[PROJ] Affine transformation using DERIVEDPROJCRS

[Bart.Duijndam at ziggo.nl]

Thanks Even, 

 

This removed the error message, and the code now compiles okay. 

Next thing is to step through the code, and see if it does what I hope it does.

 

But that will be by Friday earliest, I expect.

 

Kind regards,

 

Bart

 

 

From: Even Rouault <even.rouault at spatialys.com> 
Sent: Tuesday, 5 July 2022 23:52
To: Bart.Duijndam at ziggo.nl; proj at lists.osgeo.org
Subject: Re: [PROJ] Affine transformation using DERIVEDPROJCRS

 

 

Le 05/07/2022 à 23:35, Bart.Duijndam at ziggo.nl <mailto:Bart.Duijndam at ziggo.nl>  a écrit :

Hi Even,

 

Thanks for your help; you’re working late…

Please be advised that I already started with using nn_dynamic_pointer_cast<ProjectedCRS>(crs);

But then I got the following obscure error message:

 

D:\Source\VS19\PROJ\test\unit\test_crs.cpp(5516): error C2280: 'dropbox::oxygen::nn<osgeo::proj::crs::ProjectedCRSPtr>::nn(PtrType)': attempting to reference a deleted function

          with

          [

              PtrType=osgeo::proj::crs::ProjectedCRSPtr

          ]

  D:\Source\VS19\PROJ\include\proj\nn.hpp(126): note: see declaration of 'dropbox::oxygen::nn<osgeo::proj::crs::ProjectedCRSPtr>::nn'

  D:\Source\VS19\PROJ\include\proj\nn.hpp(126): note: 'dropbox::oxygen::nn<osgeo::proj::crs::ProjectedCRSPtr>::nn(PtrType)': function was explicitly deleted

          with

          [

              PtrType=osgeo::proj::crs::ProjectedCRSPtr

          ]

  ninja: build stopped: subcommand failed.

 

Build All failed.

Ah I see, the issue is that nn_dynamic_pointer_cast<ProjectedCRS> returns a ProjectedCRSPtr (which is a typedef for std::shared_ptr<ProjectedCRS>), which is potentially null (because nn_dynamic_pointer_cast<> might fail and return a null pointer). Whereas your function signature returns a ProjectedCRSNNPtr, which is an alias for nn<ProjectedCRSPtr>, that is a ProjectedCRSPtr that cannot be null. The conversion from ProjectedCRSPtr to nn<ProjectedCRSPtr> must be explicit, so you should typically modify the return statement to be return NN_CHECK_ASSERT(proj_crs);

 

 

So that’s why I tried ProjectedCRSNNPtr instead

That would leak to a shared pointer of a null-nullable shared pointer. Definitely not something you want.



 

Cheers,

 

Bart

 

 

 

From: Even Rouault  <mailto:even.rouault at spatialys.com> <even.rouault at spatialys.com> 
Sent: Tuesday, 5 July 2022 23:30
To: Bart.Duijndam at ziggo.nl <mailto:Bart.Duijndam at ziggo.nl> ; proj at lists.osgeo.org <mailto:proj at lists.osgeo.org> 
Subject: Re: [PROJ] Affine transformation using DERIVEDPROJCRS

 

    auto proj_crs = nn_dynamic_pointer_cast<ProjectedCRSNNPtr>(crs);

==> auto proj_crs = nn_dynamic_pointer_cast<ProjectedCRS>(crs);

-- 
http://www.spatialys.com
My software is free, but my time generally not.

-- 
http://www.spatialys.com
My software is free, but my time generally not.
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