I messed up last reply headers somehow. Trying again. I wrote:
Also mdb could catch more user errors - including "cannot happen" mutex errors from mutex lock/unlock, since some threading user errors are be non-obvious from the doc.
That is, "cannot happen" when there is no user error.
The fork() restriction needs to be documented, as does "don't open or close the same database twice in the same process".
Correction, "don't have the same database open twice at the same time in the same process".