This patch fixes a UBSAN-reported integer overflow during one of our
existing tests,
test_native_functions.py::test_mintimeuuid_extreme_from_totimestamp
when attempting to convert an extreme "date" value, millions of years
in the past, into a "timestamp" value. When UBSAN crashing is enabled,
this test crashes before this patch, and succeeds after this patch.
The "date" CQL type is 32-bit count of *days* from the epoch, which can
span 2^31 days (5 million years) before or after the epoch. Meanwhile,
the "timestamp" type measures the number of milliseconds from the same
epoch, in 64 bits. Luckily (or intentionally), every "date", however
extreme, can be converted into a "timestamp": This is because 2^31 days
is 1.85e17 milliseconds, well below timestamp's limit of 2^63 milliseconds
(9.2e18).
But it turns out that our conversion function, date_to_time_point(),
used some boost::gregorian library code, which carried out these
calculations in **microsecond** resolution. The extra conversion to
microseconds wasn't just wasteful, it also caused an integer overflow
in the extreme case: 2^31 days is 1.85e20 microseconds, which does NOT
fit in a 64-bit integer. UBSAN notices this overflow, and complains
(plus, the conversion is incorrect).
The fix is to do the trivial conversion on our own (a day is, by
convention, exactly 86400 seconds - no fancy library is needed),
without the grace of Boost. The result is simpler, faster, correct
for the Pliocene-age dates, and fixes the UBSAN crash in the test.
Fixes#17516
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Closesscylladb/scylladb#17527
fc861742d7