Thank you for your reply. The issue I reported is distinct from upstream #5538 or Debian #921741 but the upstream patch does indeed seem to incorporate my suggested fix; I assume upstream independently spotted the same problem. Note that the original fix for #5538 had a misplaced right parenthesis, corrected in
[53cac1d08bba395942df638d74526470c9fc7975] Fix parentheses in cupsdCleanJobs The latter patch is not in buster yet. (I should probably cherry-pick it for local use if you won't issue an update for buster.) As for testing again, the issue doesn't seem easy to trigger to begin with. I had deployed my suggested fix locally on jessie but not on stretch, and it hasn't come back to bite us. (I'm not saying it was never triggered, only that the spool never filled up again as a result. Unrelated changes to our printing infrastructure --- we no longer run a central CUPS server --- have probably helped.)
