Luca's meaningless thoughts  

tomas Lindquist Olsen is back!

And now LDC is updated to work with LLVM 2.7. I hope this is not an isolated event and LDC development becomes as active as it used to be =)

The sources has been moved to Bitbucket too, so if you usually keep up to date you'll have to change the repo URL.

Motivated by a couple of long waited forward references bug fixes in the DMD front-end, I decided to experiment merging it into LDC.

The task wasn't so hard, just apply the patches, ignore changes to the back-end (mostly), resolve some conflicts and you're done!

Christian Kamm kindly helped me with a couple of doubts when resolving conflicts and I got commit access to the LDC repository in the way (thanks for the vote of confidence, even when LDC are very relaxed when giving commit access :).

However I found a changeset that was a little harder to merge: r251, which added support for appending dchar to a char[] (fixing bug 111, another long waited one). The problem was, 2 new runtime functions were added (_d_arrayappendcd and arrayappendwdarrayappendwd) but I didn't know how to tell the back-end about them.

Trying to compile Dil with the new LDC with the DMD 1.055 front-end, I discovered this change also added a regression. So I tried to fix those two issues before pushing my patches, but Christian told me I should push them first and fix the problems later. I really prefer the other way around, but I won't tell the LDC developers how to run the project :), so I did it [*].

Christian disabled the new feature later because Tango is still lacking the new runtime functions, so LDC can't do much about them yet. I filled a bug so this issue don't get lost.

I would be nice to have some feedback if you try the new merged front-end in LDC :)

Finally, Debian's bug #508070 is closed! That means that LDC is officially in Debian now. The package is only in the experimental repositories for now, I hope it hits testing soon.

Thanks to Arthur Loiret for the packaging efforts!

After 5 or 6 DMD versions with important regressions, LDC has just been updated to DMD's frontend 1.051. This brings a lot of bug fixes to the LDC world (DStress results are looking good! ;).

Lots of thanks to LDC guy for merging the new frontend =)

The upcoming LLVM 2.6 will include a plug-in for Gold to implement Link Time Optimization (LTO) using LLVM's LibLTO. There is a similar project for GCC, merged into the main trunk about a week ago. It will be available in GCC 4.5.

This is all fairly new, and will be not enabled by default in LLVM (I don't know what about GCC), but it will add a lot of new optimization oportunities in the future.

So people using LDC and GDC will probably be able to enjoy LTO in a near future =)

I haven't been posting very often lately because I decided to spend some time writing my thesis document (in Spanish), which was way behind my current status, encouraged by my code-wise bad weekend =P.

Alberto Bertogli was kind enough to review my Naive GC implementation and sent me some patches, improving the documentation (amending my tarzanesque English =) and fixing a couple of (nasty) bugs [1] [2].

I'm starting to go back to the code, being that LDC is very close to a new release and things are starting to settle a little, so I hope I can finish the statistics gathering soon.

If Matt Groeing would ever written a garbage collector I'm sure he would made a book in the Life in Hell series called Debug is Hell.

You can't rely on anything: unit tests are useless, they depend on your code to run and you can't get a decent backtrace ever using a debugger (the runtime calls seems to hidden to the debugger). I don't know if the last one is a compiler issue (I'm using DMD right now because my LDC copy broken =( ).

Add that to the fact that GNU Gold doesn't work, DMD doesn't work, Tango doesn't work [*] and LDC doesn't work, and that it's already hard to debug in D because most of the mainstream tools (gdb, binutils, valgrind) don't support the language (can't demangle D symbols for instance) and you end up with a very hostile environment to work with.

Anyway, it was a very unproductive weekend, my statistics gathering code seems to have some nasty bug and I'm not being able to find it.

PS: I want to apologize in advance to the developers of GNU Gold, DMD, Tango and LDC because they make great software, much less crappier than mine (well, to be honest I'm not so sure about DMD ;-P), it's just a bad weekend. Thank you for your hard work, guys =)

I started learning some Mercurial for interacting with the LDC repository, but I disliked it instantly. Sure, it's great when you come from SVN, but it's just too limited if you come from GIT (I can't live anymore without git rebase -i).

Fortunately there is fast-export. With it I can incrementally import the Mercurial repository in a GIT repository as easy as:

hg clone http://hg.dsource.org/projects/ldc ldc-hg
mkdir ldc
cd ldc
git init
hg-fast-export.sh -r my_local_hg_repo_clone

I'm very happy to be at home again =)

My original plan was to use GDC as my compiler of choice. This was mainly because DMD is not free and there is a chance that I need to put my hands in the compiler guts.

This was one or two years ago, now the situation has changed a lot. GDC is dead (there was no activity for a long time, and this added to the fact that GCC hacking is hard, it pretty much removes GDC from the scene for me).

OTOH, DMD now provides full source code of the back-end (the front-end was released under the GPL/Artistic licence long ago), but the license is really unclear about what can you do with it. Most of the license mostly tell you how you can never, never, never sue Digital Mars, but about what you can actually do, it's says almost nothing:

The Software is copyrighted and comes with a single user license, and may
not be redistributed. If you wish to obtain a redistribution license,
please contact Digital Mars.

You can't redistribute it, that's for sure. It says nothing about modifications. Anyways, I don't think Walter Bright mind to give me permission to modify it and use it for my personal project, but I prefer to have a software with a better license to work with (and I never was a big fan of Walter's coding either, so =P).

Fortunately there is a new alternative now: LDC. You should know by now that LDC is the DMD front-end code glued to the LLVM back-end, that there is an alpha release (with much of the main functionality finished), that it's completely FLOSS and that it's moving fast and getting better every day (a new release is coming soon too).

I didn't play with LLVM so far, but all I hear about it is that's a nice, easy to learn and work, compiler framework that is widely used, and getting better and better very fast too.

To build LDC just follow the nice instructions (I'm using Debian so I just had to aptitude install cmake cmake-curses-gui llvm-dev libconfig++6-dev mercurial and go directly to the LDC specific part). Now I just have to learn a little about Mercurial (coming from GIT it shouldn't be too hard), and maybe a little about LLVM and I'm good to go.

So LDC is my compiler of choice now. And it should be yours too =)