Freeciv

struct player *city_owner

Please rename so that it's not using the same name as an existing (and relevant) function

player_by_number(research_number(presearch));

I don't think this works the way you expect it to do, especially when team shared research is enabled.

- Missing empty line between variable declarations and code
- Do not use 'default' case but list all the ranges explicitly, so that when support for a new range is added, the compiler will error if its effect on this switch is not considered
- All this should be within the "if (pobs->source.kind VUT_ADVANCE && pobs->source.value.advance vap ... ) {" , and most of it should be within "if (pcity != nullptr) {"

&& pplayers_allied(new_tech_player, city_owner)) {

Here relying on a single player as new_tech_player breaks. The wonder will get obsolete if any of the players sharing the research is allied with the city owner.

REQ_RANGE_PLAYER check breaks when pooled research is enabled (it assumes research number to match player number)

REQ_RANGE_PLAYER with pooled research still wrong. Now it checks if player is allied to someone with the research, when it should just check if player (themself) is part of the research.