using libevent-2.0.21-stable.tar.gz build without any option (./configure && make)
some of the regression test fails on my OpenBSD 4.3 i386 box :
[...]
regress:
FAIL regress_bufferevent.c:772: assert(abs(timeval_msec_diff(((&started_at)), ((&res1.read_timeout_at))) - (150)) <= 50): 61 vs 50bufferevent/bufferevent_timeout_filter:
[bufferevent_timeout_filter FAILED]
[...]
see attached log
the machine is old and slow (Pentium MMX 166MHz :)