extra exported symbols
In Debian, I noticed these extra symbols are exported with libchamplain 0.12.7 built with meson. I think you'll want to find a way to not export them:
+ _champlain_marshal_VOID__DOUBLE_DOUBLE_BOXED@Base 0.12.17
+ _champlain_marshal_VOID__OBJECT_OBJECT@Base 0.12.17
+ _champlain_marshal_VOID__POINTER_UINT_BOOLEAN@Base 0.12.17
+ _champlain_marshal_VOID__UINT_UINT@Base 0.12.17