The_Dude opened the ticket and wrote:

Hi,
I wanted to decide whether wagon can be attached depending on its cargo class (callback 1D), but if I use it on wagon, that is not defined in newgrf (I have set only with trains), game crashes.

The reason is in newgrf_engine.cpp, static uint32 VehicleGetVariable, line about 611, variable 0x47

return (cs->classes << 16) | (cs->weight << 8) | e->GetGRF()->cargo_map[cargo_type];

It wants to access wagon's GRF, which is not defined since it is original wagon, so it returns NULL and than it wants to get some NULL property.

It pretty kills the way to get cargo class of non GRF wagon/vehicle, because there is no other variable for it.

Something like

uint8 cargotype = e->GetGRF() != NULL ? e->GetGRF()->cargo_map[cargo_type] : 0xFF;
return (cs->classes << 16) | (cs->weight << 8) | cargotype;

would be nice. I think it should not crash at least.

I can provide some savegame, crashlog and newgrf upon request.

Reported version: trunk
Operating system: All

This issue was imported from FlySpray: https://bugs.openttd.org/task/6182