Re: Interrupting long external library calls

On 24.05.2012 16:04, Sandro Santilli wrote:
> On Wed, May 16, 2012 at 07:30:03PM +0300, Heikki Linnakangas wrote:
>> On 16.05.2012 15:42, Sandro Santilli wrote:
>>> But CHECK_FOR_INTERRUPTS doesn't return, right ?
>>> Is there another macro for just checking w/out yet acting upon it ?
>>
>> Hmm, no. CHECK_FOR_INTERRUPTS() checks the InterruptPending
>> variable, but on Windows it also checks for
>> UNBLOCKED_SIGNAL_QUEUE(). And even if InterruptPending is set, it's
>> not totally certain that CHECK_FOR_INTERRUPTS() won't return. I
>> think InterruptPending can be set spuriously (even if that's not
>> possible today, I wouldn't rely on it), and if you're in a
>> HOLD/RESUME_INTERRUPTS block, CHECK_FOR_INTERRUPTS() will do nothing
>> even if InterruptPending is true.
>>
>> The only sane way to make 3rd party code interruptible is to add
>> CHECK_FOR_INTERRUPTS() to it, in safe places.
>
> No place is safe if CHECK_FOR_INTERRUPTS doesn't return.
> How could caller code cleanup on interruption ?

It would only be safe to call it in places where no cleanup is
necessary. I don't know if there are any such places in the geos library.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com