RE: Threads review

From: William Kempf (williamkempf_at_[hidden])
Date: 2001-09-06 15:45:59

From: dmoore_at_[hidden]
>A review from a Windows-centric programmer:
>
>1.  Great, great, overall library
>2.  In call_once, the line:
>
>swprintf(name, L"2AC1A572DB6944B0A65C38C4140AF2F4%X%X", 
>GetCurrentProcessId(), &flag);
>
>Shouldn't you just generate a UUID for your unique naming prefix?

This would work, but wouldn't be as efficient since the same actual mutex 
would be used for all calls to call_once... even those from seperate 
programs.  Adding the GetCurrentProcessId() reduces the granularity to all 
calls to call_once within the process, while adding the address of &flag 
reduces it to just the boost::once_flag instance.

>3.  In many places in the code where there are resource allocation 
>problems, you attempt to do cleanup by calling CloseHandle() before 
>throwing the thread_resource_error() exeception (see condition::condition 
>in particular).  Calling CloseHandle(NULL) causes a Windows exception 
>(C0000008) to be thrown, which will occur before you get your chance to 
>throw thread_resource_error().

OK, I was unaware of the exception in this case.  I'll fix the code.  
Thanks.

>4.  In semaphore::up(), I hadn't seen the idiom of "!!" before.
>
>    bool ret = !!ReleaseSemaphore(reinterpret_cast<HANDLE>(m_sema),
count, &p);
>
>At first glance, I thought this was a bug (it's not), but it seems a bit 
>odd.  Would a cast from BOOL to bool or a comment be more clear?

It's a fairly common idiom (given the name "bang bang") that I expect many 
(most?) people to be aware of.  The cast may be more appropriate, it's just 
a pain to code, and a comment would be even worse yet.  I'm not sure what 
others think about this idiom.

Bill Kempf

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