[QGIS-Developer] QGIS 2.18 compiled against GDAL 3?

[Andreas Neumann]

Hi Even, 

Thank you for your feedback. Then it is probably better to compile it
with the latest 2.x GDAL then. 

The background here is that QGIS 2.18 server is still faster (better
performance) than 3.x. For this reason we'd like to continue to use 2.18
until the performance problems are addressed in 3.x. We'll share our
benchmark results soon with the QGIS (Server) devs to better find out
where QGIS-Server 3 looses time and try to address the issues. 

Thanks, 

Andreas 

On 2020-10-09 17:51, Even Rouault wrote:

> Andreas, 
> 
>> Can QGIS 2.18 be built against GDAL 3.x? 
> 
> Hum, I guess it would build, although definitely not a vetted combination. I wouldn't expect datum transformations to work very well, since QGIS would be dependent on towgs84 coming in PROJ.4 strings, and GDAL 3 / PROJ >= 6 will not populate that often now. 
> 
> You might have to add 
> 
> -DACCEPT_USE_OF_DEPRECATED_PROJ_API_H 
> 
> in CMAKE_CXX_FLAGS to get QGIS to build against PROJ >= 6 
> 
> You should check also which PROJ version your spatialite lib is linking to. 
> 
> You might instead to choose the 'internal PROJ' trick (https://trac.osgeo.org/gdal/wiki/BuildingOnUnixGDAL25dev) to have only GDAL built against PROJ >= 6 and have the rest of the stack (spatialite, QGIS) still using PROJ 5 
> 
> Even 
> 
> -- 
> 
> Spatialys - Geospatial professional services 
> 
> http://www.spatialys.com
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