proj-data cannot be installed in a cross-compiling scenario

[Sebastiaan Couwenberg]

On 2/17/23 23:08, Yuri Astrakhan wrote:
> As reported at OSGeo/PROJ-data [1] and also found on stackexchange 5 years
> ago [2], it seems it is not possible to install libproj9 in a
> cross-compilation scenario:
> 
> [1] https://github.com/OSGeo/PROJ-data/issues/94
> [2]
> https://askubuntu.com/questions/997277/multiarch-issue-with-packages-marked-as-supporting-all-architectures

The upstream PROJ-data project is for the grid shift files, it is not 
related to the proj-data package which provides the resource files [0] 
for libproj.

[0] https://proj.org/resource_files.html

> When using proj in a multi-architecture environment (compiling
> cross-platform), the `proj-data` debian package does not exist.  The
> stackexchange post [2] has some hacky solutions on how to get around this
> issue.  I was trying to use https://github.com/cross-rs/cross 's docker
> image, and inside install proj with:
> 
> `docker run --rm -it ghcr.io/cross-rs/aarch64-unknown-linux-gnu:latest`
> 
> ```bash
> dpkg --add-architecture arm64
> apt-get update
> 
> apt show libproj9:arm64
> # shows     Depends: proj-data, libc6 (>= 2.17)
> 
> apt-get install -y libproj9:arm64
> # The following packages have unmet dependencies:
> #  libproj9:arm64 : Depends: proj-data:arm64 but it is not installable
> 
> apt-get install -y proj-data:arm64
> # E: Package 'proj-data:arm64' has no installation candidate
> ```

The cross-build issue was fixed six years ago in proj (4.9.3-2~exp1):

  https://bugs.debian.org/857538

You seem to be using Ubuntu xenial with proj (4.9.2-2), you'll need 
bionic or later for the Multi-Arch changes:

  https://launchpad.net/ubuntu/+source/proj

While Launchpad marks xenial as supported, standard supported ended in 
April 2021, standard support for bionic ends in April 2023. You should 
use the latest LTS (focal) if you cannot use Debian stable (bullseye). 
The geospatial packages are not maintained in Ubuntu, so bugs don't get 
fixed there via stable updates, only the packages in Debian are actively 
maintained.

Kind Regards,

Bas

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