 support has been in GCC .4.x for ages, just varying quality and has really become really usable from around 4.7.x upwards.

What I want to do is get rid of this Frankenstein approach to an Ada compiler, have no weird separate GNAT tree based on a different lesser version of GCC than the main system compiler, had enough of that on Debian, tbh. Just because GNAT has to have an Ada compiler to build is irrelevant, we just need bootstrap packages and there are some, whether they can compile the later GNAT's I'm not so sure.

I only build FSF GNAT's so there'll be no download restrictions. But there should also be a GNAT GPL ebuild, but like you say, that can go into a separate slot as AdaCore do provide a full compiler, C, C++ and Ada (probably others too) and if you're building it from scratch, well there's no reason you cannot apply the same use flags to that ebuild.

I want to make Ada a first class GCC language at the system compiler level, i.e. USE=ada turns on the compiler support for that language.

So, is there any reason why this can't be done? What's the best way to start?

Thanks,
Luke.

miket · Posted: Mon Oct 27, 2014 2:48 pm Post subject:

Frankly, I have my doubts about the feasiblity of getting gnat via USE=ada applied to gcc. Gcc, after all, is a critical component of Gentoo, a fundamental part of the installation process. It's not hard to find discussions on how problems in new upstream versions of GCC delay stabilization of these versions. Sometimes there have to be Gentoo-specific patches.

Now throw in gnat, which, given the large size of the gnat eclass, the complexity of gnatboot, and wonkiness like that to which you allude in the language bindings in gcc 4.9, would mean even more problems for the Base System team in stabilizing new versions of GCC. Indeed, there is no mechanism in Gentoo to say that package X is stable except when the Y USE flag is applied. Considering that GCC is in the critical sys-devel category, I doubt they'd ever want that.

The main problem with Ada in Gentoo is that people like Steve Arnold and George Shapovalov have not been keeping up. From what I can gather, managing the bootstrap process is a bit tricky. Also, it is quite possible that the gcc 4.9 problems are from an upstream regression. It would be Really Bad if your Ada compiler were tied up to a new slick version of GCC that didn't play nice with its gnat side. You'd have to eselect an older gcc to make gnat work and then eselect to the newest because some package liked that one better.

So, be careful what you wish for! I really suspect it is better to think in terms of keeping up with patches applied to a version of gcc that is well known to work properly with gnat. The only thing is to do them often enough.

There are precedents for this situation of packages that are patches of other source packages. There are several kernel patchsets out and around, like tuxonice, ck, hardened, and yes, even gentoo. All of these patchsets lag behind the official Linux sources, sometimes by a good way (though gentoo-sources does stay pretty close to the tip, others are more laggy). There was a series of patches called Suhosin that applied to PHP; the maintainers gave up after trying to patch every PHP version. Gentoo's own eudev is basically a patched version of, ahem, something which will go nameless.

So, I'll take a look at the gnat-gcc ebuild. *Maybe* I'll see things about it that would make think it could be merged into sys-devel/gcc, but I'm doubtful about that. The big thing is to get up-to-date Ada support into Gentoo.

Lucretia · n00b Joined: 15 Oct 2002 Posts: 69

I'm not sure I follow everything above.

But the one thing you keep mentioning is this Gnat ebud you intend to look into. You shouldn't need tgat. I've built GCC with ada support loads of times myself, you --enable-languages=ada,... The only thing that needs adding for a native compiler is grabbing a bootstrap compiler for Ada to use in the build. That ebud is quite large and uneccessary IMO.

Luke