fix spatialite integration for windows

[nilsnolde]

fiiinalllyyy fixes #3010

been bugging me for ages..

I went through a few demos and chose a more "modern" approach to load spatialite. only tested it down to spatialite 4.3.0, which should be enough, even ubuntu 16.04 has it. it's also still a little rough around the edges maybe, let's see what you think.

I also (tried to) include a admin tile build in windows CI.

[nilsnolde]

need to put those at the end as sqlite3.h needs to be included before spatialite.h. otherwise format.sh will simply switch the includes

[nilsnolde]

also I remove all references to sqlite/spatialite from mjolnir/util.h so we now get a lot more includes in cc files

[nilsnolde]

this is basically the new syntax. spatialite_init(0) is deprecated. we need to hold a pointer to the connection's address

[nilsnolde]

trying it out on azure (worked locally ;))

[nilsnolde]

Huh strange.. of all things, the Python bindings build triggers a leak in build_tile_set()..

wasn't the bindings of course.. issue was calling spatialite_shutdown() prematurely and multiple times.

[irees]

I'm also having an issue, possibly unrelated, with spatialite header file locations being wrong (even when I manually specify it) on macOS/arm. Maybe I'll have a fix for that soon. 😄

[kevinkreiser]

i want to make a few suggestions to this. mainly i want to encapsulate the connection init and cleanup in a shared ptr and i want to cencapsulate the global init and shutdown in a singleton. i also want to join this up with the sqlite stuff that it interacts with. i think all this crap can live in a single header with the sqlite stuff. ill make a suggestion later on tonight!

the start of it will be something like this

// we call initialize once the first time its accessed and we shutdown once when it goes out of scope (end of program)
struct spatialite_singleton_t {
  static const spatialite_singleton_t& get_instance() {
    static spatialite_singleton_t s;
    return s;
  }
private:
  spatialite_singleton_t() {
    spatialite_initialize();
  }
  ~spatialite_singleton_t() {
    spatialite_shutdown();
  }
};


// wrap the connection in a shared pointer so its automatically cleaned up when no longer used
std::shared_ptr<void> make_spatialite_cache(sqlite3* handle) {
  const auto& s = spatialite_singleton_t::get_instance();
  void* conn = spatialite_alloc_connection();
  spatialite_init_ex(handle, conn, 0);
  return  std::shared_ptr<void>(conn, [](void* c){spatialite_cleanup_ex(c);});
}

[nilsnolde]

I took a stab at implementing your suggestion, thanks for that! much cleaner.

I thought I'd include it all in a private header in ./src/mjolnir/spatialite_conn.h, but the linker complained that there are multiple definitions in graphbuilder.cc and graphenhancer.cc, though I didn't see what might be causing that.

[kevinkreiser]

@nilsnolde you need to make the functions inline or make a cc file and put the guts of the implementation in there with just the definitions in the header

[nilsnolde]

ah inlining would've helped there? good to know.. but yeah, I went for your second suggestion, .h/.cc file.

[nilsnolde]

I somehow felt like 2 entries, let me know if I should remove one