AFAICT this is supposed to just open the file (specifically springsettings.cfg) for reading. I think that:
if the file doesn't exist, then "r" will fail and it is fine, and creating it via "a" is fine. It could produce a notice-level log.
if the file exists but fails to be read there should be an error message (ideally with reason like "permissions"). Retrying via "a" is probably fine but idk if there is ever a case where that would help.
if both methods fail the existing error log should say "could not read" and not "write".
https://github.com/beyond-all-reason/spring/blob/ab88be7e235eba1417dbfa07e95277b480283c0b/rts/System/Config/ConfigSource.cpp#L58-L69
AFAICT this is supposed to just open the file (specifically
springsettings.cfg) for reading. I think that: