Re: Threads review

From: dmoore_at_[hidden]
Date: 2001-09-07 06:36:35

--- In boost_at_y..., "William Kempf" <williamkempf_at_h...> wrote:

> >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.

I wasn't actually suggesting a runtime UUID generation, but rather 
that the constant string could be a UUID generated once at compile or 
coding time, guaranteeing uniqueness:

swprintf(name, L"415C0481-8E15-11D3-8861-00104B2D65E0%X%X", 

I'm not actually suggesting that there is a real probability of a 
collision with your random prefix string, but this code is in a 
Windows implementation, and a UUID seemed more MS-ish.  Which is a 
long winded way of saying "no big deal"

> >4.  In semaphore::up(), I hadn't seen the idiom of "!!" before.
> >
> >    bool ret = !!ReleaseSemaphore(reinterpret_cast<HANDLE>(m_sema),
> count, &p);
> 
> 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.

Ok, I'll get back on the turnip truck!  Ha.

The only other thing I thought of on further reflection is that 
HANDLEs become 64 bits in the next couple of years, and just jamming 
them into "int" won't work at that point.  Not a truly pressing 
issue, but typdefing those entities where POSIX==int and MS==HANDLE 
might be a great idea on the implementation side of things.

Regards,
Dave