We find clang an extremely useful development compiler. Not only does it pick up errors that GCC tends to ignore, but it also provides us with a completion mode in emacs that works surprisingly well.
So it was with great sadness that, for some inexplicable reason, our
clang 3.1 build started failing after a dist-upgrade. After trying
some obvious fixes such as doing a clean build and so on - to no
avail - I decided to investigate clang 3.2, which has already hit
experimental. Hey, worth a go right?! I've never been brave enough to
start pinning packages from experimental into testing - always afraid
to upgrade something by mistake. Clang tends to be really easy to
install by hand so its not a problem to handle dependencies
manually. This was almost the case with 3.2.
First start by removing all the old LLVM and clang packages you got lying around. They are actually side-by-side installable for the most part, but I strongly believe its a bad idea to have these versions lying around unless you have very good reason to do so. Last thing you need is to use the incorrect version of the compiler and start getting some weird errors.
Downloading the required packages is pretty straightforward:
mkdir clang-3.2 cd clang-3.2 wget http://ftp.us.debian.org/debian/pool/main/c/clang/libclang-dev_3.2-1~exp8_amd64.deb wget http://ftp.us.debian.org/debian/pool/main/c/clang/libclang1_3.2-1~exp8_amd64.deb wget http://ftp.us.debian.org/debian/pool/main/l/llvm-3.2/llvm-3.2-runtime_3.2-3_amd64.deb wget http://ftp.us.debian.org/debian/pool/main/l/llvm-3.2/llvm-3.2_3.2-3_amd64.deb wget http://ftp.us.debian.org/debian/pool/main/l/llvm-3.2/llvm-3.2-dev_3.2-3_amd64.deb wget http://ftp.us.debian.org/debian/pool/main/l/llvm-3.2/libllvm3.2_3.2-3_amd64.deb wget http://ftp.us.debian.org/debian/pool/main/c/clang/libclang-common-dev_3.2-1~exp8_amd64.deb wget http://ftp.us.debian.org/debian/pool/main/c/clang/compiler-rt_3.2-1~exp8_amd64.deb wget http://ftp.us.debian.org/debian/pool/main/c/clang/clang-3.2_3.2-1~exp8_amd64.deb
To install them su to root and dpkg them in the correct order:
dpkg -i libllvm3.2_3.2-3_amd64.deb dpkg -i llvm-3.2-runtime_3.2-3_amd64.deb dpkg -i llvm-3.2_3.2-3_amd64.deb dpkg -i llvm-3.2-dev_3.2-3_amd64.deb dpkg -i libclang1_3.2-1~exp8_amd64.deb dpkg -i libclang-common-dev_3.2-1~exp8_amd64.deb dpkg -i libclang-dev_3.2-1~exp8_amd64.deb dpkg -i compiler-rt_3.2-1~exp8_amd64.deb dpkg --force-depends -i clang-3.2_3.2-1~exp8_amd64.deb
You won't fail to notice the extremely worrying --force-depends at
the very end. This is because to reasons unknown to me, clang now
depends on libgcc-4.7-dev and libobjc-4.7-dev. These packages are not
yet available in testing and last thing you need is to pull GCC
straight of unstable. Assuming that any dependency between clang and
GCC is probably either a mistake or something optional, I decided to
force an install anyway and see how the compiler behaved. As it turns
out the compiler worked just fine so I'm not loosing any sleep over
the missing dependency just yet.
Unfortunately the hacks don't end there. We also found that
libprofile_rt never quite gets found, so an additional hack is
required (as root):
cd /usr/lib rm libprofile_rt.a libprofile_rt.so ln -s /usr/lib/llvm-3.2/lib/libprofile_rt.a ln -s /usr/lib/llvm-3.2/lib/libprofile_rt.so
Interestingly, the warnings on clang 3.2 are even better than on 3.1 and so it picked up a number of unused member variables in your code, which we duly fixed. Hopefully it will all go green on tomorrow's clean builds.
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