The master branch is currently being built each time that a commit to master is made. The build is started sometime after the commit, so this will not stop any bad commits, just report them. See the build pages at:
Look the the SWIFT build.
The build also compiles using several different configure options: with/without METIS and FFTW as well as with parallel HDF5, and all the different hydro schemes, as well as testing the distribution tarball can build, so take care to understand which build is failing.
Some tests also run
make check, so any failing tests should be reported as well.
Finally each merge request, that is not mark WIP, is checked against a smaller set of build targets. These are just to reduce the number of failures seen on merge to master.