Note ccache

ccache is a tool which provides a cache for C/C++/Objective-C compiler operations. We've found that it makes LLVM recompilation a bit easier to handle, and not everyone knows about it yet!

After installing the ccache package using your preferred package manager (i.e. apt-get, yum, pacman), you need to prioritize ccache so that it intercepts calls to the compiler. There are three methods for doing so.

The first method is to pass --enable-ccache when you run configure.

The second method is symlink ccache to a higher priority directory in $PATH, e.g. /usr/local/bin.

$ sudo ln -s /usr/bin/ccache /usr/local/bin/gcc
$ sudo ln -s /usr/bin/ccache /usr/local/bin/g++
$ sudo ln -s /usr/bin/ccache /usr/local/bin/cc

The third method is to edit ~/.bashrc and add ccache's bin directory into the beginning of your $PATH. Please note that depending on your distro, the binaries will be in one of two different locations:

export PATH=/usr/lib/ccache/bin:/usr/lib/ccache:${PATH}

Then you can verify that ccache is being used during builds:

ccache --show-stats

There are also some concerns using ccache with clang that should be noted. (The combination configure --enable-ccache --enable-clang already does magic to address these concerns.)