Hi Harald and all - well, Paul or Jim or any other automake worker will know better than me, but my reactions, FWIW:
This caused intermittent failures in automake's t/subobj.sh test, which This problem seems like the tip of the iceberg to me. With this change, any dependency which gets updated in the same second as the target will now have to get remade. Possibly looping forever, it seems to me? I have not seen a deluge of (or any) reports about timestamp precision being a problem before this. runs aclocal+automake, modifies configure.ac, and immediately re-runs aclocal+automake. On sufficiently fast computers, this would not update the cache files. Maybe aclocal and/or automake and/or other autoprograms should just sleep 1 before exiting (or at whatever crucial junctures) if this problem must be avoided at all costs. But better -- as Paul, I guess, said, how about if up_to_date_p uses subsecond timestamps if available, so the < test remains unchanged? After all, if subsecond timestamps are not available, it's highly probable that it's an old machine and it's all a non-issue. --best, karl.