On Aug 22, 2007, at 10:42 AM, David Abrahams wrote:
on Wed Aug 22 2007, Howard Hinnant <hinnant-AT-twcny.rr.com> wrote:
"However if the external mutex is (or is layout compatible with) a pthread_mutex_t, then there is no need for the internal pthread_mutex_t. When one wants to wait, one simply waits on the external pthread_mutex_t with the internal pthread_cond_t."
This smells a little fishy. It seems to imply that pthreads can wait on any old data type that happens to be layout-compatible with pthread_mutex_t. Is that really true?
Perhaps the wording isn't precise enough.
The intent is that on pthreads:
<snip explanation that doesn't mention layout-compatibility>
Sure. But where does the layout-compatibility thing come in? Your example uses the native pthread types, not arbitrary types layout-compatible with those.
The vendor will decide on which mutex types it is appropriate to make this specialization/optimization. I used "layout-compatible" in an attempt to communicate which std-defined mutex types would be appropriate for the vendor to specialize on. -Howard