[postgis-devel] [off-topic] Integrating C++ singletons into postgresql extensions???

[Mateusz Łoskot]

FYI, Stephen has posted the same question to PostgreSQL ml, here
http://www.postgresql.org/message-id/5441AD7A.3070809@swoodbridge.com
where it received helpful and detailed answers

M

On 17 October 2014 20:32, Stephen Woodbridge <woodbri at swoodbridge.com> wrote:
> Hi,
>
> I've been writing some new VRP solutions for pgRouting in C++ and I have a
> few singleton classes like:
>
> 1. Config object that holds some general configuration information.
> 2. Stats object for global stats collection.
> 3. Logger object for enabling/disabling debug logging to a file.
> 4. curlpp class for making outbound calls to OSRM from the c++ code
>
> I can probably do without 1-3 if I had to when the code is integrated, but
> they are handy to keep around in the code for when we are developing and
> working outside the postgresql database. And, would like to avoid cluttering
> the code with tons of #ifdef.
>
> Item 4 is a little more problematic and needs to be kept around or something
> else implemented to take its place.
>
> So my question(s) are:
>
> 1. Any insights into singletons working/not working within the postgresql
> server extensions? My understanding is that these are implemented as global
> static classes with a lifetime of the process and they have no destructor,
> so I'm a little worried about memory leaks or multiple queries sharing the
> singleton.
>
> 2. Is there another way of doing this for C++ code in the server?
>
> 3. What does PostGIS or GEOS do for logging?
>
> Any help or ideas would be appreciated.
>
> Thanks,
>   -Steve
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-- 
Mateusz  Łoskot, http://mateusz.loskot.net