Re: [boost] [thread] RFC standard proposed mutex, read-write mutex, condition

From: Peter Dimov (pdimov_at_[hidden])
Date: 2007-08-25 11:11:59

Howard Hinnant:

> On Aug 22, 2007, at 11:55 AM, Howard Hinnant wrote:
>
>> Here's checked_condition:
>
> After investigating the use cases for the "unchecked condition", I
> realized that my earlier checked_condition that I posted here wasn't
> quite right, at least if you considered it a debug tool.  To this end
> I've rewritten it, and renamed it to condition_debug to emphasize its
> role.  The previous version was allowing default constructed
> conditions to wait on different mutexes at the same time.  This
> revised condition_debug allows default constructed conditions to only
> wait on different mutexes at different times.  All simultaneous waits
> must be on the same mutex (even for a default constructed condition).

...

The checks seem too strict. It's valid to notify_all and then rebind the 
condition to a different mutex, but your condition_debug will likely 
assert/throw as the awakened threads have not yet executed their postchecks. 
(Unless I'm overlooking something.)

It's quite likely that only the implementor of pthread_cond_t may catch all 
errors in the general case. This does not diminish the utility of a checked 
condition that catches most errors in the typical case IMO.