Nathan Bossart <nathandbossart@gmail.com> writes: > Even if the glibc issue doesn't apply to Postgres, I'm tempted to suggest > that we make it project policy that comparison functions must be > transitive. There might be no real issues today, but if we write all > comparison functions the way Mats is suggesting, it should be easier to > reason about overflow risks.
A comparison routine that is not is probably broken, agreed. I didn't look through the details of the patch --- I was more curious whether we had a version of the qsort bug, because if we do, we should fix that too.
The patch basically removes the risk of overflow in three routines and just returns -1, 0, or 1, and adds a comment in one.
The routines modified do a subtraction of int:s and return that, which can cause an overflow. This method is used for some int16 as well but since standard conversions in C will perform the arithmetics in "int" precision, this cannot overflow, so added a comment there. It might still be a good idea to follow the same pattern for the int16 routines, but since there is no bug there, I did not add them to the patch.