TYPO3 Core

Rarely, but sometimes it happens that the temp_CACHED_..._ext_tables.php file remains empty.
(This probably happens because of a PHP-timeout during writing while high server load or disk error etc...)

With this empty file you can still log into the BE (in 4.2 you can even see some modules; but no extension-modules or -contents).
Also, everything that's in the cache is displayed correctly in the FE. Uncached elements in FE however result in the known enableFields()-error.

Now, this all isn't too grave but we get to our problem by speaking of CronJobs.
As an example I'll take direct_mail to explain the problem:
dmail uses the following function to check for deleted emails:

t3lib_BEfunc::deleteClause('sys_dmail')

This returns '' if extension-tca is empty:

http://doxygen.frozenkiwi.com/typo3/html/d4/da8/class_8t3lib__befunc_8php_source.html#l00203

Now, direct_mail happily starts sending deleted newsletters if temp_CACHED_..._tables.php is empty.
Probably, there are more extensions/cronjobs etc. that use this and similar functions and therefore are doing weird things...

The solution now probably would be to treat empty temp_CACHED_* files as they wouldn't exist and to newly build them...
This would also help to avoid many of "there is no TCA-Definition"-errors on up and running live-sites.

This Bug affects all TYPO3-Versions from 4.2 to 4.5