It looks like Walter is willing to (finally) give the copyright assignment of the DMD front-end to the FSF, so GDC can have a chance at being merged to the official GCC distribution.

Let's see how this turns out...

Here are some details on how to try CDGC, as it needs a very particular setup, specially due to DMD not having precise heap scanning integrated yet.

Here are the steps (in some kind of literate scripting, you can copy&paste to a console ;)

# You probably want to do all this mess in some subdirectory :)
mkdir cdgc-test
cd cdgc-test

# First, checkout the repositories.
git clone git://git.llucax.com/software/dgc/cdgc.git
# If you have problems with git:// URLs, try HTTP:
# git clone https://git.llucax.com/r/software/dgc/cdgc.git
svn co http://svn.dsource.org/projects/tango/tags/releases/0.99.9 tango

# DMD doesn't care much (as usual) about tags, so you have to use -r to
# checkout the 1.063 revision (you might be good with the latest revision
# too).
svn co -r613 http://svn.dsource.org/projects/dmd/branches/dmd-1.x dmd

# Now we have to do some patching, let's start with Tango (only patch 3 is
# *really* necessary, but the others won't hurt).
cd tango
for p in 0001-Fixes-to-be-able-to-parse-the-code-with-Dil.patch \
         0002-Use-the-mutexattr-when-initializing-the-mutex.patch \
         0003-Add-precise-heap-scanning-support.patch \
         0004-Use-the-right-attributes-when-appending-to-an-empty-.patch
do
   wget -O- "https://llucax.com/blog/posts/2010/10/10-trying-cdgc-howto/$p" |
         patch -p1
done
cd ..

# Now let's go to DMD
cd dmd
p=0001-Create-pointer-map-bitmask-to-allow-precise-heap-sca.patch
wget -O- "https://llucax.com/blog/posts/2010/10/10-trying-cdgc-howto/$p" |
      patch -p1

# Since we are in the DMD repo, let's compile it (you may want to add -jN if
# you have N CPUs to speed up things a little).
make -C src -f linux.mak
cd ..

# Good, now we have to wire Tango and CDGC together, just create a symbolic
# link:
cd tango
ln -s ../../../../../cdgc/rt/gc/cdgc tango/core/rt/gc/

# Since I don't know very well the Tango build system, I did a Makefile of my
# own to compile it, so just grab it and compile Tango with it. It will use
# the DMD you just compiled and will compile CDGC by default (you can change
# it via the GC Make variable, for example: make GC=basic to compile Tango
# with the basic GC). The library will be written to obj/libtango-$GC.a, so
# you can have both CDGB and the basic collector easily at hand):
wget https://llucax.com/blog/posts/2010/10/10-trying-cdgc-howto/Makefile
make # Again add -jN if you have N CPUs to make a little faster

# Now all you need now is a decent dmd.conf to put it all together:
cd ..
echo "[Environment]" > dmd/src/dmd.conf
echo -n "DFLAGS=-I$PWD/tango -L-L$PWD/tango/obj " >> dmd/src/dmd.conf
echo -n "-defaultlib=tango-cdgc " >> dmd/src/dmd.conf
echo "-debuglib=tango-cdgc -version=Tango" >> dmd/src/dmd.conf

# Finally, try a Hello World:
cat <<EOT > hello.d
import  tango.io.Console;

void main()
{
   Cout("Hello, World").newline;
}
EOT
dmd/src/dmd -run hello.d

# If you don't trust me and you want to be completely sure you have CDGC
# running, try the collect_stats_file option to generate a log of the
# collections:
D_GC_OPTS=collect_stats_file=log dmd/src/dmd -run hello.d
cat log

Done!

If you want to make this DMD the default, just add dmd/src to the PATH environment variable or do a proper installation ;)

Let me know if you hit any problem...

There is a lot of activity lately in the GDC world, both the repository and the mailing list (mostly closed bug reports notification).

The reborn of GDC is a courtesy of Vincenzo Ampolo (AKA goshawk) and Michael P. (I'm sorry, I couldn't find his last name), but it received a big boost lately since Iain Buclaw (apparently from Ubuntu, judging from his e-mail address) got commit access to the repository in July.

They are working in updating both the DMD front-end and the GCC back-end and judging from the commits, the front-end is updated to DMD 1.062 and 2.020 (they are working on Druntime integration now) and the back-end works with GCC 3.4, 4.1, 4.2, 4.3 and 4.4 is in the works.

