You can get the code for Mistral 1.550 which won several categories in the last CSP solver competition. However, it is no longer maintained.

To build the xcsp solver executable: $make xsolve
To run it: $bin/xsolve < xcsp file >

You can also use the API to model a problem and solve it. Many examples are in models/src/.
To compile models/src/xxx.cpp: $make xxx

To run it: $bin/xxx

A new version of Mistral is available from GitHub. The clone link is https://github.com/ehebrard/Mistral-2.0.git (use $git clone https://github.com/ehebrard/Mistral-2.0.git).

To compile examples/src/xxx.cpp: $make xxx

To run it: $bin/xxx