... so that the testbench continues to work

it permits to specifiy if asynchronous writing should be done or not

some versions of autotools seem to require it. The file itself is NOT
of interest for the project

Further testing turned out that the rsyslog core works correctly and
this fix is not needed. The concurrency we saw was actually caused by
other actions (even processes) during directory creation. See commit
9e5b31fc44136dbcc1e443cfe7714e9daf97d844 for further details.

Some types of malformed messages could trigger an off-by-one error
(for example, \0 or \n as the last character, and generally control
character escaption is questionable). This is due to not strictly
following a the \0 or string counted string paradigm (during the last
optimization on the cstring class). As a temporary fix, we have
introduced a proper recalculation of the size. However, a final
patch is expected in the future. See bug tracker for further details
and when the final patch will be available:
http://bugzilla.adiscon.com/show_bug.cgi?id=184
Note that the current patch is considered sufficient to solve the
situation, but it requires a bit more runtime than desirable.

This bug was triggered by an open failure. The the cache was full and
a new entry needed to be placed inside it, a victim for eviction was
selected. That victim was freed, then the open of the new file tried. If
the open failed, the victim entry was still freed, and the function
exited. However, on next invocation and cache search, the victim entry
was used as if it were populated, most probably resulting in a segfault.

If multiple files try to create a directory at (almost) the same time,
some of them may fail. This is a data race and also exists with other
processes that may create the same directory. We do now check for this
condition and gracefully handle it.

The old code looks a bit "strange", though not necessarily incorrect.
The new code looks correct and is probably less irritating during bug
hunting.