Fix building with GCC 14

[hummeltech]

Fails to build with GCC 14.

/usr/bin/ld: /tmp/cc90QIs2.ltrans0.ltrans.o: in function `main':
<artificial>:(.text.startup+0xb1): undefined reference to `mapnik::singleton<mapnik::datasource_cache, mapnik::CreateStatic>::instance()'
/usr/bin/ld: <artificial>:(.text.startup+0x278): undefined reference to `mapnik::singleton<mapnik::datasource_cache, mapnik::CreateStatic>::instance()'
collect2: error: ld returned 1 exit status
make[2]: *** [utils/geometry_to_wkb/CMakeFiles/geometry_to_wkb.dir/build.make:115: out/geometry_to_wkb] Error 1
make[1]: *** [CMakeFiles/Makefile2:1724: utils/geometry_to_wkb/CMakeFiles/geometry_to_wkb.dir/all] Error 2

[tomhughes]

That looks very similar to https://src.fedoraproject.org/rpms/mapnik/blob/rawhide/f/mapnik-gcc14.patch ;-)

[hummeltech]

Indeed, it is basically the same, except that one source file has already had the patch applied and another source file has been renamed such that it cannot be applied directly as that patch is targeting Mapnik v3.1.

Thanks for the help!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.00%. Comparing base (d9a6494) to head (0526c60).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4456      +/-   ##
==========================================
- Coverage   72.00%   72.00%   -0.01%     
==========================================
  Files         524      524              
  Lines       33419    33418       -1     
  Branches     4145     4145              
==========================================
- Hits        24065    24064       -1     
  Misses       9352     9352              
  Partials        2        2              

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[hummeltech]

Unfortunately this patch needs more work as it is breaking Windows builds.

[mathisloge]

Unfortunately this patch needs more work as it is breaking Windows builds.

I think you just need to add a connection_manager.cpp to postgis with

template class MAPNIK_DECL singleton<ConnectionManager, CreateStatic>;

However, for pgraster plugin it might get a bit weird, since it has been used header sources from the postgis plugin (which might be understandable, but isn't the greatest thing in terms of low coupling :D)

[hummeltech]

Thanks for the suggestion @mathisloge, unfortunately I wasn't having much luck, especially since I don't have a Windows system at the ready to use for building this. Could you provide a little more detail? Thanks again!

[hummeltech]

Alright @mathisloge, I have included a workaround to get Windows builds passing in addition to fixing GCC 14 builds.