[6/7] vcomp: Implement _vcomp_enter_critsect and _vcomp_leave_critsect.

[Sebastian Lackner]

On 07.08.2015 09:13, Nikolay Sivov wrote:
> On 07.08.2015 10:04, Sebastian Lackner wrote:
>> On 07.08.2015 08:57, Nikolay Sivov wrote:
>>> On 07.08.2015 9:22, Sebastian Lackner wrote:
>>>> However, this does not fully prevent a
>>>> leak when frequently unloading / reloading a library using OpenMP... sounds a bit
>>>> like a design flaw to me.
>>>
>>> You could keep a list of allocations to fix that if it's really a problem.
>>>
>>
>> Vcomp wouldn't get notifications for loads/unloads of other libraries, and we also don't
>> know which critical sections belong to which library. A list of allocations could only
>> be used to clean up on process exit. If it is really a problem in practice, I would
>> guess that Windows is affected in a similar way.
>>
> 
> Is it possible it allocates one section per thread or something like that? E.g. what do two consecutive _vcomp_enter_critsect() calls return for NULL input, is it same pointer every time for example?
> 

No, it returns a different pointer each time. It also returns a new pointer when calling
_vcomp_enter_critsect() after the critical section was manually set to zero. Different critical
sections are necessary because all "#pragma omp critical" regions should be independent,
except they have the same name (then the compiler would use the same static variable).