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270

Summary: The primary reason for switching from GCC to Clang is the incompatibility of GCC's GPL v3 license with the goals of the FreeBSD project. There are also political issues to do with corporate investment, as well as user base requirements. Finally, there are expected technical advantages to do with standards compliance and ease of debugging. Real world ...


30

One thing worth considering is that FreeBSD is currently using GCC 4.2.1 as noted in ire_and_curses answer thus the performance comparisons aren't of 4.5 or even 4.6 aren't truly relevant to the project. Therefore, the questions you should be asking are: What are the performance gains of the new Clang vs the older GCC that the project uses? How do the same ...


11

Even though GCC is GPLv3, the resulting binaries produced by GCC never had any license constraint. In clear you can use GCC to build software that falls under the license you want. Even the C library that comes with GCC and that is included in the binary is license-free. http://www.gnu.org/licenses/gcc-exception-faq.html Section 2 of the GNU GPLv3: You ...


5

Not yet. According to this currently open bug report it seems even the kernel itself fails to compile.


4

I'm no expert, but my understanding is Clang/LLVM uses fewer resources than GCC and is quicker. http://clang.llvm.org/features.html#performance If you're running an environment where you need to build a lot of stuff, a lot of times, that performance may turn into real savings in energy costs and time. If it's real.


3

As a late response to this question, what @jmtd said is exactly what happens periodically in the Debian archive. Packages are recompiled with newer toolchains (compilers, linkers, etc.) and, when recompilation fails, bugs against the packages that failed to be compiled are filed with the indication of FTBFS ("failed to build from source"). Such bugs are ...


3

I was able to build clang by following a modified version of steps you took. # Preliminary: # Get source # Extract source # Set environmental variables cd /home/avilella/src/llvm/latest # Clang is expected to be at `tools/clang`. mv tools/cfe-3.3.src tools/clang # You should clean before configuring, not after. make clean # The missing config.h file is ...


2

Generally it's not a good idea to simply unpack an RPM and try to use it's content because: you have to resolve the dependencies you lose the so called RPM scripts, which might be vital for proper functioning you lose the original directory structure, which might be vital for proper functioning Number 2 and 3, are in fact rarely a problem (only happens ...


1

I think the problem is that you don't want the first two lines you put in /etc/apt/sources.list, namely deb http://llvm.org/apt/trusty/ llvm-toolchain-trusty main deb-src http://llvm.org/apt/trusty/ llvm-toolchain-trusty main I suspect these correspond to 3.5 (trunk). You can verify this by running apt-cache policy pkg1 ... pkgn where the pkgs run ...


1

Since Apple has bundled it's own version of gcc/llvm, you need to enable homebrew/versions repo before you can install different version of GCC. brew tap homebrew/versions brew install gcc48 Replace gcc48 with the version of gcc you want. See also https://github.com/mxcl/homebrew/wiki/Custom-GCC-and-cross-compilers


1

If you want a later version of clang installed on a regular basis you might want to add one of the PPAs on LaunchPad e.g. this one or this one. Once you have the PPA added to your /etc/apt resources, the package can update the package with the normal system update/upgrade just like gcc-snapshot would do. These PPAs are normally the latest, which means not ...


1

Whilst the end-user binaries are not built with clang/llvm, most of the Debian archive has been built (and rebuilt) with clang/llvm (and binutils-gold and other bits and pieces) by people who want to expose portability bugs in the software suite (and the compilers themselves).



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