Freeciv

- The new string should be marked for translation
- Master patch should include gtk-4.0 change (I'll test the compile (the only kind of test that we can do in gtk3x-client's current state) if you can't)

- You are calling g_value_set_static_string() with string from a local buffer with limited lifetime.
g_value_set_static_string() documentation ( https://developer.gnome.org/gobject/stable/gobject-Standard-Parameter-and-Value-Types.html#g-value-set-static-string ) says: "The string is assumed to be static, and is thus not duplicated when setting the GValue." You may have garbage in that memory area by the time string is used.
- I think it would be better for translatability if you refactored so that you would have entire "%s (gives shared vision)" as one translatable string, so that translator have control over placing of the player name parameter. Probably required at least by the right-to-left written languages.

Right, that's why I hate doing this kind of stuff in C.

Re. translations: I'm not exactly happy about the phrasing anyway. I would have just put some symbol or one-letter marker there (like the qt client does), but that would be a bit obfuscated without some additional text. And I don't have to much gtk experience to hack on that dialog any more than necessary.