FreeBSD 10 was the first release that officially released with Clang as the default, base compiler.
Most ports, unless specially marked, now compile using the base ("pre-installed") clang.
However, clang development is moderately rapid, and so the version of clang in base can be out of date frequently – not only do we have to wait for clang to be imported into base, but then we have to recompile from base (make world) to install it; the other alternative for the more enterprising operator would be to navigate the source tree and attempt to rebuild and reinstall just clang.
It would be a lot easier to just use the version of clang that's in ports under lang/clangXX.
Installing that's easy enough, but then how does one modify the ports infrastructure to use that install of clang instead of the base install of clang?
Best Answer
You would treat the ports clang as an alternative compiler, just like when GCC was the default.
As per the FreeBSD wiki, add the following lines to /etc/make.conf (if you want to use clang for everything, even ports), or /etc/src.conf (if you want to use clang just for world and kernel):
Check where the ports clang binaries where installed under /usr/local and adjust accordingly.