Suppressing SIGBUS signals

- The operating system† should protect the user from incompetently-written software. Poorly written software should not cause any part of the operating system to crash.
- Depending on your security model, the application may be considered untrusted, in which case it should not be allowed to bring down the compositor (as that would be a denial-of-service attack).
- The application calling ftruncate might not even be the same application which created the file, if the latter leaves a directory entry lying around.

† Outside of the FOSS world, the compositor is universally considered to be part of "the operating system."