Reproduction steps:
1. Fill up the disk, which has Editor.log file, leave some MB free space
2. Open repro project
3. Press play
4. Wait until disk fills up completely

Actual result: Now Unity sometimes freezes, other times no prompt of no disk space is given, no error, anything. All the log goes nowhere.
Expected: At least error, cause otherwise it might be a problem for people who leave program for testing for a long time.

If it doesn't freeze, it crashes when exiting.

Reproduced on: 5.5.1f1, 5.6.2p1, 2017.1.0f1, 2017.2.0b3

Notice that this case is very similar to https://fogbugz.unity3d.com/f/cases/706334/