Really great news! Thanks for the good work!

Big news: DMD 64 bits support has just been started! It almost shadows the born of the new public DMD test suite (but I think the latter if far more important in the long term).

After some repetitive discussions about how to improve error messages (usually inspired by clang), it looks like now the DMD frontend can suggest the correct symbol name when you have a typo =)

Some time ago I wrote a partial patch to fix DMD's issue 3420:

Allow string import of files using subdirectories

const data = import("dir/data.txt");

Specifying -J. for DMD 1.041 is sufficient to allow this to compile.

I couldn't find an option for DMD 1.042 and newer which would allow this to compile.

It's a partial patch because it's implemented only for Posix OSs. The patch passed unnoticed until changeset 389, when the restrictions on string imports became even more evident, and I commented the issue in the DMD internals ML. Fortunately Walter accepted the patch; well accept might be a very strong word, since Walter never really accepts a patch, he always write a new patch based on the submitted one, don't even dream on getting some feedback about it.

But well, that's how he works. At least now in Posix (he said he didn't find a way to do this in Windows) there are no silly restrictions on string imports, without sacrificing security =)

Wow! Google's Go (remember there is another Go) programming language front-end for GCC has been accepted for merging into GCC 4.5.

Just when there was some discussion (started by Jerry Quinn [*]) in D on how the DMD front-end could be pushed to be merged in GCC too, but DigitalMars (Walter) doesn't want to give away the copyright of his front-end (they are exploring some alternative options though). Maybe the inclusion of Google's Go makes Walter think harder for a solution to the legal problems :).

After some discussion [*] in the D newsgroup about the value of having release candidates for DMD (due to the high number of regressions introduced in new versions mostly), Walter agreed to make public what he called beta versions of the compiler, which he sent privately to people who asked for them (like some Tango developers).

The new DMD betas are announced in a special mailing list (available through Gmane too). It seems like Walter want to keep the beta releases with some kind of secrecy, or only for people really interested on them (the zip files are even password protected! But the password is announced in a public mailing list, that doesn't make much sense =/). I think he should encourage people to try them as much as possible instead, but one step at the time, at least now people have a way to test the compiler before it's released.

I can say without fear that the experience has been very successful already, even when there is no DMD release yet that came from a beta pre-release, you can see in the beta mailing list that multiple regressions have been discovered and fixed because this new beta releases. I think the reliability of the compiler has been increased already. Is really interesting to see how the quality of a product increases proportionally to the level of openness and the numbers of eyes doing peer review.

The new DMD release should be published very soon, as all the regressions seems to be fixed now and big projects like Tango, GtkD and QTD compiles (a lot of focus on fixing bugs that prevented the later to compile has been put into this release, specially from Rainer Schuetze, who submitted a lot of patches).

So kudos for a new era in D, I think this is another big milestone for having a reliable compiler.

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 :)

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 =)

I'm very glad that yesterday DMD had the first releases (DMD 1.050 and DMD 2.035) with a decent revision history. It took some time to Walter Bright to understand how the open source development model works, and I think he still has a lot more to learn, but I have some hope now about the future of D.

Not much time ago, neither Phobos, DMD nor Druntime had revision control. Druntime didn't even exist, making D 1 split in two because of the Phobos vs Tango dichotomy. DMD back-end sources were not available either, and Walter Bright was the only person writing stuff (sometimes not because people didn't want to, but because he was too anal retentive to let them ;). It was almost impossible to make patches back then (your only chance was hacking GDC, which is pretty hard).

Now I can say that DMD, Phobos and Druntime have full source availability (DMD back-end is not free/libre though), almost all the parts of DMD have the sources published under a source control system. The core team has been expanded and even when Walter Bright is still in charge, at least 3 developers are now very committed to D: Andrei Alexandrescu (in charge of Phobos), Sean Kelly (in charge of Druntime) and Don Clugston (squashing DMD bugs at full speed, specially in the back-end). Other people are contributing patches in a regular basis. There were about 72 patches submitted to bugzilla before DMD was distributed with full source (72 patches in ~10 years) , since then, 206 patches were submitted (that is, 206 patches in less than 8 months).

But even with this great improvement, there is much left to do yet (and I'm talking only about the development model). This is a small list of what I think it's necessary to keep moving to a more open development model:

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 =)