Because of my stupidity, I wrote code that executed mysql_query(&dbh)
with dbh being uninitialized. Of course, the results of this are
undefined, however, they were quite interesting: instead of a segfault,
the process blocked consuming 99% of the CPU waiting for something to
happen. Although technically speaking, illegal behaviour can produce
only unpredictable results, so you cannot call this a bug, if some
thinks this may be exposing the actual bug in something, I will post
more info with mysqlbug.