Hey fellow RIOTers,
we've just merged [1], which will enforce certain rules about the C header guards. See [2] for more details.
In order to adapt your git tree,
$ dist/tools/headerguards/check.sh
... will show which files might need a header guard fix. The checker outputs unified diff, which can be piped directly into "patch -p0".
Cheers, Kaspar
[1] https://github.com/RIOT-OS/RIOT/pull/7095 [2] https://github.com/RIOT-OS/RIOT/wiki/Coding-conventions#header-guards