Created attachment 42314 [details]
Evil patch to register start_wqthread thread

I tried using valgrind with the patches for 10.6 applied. Both helgrind and drd tools fail quickly with a message like this:

Helgrind: hg_main.c:618 (map_threads_lookup): Assertion 'thr' failed.

After tracking it down some more, the issue is that pre_thread_ll_create is not called for the thread start_wqthread which probably is part of the work queue of OS X. This thread exists in my process although there is no direct use of work queue APIs.

I could get helgrind to work with the attached utterly awful and probably disastrous patch. It's not meant as a solution, but as a pointer for someone more knowledgable in the valgrind darwin port.