Re: BUG #5590: undefined shift behavior

"John Regehr" <regehr(at)cs(dot)utah(dot)edu> writes:
> Bug reference: 5590
> Logged by: John Regehr
> Email address: regehr(at)cs(dot)utah(dot)edu
> PostgreSQL version: head 8/2/10
> Operating system: OSX
> Description: undefined shift behavior
> Details:

> During a "make check" the left-shift operator at tsquery_util.c 48:18 is
> passed a negative right-hand argument a number of times.

Hmm. valcrc is declared as signed int32, so depending on what your
compiler thinks the semantics of % is, this clearly can potentially
happen. I notice the same problem in makeTSQuerySign() in tsquery_op.c.

The fix is presumably to cast the valcrc value to unsigned int before
executing %. However, I'm a bit worried about whether this could change
the results, and if it did whether that would invalidate any on-disk
data structures. Oleg, Teodor, do either TSQuerySign or QTNode.sign
ever get to disk?

John: how did you detect this?

regards, tom lane