Using CCache to speed up compilation

.. _c_cache:

CCache <http://ccache.samba.org/>_ is nothing more than a cache for your compiler. ccache is usually very easy to install. Here's an example for Ubuntu systems::

sudo apt-get install ccache

ccache will cache previous compilations, detect when the same compilation is being done again, and reuse its cache instead of recompiling the source code again. This can speed up your compilation by many orders of magnitude, especially in those situations where your file timestamps change, and make is triggering a recompile.

To enable ccache, simply add '/usr/lib/ccache' to the beginning of your PATH. This directory contains symlinks to ccache, and ccache is smart enough to look at the name of the calling executable to determine which real executable to run. I.e. there is a symlink from '/usr/lib/ccache/g++' to just 'ccache', but it actually runs the equivalent of 'ccache g++'.

Using colorgcc to colorize output

colorgcc <https://github.com/johannes/colorgcc>_ is a colorizer for the output of GCC, and allows you to better interpret the compiler warnings/errors.

To enable both colorgcc and ccache, perform the following steps:

Install colorgcc on an Ubuntu system with ::

sudo apt-get install colorgcc

To enable colorgcc, perform the following steps:

.. code-block:: shell

cp /etc/colorgcc/colorgccrc $HOME/.colorgccrc

edit the $HOME/.colorgccrc file, search for the following lines:

.. code-block:: text

g++: /usr/bin/g++
gcc: /usr/bin/gcc
c++: /usr/bin/g++
cc:  /usr/bin/gcc
g77: /usr/bin/g77
f77: /usr/bin/g77
gcj: /usr/bin/gcj

and replace them with:

.. code-block:: text

g++: ccache /usr/bin/g++
gcc: ccache /usr/bin/gcc
c++: ccache /usr/bin/g++
cc:  ccache /usr/bin/gcc
g77: ccache /usr/bin/g77
f77: ccache /usr/bin/g77
gcj: ccache /usr/bin/gcj

create a $HOME/bin or $HOME/sbin directory, and create the following softlinks in it

.. code-block:: shell

ln -s /usr/bin/colorgcc c++
ln -s /usr/bin/colorgcc cc
ln -s /usr/bin/colorgcc g++
ln -s /usr/bin/colorgcc gcc

make sure that $HOME/bin or $HOME/sbin is the first directory in your $PATH, e.g.::

export PATH=$HOME/bin:$PATH

or::

export PATH=$HOME/sbin:$PATH

depending on where you stored the colorgcc softlinks, so that when cc/gcc/g++/c++ is invoked the freshly created softlinks get activated first and not the global /usr/bin/{cc,gcc,g++,c++}.